Advances in laser-induced graphene: materials, fabrication, and emerging applications in flexible electronics

Laser-induced graphene (LIG) has evolved from a rapid polymer-to-carbon conversion method into a versatile platform for fabricating high-performance flexible electronics. This review provides a comprehensive understanding of the photothermal and photochemical mechanisms governing LIG formation, emphasizing how laser parameters wavelength, fluence, and scanning speed determine graphitization pathways and resulting electrical characteristics. Beyond process fundamentals, we highlight recent advances in conductivity engineering achieved through pre- and post-treatment strategies, including metal nanoparticle incorporation, catalytic doping, and rapid Joule annealing. These modifications enable sheet resistances below 10 Ω/sq and significantly enhance electrochemical and mechanical performance. Finally, we discuss the integration of LIG in flexible sensors, energy harvesters, and bioelectronic systems, underscoring its scalability, design freedom, and environmental sustainability. By unifying insights across mechanism, processing, and application, this review outlines a coherent roadmap for harnessing LIG as a key material in next-generation soft electronics and wearable technologies.

1 Introduction

Graphene, a revolutionary two-dimensional material composed of a single layer of carbon atoms arranged in a hexagonal lattice, has captured the scientific community’s attention owing to its exceptional properties (Geim and Novoselov, 2007; Lee et al., 2008). With an intrinsic tensile strength of approximately 130 GPa and a Young’s modulus of about 1.0 TPa (Lee et al., 2008), electron mobility exceeding 200,000 cm²/Vs (Bolotin et al., 2008), and thermal conductivity up to 5,300 W/mK (Balandin et al., 2008), graphene exhibits an extraordinary combination of mechanical, electrical, and thermal characteristics that make it a transformative material for diverse technological applications.

The remarkable properties of graphene have driven extensive research into various fabrication approaches, each offering distinct advantages. The first graphene was produced via mechanical exfoliation using adhesive tape, enabling measurement of its intrinsic, defect-free physical properties (Novoselov et al., 2004). However, this physical peeling technique is inherently limited in scalability. CVD, capable of producing high-quality monolayer graphene, provides excellent uniformity and is widely used in advanced applications (Karu and Beer, 1966). Alternatively, chemical reduction methods employing oxidation and subsequent reduction of graphene oxide offer cost-effective routes for large-scale production, albeit at the expense of higher defect density (Chen et al., 2016). While these methods have significantly advanced the field, challenges remain in achieving processes that are simultaneously simple, scalable, and cost-efficient, without the drawbacks of complex experimental variables, substrate transfer, or defect generation.

In this context, laser-induced graphene (LIG) has emerged as a distinctive and cost-effective fabrication strategy capable of addressing many of these technological limitations (Lin et al., 2014; Liu et al., 2023). LIG synthesis operates through direct laser irradiation of carbon-rich substrates under ambient conditions, enabling on-demand, mask-free patterning, substrate-integrated processing without transfer steps, and scalability compatible with roll-to-roll manufacturing (Hou et al., 2022; Wang et al., 2018). Through localized photothermal energy conversion, LIG transforms polymer precursors into porous graphene architectures, providing exceptional design flexibility for complex three-dimensional structures and broad substrate compatibility (Le et al., 2022).

However, LIG’s rapid, non-equilibrium carbonization process results in microstructural and compositional characteristics distinct from graphene produced by equilibrium methods. Typically, LIG exhibits a porous, foam-like morphology with mixed sp²/sp³ hybridization, a higher defect density, and oxygen- or nitrogen-containing functional groups that influence electrical conductivity (Lin et al., 2014; Qiu et al., 2023). While these features can be advantageous for applications such as electrochemical sensing and energy storage where large surface area and functional groups enhance reactivity they pose challenges for applications requiring pristine electrical transport comparable to mechanically exfoliated or CVD-grown graphene.

The recognition of these distinctive material features has catalyzed a vibrant research direction focused on enhancing LIG conductivity. Rather than viewing these traits as limitations, researchers have leveraged them as opportunities for targeted optimization. Recent advances have demonstrated that through precise tuning of laser parameters, strategic pre- and post-treatment techniques, and innovative substrate engineering, the electrical performance of LIG can be significantly improved while retaining its processing advantages. These developments have broadened LIG’s potential for high-performance flexible electronics, where a balance of superior conductivity, mechanical robustness, and manufacturing versatility is essential.

Figure 1 provides an overview of the LIG fabrication process, highlighting its cost-effectiveness, rapid processing, and versatility across various substrates. The schematic summarizes the key stages of LIG synthesis from direct laser irradiation of carbon-rich precursors to post-treatment and device integration along with representative approaches for enhancing electrical conductivity and expanding application scope. A detailed examination of the fundamental mechanisms underlying LIG formation and substrate effects is presented in Section 2, focusing on how laser-material interactions govern graphitic structure and conductivity. Section 3 discusses the influence of key laser processing parameters, including energy, spatial distribution, and environmental conditions. Section 4 explores modification strategies for boosting conductivity through pre- and post-treatment approaches. Section 5 reviews major applications of LIG-based flexible devices, illustrating how conductivity enhancement translates to improved performance in sensors, energy storage, and related technologies. Finally, this section outlines the future prospects and remaining challenges of LIG research, highlighting ongoing directions toward scalable, high-performance soft electronic systems.

Figure 1

Figure 1. Overview of laser-induced graphene (LIG) fabrication, modification strategies, and representative applications.

2 Material-laser interaction

2.1 Mechanisms of laser-induced graphitization

2.1.1 Graphene and laser induced graphene

A critical prerequisite for evaluating the electrical behavior of LIG is determining whether it can be regarded as “graphene” in the strict scientific sense. Graphene is conventionally defined as a single atomic layer of carbon atoms arranged in a two-dimensional honeycomb lattice through sp² hybridization (Novoselov et al., 2005) (Figure 2a). Within the broader graphene family, bilayer and few-layer graphene (FLG) are also widely studied because they retain structural continuity and exhibit tunable electronic properties; however, their band structure, symmetry, and interlayer interactions differ markedly from those of monolayer graphene (Park et al., 2010; Craciun et al., 2011; Fang et al., 2015).

Figure 2

Figure 2. Chemical and atomic structure of LIG. (a) Formation of sp² hybrid orbitals from carbon 2s and 2p states, illustrating the basis of planar graphene bonding (Reproduced with permission from Yang et al., 2018). (b,c) High-resolution transmission electron microscopy (HRTEM) images of LIG showing turbostratic multilayer graphene domains, non-hexagonal ring configurations, and defect-rich sp² networks (Lin et al., 2014). (d) Atomistic simulation of LIG surface reconstruction highlighting vacancy defects, pentagon–heptagon rearrangements, and locally strained carbon rings (Vashisth et al., 2020). (e) HRTEM image and corresponding atomic overlay showing reconstructed carbon rings and vacancy complexes within LIG (Lin et al., 2014).

In contrast, the formation mechanism of LIG is fundamentally distinct. LIG is produced through a highly non-equilibrium photothermal process in which the laser breaks covalent bonds in carbon-rich precursors and releases volatile species (Wang et al., 2000; Liu et al., 2021; Carvalho et al., 2018). The remaining carbon atoms reorganize into partially graphitized domains characterized by turbostratic stacking, heterogeneous sp²/sp³ hybridization, and a highly porous, foam-like architecture (Figures 2b,c). The structural outcome depends sensitively on both substrate chemistry and laser parameters—including fluence, pulse duration, and scanning speed—which govern the dynamics of carbonization and graphitization (Lin et al., 2014, Wang L et al., 2025). As described in Section 2.2 in detail, variations in sp²/sp³ ratios, defect density, crystalline domain size, and stacking disorder strongly modulate the electrical responses of LIG.

A growing body of literature highlights this intrinsic heterogeneity. Duy et al. identified partially ordered graphitic domains embedded within an amorphous, defect-rich matrix through Raman and XRD analyses, underscoring the incomplete and spatially non-uniform nature of LIG graphitization (Duy et al., 2018). More recently, Yang et al. demonstrated that refined control of laser operating conditions can yield LIG with highly crystalline, sp²-rich regions; in some cases, these domains show electronic behaviors approaching those of FLG despite the persistence of turbostratic stacking (Yang et al., 2024). Nonetheless, the typical LIG structure lacks the long-range order, atomically precise stacking, and uniform electronic landscape characteristic of pristine monolayer graphene or FLG. These features collectively indicate that LIG should not be classified as graphene in the strict sense. Instead, LIG is more appropriately described as a laser-synthesized porous carbon material whose properties can be extensively tuned through laser–substrate interactions. The common description of LIG as a “three-dimensional form of graphene” is therefore an oversimplification and risks conflating fundamentally distinct materials.

The electronic behavior of LIG further underscores these differences. In pristine graphene, exceptionally high carrier mobility arises from its linear energy–momentum dispersion near the K and K′ points, a consequence of its delocalized π-electron system and extended sp²-hybridized lattice (Geim and Novoselov, 2007; Novoselov et al., 2005). This band structure supports massless quasiparticle transport with minimal backscattering, enabling near-ballistic conduction under ambient conditions. By comparison, LIG exhibits substantial structural and electronic heterogeneity. Point defects, vacancies, edge terminations, functional groups, and regions of sp³ hybridization interrupt π-electron delocalization and significantly limit long-range carrier transport (Yang et al., 2020; Peng et al., 2015; Le et al., 2022). These deviations from the ideal graphene lattice contribute to the lower and more variable electrical performance typically reported for LIG.

2.1.2 Photochemical and photothermal effect

The mechanism of laser-induced carbonization arises from a coupled interplay of photochemical and photothermal effects (Zhang et al., 2010). Although the precise temporal sequence and dominance of each mechanism remain complex and not yet fully resolved, several consistent trends have been established across experimental observations, analytical studies, and simulation-based investigations. Here, we organize the current understanding of LIG synthesis by integrating these multi-scale insights.

Photochemical processes tend to dominate when short-wavelength, ultrashort-pulse lasers—typically in the picosecond to femtosecond regime—are employed. In contrast, longer wavelengths and longer pulse durations, such as CO₂ lasers operating at 10.6 μm, generally result in photothermal-dominated carbonization (Lin et al., 2014). Fundamentally, laser-induced graphitization initiates through photon–electron interactions (Medvedev et al., 2013). When the energy of a single photon exceeds a critical threshold, electrons in carbon-rich polymers can be excited from the valence band to the conduction band or even fully ejected. Because many polymers contain localized covalent bonds and large bandgaps—particularly those incorporating π-conjugated aromatic rings—electronic excitation requires photon energies exceeding this bandgap (Olejnik et al., 2023; Sarkar et al., 2024). Zhang et al. demonstrated the photochemical reduction of graphene oxide (GO) films under femtosecond laser irradiation, where XPS analysis revealed a decrease in the O1s signal, indicative of oxygen loss and cleavage of C–O and C=O functionalities (Zhang et al., 2010). When photon energy is insufficient, excited electrons rapidly relax to the ground state, restoring equilibrium without breaking covalent bonds; this is particularly relevant for infrared-regime lasers, which mainly excite molecular rotations and do not induce chemical transformations (Smith, 1991).

However, the regime changes drastically under ultrashort laser pulses. Femtosecond-scale irradiation introduces nonlinear absorption phenomena—most notably multiphoton absorption—in which several photons are simultaneously absorbed by a single electron (Wang et al., 2014). The extremely high photon flux enables electronic excitation and covalent bond rupture even when the energy of an individual photon lies below the required threshold (Medvedev et al., 2013). These nonlinear pathways are highly relevant to laser-induced graphitization, as they facilitate bond dissociation within aromatic structures or C–C frameworks and initiate carbon network reorganization independently of direct thermal activation.

By contrast, photothermal effects are more intuitively understood, as increases in laser power directly elevate the local temperature and drive thermally activated carbonization processes. Laser-induced heating excites lattice vibrations and can generate extremely high localized temperatures, promoting the cleavage of C–O, C=O, and C–N bonds. Under sufficiently high-temperature and high-pressure conditions, carbon atoms undergo rehybridization from sp³ to sp² configurations, enabling the formation of aromatic clusters (Biswas et al., 2020). Significant correlations between temperature and graphitic ordering have been established through molecular dynamics simulations. Vashisth et al. employed reactive force field (ReaxFF) simulations to investigate temperature-dependent pathways in LIG formation (Vashisth et al., 2020). Their results showed that temperatures below 2000 K predominantly yield amorphous carbon, whereas temperatures between 2500 and 3500 K provide optimal conditions for creating graphitic domains composed of hexagonal, heptagonal, and other polyaromatic motifs. At temperatures above 3500 K, thermal degradation becomes likely despite the intrinsic thermal stability of graphene.

Dong et al. further applied ReaxFF simulations to polyimide (PI), demonstrating the emergence of double-layered graphene-like structures at approximately 3000 K (Dong et al., 2016), as shown in Figures 2d,e. Their findings also revealed that carbon clusters grow more extensively at higher targeted temperatures, indicating that thermal energy is a dominant factor governing the expansion of graphitic domains. Collectively, these studies confirm that temperature is a critical determinant of laser-induced graphitization, dictating both structural order and dimensional evolution of the resulting graphene-like networks.

2.2 Influence of laser processing parameter

The photochemical and photothermal mechanisms described above are strongly modulated by external laser parameters such as wavelength, pulse duration, fluence, and scanning speed. These parameters determine not only the magnitude and spatial distribution of deposited energy but also the temporal dynamics of electronic excitation and thermal accumulation. Consequently, they exert a critical influence on the structural ordering, morphology, and electrical performance of the resulting LIG. In this section, we examine how individual laser parameters govern carbonization pathways, with particular attention to the interplay between spatial and temporal energy delivery.

2.2.1 Laser source parameter

Laser wavelength is a primary determinant of LIG formation because it dictates how the substrate absorbs and dissipates incident photon energy. Each polymer exhibits a characteristic absorption spectrum, and materials such as PI absorb far more strongly in the ultraviolet (UV) compared to the infrared (IR) region (Dyer, 2003; Zhang et al., 2010). Thus, short-wavelength lasers such as 355 nm UV produce highly localized, surface-confined carbonization dominated by photochemical decomposition, whereas longer-wavelength sources such as 532 nm or 1064 nm—and especially CO₂ lasers operating at 10.6 μm—induce deeper thermal penetration and photothermal-driven graphitization (Fiodorov et al., 2023).

Comparative studies demonstrate that UV-induced LIG (UV-LIG) typically forms compact, uniform microstructures with high graphitic crystallinity, reflected by lower D/G ratios in Raman spectra and richer oxygen-containing functionalities in XPS (Kaidarova et al., 2020; Wang et al., 2022b). Such surface chemistry enhances electrochemical reactivity and makes UV-LIG particularly advantageous for sensing applications. In contrast, IR-induced LIG (IR-LIG), especially that prepared using CO₂ lasers, yields a more porous, deeply etched morphology with extensive thermally interconnected carbon frameworks (Wang et al., 2022b). This architecture affords lower sheet resistance—often as low as 8–9.2 Ω/sq compared to 18–27.5 Ω/sq for UV-LIG—but at the cost of reduced mechanical integrity and higher defect density. These contrasts reflect the underlying mechanisms: UV photons initiate direct bond scission via high photon energy, whereas IR processing is governed predominantly by pyrolytic transformation driven by thermal accumulation (Figures 3a,b). To provide a clear comparison, the distinct characteristics and performance metrics of LIG derived from different laser wavelengths are summarized in Table 1 (Lin et al., 2014; Wang et al., 2020; Vaughan et al., 2020; Stanford et al., 2020; Santos et al., 2021).

Figure 3

Figure 3. Influence of laser source parameters on LIG formation. (a) Photothermal carbonization under IR laser irradiation (CO₂, 10.6 µm; IR, 1064 nm), where strong lattice heating drives C–OH bond scission and bulk pyrolytic graphitization. (b) Photochemical pathway activated by UV laser irradiation (355 nm), in which high-energy photons induce direct C–O–H bond dissociation with minimal thermal diffusion. (c) Schematic comparison of short-pulse, long-pulse, and continuous-wave laser modes, illustrating differences in peak power delivery and the resulting heat-affected zones during carbonization (Moldovan et al., 2021).

Table 1

Table 1. Comparison of UV, VIS, and IR laser-induced graphene characteristics.

Beyond wavelength, the temporal mode of laser operation—specifically the distinction between continuous-wave (CW) and pulsed regimes—plays a decisive role in determining LIG morphology. CW lasers, such as CO₂ systems, provide a steady, uninterrupted energy flux that facilitates sustained photothermal carbonization of PI substrates (Li et al., 2020a). This uninterrupted heating produces gradual in-plane and through-thickness temperature buildup, often surpassing 1300 K at the surface and maintaining elevated thermal gradients over several milliseconds. Such sustained conditions support layer-by-layer graphitization, continuous volatile release, and formation of uniform conductive patterns. Infrared imaging and numerical models further reveal that CW-induced heat accumulation along scan paths produces efficient carbonization distinct from the rapid quenching characteristic of pulsed systems (Ruan et al., 2018).

Pulsed lasers operate through fundamentally different mechanisms, with pulse duration controlling the balance between photothermal and photochemical effects. In the nanosecond regime (10⁻⁹ s), pulse durations are sufficiently long for thermal diffusion and lattice heating, yielding localized melting, moderate ablation, and measurable heat-affected zones (Chichkov et al., 1996; Momma et al., 1996). As pulse durations decrease toward the femtosecond regime (10⁻¹⁵ s), energy deposition becomes increasingly nonthermal. Ultrafast pulses trigger multiphoton absorption and direct bond dissociation before electron–phonon coupling can induce heating, resulting in “cold ablation” with minimal collateral thermal damage (Stuart et al., 1996; Küper and Stuke, 1987). This ultrafast regime enables high-precision LIG patterning with reduced debris, sharply defined features, and minimal heat-affected zones—attributes crucial for applications requiring fine spatial resolution (Gattass and Mazur, 2008). The transition from thermal to nonthermal interactions generally occurs around the picosecond timescale, where the pulse duration matches the intrinsic electron–phonon coupling time (Anisimov et al., 1974) (Figure 3c).

Overall, the selection of laser source parameters must be tailored to the intended application. For sensing platforms requiring uniform microstructures and high surface reactivity, UV-LIG offers superior crystallinity and advantageous oxygen-containing functional groups. For applications prioritizing low sheet resistance and high conductivity, IR-LIG provides extensive carbon connectivity and low electrical impedance despite trade-offs in mechanical robustness. Likewise, pulse duration serves as a key design parameter: femtosecond pulses enable high-resolution, low-damage patterning, while CW irradiation maximizes processing throughput for large-area fabrication. Thoughtful parameter selection therefore enables precise control over LIG properties, supporting its integration into diverse electrochemical and electronic systems.

2.2.2 Laser processing parameters

While the wavelength and pulse duration of a laser establish the fundamental interaction mechanisms between photons and matter, the practical realization of LIG formation depends critically on the effective energy density (fluence) delivered to the substrate. This fluence is fundamentally modulated by the interplay between laser power and scanning speed, which together determines the local energy dosage and thereby control carbonization thresholds, graphitization pathways, and the ultimate morphology and electrical performance of the resulting LIG.

Laser fluence represents the central parameter dictating both the onset and quality of LIG formation. Defined as the energy density in J/cm², fluence delineates distinct processing regimes that govern the conversion of polymer substrates into conductive carbon networks. Each polymer exhibits a characteristic fluence threshold, below which carbonization cannot proceed. For PI under CO₂ laser irradiation, experimental studies indicate a threshold of approximately 1.3–5.0 J/cm²; values below this range result only in surface bleaching or partial chemical modification without substantive carbon network formation (Mamleyev et al., 2019; Wang et al., 2020). Once this threshold is exceeded, pyrolytic decomposition commences rapidly, and Raman spectra display the characteristic D and G peaks (∼1350 and ∼1580 cm^-1), signaling the development of disordered and graphitic carbon domains (Duy et al., 2018). More pronounced graphitization is evidenced by a strong 2D peak at ∼2700 cm^-1, characteristic of multilayer graphene with improved crystallinity (Ferrari et al., 2006; Malard et al., 2009).

Single-pulse vector-mode experiments further underscore fluence as a decisive factor. Carbonization onset was confirmed near 5.0 J/cm²: below this value (e.g., 4.4 J/cm²), Raman spectra exhibited only intrinsic PI signals, while D and G peaks emerged at 4.9 J/cm². At fluences above 5.5 J/cm², the 2D peak became evident, marking graphene-like structure formation. Increasing fluence also induced systematic morphological transitions—from sheet-like structures to fibers and eventually to droplets—consistent with thermal decomposition dynamics and hydrodynamic behavior of PI. Under high fluence (≥40 J/cm²) and low pulse density (pulses per inch, PPI <500), vertically aligned LIG fibers (LIGF) grew up to 1 mm in thickness. Conversely, at high PPI (≈1000), stronger pulse overlap confined carbonization to thin sheet-like layers. These findings establish fluence and PPI as coupled parameters dictating LIG versus LIGF formation (Figure 4a) (Duy et al., 2018).

Figure 4

Figure 4. Influence of laser processing parameters on LIG morphology, structure, and electrical performance. (a) SEM images and Raman spectra of LIG fabricated at increasing fluence levels (4.4–5.8 J cm^-2), highlighting the transition from partially carbonized domains to well-developed graphitic networks (Duy et al., 2018). (b) Optical micrographs of UV-LIG fabricated 5 mm above the focal plane, showing the emergence of triangular patterns at different scan speeds (50 and 150 mm s^-1). (c) Schematic illustrating the origin of triangular feature formation as a function of laser scan speed and the resulting heat-affected region (Kulyk et al., 2022). (d) Design-of-Experiments (DoE) optimization of LIG sheet resistance using response-surface modeling across varied laser power and scan-speed conditions, identifying two optimal operating regimes (Murray et al., 2021). (e) Representative fabrication setups for LIG production under ambient and controlled atmospheres, including gas-assisted processing and sealed-chamber configurations enabling tunable surface wettability from superhydrophilic to superhydrophobic (Li et al., 2017).

Fluence requirements also vary across laser systems. For CO₂ lasers (10.6 µm), effective LIG formation generally occurs at fluences of 31–110 J/cm², producing sheet resistances as low as 8–36 Ω/sq under optimized conditions (Mamleyev et al., 2019; Wang et al., 2020). UV pulsed lasers (355 nm) typically require 5.5–50 J/cm² due to their surface-limited energy deposition, yielding LIG with superior uniformity but moderately higher sheet resistance (18–160 Ω/sq) (Hristovski et al., 2022; Wang et al., 2020). Visible lasers (405 nm) exhibit threshold fluences around 83.4 J/cm² and generate resistances of 20–50 Ω/sq (Stanford et al., 2020). In a systematic study, fluence sweeping through defocusing and tilted-substrate strategies revealed three major transitions: carbonization onset at ∼5 J/cm² (T₀), morphological shift from isotropic porous structures to anisotropic cellular networks at ∼12 J/cm² (T₁), and formation of aligned “woolly nanofibers” at ∼17 J/cm² (T₂). The cellular regime exhibited the strongest 2D Raman signatures and highest conductivity (∼0.4–0.5 kΩ/mm, ∼5 S/cm), whereas both sub-threshold porous and overexposed fibrous structures showed inferior conductivity (Abdulhafez et al., 2021).

These fluence requirements are inextricably linked to the beam dwell time, which serves as a temporal regulator of thermal accumulation. For instance, optimal graphitization in CO₂ laser systems is typically achieved when the scanning speed is precisely tuned to maintain surface temperatures between ∼2600 and 3600 K. This specific range facilitates the sp³-to-sp² transition while minimizing structural degradation. Excessively low speeds (e.g., <75 mm/s) lead to disproportionately high energy accumulation and temperatures (>5000 K), causing uncontrolled ablation and defect-rich carbon with I_D/I_G ratios exceeding 1.5. Conversely, high scanning speeds (>250 mm/s) result in an insufficient thermal budget, yielding amorphous or near-insulating phases (Adiraju et al., 2024; Dong et al., 2016; Vashisth et al., 2020). The impact of such temporal energy control is clearly evidenced in UV-based LIG studies (Figures 4b,c). Under optimized dwell times (e.g., at 50 mm/s), UV-LIG electrodes exhibit minimal sheet resistance and stable, linear sensor responses to humidity and temperature. As the dwell time decreases with higher scanning speeds, the incomplete carbonization leads to a marked degradation in electrical performance (Kulyk et al., 2022). These findings emphasize that while fluence defines the energy density, the temporal delivery of that energy—governed by the scanning speed—is what ultimately dictates the structural and functional integrity of the LIG.

Atmospheric control during irradiation further modulates LIG surface chemistry and functionality. Studies employing environments such as air, argon, nitrogen, hydrogen, and humid nitrogen demonstrated tunable wettability from superhydrophilic (∼0°) to superhydrophobic (>150°). Under hydrogen, LIG exhibited low oxygen content (O/C ratio), high sp² carbon fraction, and distinct 2D Raman peaks, indicating high crystallinity and enabling applications in microfluidics and waterproofing without additional chemical treatments (Figure 4d) (Li et al., 2017). Similarly, vacuum processing suppresses oxygen reactions and enhances sp² bonding, reducing sheet resistance by ∼3× compared to air-processed LIG (≈56 Ω/sq vs. ≈170 Ω/sq), highlighting the strong influence of gaseous environments on structural ordering (Dallinger et al., 2023).

To optimize LIG quality, dynamic fluence-based design combined with Response Surface Methodology (RSM) has been employed. By incorporating nonlinear interactions up to fifth-order terms, key operational regions were identified: Region 1 (low power, low speed) achieved minimal sheet resistance (15.7 Ω/sq), while Region 2 (high power, high speed) achieved ∼36 Ω/sq at 5× faster scanning. Notably, Region 2 maintained similar Raman characteristics and capacitive sensor performance despite substantially higher throughput. These results demonstrate that dynamic fluence can serve as a powerful design parameter rather than an absolute criterion, enabling efficient exploration of high-speed, high-performance LIG fabrication regimes (Figure 4e) (Murray et al., 2021).

3 Modification strategies for enhancing LIG electrical conductivity

3.1 Pre-treatment approaches

Although optimized laser parameters can significantly improve LIG quality, the intrinsic electrical conductivity of pristine LIG often remains insufficient for high-performance applications. Consequently, pre-modification strategies have emerged as essential methods for overcoming these inherent limitations. These strategies enable substantial improvements in electrical and functional properties beyond what is achievable through laser parameter tuning alone.

Broadly, pre-modification methods can be categorized into solution doping, surface coating, and substrate pre-treatment. Each strategy provides unique advantages depending on the targeted application and desired electronic, mechanical, or chemical characteristics.

One approach involves embedding metal precursors directly into the polymer matrix prior to laser processing. In this work, LIG/Cu composite films were fabricated by incorporating copper precursors (CuCl₂) into a polyamic acid (PAA) solution. The precursor solution was spin-coated onto glass substrates and thermally imidized to yield PI/Cu²⁺ films (Figure 5a). During subsequent CO₂ laser irradiation (10.6 µm, ambient conditions), the polyimide matrix undergoes rapid photothermal pyrolysis, generating localized high-temperature and oxygen-deficient environments. Under these conditions, carbonization of the polymer backbone and carbothermal reduction of Cu²⁺ ions proceed concurrently, leading to the in-situ formation of well-crystallized LIG embedded with metallic Cu nanoparticles. Because Cu ions are homogeneously distributed within the polymer matrix prior to irradiation, nanoparticle nucleation occurs throughout the evolving graphene network rather than at the surface, resulting in uniform dispersion and strong interfacial anchoring. SEM imaging (Figure 5b) confirmed a porous 3D graphene network containing ∼10 nm Cu nanoparticles homogeneously distributed throughout the matrix. This uniform dispersion is crucial because abundant Cu–graphene interfaces facilitate efficient electron transfer from metallic Cu to the graphene lattice. As a result, electrical conductivity dramatically increased to 0.37 × 10⁷ S/m, approximately 3000-fold higher than that of pristine LIG. The improvement was attributed to the synergistic combination of enhanced crystallinity and effective charge transfer mediated by Cu–C bonding. This general, scalable approach enables the tuning of LIG conductivity for applications in flexible electronics, electromagnetic interference (EMI) shielding, energy storage, and other advanced functional systems (Chen et al., 2023).

Figure 5

Figure 5. Pre-modification strategies for enhancing LIG electrical properties. (a) Cu2⁺ solution doping and CO₂ laser processing yield LIG/Cu films with uniformly distributed Cu nanoparticles; (b) SEM confirms homogeneous ∼10 nm Cu domains that significantly increase conductivity (Chen et al., 2023). (c) ZnO surface-coated PI substrates produce ZnO/LIG composites after laser irradiation; SEM images (d) show ZnO–carbon hybrid networks suitable for optoelectronic and sensing applications (Rodrigues et al., 2019). (e) AgNO₃-based substrate pretreatment forms Ag-modified porous LIG structures, as seen in SEM (f), enabling high-performance strain sensing on flexible PI (Zhong et al., 2024).

Metal-assisted photothermal enhancement represents another pre-modification route. In one study, a polymer matrix was blended with 20% nickel, creating a laser-responsive composite in which Ni acted both as a photothermal enhancer and as a graphitization catalyst. Under CO₂ laser irradiation at 7,958 W/cm² and 2 mm/s, the composite yielded multi-layered, porous LIG exhibiting an electrical conductivity of approximately 20,000 S/m. This mask-free, direct-write approach enables the fabrication of high-conductivity embedded electronics particularly suited for flexible devices, wireless sensors, and deployable aerospace systems (Yu et al., 2024).

Substrate engineering through polymer chemistry modification also offers a powerful strategy for improving LIG performance. In another study, a semi-interpenetrating polymer network was prepared by blending polybenzoxazine with PI to enhance mechanical robustness and thermal stability prior to laser irradiation. After pre-curing, the blended films were subjected to CO₂ laser treatment, which transformed the polymer alloy into a multilayered, porous LIG structure with enhanced graphitization. The optimized LIG demonstrated a sheet resistance as low as 3.61 Ω/sq, along with a crystalline graphene framework and high surface porosity that promote efficient electron transport and charge storage. This material design strategy provides a promising pathway for developing high-performance microsupercapacitors and other energy storage platforms where conductivity, accessible surface area, and structural stability are simultaneously required (Lawan et al., 2024).

Surface coating methodologies offer a powerful route for introducing functional materials onto polymer substrates prior to laser processing, enabling enhanced electrical performance and added chemical or optical functionalities. A representative example is ZnO decoration, wherein PI substrates are coated with a Zn/ZnO precursor paste and subsequently irradiated using a CO₂ laser (10.6 μm). Due to the increased thermal mass of the coating layer, higher laser powers (10–15 W) are required relative to standard LIG processing. The resulting carbon structures contain randomly distributed ZnO microparticles, and spectroscopic characterization confirms the coexistence of sp²-hybridized carbon networks with wurtzite-phase ZnO. Photoluminescence spectra display broad visible emission bands associated with ZnO defect states. The optimized ZnO-decorated LIG exhibits a low sheet resistance of 4.9 Ω/sq, improved surface wettability, and increased electrochemical surface area—all of which enhance charge-transfer kinetics. These attributes position ZnO-coated LIG as a compelling platform for flexible optoelectronic devices and electrochemical sensors, where the interplay of conductivity and surface reactivity is critical (Figures 5c,d) (Rodrigues et al., 2019).

A related surface-coating strategy utilizes silver-based materials to enhance the electrochemical behavior of LIG. In this approach, Ag nanoparticles were incorporated via three routes: (i) direct coating of AgNO₃ on PES, (ii) post-deposition onto preformed LIG, and (iii) laser processing of a silver/chitosan colloid. Among these methods, the laser-processed silver/chitosan system produced the most uniform nanoparticle distribution (13–19 nm, SEM analysis) and exhibited the lowest electron-transfer resistance (20.3 Ω) and highest double-layer capacitance (71.6 μF).

This enhanced performance can be attributed to the hybrid photothermal–chemical environment generated during laser irradiation of the silver/chitosan matrix, in which the organic chitosan component facilitates controlled reduction of Ag⁺ ions, nanoparticle nucleation, and spatial confinement within the evolving carbonized network. The resulting strong Ag–graphene interfacial coupling promotes efficient charge transfer while suppressing nanoparticle aggregation. In contrast, direct laser irradiation of AgNO₃ leads to poor graphitization, as evidenced by the absence of the 2D Raman band near 2700 cm^-1, due to the lack of a stabilizing carbonaceous matrix. Despite these differences, all configurations maintained notable antibacterial activity, highlighting their potential for multifunctional biosensing and wearable electronics applications (Sharma et al., 2024).

Pre-treatment strategies provide an additional pathway to regulate LIG formation by modifying the substrate surface prior to laser exposure. In one representative study, polyimide substrates were immersed in a 0.03 M AgNO₃ solution before single-step CO₂ laser irradiation. Under laser exposure, the pre-adsorbed Ag⁺ ions acted as localized nucleation seeds, undergoing in-situ reduction while the surrounding polymer matrix simultaneously transformed into a porous graphene network.

SEM analysis revealed that this concentration enabled the most uniform integration of Ag nanoparticles throughout the LIG matrix. The resulting strain sensors exhibited a baseline resistance of 183.4 Ω, an ultra-high gauge factor of 426.8, and rapid response and recovery times of approximately 150 ms and 200 ms, respectively. The synchronized formation of LIG and embedded Ag nanoparticles accounts for the excellent electrical stability and mechanical robustness observed under cyclic tensile loading for up to 8000 s without signal degradation. These results demonstrate the effectiveness of silver-assisted pre-treatment for producing highly sensitive and durable strain sensors suitable for wearable health monitoring, soft robotics, and human–machine interfaces (Figures 5e,f) (Zhong et al., 2024).

Sequential infiltration synthesis (SIS) provides an alternative chemical pre-treatment by introducing alumina-infiltrated organic–inorganic hybrid structures into polyethersulfone membranes via alternating exposures to trimethylaluminum vapor and water. This process confers thermal stability above the polymer’s glass transition temperature (∼230 °C), enabling selective surface carbonization into LIG while preserving the subsurface porosity. Following CO₂ laser irradiation, SIS-treated membranes retained over 90 μm of membrane thickness with minimal pore collapse, whereas untreated membranes exhibited substantial structural deformation. The resulting conductive membranes possessed a sheet resistance of 37.7 ± 0.7 Ω/sq, comparable to carbon nanotube (CNT)-based conductive membranes, while maintaining high water permeability (∼872 L m^-2 h^-1 bar^-1) and electrochemical stability under 10 mA/cm² for more than 14 days. This method offers a scalable route for producing conductive porous membranes suitable for electrically active filtration, antifouling water treatment, and electrochemical sensing, with compatibility for roll-to-roll fabrication (Bergsman et al., 2020).

Deep eutectic solvent (DES) pre-treatment also enables LIG formation from lignocellulosic biomass through selective component extraction and surface chemical modification. Various DES systems—such as choline chloride:oxalic acid (ChCl:OA), choline chloride:formic acid, and choline chloride:ethylene glycol—were evaluated for biomass fractionation. Among these, ChCl:OA treatment produced cellulose pulp that could be directly carbonized into LIG through single-step CO₂ laser irradiation without requiring additional surface preparation. The resulting LIG exhibited three-dimensional porous architectures with high graphitic crystallinity, validated through Raman spectroscopy and SEM characterization. The presence of pseudo-lignin formed during DES pretreatment acted as an additional aromatic carbon source, promoting carbonization and improving LIG yield and conductivity. Moreover, lignin recovered from the DES solution was successfully re-deposited onto cellulose, further enhancing LIG production efficiency. This sustainable and low-toxicity strategy demonstrates the feasibility of producing biomass-derived porous graphene materials for applications in energy storage, flexible electronics, and environmentally friendly sensing technologies, paving the way for circular graphene fabrication from renewable feedstocks (Zhang et al., 2022).

3.2 Post-treatment strategies

Although LIG provides a simple and scalable route for patterning conductive carbon networks directly onto polymer substrates, its as-produced form frequently exhibits suboptimal electrical and electrochemical performance. These limitations arise from incomplete graphitization, high defect density, and inherently hydrophobic surface characteristics. To overcome these bottlenecks, a range of thermal, chemical, and surface engineering approaches has been developed to systematically enhance LIG’s conductivity, wettability, and accessible surface area. Figure 6 presents a representative workflow consisting of three major post-treatment routes: flash Joule thermal annealing, sulfur-based chemical doping, and surfactant-assisted surface modification combined with oxygen plasma activation (Movaghgharnezhad and Kang, 2024; Crapnell et al., 2025).

Figure 6

Figure 6. Post-treatment strategies for upgrading LIG. (a) Flash Joule annealing (5–20 A, ∼20 ms) heals defects and reorganizes disordered carbon into more continuous graphitic layers, improving conductivity (Cheng et al., 2024). (b) Sulfur vapor doping followed by 350 °C activation introduces ∼5 at% S; SEM shows pore-wall roughening and increased porosity that enhance electrochemical activity (Shahsavarifar et al., 2025). (c) Surfactant/MXene intercalation using CTAB-functionalized Ti₃C₂T_x nanosheets, combined with mild O₂ plasma, expands channels and grafts oxygen groups, yielding superhydrophilic, high-surface-area LIG electrodes (Wang L. et al., 2025).

As shown in Figure 6a, flash Joule annealing constitutes the initial step. In this process, a high-intensity, millisecond-scale electrical pulse (5–20 A, ∼20 ms) is delivered across the LIG-patterned PI substrate. The resulting rapid resistive heating elevates the carbon network temperature to 600–1,200 °C within milliseconds, promoting selective defect healing and structural reorganization. Such ultrafast thermal exposure facilitates the coalescence of small, disordered sp² domains into larger, contiguous graphitic regions, while retaining the intrinsic microporous morphology of LIG. High-resolution transmission electron microscopy (HR-TEM) confirms the transformation from vacancy-rich amorphous carbon into well-ordered hexagonal graphene lattices (Cheng et al., 2024).

Following thermal annealing, sulfur-based chemical doping is employed to further enhance carrier transport and electrochemical behavior (Figure 6b). A vapor-phase dopant such as thiourea is introduced into the porous LIG framework, where subsequent activation at ∼350 °C drives incorporation at defect sites and grain boundaries. This process increases carrier concentration through the formation of shallow donor states and promotes extended π-electron delocalization. SEM imaging reveals notable morphological evolution, with initially smooth pore walls developing increased roughness and porosity due to dopant-induced etching and bridging. Optimized sulfur incorporation (∼5 at% S) yields a 20%–30% reduction in sheet resistance and significant improvements in areal capacitance, underscoring the suitability of S-doped LIG for high-performance energy storage and electrochemical sensing applications (Shahsavarifar et al., 2025).

The final step integrates surfactant-assisted intercalation and oxygen plasma functionalization to tune wettability and ion-transport kinetics (Figure 6c). cetyltrimethylammonium bromide (CTAB)-functionalized Ti₃C₂T_x nanosheets are first grafted onto LIG via immersion, expanding interlayer spacing and creating additional ion-diffusion pathways. Subsequent mild oxygen plasma treatment removes residual organics and introduces oxygen-containing functional groups (–OH, C=O), shifting the surface from hydrophobic to superhydrophilic (contact angle <5°). SEM characterization illustrates the progression from native LIG channels to CTAB@Ti₃C₂T_x -coated frameworks and ultimately to a uniformly functionalized, plasma-activated network. This dual-modification approach reduces charge-transfer resistance by ∼50%, doubles ion-diffusion coefficients, enables sub-μM detection limits in sensors, and delivers >20 µWh cm^-2 areal energy density in flexible micro-supercapacitors (Wang L. et al., 2025).

Collectively, the integration of rapid thermal annealing, targeted chemical doping, and engineered surface modification yields substantial improvements in the structural, electronic, and interfacial properties of LIG. Each post-treatment route addresses a specific limiting factor—defect healing, carrier density modulation, and wettability or ion-accessibility enhancement—thereby transforming LIG into a highly conductive, electrochemically active, and application-ready carbon electrode. These advances establish a rational design framework for next-generation carbon-based electronics, sensors, and energy storage platforms that leverage the intrinsic scalability and versatility of laser-induced graphene.

4 Applications of LIG-based flexible devices

4.1 Physical sensor

LIG has rapidly become a foundational material for flexible physical sensing platforms, owing to its tunable microstructure, mechanical compliance, and ability to be patterned directly onto diverse substrates. In this section, we outline the dominant sensing mechanisms and summarize representative LIG-based devices developed for pressure, strain, and temperature detection, with emphasis on performance characteristics and emerging application areas.

Three primary mechanisms govern signal generation in LIG-based physical sensors. First, piezoresistive modulation arises from deformation-induced changes in the percolated sp²-carbon network, leading to resistance variations under applied strain. Second, sensors leveraging contact resistance changes detect pressure via modulation of interfacial contact between LIG microstructures—such as layers, flakes, or junction networks—providing high sensitivity in devices where mechanical compression alters electrode–electrode contact area. Third, structural deformation effects involving corrugations, hierarchical porosity, or microsphere-spaced architectures enable mechanical stress redistribution and localized electric-field modulation, thereby amplifying sensitivity and extending dynamic range in pressure- and strain-responsive designs. These combined mechanisms underpin the versatility of LIG across diverse physical sensing modes.

4.1.1 Pressure sensor

A notable example is a bean pod–inspired pressure sensor employing a sandwich structure composed of LIG and polystyrene (PS) microspheres, which demonstrates ultrahigh sensitivity and a broad dynamic sensing range (Figure 7a). In this device, LIG is laser-scribed onto PI and subsequently transferred onto polyurethane (PU) substrates to form flexible conductive layers. PS microspheres (1.3 μm) inserted between two LIG/PU layers act as dynamic spacing elements that modulate the effective electrode contact area under external pressure. This architecture yields distinct sensing regimes, with sensitivities of 149 kPa^-1 (0–1 kPa), 659 kPa^-1 (1–10 kPa), and 2048 kPa^-1 (10–100 kPa) (Figure 7b). The device also provides a fast response time of 16 ms and maintains stable output over 1,000 pressure cycles at 100 kPa, indicating excellent mechanical durability (Figure 7c). Owing to its ultrahigh sensitivity, wide pressure range, and compliant construction, this sensor is particularly promising for wearable health monitors, electronic skin systems, and human–machine interfaces (Tian et al., 2020).

Figure 7

Figure 7. Laser-induced graphene (LIG)–based sensors for pressure, strain, and temperature monitoring. (a) Schematic of a flexible LIG pressure sensor under compressive load. (b) Sensitivity comparison with other graphene-based piezoresistive sensors below 100 kPa. (c) Dynamic switching response under 1.5 kPa. (d) Concept of an on-skin LIG strain gauge. (e) Gauge-factor characteristics of an LIG–SEBS strain sensor across wide strain ranges. (f) Hysteresis behavior during cyclic stretching from 0% to 100%. (g) Concept of a skin-mounted LIG temperature sensor. (h) Relative-resistance–temperature curves before and after NiO doping. (i) Heating/cooling cycles showing thermoresistive stability. (j) Long-term resistance stability under different temperatures. (k) Stability comparison before and after 24 h air exposure [(a–c) Tian et al., 2020; (d–f) Liu et al., 2024; (g–k) Wang et al., 2024].

Beyond this architecture, several additional LIG-based pressure sensing designs have expanded the functional capability of the material. A dual-functional LIG–polydimethylsiloxane (PDMS) pressure/proximity sensor achieves a sensitivity of 1.44 kPa^-1 (0–2 kPa) and uniquely enables non-contact gesture detection in the 1–10 mm range through fringe-field modulation (Ye et al., 2024). A corrugated PI diaphragm–based LIG sensor exhibits approximately threefold enhancement in pressure sensitivity (0.4%/kPa, 0–20 kPa) relative to planar counterparts, due to its bilaterally patterned compliant structure (Oda et al., 2025). Furthermore, a marine-grade LIG sensor embedded within an elastomeric encapsulation maintains excellent linearity (R² > 0.997) and stability under pressures up to 10 MPa. Its corrosion resistance and structural resilience highlight its suitability for extreme aquatic environments, including subsea robotics, offshore structural monitoring, and autonomous underwater vehicles (AUVs) (Van Volkenburg et al., 2023).

4.1.2 Strain sensors

LIG–based strain sensors have demonstrated exceptional performance in wearable systems aimed at human-motion monitoring and physiological signal detection (Figure 7d). A representative example is a full-range strain sensor constructed from a composite of LIG and a styrene–ethylene–butylene–styrene (SEBS) elastomer. In this design, LIG is uniformly patterned onto the SEBS substrate through CO₂ laser processing, forming a percolated and highly stretchable conductive network. Mechanical and electrical evaluation revealed remarkably high gauge factors ranging from 413 to 3118 across different strain regimes, with strain limits exceeding 100% and minimal hysteresis. As illustrated in Figure 7e, the gauge factor increases nonlinearly with strain, reflecting the progressive disruption and reformation of conductive pathways within the porous LIG framework. Cyclic stretching tests (0%–100% strain, Figure 7f) show nearly overlapping loading and unloading curves, confirming excellent repeatability and mechanical durability of the LIG/SEBS composite. When integrated with a wireless communication module, the system enables real-time monitoring via smartphone interfaces, demonstrating its suitability for continuous health tracking, rehabilitation monitoring, and next-generation wearable diagnostics (Liu et al., 2024).

Beyond this full-range design, LIG-based strain sensors have been increasingly adopted in diverse healthcare and motion-tracking contexts. Devices with moderate sensitivity—for example, a gauge factor of 15.79—have been utilized to monitor finger and facial muscle movements under repeated deformation, enabling real-time gesture recognition and emotion sensing (Li et al., 2025). Sensors with enhanced precision, including a detection limit of 0.05%, have shown promise in fine motor control, subtle movement tracking, and neuromuscular health assessments (Zhong et al., 2024). More structurally engineered devices, such as kirigami-inspired LIG architectures, offer improved mechanical adaptability and conformal strain distribution, making them suitable for joint-angle tracking and soft-robotic feedback systems (Biswas et al., 2023). Additionally, hybrid LIG systems—such as porous thermoelectric LIG sensors—enable dual-mode detection of strain and temperature, expanding their utility to applications such as wound healing assessment and fire safety alerts, where multimodal physical sensing is advantageous (Yang et al., 2025).

4.1.3 Temperature sensors

LIG–based temperature sensors have advanced substantially in recent years, with strategic doping and structural engineering approaches driving notable improvements in sensitivity, linearity, and long-term signal stability (Figure 7g). A representative example involves the incorporation of NiO nanoparticles into PI precursors, followed by 355 nm UV laser processing to produce NiO-doped LIG films. The resulting flexible temperature sensors exhibit a markedly enhanced temperature coefficient of −0.079%/ °C, corresponding to a 19.3% improvement relative to undoped LIG devices, along with excellent linearity across a broad temperature window (30 °C–100 °C, R² = 0.999) (Figures 7h–k). Resistance–temperature cycling tests confirm minimal hysteresis, highly reproducible thermal responses, and stable operation over 24 h under ambient conditions. Complementary Raman and XRD analyses attribute these improvements to enhanced graphitization and partial reduction of NiO to metallic Ni within the LIG matrix, which collectively promote more efficient charge transport. Owing to their high sensitivity, flexibility, and operational robustness, these NiO-doped LIG sensors are well suited for wearable temperature monitoring, electronic skin, and precision thermal diagnostics in medical and industrial settings (Wang et al., 2024).

Beyond NiO doping strategies, a variety of LIG-based configurations have demonstrated excellent thermal sensing performance for both wearable and environmental monitoring applications. A temperature sensor fabricated by transferring LIG onto an Ecoflex elastomer achieved ±0.15 °C accuracy in the 30 °C–40 °C physiological range and maintained stable output under mechanical deformation, highlighting its suitability for body-temperature tracking in continuous health monitoring (Kun et al., 2021). In another approach, vanadium oxide (VO_x) dopants were integrated into LIG foam composites to create a dual-function platform capable of temperature sensing across 10 °C–110 °C and ppb-level detection of nitrogen oxides (NO_x), offering long-term stability and low detection limits for environmental surveillance (Yang et al., 2023). Meanwhile, direct LIG patterning on PI has enabled durable temperature sensors exhibiting negative temperature-coefficient behavior and linear responses from 25 °C to 80 °C, with facile scalability to spatially resolved array structures suitable for electronic skin, robotics, and thermal mapping applications (Park and Pak, 2024). Together, these examples highlight the versatility of LIG as a foundational material for developing flexible, accurate, and multifunctional thermal sensing systems.

Despite the significant progress achieved across LIG-based physical sensors, several challenges remain for reliable real-world deployment. Long-term stability and environmental robustness continue to be concerns for wearable systems exposed to sweat, fluctuating humidity, and repeated mechanical strain. Variations in contact resistance and mechanical fatigue can degrade signal fidelity in strain and pressure sensors, particularly those relying on high gauge factors or soft substrates. Temperature sensors often require compositional tuning (e.g., NiO, VO_x doping) or additional structural engineering to ensure high linearity and low detection limits, which can introduce fabrication complexity and impact reproducibility. Furthermore, integrating multimodal sensing—such as decoupling strain-temperature cross-talk in dynamic environments—demands improved material engineering, structural design, and advanced signal-processing strategies. Addressing these challenges will be essential to fully realize the practical potential of LIG-based sensing technologies for next-generation wearable health monitoring, soft robotics, and environmental diagnostics.

4.2 Electrochemical sensor

LIG integrates high electrical conductivity, large electrochemical surface area, and inherent mechanical flexibility, making it an exceptional platform for next-generation electrochemical sensing systems. Its three-dimensional porous morphology provides abundant active sites for biomolecule adsorption and redox reactions, thereby enhancing sensitivity and facilitating rapid electron transfer (Behrent et al., 2024). Meanwhile, the material’s mechanical compliance enables seamless incorporation into wearable and portable devices designed for real-time monitoring (Vivaldi et al., 2021). This section highlights key advances in LIG-based electrochemical sensing, with emphasis on biomolecule detection, food safety monitoring, environmental surveillance, and agricultural smart sensing.

In Figure 8a, Park et al. (2025) present a dopamine biosensor designed to support neurological disorder diagnostics and therapeutic drug monitoring. The device is fabricated by CO₂ laser scribing UV/ozone-treated PI coated with a CeO₂ precursor, producing a hybrid LIG structure (UV-LC) decorated with firmly anchored CeO₂ nanoparticles. This modification increases the electrochemical surface area from 1.31 to 3.35 cm², significantly improving signal transduction. The sensor achieves a linear detection range of 0–10 μM dopamine, a sensitivity of 25.09 μA/μM·cm², and a detection limit of 0.38 μM. Selectivity studies further demonstrate that common interfering species such as glucose, ascorbic acid, and uric acid contribute less than 55% of the dopamine signal, underscoring the platform’s applicability for practical biosensing.

Figure 8

Figure 8. Multifunctional LIG Electrochemical Sensors. (a) UV/ozone-treated polyimide followed by CO₂-laser writing to form CeO₂-decorated LIG for dopamine detection (0–10 µM) (Park et al., 2025). (b) Amperometric response of a flexible LIG/PEDOT/Au/GOx electrode showing sequential current steps for 5 × 10^-6–2.5 × 10⁻³ M glucose (Zhang et al., 2024). (c) Real-time resistance change of a laser-induced paper sensor during wireless monitoring of temperature and volatile-gas evolution associated with food spoilage (Jung et al., 2022). (d) Calibration curve of a Pt-NP/GlyOX-modified LIG biosensor integrated with a fern-leaf microcollector for on-site glyphosate detection (10–260 µM) (Jared et al., 2024). (e) Square-wave anodic-stripping voltammograms of porous laser-derived graphene electrodes enabling simultaneous, modification-free detection of Cd²⁺ and Pb²⁺ (Jeong et al., 2022). (f) Dynamic resistance response of a stretchable, moisture-tolerant LIG gas sensor to 1 ppm NO, fabricated using different laser powers (Yang et al., 2022). (g) Chronoamperometric signal from a wearable reverse-iontophoretic LIG electrode extracting and quantifying salicylic acid from plant leaves (10–1000 µM) (Perdomo et al., 2024). (h) Evolution of leaf impedance over 4 days after ozone exposure, measured using transparent PEDOT-Cl tattoo electrodes (Kim et al., 2020).

Figure 8b highlights noninvasive glucose sensing. Zhang et al. (2024) developed a portable electrochemical glucose sensor built on a flexible LIG composite electrode. The LIG substrate was enhanced by potentiostatic deposition of PEDOT and Au nanoparticles (AuNPs), forming a conductive, stable composite. Glucose oxidase (GO_x) was immobilized using glutaraldehyde, yielding a robust enzyme–electrode interface. The resulting sensor exhibits a linear detection range of 5.0 × 10⁻⁶ to 2.5 × 10⁻³ mol L^-1, a high sensitivity of 341.67 mA/mM·cm², and a detection limit of 2.0 × 10⁻⁶ mol L^-1, positioning it as a competitive candidate for next-generation portable glucose monitoring systems.

In the area of food safety monitoring, Figure 8c illustrates a laser-induced paper sensor (LIPS) developed by Jung et al. (2022). This system directly carbonizes commercial paper substrates via laser irradiation, yielding a porous LIG/paper hybrid with a sheet resistance of 10⁵ Ω·sq⁻¹. The resulting platform exhibits both chemical- and thermal-sensing capabilities, enabling real-time assessment of food spoilage indicators such as temperature and vapor-phase degradation products. The LIPS device demonstrated a temperature coefficient of 0.15%·°C⁻¹ and a gas-response coefficient of 0.0041%·ppm^-1, with wireless data transmission to mobile devices. Its biodegradable construction offers an environmentally sustainable and scalable solution for smart food packaging applications.

Figure 8d presents an agricultural pesticide monitoring system reported by Jared et al. (2024), addressing the global need for improved pesticide tracking and environmental protection. The researchers developed a biomimetic “fern leaf” patch fabricated using high-throughput CO₂ laser processing of PI to form patterned LIG structures. A three-electrode LIG sensor functionalized with electrodeposited platinum nanoparticles and glycine oxidase enables rapid glyphosate detection, achieving a linear range of 10–260 μM, a detection limit of 1.15 μM, and a sensitivity of 5.64 nA μM^-1. This “collect-and-sense” design captures pesticides consistently 24–48 h after spraying, aligning with restricted-entry intervals in agricultural fields. The system advances precision agriculture by enabling spatial mapping of pesticide distribution while reducing environmental exposure risks.

In environmental monitoring, LIG has emerged as a powerful platform for electrochemical detection of heavy metals and atmospheric pollutants, owing to its high conductivity, large specific surface area, and facile chemical modification capabilities (Jeong et al., 2022). Figure 8e highlights a representative example developed by Jeong et al., in which LIGF electrodes were engineered for simultaneous detection of cadmium (Cd²⁺) and lead (Pb²⁺) ions in aqueous environments. Bismuth electrodeposition onto LIGF enhanced both selectivity and stripping-voltammetry sensitivity, enabling detection sensitivities of 0.19 μA μg^-1·L for Cd and 0.20 μA μg^-1·L for Pb, along with wide linear ranges (1–140 μg L^-1) and low detection limits (0.4 μg L^-1 for both ions). Additionally, the sensor demonstrated excellent stability (relative standard deviation (RSD) < 2.3%) and high accuracy when applied to real tap and drinking water samples (R² > 0.99). These results underscore the practicality of LIGF-based electrodes as scalable, rapid, and non-toxic platforms for heavy-metal detection, with performance comparable to, or exceeding, conventional carbon-based sensing technologies.

Figure 8f illustrates LIG-based gas sensing for air pollution monitoring, an area of growing importance due to the rising levels of ozone (O₃) and nitrogen oxides (NO_x) associated with climate change. Increased ground-level ozone—particularly in agricultural regions—causes oxidative injury to plants, leading to reduced yields and long-term ecosystem damage. Yang et al. (2022) developed a highly stretchable LIG-based NO_x sensor designed for both environmental monitoring and breath analysis. Their architecture incorporates LIG encapsulated between a soft elastomeric substrate and a moisture-resistant semipermeable layer, while optimized laser parameters (power, image density, and defocus distance) produce LIG morphologies ideal for gas adsorption. The sensor exhibits strong responses of 4.18‰·ppm^-1 (NO) and 6.66‰·ppm^-1 (NO₂), ultralow detection limits (8.3 ppb NO, 4.0 ppb NO₂), rapid response/recovery times, and excellent selectivity. The use of serpentine LIG electrode geometries and strain-isolating rigid islands enables up to 30% stretchability, while maintaining stable performance even at 90% relative humidity. Such robustness supports deployment in breath-analysis systems, environmental sensors, and climate-resilient monitoring platforms.

In agricultural smart sensing, LIG enables real-time monitoring of plant physiology and environmental stressors with minimal invasiveness. Figure 8g presents a wearable, non-destructive salicylic acid (SA) sensor developed by Perdomo et al. (2024) for tracking abiotic stress responses in plants. SA is a key phytohormone that modulates responses to drought, salinity, and pathogen attack. The researchers integrated a reverse iontophoretic extraction module with a LIG electrode to achieve highly sensitive and continuous SA monitoring in avocado plants exposed to drought and salt stress. The platform demonstrated a high sensitivity of 82.3 nA/μmol·L^-1·cm^-2, a low detection limit of 8.2 μmol L^-1, and a rapid sampling response of 20 s. Notably, the system revealed distinct SA accumulation profiles: drought stress produced a faster and more pronounced SA increase than salt stress. Minimal interference from off-target metabolites allowed for high measurement precision, while the rapid extraction enabled efficient, near-real-time analysis. This capability opens new opportunities for precision agriculture and stress-responsive crop management.

For early detection of plant disease and real-time physiological diagnostics, LIG-based systems can be directly integrated into living plant tissues. Figure 8h highlights the PEDOT-Cl “tattoo sensor” developed by Kim et al. (2020), capable of detecting both immediate and delayed ozone-induced damage. While leaves appeared visually unchanged 24 h after exposure, impedance spectra revealed continued cellular degradation, demonstrating the sensor’s ability to detect subclinical oxidative stress. The tattoo sensors were tested across various fruiting plants—multiple grape varieties and apple trees—and consistently captured characteristic changes in impedance and phase associated with ozone exposure. The authors propose deploying tattooed seedlings or cuttings at strategic field locations as long-term, living sensors of ground-level ozone. This approach enables continuous, on-site health monitoring of crops throughout entire growing seasons, offering major advantages over conventional laboratory-based assays.

Collectively, LIG-based sensors demonstrate exceptional multifunctionality, environmental robustness, and scalability across diverse real-world monitoring scenarios. Their low-cost fabrication, excellent electrical and electrochemical properties, tunable surface chemistry, and broad substrate compatibility position them as transformative components for next-generation smart diagnostics, sustainable agriculture, and environmental surveillance. As innovations in LIG processing and materials engineering continue—and as integration with Internet of Things (IoT) and distributed sensor networks accelerates—LIG-enabled platforms are poised to play a pivotal role in advancing sustainable, intelligent, and data-driven environmental monitoring ecosystems.

4.3 Energy harvesting and storage device

The rapid expansion of wearable electronics, implantable medical systems, and distributed IoT infrastructures has intensified the demand for self-powered platforms, particularly in scenarios where battery replacement or wired power delivery is impractical or impossible (Chen et al., 2016). Conventional energy-harvesting modules typically depend on complex fabrication processes—such as vacuum deposition, multistep lithography, or material-specific transducer engineering—thereby limiting large-scale deployment (Dowarah et al., 2024).

LIG presents a compelling alternative due to its mask-free, catalyst-free, and vacuum-free fabrication through single-step laser scribing of polymer substrates. The tunable morphology and high electrical conductivity of LIG allow seamless adaptation to a broad range of energy-harvesting modalities. Triboelectric nanogenerators benefit from LIG’s enlarged surface area and enhanced dielectric constant under ambient laser-scribing conditions (Choi et al., 2020). Thermoelectric modules leverage the improved conductivity and structural uniformity achieved via inert-atmosphere laser processing (Bressi et al., 2023). Photothermal systems exploit LIG’s broadband optical absorption and efficient solar-to-thermal conversion, particularly when produced via pulsed laser irradiation (Devinder et al., 2023). Furthermore, the inherent mechanical compliance of LIG facilitates tight integration with skin, textiles, soft robotic systems, and deformable substrates (Wang et al., 2022a).

These combined features establish LIG as a highly scalable and versatile material platform for energy harvesting in wearable biosensing, autonomous environmental monitoring, and next-generation IoT devices. The following sections highlight recent developments in human-derived, mechanical, and ambient energy harvesting using LIG systems.

4.3.1 Human-derived energy harvesting for LIG devices

LIG has recently gained substantial attention as a multifunctional material for harvesting energy directly from human physiological signals—such as motion, temperature gradients, and biochemical secretions. The porous, compliant nature of LIG supports intimate skin interfacing, enabling efficient conversion of subtle body-generated stimuli into electrical output. Such capability is crucial for wearable electronics, where conventional batteries introduce limitations associated with rigidity, size, or replacement frequency. This section outlines recent advances in LIG systems designed for autonomous sensing, actuation, and on-body health monitoring.

Figure 9a showcases a stretchable laser-rewritable LIG@PI/PDMS/polyethylenimine ethoxylated (PEIE) patch that integrates biosignal acquisition (electrocardiogram (ECG) and electromyogram (EMG)), sweat-based biochemical sensing, radio-frequency (RF) energy harvesting, and electrical stimulation into a unified epidermal platform. Operating at the skin interface, the system provides real-time electrophysiological monitoring (SNR ≈24.7 dB), glucose detection with a sensitivity of 2.05 μA cm^-2·mM^-1, and efficient wireless power reception (Figure 9b, top). The porous LIG electrode (sheet resistance ∼0.175 kΩ^-1; adhesion ∼63.4 N m^-1) forms a conformal, adhesive-free, and breathable interface with the skin (Figure 9b, bottom). This multifunctional design supports battery-free, reprogrammable electronic-skin systems capable of wearable diagnostics, closed-loop therapy, and mobile health monitoring in dynamic or resource-limited environments (Zhu et al., 2024).

Figure 9

Figure 9. Representative LIG-based systems for energy harvesting, classified by stimulus source and functional domain. (a,b) Wearable LIG e-skin for multimodal human-signal acquisition (ECG/EMG, biochemical sensing, thermal modulation) with conformal skin adhesion (Zhu et al., 2024). (c,d) Thermoelectric LIG platforms for simultaneous strain–temperature sensing and real-time wound evaluation (Yang et al., 2025). (e,f) LIG-enabled tactile/mechanical energy harvesters supporting robotic manipulation, tactile pattern recognition, and wireless control (Guo et al., 2023). (g,h) Solar-driven LIG systems for interfacial steam generation, desalination, and textile-integrated light-absorption modulation (Le et al., 2024). (i) Environmental harvesters combining wind, rain, and motion-driven energy conversion with self-charging capability (Li et al., 2020a).

Expanding multimodal sensing capabilities, Figure 9c illustrates a platform that integrates porous LIG, ion-conducting hydrogel, and PEDOT:PSS to achieve simultaneous yet decoupled detection of strain and temperature, enabling multimodal physiological analysis (Yang et al., 2025). The system achieves a Seebeck coefficient of 37.33 μV °C⁻¹, allowing conversion of skin-air thermal gradients into continuous electrical output (Figure 9d). This design provides real-time wound-healing assessment and multimodal diagnostics in soft wearable formats.

Further advancing dual-mode sensing and thermoelectric functionality, Zhang et al. introduced a stretchable thermoelectric sensor constructed from porous LIG foam and an ionic hydrogel (Zhang et al., 2025). The sensor achieves a high strain gauge factor (∼105.9), sub-degree temperature resolution (∼0.1 °C), and a Seebeck coefficient of −189.9 μV K⁻¹. Utilizing both the Soret effect and redox-driven thermodiffusion, the system generates more than 100 mV from a modest 20 °C gradient—sufficient to intermittently power flexible amplifiers or thermochromic displays. Such capabilities support closed-loop monitoring of respiration, motion, and thermoregulation without external power, enabling applications in personalized medicine, smart clothing, and mobile diagnostics.

Mechanical-actuation-assisted harvesting has also been demonstrated. Zhang et al. developed a triboelectric generator using a MXene/leather composite paired with Au-doped LIG (Zhang et al., 2023). Operating in single-electrode triboelectric nanogenerator (TENG) mode, the device produces up to 199.6 V and 0.469 mW cm^-2 from contact with a PU film. A 3 × 3 array captures tactile signals for gesture recognition, robotic actuation, and human–machine interaction. By transducing touch into electrical signals without external power, this system functions as a self-powered interface suitable for intelligent prosthetics, adaptive soft robotics, and immersive control systems.

Together, these examples demonstrate how human-integrated LIG harvesters combine mechanical flexibility, skin conformity, and multimodal transduction in a single material framework. By operating within physiologically safe thermal and mechanical regimes, LIG-based harvesters enable continuous on-body energy extraction from diverse stimuli. When coupled with soft energy-storage modules (e.g., flexible supercapacitors) and wireless communication circuits, these architectures support fully autonomous wearable systems for long-term personalized healthcare, biosignal feedback, and mobile diagnostics.

4.3.2 Artificially induced mechanical energy harvesting for LIG devices

Beyond human-derived physiological cues, externally applied mechanical stimuli offer additional opportunities for energy harvesting in LIG-based platforms. Recent advances demonstrate how engineered mechanical inputs—including structural vibrations, robotic motions, and externally programmed tactile interactions—can be leveraged to create fully self-powered LIG systems that unify energy harvesting, sensing, and communication within a single architecture. Such platforms are particularly well suited for robotic interfaces, intelligent surfaces, and structural monitoring systems, where autonomous operation and rapid responsiveness are essential.

Guo et al. developed a multilayer, self-powered triboelectric interface incorporating dual-mode LIG-based TENGs capable of simultaneous wireless motion control and tactile sensing (Guo et al., 2023). Operating in both freestanding and single-electrode modes, the interface autonomously harvests mechanical signals originating from rolling motion, contact pressure, or structural deformation. A rolling nylon pellet interacting with a PVDF-HFP/LIG electrode array generates up to ∼8 V, while the tactile layer achieves a sensitivity of 2.2 V kPa^-1, a pressure resolution of 60 Pa, and stability over >10,000 cycles. These mechanical excitations are directly converted into electrical outputs, enabling closed-loop actuation without the need for external power. As shown in Figure 9e, the system mounted on a robotic arm functions as a battery-free controller that modulates movement direction and speed. Figure 9f illustrates the stacked configuration consisting of control, shielding, and tactile layers, underscoring its potential for autonomous soft robotic systems capable of real-time environmental interaction.

Li et al. advanced this concept with a flexible single-electrode TENG integrating a LIG/MoS₂ charge-trapping layer engineered for wide-range force detection (5–100 N), multi-frequency responsiveness (0.4–2 Hz), and non-contact sensing (Li et al., 2024). By harvesting ambient mechanical cues—pressure, vibration, or proximity—the device generates electrical signals without external powering, enabling real-time perception in machines and autonomous systems. When integrated with AI-based processing algorithms, the interface supports smart unlocking, anomaly detection, and material classification. This scalable approach provides a robust tactile interface suitable for autonomous vehicles, smart infrastructure, and adaptive robotic platforms requiring continuous, self-powered environmental feedback.

Expanding LIG functionality into structural monitoring, Jeong et al. fabricated porous LIG directly onto colorless PI (CPI) using femtosecond laser writing (Jeong et al., 2023). Fluorinated CPI facilitated the formation of high-surface-area LIG (∼132 m² g^-1), yielding piezoresistive sensitivity of 60.34 kPa^-1 under <1.5 kPa loads and triboelectric output of 411.4 mW m^-2 under low-frequency excitation typical of mechanical or architectural vibration sources. The air-gap-rich design withstands cyclic deformation while maintaining stable performance, demonstrating its suitability as a scalable sensing–harvesting module for embedded monitoring within bridges, building components, robotic joints, and other structural systems.

Collectively, mechanically induced LIG energy harvesters extend the capabilities of LIG-based systems from passive wearable platforms to actively engineered environments requiring autonomous operation. By leveraging externally applied mechanical inputs—programmable actuation, structural motion, or contact dynamics—these devices support on-demand energy generation and self-sufficient signal acquisition. The intrinsic flexibility, tunability, and multifunctionality of LIG enable seamless integration of energy harvesting, sensing, and embedded signal processing within a unified framework. When coupled with local energy storage and wireless communication, such systems offer robust, repeatable, and long-duration performance for deployment in dynamic, untethered settings.

4.3.3 Nature-derived energy harvesting for LIG devices

Beyond engineered mechanical or physiological stimuli, environmental energy sources such as sunlight, wind, and moisture offer abundant and sustainable opportunities for autonomous power generation. LIG’s broadband optical absorption, intrinsic porosity, and high electrical/thermal conductivity make it exceptionally well suited for converting natural energy flows into usable electrical or chemical energy. These properties enable LIG-based systems to function in off-grid, resource-limited, or harsh outdoor environments where conventional power sources cannot be deployed. The following representative studies highlight how LIG architectures leverage photothermal, triboelectric, and ion-interactive mechanisms to achieve sustainable, maintenance-free operation.

Le et al. developed a three-dimensional solar evaporator incorporating a wavy LIG-coated surface integrated with a cotton-based capillary wick, as illustrated in Figure 9g (Le et al., 2024). Designed for freshwater generation under off-grid conditions, the system employs passive interfacial evaporation enhanced by dual-sided vapor release and salt-rejection functionality. Through a single-step UV laser treatment of fabric (Figure 9h), the absorber achieves ∼99% solar absorptance and reaches ∼84.5 °C under 1 sun without external concentration. The synergistic combination of LIG’s broadband absorption and the underlying microfiber network facilitates rapid light-to-heat conversion and efficient water transport, providing a scalable pathway for decentralized desalination and field-deployable water purification.

Expanding the concept to weather-driven stimuli, Li et al. introduced a flexible self-charging device that harvests energy from both wind and raindrops using a dual-mode LIG-based triboelectric–electrostatic architecture (Li et al., 2020b). The superhydrophobic, porous LIG electrode (contact angle ∼150°, sheet resistance ∼24 Ω) enables voltage outputs up to 170 V and stable operation over >10,000 cycles. Fabricated via laser writing and bioinspired molding (Figure 9i), the device autonomously powers low-energy modules even under fluctuating humidity and rainfall. Its robust, weather-adaptive design makes it suitable for deployment in agricultural fields, forested ecosystems, or remote environmental monitoring sites where sustained maintenance-free operation is essential.

Integrating energy conversion with on-board storage, Speranza et al. demonstrated a compact solar–storage hybrid module that couples a dye-sensitized solar cell (DSSC) with a supercapacitor using bifunctional LIG electrodes (Speranza et al., 2023). In this architecture, LIG serves simultaneously as the catalytic counter electrode and as the current collector, enabling efficient photon-to-charge conversion and direct charge storage without noble-metal components. The high porosity and conductivity (∼24 Ω) of the LIG layer support rapid ion transport and efficient solar harvesting under AM 1.5G illumination, allowing the system to operate autonomously in outdoor or building-integrated IoT configurations. This monolithic integration of harvesting and storage represents an important step toward compact, maintenance-free, energy-autonomous nodes for distributed sensor networks.

LIG has also been leveraged for solar-thermal chemical extraction. Zhao et al. reported a floating 3D LIG/MnO₂ platform designed for solar-driven lithium recovery from brine (Zhao et al., 2025). Benefiting from LIG’s broadband absorption (∼96.3%) and high thermal conductivity, the device reaches 82.4 °C and achieves an evaporation rate of ∼2.99 kg m^-2 h^-1 under 1 sun illumination. MnO₂ integrated within the LIG matrix provides selective Li⁺ capture (13.48 mg g^-1) over competing ions such as Mg²⁺. The conductive LIG backbone enhances ion diffusion and maintains structural stability during redox cycling. This lightweight, modular, floatable design enables entirely solar-powered lithium extraction from saline or geothermal reservoirs, offering a decentralized alternative to energy-intensive industrial processes.

Collectively, LIG-based systems driven by natural environmental stimuli demonstrate remarkable potential for off-grid and resource-constrained applications. By combining photothermal conversion, superhydrophobic triboelectric interfaces, and integrated storage capabilities, these platforms deliver continuous, maintenance-free operation under highly variable outdoor conditions. Their compatibility with lightweight substrates and scalable laser fabrication further enhances suitability for decentralized IoT nodes, autonomous water purification, agricultural monitoring, and long-term environmental sensing deployed far from conventional power infrastructure.

To place these diverse examples into a broader technological context, Table 2 summarizes representative LIG-enabled devices across physical sensing, electrochemical detection, and energy-harvesting modalities. Organizing the systems by function, application domain, fabrication route, and key performance features highlights how variations in laser–substrate interactions, precursor chemistry, and post-treatments produce highly customized device architectures. From wearable physiological monitors and biochemical sensors to structural vibration harvesters and autonomous soft-robotic interfaces, the breadth of these implementations underscores LIG’s role as a unified materials platform capable of operating seamlessly across healthcare, environmental monitoring, agriculture, and untethered intelligent systems.

Table 2

Table 2. Functional landscape of LIG across physical sensing, electrochemical detection, and energy-harvesting modalities.

5 Future prospects and challenges

LIG has emerged as one of the most transformative approaches for scalable graphene fabrication, redefining how carbon materials can be patterned, functionalized, and integrated directly onto flexible, low-cost substrates. Compared to CNT or rGO, a defining strength of LIG lies in its ability to form conductive sp² carbon networks directly on polymer substrates through a single-step, direct-write process, enabling simultaneous material synthesis, patterning, and device integration without the need for binders, transfer steps, or chemical reduction. Yet its continued advancement relies on deepening our understanding of the complex laser–polymer interaction mechanisms that govern graphitization, defect evolution, and morphology formation. Establishing precise parameter–property correlations will be essential for tailoring LIG to meet the increasingly stringent requirements of next-generation electronic, sensing, and energy systems.

A major opportunity lies in strategic material engineering through pre- and post-treatment routes, which enable property modulation far beyond what laser parameter tuning alone can achieve. Pre-treatments—including precursor doping, metal-ion incorporation, and polymer alloying—allow researchers to pre-define how a substrate responds to laser irradiation. Post-treatments, such as flash-Joule annealing, heteroatom doping, and plasma functionalization, offer fine adjustment of crystallinity, carrier concentration, and wettability. Together, these approaches provide a rational design framework wherein the required physical or electrochemical property is first identified, and LIG morphology or chemistry is then engineered backward to meet that target. This process-level flexibility allows LIG to span a broad performance envelope—from highly conductive graphitic networks to defect-rich, electrochemically active surfaces—within a single material platform. Such methodologies allow LIG to match or surpass conventional graphene, while maintaining its inherent advantages of mask-free, chemical-free, and roll-to-roll compatible processing.

Across current applications, LIG continues to deliver exceptional performance by exploiting its intrinsic porous morphology, tunable conductivity, and mechanical compliance. In physical sensors, the interconnected sp² network and microstructured topography enable ultrahigh sensitivity in strain and pressure sensing, often with gauge factors above 400, supporting applications in human–machine interfaces and skin-mounted wearables. In electrochemical sensing, LIG’s high surface area, defect-rich edges, and functionalization-friendly surface chemistry support detection limits extending to the sub-micromolar regime for neurotransmitters, metabolites, heavy metals, and plant hormones. In energy systems, LIG enables multimodal harvesting from human motion, vibration, solar irradiation, and environmental stimuli, and its compatibility with soft substrates allows seamless integration into autonomous IoT nodes and self-powered biosensing systems.

At a broader technological scale, LIG’s mask-free fabrication, minimal chemical waste, and low energy consumption position it as a sustainable manufacturing route for green electronics. Its deterministic patterning capability and substrate-level integration enable device architectures that are difficult to realize through solution-based or transfer-dependent carbon materials. Its demonstrated versatility—ranging from self-powered e-skin to agricultural biosensors and solar-driven desalination—highlights how LIG architectures can be systematically aligned with application-specific demands: using porosity for enhanced charge transfer, flexibility for conformable wearables, and conductivity tuning for optimized energy conversion.

Despite this rapid progress, several key challenges remain. Precision control over laser-induced graphitization is still limited by the complex interplay of heat diffusion, polymer chemistry, and photothermal conversion. Current LIG systems also face variability across different polymer substrates, limiting cross-platform compatibility. Achieving large-area uniformity, high-frequency mechanical durability, and stable performance under fluctuating humidity or chemical exposure remains difficult, particularly for long-term wearable and environmental applications. Additionally, the integration of LIG with advanced microfluidic, biomedical, or semiconductor manufacturing workflows will require improved adhesion, encapsulation, and surface passivation strategies.

Looking forward, the next decade of LIG innovation will likely be defined by three major trajectories. First, AI-driven optimization—leveraging machine learning, inverse design, and high-throughput simulation—will accelerate the discovery of optimal laser parameter spaces and predictive design of LIG morphology. Second, hybrid materials engineering, including polymer alloying, multi-element doping, and integration with MXenes, metal oxides, or biomaterials, will expand LIG’s functional palette. Third, application-centric architectures—ranging from soft bioelectronics to distributed environmental sensor networks—will push LIG toward system-level integration, requiring advances in encapsulation, wireless communication, and on-device processing.

As global demand grows for sustainable, lightweight, and scalable electronics manufacturing, LIG is poised to play an increasingly central role. Its unique convergence of fabrication simplicity, structural adaptability, and multifunctional performance enables LIG to serve not merely as an alternative carbon material, but as a platform technology that unifies material synthesis and device engineering. Its unique synergy of fabrication simplicity, material tunability, and multifunctionality positions it as a foundational technology capable of reshaping how graphene-based devices are designed and produced in the decades ahead.

Author contributions

IO: Conceptualization, Data curation, Investigation, Visualization, Writing – original draft. DK: Data curation, Investigation, Visualization, Writing – original draft. S-YK: Conceptualization, Investigation, Writing – original draft. SC: Investigation, Visualization, Writing – original draft. W-HY: Supervision, Writing – review and editing. H-RL: Funding acquisition, Project administration, Supervision, Writing – review and editing.

Funding

The author(s) declared that financial support was received for this work and/or its publication. This work was supported by the Korea Basic Science Institute (National Research Facilities and Equipment Center) grant funded by the Ministry of Science and ICT (MSIT) (No. RS-2024-00404971), and by the National NanoFab Center (NNFC) grant funded by the Korea government (MSIT) (No. RS-2024-00440903).

Acknowledgements

The authors acknowledge the support from the Korea Basic Science Institute (National Research Facilities and Equipment Center) and the National NanoFab Center (NNFC), funded by the Ministry of Science and ICT (MSIT), Republic of Korea.

Conflict of interest

The author(s) declared that this work was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Generative AI statement

The author(s) declared that generative AI was used in the creation of this manuscript. Generative AI tools were used only to enhance the stylistic consistency of the schematic in Figure 1, after the authors had created the original illustration. They were not used for any other part of the study.

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