Cellular Materials & 3D Printing

Cellular materials are widely used in several technological fields as they offer distinctive features that derive from their porous internal morphology. Hierarchical porous structures outperform their non-hierarchical counterparts in terms of mechanical behavior and accessible active surface. Nature has often chosen optimized hierarchically structured foams to shape life on our planet, where high performances are reached at a minimum material cost. Natural cellular materials, such as bamboo and beeswax honeycomb, usually have complex hierarchical geometries allowing to carry out a specific task or optimize a specific property. For example, natural cellular structures have higher stiffness-to-weight ratio, higher crash energy absorption, higher fire resistance, lower flammability, lower toxicity, lower thermal conductivity, lower magnetic permeability, and lower density than their counterparts without pores. Scientists often take inspiration from natural cellular materials for engineering applications. Recently, many efforts have been made to 3D-print complex fluids into hierarchical foams or mesh structures by piling up extruded strands, where macro-, micro-, or nano-scale pores are generated by computer-designed spacing between the filamentary struts.
The most common solutions to produce 3D-printed cellular materials are based on a two-stage approach: in the first step, the structures are printed with inter-strand porosity, then the intra-strand porosity is produced by freeze-drying or batch-foaming. More recent solutions have been proposed where inter- and intra-strand porosities are produced in one step by means of the solubilization of a physical blowing agent. The available technologies allow to obtain different cellular morphologies, which, in turn, affect the properties of the 3D-printed structures. However, the mutual interactions among the process variables, the cellular morphologies, and the properties of the 3D-printed structures are not yet fully understood. Therefore, enhancing their comprehension is highly demanded to enable the full exploitation of 3D-printed cellular materials, both in terms of optimization of the properties of the materials and development of less expensive and less time-consuming manufacturing processes based on greener and more sustainable technologies.
The scope of this Research Topic is to increase the understanding of the design, control, and manufacturing of cellular materials and 3D printing processes, both from the fundamental and the applicative point of view. The subjects involved in this research topic are at the intersection among several branches of science (e.g., physics, chemistry, and biology) and engineering (such as the chemical, materials, biomedical, and mechanical fields). Covered topics include (but are not limited to):
• soft matter and viscoelastic fluids,
• (bio-)polymers with high sustainability quantified by life cycle assessments,
• foams with micro- and nano-bubbles,
• smart and hierarchical materials and structures with tunable properties,
• additive manufacturing, especially 4D printing,
• applications of artificial intelligence/machine learning.
Contributions either based on experiments, modelling, or numerical simulations are welcome. The manuscripts can be in the form of short articles (up to 3000 words), long articles or reviews.

Keywords: 3D Printing, Cellular materials, Complex fluids, Foaming, Composites, Smart Structures, Micro- and nano-structure

Important Note: All contributions to this Research Topic must be within the scope of the section and journal to which they are submitted, as defined in their mission statements. Frontiers reserves the right to guide an out-of-scope manuscript to a more suitable section or journal at any stage of peer review.