Multi-layer cryolithography for additive manufacturing

A new technique is introduced which addresses the need for faster additive manufacturing methods for tissue scaffolds and frozen foods in large-scale industrial applications, inspired by print lithography. It is particularly relevant to biological matter, which is composed mostly of water. Instead of point-by-point printing in three dimensions (3D) with 3D printers, multiple single 2D layers can be assembled or printed separately, in parallel, on areas coated with hydrophilic materials to bind water-based compounds and hydrophobic materials to reject water-based compounds and bind hydrophobic molecules. This technique keeps the layers attached to the surface, opposing gravity, and thereby facilitating the transport and the assembly of the 2D layers, regardless of the direction of the surface relative to gravity. The individual layers are deposited one on top of the other and linked by chemical cross-linking and freezing to generate a 3D structure. Examples show how complex and large hydrogel-based structures can be manufactured by multi-layer cryolithography from fusion and freezing of 2D layers. Applications involve tissue engineering and food engineering, with particular emphasis on the ability to assemble a biological object, while every volume is frozen under optimal conditions during the assembly. Scanning electron microscopy demonstrates the ability to control and produce uniform microstructures in the 3D objects produced by cryolithography.