Material Design for 3D Multifunctional Hydrogel Structure Preparation

Hydrogels are recognized as one of the most promising materials for e‐skin devices because of their unique applicable functionalities such as flexibility, stretchability, biocompatibility, and conductivity. Beyond the excellent sensing functionalities, the e‐skin devices further need to secure a target‐oriented 3D structure to be applied onto various body parts having complex 3D shapes. However, most e‐skin devices are still fabricated in simple 2D film‐type devices, and it is an intriguing issue to fabricate complex 3D e‐skin devices resembling target body parts via 3D printing. Here, a material design guideline is provided to prepare multifunctional hydrogels and their target‐oriented 3D structures based on extrusion‐based 3D printing. The material design parameters to realize target‐oriented 3D structures via 3D printing are systematically derived from the correlation between material design of hydrogels and their gelation characteristics, rheological properties, and 3D printing processability for extrusion‐based 3D printing. Based on the suggested material design window, ion conductive self‐healable hydrogels are designed and successfully applied to extrusion‐based 3D printing to realize various 3D shapes. Materials design insight is provided to prepare multifunctional hydrogels and their target‐oriented 3D structures. Each material design parameter is systematically investigated to define the direct correlation among material design, material properties, and their 3D shape forming characteristics. Furthermore, the material design window, which enables successful 3D shape formation, is established based on the direct correlation of materials property to 3D printing processability as well as the quality of 3D shapes.