Joining of Soft and Hard Materials by Liquid Infill Method Using Gyroid

Joining soft and hard materials, such as silicone rubber and a plastic part, is an obstacle to inexpensive and simple prototyping. This study proposes a liquid infill (LIF) method for joining soft and hard materials. We selected the gyroid for the porous structure, which is well known as one of the infill structures of 3D printed parts made using fused deposition manufacturing. Our proposed manufacturing process only requires a 3D printer and silicone rubber molding equipment. The joining strength of samples made by LIF is evaluated with tension tests. The results indicate that material hardness affects tensile strength, while infill density had little effect. Meanwhile, the amount of strain at break decreased with increased infill density. In addition, we compared the tensile strength of samples made by LIF with samples joined by anchor and adhesive. As a result, the tensile strength of LIF exceeds the two other types of samples. Furthermore, we captured slice images using a CT scanner and confirmed that the silicone rubber was filled in gyroid structures. Finally, we fabricated the backbone mechanism and the finger mechanism.