Mechanically strengthened silicone-based origami structures via hierarchical interfacial shrink fitting

Soft structured materials-e.g., silicone-based elastomer, capable of programmable morphologies and mechanical strength-are promising for high-performance structure construction in metamaterials and soft robots. However, once prototyped, polydimethylsiloxane (PDMS)-based silicone elastomer is limited in mechanical strength and programmable spatial construction due to the flexible polymer matrix and mismatched interface with other materials. We propose a mechanically strengthened PDMS-based origami structure (MSOS) via polymethyl methacrylate (PMMA)/acetone solution swelling. The planar elastomer precursor can be swollen-folded into programmable spatial construction based on mechanically strengthened creases during solvent diffusion and de-gelatinization. This strengthened crease is induced by a hierarchical shrink-fitting based on solute molecular chain insertion and a seamless coupling interface between elastomer microstructures and solidified PMMA. We present a programmable MSOS to support a load more than 58,100 times of its own weight and a pillbug-inspired ringbot to resist heavy impact. Our work provides a strategy toward customized mechanically strengthened soft material for developing functional structural architectures and soft origami robots.