One-pot fabrication of bio-inspired shape-morphing bilayer structures

Abstract

• Shape-morphing polymeric bilayers with a seamless interface are fabricated via the sedimentation of NaCl particles within liquid polymers. • The differential swelling between the NaCl particle-depleted and particle-enriched layers drives the shape morphing of bilayer structures. • Shape-morphing dynamics can be controlled by tuning the particle precipitation kinetics, NaCl content, and polymer matrix crosslinking level. • Bilayer structures fabricated using this one-pot strategy exhibit more complex shape-morphing responses compared to conventional ones. Soft bilayer structures capable of shape morphing in response to external stimuli have been commonly adopted in the design of soft robots, flexible electronics and many other smart systems. However, existing methods to fabricate such structures generally require multiple steps and may end up a weak interface between the two layers. Here, we report a one-pot fabrication strategy to generate elastomer-based shape-morphing bilayer structures with a seamless interface. Our strategy leverages on a recently developed bioinspired polymer-NaCl particle composite system which can undergo significant osmotic swelling in water. Bilayer structures are readily formed after the precipitation of NaCl particles in liquid polymers under gravity and the crosslinking of the polymers. The shape-morphing behavior of the fabricated bilayer structures can be well controlled by tuning the particle precipitation kinetics, NaCl content, and crosslinking level of the polymer matrix. More importantly, the bilayer structures fabricated using this strategy exhibit more complex shape-morphing responses than typical bilayer structures. Considering the wide applicability of NaCl particle-induced osmotic swelling of polymer composites, our one-pot bilayer formation strategy will greatly benefit many shape-morphing applications with a simplified fabrication workflow and enhanced configurational versatility.