Biomimetic,\nInterface-Free Stiffness-Gradient PDMS-Co-Polyimide-Based\nSoft Materials for Stretchable Electronics and Soft Robotics

Soft materials play a pivotal role in the efficacy of\nstretchable\nelectronics and soft robotics, and the interface between the soft\ndevices and rigid counterparts is especially crucial to the overall\nperformance. Herein, we develop polyimide–polydimethylsiloxane\n(PI–PDMS) copolymers that, in various ratios, combine on a\nmolecular level to give a series of chemically similar materials with\nan extremely wide Young’s modulus range starting from soft\n2 MPa and transitioning to rigid polymers with up to 1500 MPa. Of\nparticular significance is the copolymers’ capacity to prepare\nseamless stiffness gradients, as evidenced by strain distribution\nanalyses of gradient materials, due to them being unified on a molecular\nlevel. The copolymers and gradient materials were successfully used\nas substrates for stretchable thin-film conductors and tested as dielectric\nelastomer actuators, demonstrating their potential application as\nenabling components in stretchable electronics and soft robots.