(77a) Autonomous Alignment and Healing in Multilayer Soft Electronics Using Immiscible Dynamic Polymers

Self-healing soft electronic and robotic devices, like human skin, can recover autonomously from some forms of damage. Existing multi-layer devices generally employ a single type of dynamic polymer embedded with different functional nano–micro materials for each layer, to provide a cohesive interface between layers. In such devices, successful healing from damage requires precise manual alignment and re-contacting of the fractured interfaces, limiting functional recovery from diverse forms of damage, such as processes leading to imperfect registry of device layers. These limitations are especially prevalent for devices containing thin layers (< 100 µm). To overcome these limitations, we have designed a pair of dynamic polymers, which have immiscible polymer backbones, but similar dynamic bonding units (bisurea-based hydrogen bonding interactions), to maintain interlayer adhesion while providing selectively self-healing layers with similar viscoelastic behavior (and thus self-healing dynamics) over a convenient range of temperatures (25–100°C). Upon lamination, these dynamic polymers exhibit a weakly interpenetrating and adhesive interface, whose width and toughness are tunable with processing temperature. When multilayered polymer films are misaligned after damage, these structures autonomously realign during the healing process to minimize their interfacial free energy through a diffusion-mediated mechanism. Our experimental observations are captured by both coarse-grained molecular dynamics simulations and continuum phase field simulations, suggesting the generality of the proposed mechanism to other pairs of polymer backbones or dynamic bonding chemistries. As a demonstration of the utility of our approach, we fabricated several devices with conductive, dielectric, and magnetic particles that functionally heal after damage, enabling thin film pressure sensors, magnetically assembled soft robots, and damage-sensing electronic skins.

Cooper, C.^†; Root, S. E.^†; Michalek, L.; Wu, S.; Lai, J-C.; Khatib, M.; Oyakhire, S.; Zhao, R.; Qin, J.; Bao, Z.*; Autonomous alignment and self-healing in multilayer soft electronics using dynamic polymers with immiscible backbones. Science, 2023