Biomimetic fibrous semiconducting micromesh via tuning phase separation for high-performance stretchable optoelectronic synapses.

Polymer semiconductors hold great potential for next-generation bionic devices, due to their inherent flexibility and biocompatibility. However, endowing them both robust mechanical properties and significant functionalities remains challenging. Bioinspired microstructures can effectively boost semiconducting properties and functionality, yet the structure engineering strategy in conjugated polymers (CPs) systems is underdeveloped. Here, we fabricate biomimetic hybrid semiconducting films featuring geometry-deformable micromesh and nanofibril substructure, through the Van der Waals force-mediated phase-separation. Poly(butyleneadipate-co-terephthalate) (PBAT), an aggregating polymer with abundant intermolecular interactions, is employed as plastic component to facilitate the formation of hierarchically biomimetic structure. Consequently, this geometry-deformable micromesh and interpenetrating phases significantly enhance mechanical and electrical stretchability of the semiconductors. The dependence of strain dissipation mechanism on structural parameters is identified for micromesh structure optimization. Moreover, the nanofibril substructure significantly improves photosensitivity by 100%. Leveraging the synergistic effect of micromesh and nanofibril, synaptic phototransistors are fabricated, which exhibit superior synaptic plasticity and robust performance under strains up to 125% and 1000 repeated cycles at 50% strain, well imitating the phototransduction and memory functionalities of visual system. This strategy shows great potential for processing ultra-stretchable and high-performance conjugated polymer films aiming at stretchable bioelectronics.