Wood-Inspired Porous Polymeric Material with High Flexoelectric Effect

The development of energy-efficient and eco-friendly functional materials and devices holds substantial potential to tackle the challenges in energy and the environment. Since the 1950s, wood-based materials have been demonstrated to generate electricity when subjected to deformation, which enables potential sustainable applications. However, the precise mechanisms of the electromechanical coupling effect of wood-based materials remain unclear. Here, a systematic study of the mechanisms for the electromechanical coupling effect of the balsa wood sponge is conducted via experiments, molecular dynamic simulations, and theoretical modeling. The dominant influence of the flexoelectric effect in the wood sponge is identified and verified after comprehensively assessing triboelectricity, electret, and piezoelectricity. Leveraging this fundamental insight, the bionic porous polydimethylsiloxane (PDMS) is fabricated by mimicking the microstructures of the wood sponge. The bionic porous PDMS exhibits significantly enhanced performance metrics, with current-strain sensitivity and equivalent piezoelectric coefficient being 1600 times and 340 times greater than those of solid PDMS, respectively. The application of bionic porous PDMS as self-powered impact sensors is demonstrated to identify different levels of impact energy. This work establishes a transferable methodological approach for analyzing electromechanical coupling in diverse structured materials, and introduces a bionic design strategy for developing enhanced performance of multifunctional materials.