Porous Sponge Gourd Network Opens up a New Strategy for Flexible Generators

Beihang University School of Aeronautics and Astronautics, Peking University and the research team from the University of Houston in the United States have proposed a new strategy for applying porous biomaterials to green and environmentally friendly flexible generators and other smart devices, inspired by the giant flexoelectric effect of natural biomaterials - porous loofah network. The research results were published in the Proceedings of the National Academy of Sciences of the United States.

Traditionally, flexible materials with the force-electric coupling effect can achieve the mutual conversion between electrical signals and deformation under mechanical stimulation or electric field, so they have broad application prospects in the fields of soft robots, artificial muscles, and biomedical engineering. Flexoelectric effect is a common force-electric coupling effect, that is, non-uniform deformation (such as bending) induces material polarization and generates voltage. Compared with other force-electric coupling effects, the flexoelectric effect is not limited by material symmetry and exists in all dielectrics. However, the flexoelectric output of flexible materials is relatively low, so how to improve the flexoelectric output of flexible materials has been the focus of research.

The research team found a natural porous material called vegetable sponge, which exhibits a significant flexoelectric effect and established a force-electric coupling model to reveal its force-electric coupling mechanism. Vegetable sponge is a flexible material that shows a considerable flexoelectric effect.

The researchers explained that the vegetable sponge has a sponge-like morphology with a two-level pore structure of different scales. The first-level structure is composed of macro-porous tissue interwoven by vegetable sponge ligaments, while the other level is composed of micro-porous structures formed by honeycomb-like ducts inside the vegetable sponge ligaments. This unique two-level porous structure endows the vegetable sponge with light weight and small-sized microstructures that are prone to high strain gradients, providing favorable conditions for the giant flexoelectric response. The researchers noted that as a green, environmentally friendly, high-yield, and low-cost natural material, vegetable sponge demonstrates tremendous potential in terms of force-electric response performance.