Bioinspired hydrophobic pseudo-hydrogel for programmable shape-morphing
Zhigang Wang, Haotian Hu, Zefan Chai, Yuhang Hu, Siyuan Wang, Cheng Zhang, Chunjie Yan, Jun Wang, Wesley Coll, Tony Jun Huang, Xianchen Xu, Heng Deng
Abstract
Inspired by counterintuitive water “swelling” ability of the hydrophobic moss of the genus Sphagnum (Peat moss), we prepared a hydrophobic pseudo-hydrogel (HPH), composed of a pure hydrophobic silicone elastomer with a tailored porous structure. In contrast to conventional hydrogels, HPH achieves absorption-induced volume expansion through surface tension induced elastocapillarity, presenting an unexpected absorption-induced volume expansion capability in hydrophobic matrices. We adopt a theoretical framework elucidating the interplay of surface tension induced elastocapillarity, providing insights into the absorption-induced volume expansion behavior. By systematically programming the pore structure, we demonstrate tunable, anisotropic, and programmable absorption-induced expansion. This leads to dedicated self-shaping transformations. Incorporating magnetic particles, we engineer HPH-based soft robots capable of swimming, rolling, and walking. This study demonstrates a unusual approach to achieve water-responsive behavior in hydrophobic materials, expanding the possibilities for programmable shape-morphing in soft materials and soft robotic applications. Shape-changing materials have potential in a range of applications, but these transformations can be challenging to control. Here, the authors report the hydrophobic pseudo-hydrogel, which utilizes absorption-induced expansion via elastocapillarity to enable versatile soft robotic applications.