Skin-inspired cross-hierarchical curved wrinkles for programmable surface engineering and E-skin sensing

Surface wrinkles have shown broad potential in enhancing device performance and enriching functional diversity. Inspired by the hierarchical texture and sensing functions of animal skin, we developed a bioinspired strategy to construct cross-hierarchical curved wrinkles (CHCW). This approach induces wrinkling via boundary-stress engineering, enabling the ordered formation of secondary wrinkles on a primary microcylinder array. By precisely tuning processing parameters such as the curing agent ratio, sputtering time, and spin coating time, the surface morphology can be programmably modulated. Response surface methodology was further employed to reveal the quantitative relationship between fabrication parameters and structural characteristics, while finite element simulations and theoretical modeling elucidated the underlying mechanics of the CHCW. Based on the CHCW, an e-skin with multidirectional sensing capability was fabricated, exhibiting high sensitivity and a broad strain detection range (GF_X = 646.17, 32% strain and GF_Y = 2529.53, 30% strain), and maintaining reliable performance over 10,000 loading cycles. More importantly, the curved hierarchical design effectively overcomes the limitations of planar single-direction wrinkles, offering a universal structural platform for multifunctional sensing and providing new insights for next-generation e-skin design.