Sea urchin spines are not only for defence—they also act as natural sensors. A research team led by Prof. WANG Zuankai, Associate Vice President (Research and Innovation), Dean of Graduate School, Kuok Group Professor in Nature-Inspired Engineering and Chair Professor of the Department of Mechanical Engineering of The Hong Kong Polytechnic University (PolyU), together with scholars from City University of Hong Kong (CityU) and Huazhong University of Science and Technology (HUST), has discovered the mechanoelectrical perception in sea urchin spines, originating in their gradient porous structure, that allows the spines to instantly detect water flow. Using 3D printing, the team has replicated this structure and developed a bionic metamaterial sensor, which holds promise for breakthroughs in sensing technology. This innovation will drive the advancement of deep-sea technology such as marine monitoring and underwater infrastructure management, and can be extended to other emerging fields like brain-computer interfacing and aerospace.