CityUHK Team 3D-Prints Sea Urchin-Inspired Smart Material

The research, led by Professor Lu Jian at City University of Hong Kong, identified this unexpected mechanoelectrical sensing capability in the long-spined sea urchin, *Diadema setosum*. Published in *Nature*, the study revealed that the spine's porous ceramic structure generates a measurable voltage of about 100 mV from stimuli like falling water droplets. This response is remarkably fast, occurring within tens of milliseconds—over a thousand times quicker than the urchin's own visual perception. The sensing ability is not biological but intrinsic to the material's microstructure. Sea urchin spines are composed of a porous skeleton called a stereom, which has a gradient of pore sizes. This structure enhances the separation of charges at the solid-liquid interface, creating a "streaming potential" as water flows through its microchannels. Using vat photopolymerization, a form of 3D printing, the team fabricated ceramic and polymer replicas of the spine's gradient structure. These biomimetic versions showed a threefold increase in voltage output and an eightfold increase in signal amplitude compared to control structures without the gradient design. This confirmed that the sensing capability is governed by the topological structure rather than the specific material. This discovery opens new possibilities for advanced functional materials. Potential applications include highly sensitive underwater sensors for environmental monitoring, intelligent systems for underwater exploration, and new types of biomedical devices. The work provides a foundational platform for next-generation materials that integrate structure and function.