Researchers Create Smart Material Inspired by Sea Urchins

The research, published in the journal *Nature*, was led by Professor Lu Jian, Dean of the College of Engineering at City University of Hong Kong. His team discovered that the porous ceramic structure of sea urchin spines can generate a measurable voltage when water moves over them. This response is remarkably fast, occurring within tens of milliseconds. This "mechanoelectrical" effect is not biological but stems from the spine's physical microstructure. The researchers observed this phenomenon in the long-spined sea urchin, *Diadema setosum*, where a falling water droplet induced a transient potential of about 100 millivolts. This sensory capability is over a thousand times faster than the sea urchin's own visual perception. The key to this ability is the spine's "gradient cellular structure," a porous skeleton with pores that are smaller at the apex. This design enhances the separation of interfacial charges between the solid surface and the liquid, generating a streaming potential as water flows through the microchannels. Using vat photopolymerization 3D printing, the team fabricated biomimetic structures that mimicked this natural design. The 3D-printed versions with the gradient structure showed a threefold increase in voltage output and an eightfold increase in signal amplitude compared to gradient-free structures. This demonstrates that the sensing capability is determined by the topological structure rather than the specific material used. The team has already built a prototype mechanoreceptor that can detect underwater flow intensity in real-time without needing an external power source. This breakthrough opens up possibilities for a new generation of self-sensing intelligent materials. Potential applications include marine environmental monitoring, intelligent underwater exploration, and advanced biomedical devices.