Researchers Create 'Smart' Sea Urchin Material

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 within the spines of the long-spined sea urchin, *Diadema setosum*, possesses a natural ability for mechanoelectrical perception. This natural perception is surprisingly rapid. When a water droplet lands on the spine's surface, it generates a measurable voltage of about 100 mV within tens of milliseconds. This response is more than a thousand times faster than the sea urchin's own visual perception, and it occurs even without any living cellular tissue, proving it's an intrinsic property of the material's microstructure. The secret lies in the spine's internal structure, known as the stereom, which is a bicontinuous porous skeleton. This structure has a gradient of pore sizes, with smaller pores near the tip, which enhances the separation of charges at the solid-liquid interface as water flows through, generating a streaming potential that acts like a micro-sensor. By replicating this gradient structure using vat photopolymerization 3D printing, the researchers created a biomimetic material with even greater capabilities. Their 3D-printed versions showed a threefold increase in voltage output and an eightfold increase in signal amplitude compared to structures without the gradient design. This new smart material can be used to create mechanoreceptors that can detect the intensity and direction of underwater flows in real-time without needing an external power source. Potential applications are vast, ranging from marine environmental monitoring and underwater exploration to biomedical devices and even aerospace engineering.