Researchers Develop 'Smart' 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 studied the long-spined sea urchin (*Diadema setosum*) and discovered its spines could generate a transient potential of about 100 mV from a single water droplet. This electrical response is not biological; it occurs even without any living tissue. The effect comes from the spine's unique internal structure, a porous skeleton with a gradient of pore sizes that creates a streaming potential as water moves through it. The team's analysis revealed this mechanoelectrical perception is incredibly fast, occurring within tens of milliseconds. This is more than a thousand times faster than the sea urchin's own visual perception, demonstrating a highly sensitive and rapid tactile response. To mimic this, the researchers used a 3D printing technique called vat photopolymerization. The artificial structures they created with a similar gradient design showed a threefold increase in voltage output and an eightfold increase in signal amplitude compared to non-gradient versions. This breakthrough demonstrates that the sensing capability is governed by the structure rather than the material's composition. It challenges the long-held view that such natural porous structures only serve a mechanical, protective function. Potential applications for this new generation of self-sensing intelligent materials are vast. They could be used for marine monitoring, underwater exploration, advanced water management systems, and even in aerospace engineering.