Smart Material Inspired by Sea Urchins
A research team at City University of Hong Kong has developed a new 3D-printed smart material inspired by the porous structure of sea urchin spines. The biomimetic "mechanoelectrical" material shows promise for applications in advanced sensors and energy harvesting devices.
The research, led by Professor Lu Jian at the City University of Hong Kong, was published in the journal *Nature* and pinpointed the long-spined sea urchin (*Diadema setosum*) as the model organism. The team discovered that the natural porous ceramic structure of the urchin's spines can generate a measurable voltage signal from the movement of water over its surface. This electrical response is remarkably fast, occurring within tens of milliseconds, which is over a thousand times faster than the sea urchin's own visual perception. When a single water droplet landed on a spine, it induced a transient potential of about 100 millivolts, demonstrating a highly sensitive tactile response. Crucially, this mechanoelectrical effect is an intrinsic property of the spine's physical microstructure, not a result of living cells or nerves. The spine's skeleton, known as the stereom, has a gradient of pore sizes, which is key to its function. The smaller pores and larger surface area at the spine's tip enhance charge separation at the solid-liquid interface, generating a streaming potential as water moves through. Using a 3D printing technique called vat photopolymerization, the researchers fabricated a biomimetic replica of this gradient structure. The engineered material showed a threefold increase in voltage output and an eightfold increase in signal amplitude compared to similar structures without the pore-size gradient. This demonstrates that the sensing capability is primarily governed by the material's topological structure rather than its chemical composition. The team constructed a prototype mechanoreceptor that can detect the intensity and direction of underwater flows in real-time without needing an external power source. Beyond underwater applications, this biomimetic design holds potential for advancements in marine environmental monitoring, water resource management, and even aerospace engineering. The project was a collaborative effort involving the City University of Hong Kong, The Hong Kong Polytechnic University, and Huazhong University of Science and Technology.
