Researchers 3D-Print 'Sea Urchin' Smart Material
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 material has unique "mechanoelectrical" properties, converting mechanical stress into electrical signals, with potential uses in advanced sensors.
The research, published in the journal *Nature*, was led by Professor Lu Jian at the City University of Hong Kong. His team discovered that the natural porous ceramic structure of sea urchin spines had an innate ability for mechanoelectrical perception. This finding challenges the conventional view that such natural structures primarily serve a mechanical or protective function. In-situ observations of the long-spined sea urchin, *Diadema setosum*, revealed that a falling seawater droplet would induce a rapid rotation of the spine. This reaction is a highly sensitive tactile response, generating a transient potential of approximately 100 millivolts that occurs within tens of milliseconds. This is more than a thousand times faster than the sea urchin's visual perception. The team's analysis showed that the spine's porous skeleton, known as a stereom, has a gradient of pore sizes along its axis. The apex has smaller pores and a greater surface area, which enhances charge separation at the solid-liquid interface as water flows through. This interaction generates a streaming potential, turning the spine into a natural micro-sensor. Using vat photopolymerization 3D printing, the researchers fabricated biomimetic polymer and ceramic samples that mimicked this gradient structure. The engineered material demonstrated a threefold increase in voltage output and an eightfold increase in signal amplitude compared to non-gradient structures. This confirmed that the mechanoelectrical effect is primarily governed by the structure rather than the specific material. A key advantage of the 3D-printed material is its ability to function as a self-powered sensor. The team constructed a prototype mechanoreceptor that could detect underwater flow direction and intensity in real-time without needing any external power source. This bio-inspired approach of integrating structure with function opens new possibilities for next-generation smart materials. Potential applications are widespread, including marine environmental monitoring, intelligent underwater exploration, water resource management, and even aerospace engineering.
