Researchers Create Smart Material from Sea Urchins

The research, led by Professor Lu Jian at the City University of Hong Kong, was published in the journal *Nature*. The team's work was a collaborative effort with The Hong Kong Polytechnic University and Huazhong University of Science and Technology. Their investigation began with the long-spined sea urchin, *Diadema setosum*, observing that its spines would rotate in response to a single drop of seawater. This reaction, occurring within a second, pointed to a highly sensitive tactile system. Researchers discovered that this rapid response is due to the spine's porous ceramic structure, which generates a measurable voltage of about 100 mV when stimulated by water. This electrical signaling is more than a thousand times faster than the sea urchin's own visual perception. Crucially, the electrical response occurs even in spines without any living tissue, proving the capability is an intrinsic property of the material's microstructure, not its biology. The secret lies in the spine's pore-size gradient, which enhances charge separation at the solid-liquid interface as water passes through. Using a 3D-printing technique called vat photopolymerization, the team fabricated a synthetic version of the sea urchin spine structure. The 3D-printed biomimetic designs showed a threefold increase in voltage output and an eightfold increase in signal amplitude compared to structures without the gradient design. This new material can detect underwater flow intensity and direction in real-time without needing an external power source. Potential applications are vast, ranging from marine environmental monitoring and intelligent underwater exploration to biomedical devices and aerospace engineering.