Researchers 3D-Print Sea Urchin-Inspired Smart Material

The breakthrough comes from a team led by Professor Lu Jian, Dean of the College of Engineering at City University of Hong Kong. Their study, published in the journal *Nature*, pinpointed the long-spined sea urchin (*Diadema setosum*) as the source of inspiration. The team discovered the sea urchin's spines are not just for defense; their porous internal structure has an innate ability for mechanoelectrical perception. When a single droplet of seawater lands on a spine, it can generate a transient potential of approximately 100 millivolts. This electrical response is incredibly fast, occurring within tens of milliseconds—more than a thousand times faster than the sea urchin's own visual perception. This effect is not biological; it stems from the spine's physical microstructure, which continues to function even without any living tissue. The structure, known as a stereom, has a gradient of pore sizes that enhances charge separation at the solid-liquid interface as water flows through, generating a streaming potential. Using a 3D printing technique called vat photopolymerization, the researchers successfully replicated this gradient architecture. The biomimetic copies outperformed non-gradient structures, exhibiting a threefold increase in voltage output and an eightfold jump in signal amplitude, proving the principle is based on the topological structure, not the specific material. As a proof of concept, the team has already constructed a biomimetic mechanoreceptor. This device can detect the intensity and direction of underwater currents in real-time without the need for an external power source. This research, a collaboration with The Hong Kong Polytechnic University and Huazhong University of Science and Technology, opens doors for a new class of self-sensing intelligent materials. Potential applications range from marine environmental monitoring and underwater exploration to innovations in biomedical devices and aerospace engineering.