Researchers 3D-Print 'Smart Material' from Sea Urchins
A research team at City University of Hong Kong has developed a new type of 3D-printed "mechanoelectrical" smart material. The design is inspired by the porous, shock-absorbing structure of sea urchin spines. This biomimetic material could have applications in creating advanced sensors and protective equipment.
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. The team's work revealed that the natural porous ceramic structure of sea urchin spines can generate measurable voltage signals when water flows over them. This newly discovered mechanoelectrical effect is remarkably efficient, with a response speed over a thousand times faster than the sea urchin's own visual perception. The team studied the long-spined sea urchin (*Diadema setosum*) and found that even a single droplet of seawater could induce a transient potential of about 100 millivolts. The key to this phenomenon lies in the spine's gradient cellular structure. The pores are smaller and have a higher surface area near the tip, which enhances the generation of a streaming potential as fluid moves through the microchannels, turning the spine into a natural micro-sensor. This process works even without any living biological tissue, proving it's an intrinsic property of the material's structure. Using vat photopolymerization, a form of 3D printing, the researchers fabricated biomimetic samples that mimicked this gradient design. These artificial structures showed a threefold increase in voltage output and an eightfold increase in signal amplitude compared to designs without the gradient structure. This demonstrates that the sensing capability is governed by the architecture rather than the specific material. Sea urchin spines are known for being both strong and lightweight, made from a single crystal of calcite arranged in a porous structure. This unique combination of properties allows them to absorb impacts and stress, while also being able to snap off as a defense mechanism against predators. The team has already built a prototype mechanoreceptor that can detect the intensity and direction of underwater flow in real-time without needing an external power source. Potential future applications for this technology are vast, including marine environmental monitoring, underwater exploration, water resource management, and even aerospace engineering.
