Researchers Create Smart Material from Sea Urchin Spines

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. His team discovered that the porous ceramic structure of sea urchin spines can generate a measurable voltage when water comes into contact with them. The specific species studied was the long-spined sea urchin, *Diadema setosum*. When a droplet of seawater landed on a spine, it induced a transient potential of approximately 100 millivolts. This electrical response is a result of the material's intrinsic microstructure and not any living tissue, as the effect persists even without viable cells. This natural sensing ability is remarkably fast, with a response time in the tens of milliseconds, which is over a thousand times faster than the sea urchin's own visual perception. The team analyzed the spine's structure using scanning electron microscopy and found a gradient in its pore sizes, which is key to its electrical properties. To mimic this, the researchers utilized a 3D printing technique called vat photopolymerization to create a replica of the spine's architecture. The 3D-printed biomimetic structures showed a threefold increase in voltage output compared to non-gradient structures, confirming that the unique topology is the source of this capability. This breakthrough in biomimetic design opens up possibilities for a new class of self-sensing intelligent materials. Potential future applications include underwater monitoring, management of water resources, and advancements in biomedical devices and aerospace engineering. Sea urchin spines have previously inspired research for applications like bone defect repair due to their lightweight and load-bearing properties.