Researchers 3D-Print Smart Material Inspired by Sea Urchins
A research team at City University of Hong Kong has developed a new method for 3D-printing biomimetic "mechanoelectrical" smart materials. The innovation was inspired by the porous structure of sea urchin spines, which naturally convert mechanical forces into electrical signals. This breakthrough could have applications in smart sensors and biomedical devices.
The research, led by Professor Lu Jian, was published in the journal *Nature* and specifically studied the long-spined sea urchin, *Diadema setosum*. The team discovered that the spine's natural porous ceramic structure generates a measurable voltage of about 100 mV when stimulated by water droplets. This electrical response is remarkably fast, occurring within tens of milliseconds. This mechanoelectrical effect is not biological; it stems from the material's intrinsic microstructure. The spine's skeleton, known as the stereom, has a gradient of pore sizes that enhances the separation of charges at the solid-liquid interface as water flows through. This movement creates what is known as a streaming potential, turning the spine into a natural micro-sensor. Using a 3D-printing technique called vat photopolymerization, the researchers fabricated polymer and ceramic replicas of the spine's gradient porous structure. Their biomimetic designs demonstrated a threefold increase in voltage output and an eightfold increase in signal amplitude compared to similar structures without the pore gradient. This breakthrough demonstrates that the complex topological structure, rather than just the material's composition, is key to this sensory ability. The team built a proof-of-concept mechanoreceptor that can detect the direction and intensity of underwater flows in real-time without needing an external power source. Sea urchin spines themselves are a marvel of natural engineering. Despite being composed of calcite, a typically brittle material, their intricate, porous internal structure makes them both lightweight and surprisingly strong. The potential applications extend beyond underwater monitoring to aerospace engineering and water resource management. In the biomedical field, such self-sensing, power-free materials could be foundational for a new generation of smart devices and implants.
