Hong Kong Team Creates Smart Materials

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 has a natural ability for mechanoelectrical perception. Through observations of the long-spined sea urchin, researchers found that a water droplet falling on a spine causes it to rotate in about one second. This rapid tactile response is over a thousand times faster than the sea urchin's visual perception and generates a measurable voltage of approximately 100 mV. This electrical response is not biological; it occurs even without any living tissue, stemming from the material's intrinsic microstructure. The spine's surface has a gradient of pore sizes, which creates a streaming potential as water moves through it, effectively acting as a natural micro-sensor. Using vat photopolymerization 3D printing, the team fabricated materials that mimic this natural design. The biomimetic structures showed a threefold increase in voltage output and an eightfold increase in signal amplitude compared to structures without the gradient design. This breakthrough challenges the conventional view that natural porous structures mainly serve a mechanical purpose, revealing their latent sensing capabilities. It opens new possibilities for self-powered devices that can monitor underwater environments in real-time. The principles discovered could be applied to a wide range of fields, including marine environmental monitoring, intelligent underwater exploration, and even biomedical devices and aerospace engineering. These piezoelectric materials can convert mechanical energy into electricity, making them suitable for sensors, energy harvesters, and medical actuators.