Sea Urchin Spines Inspire New Smart Material
A research team at City University of Hong Kong has developed a new 3D-printed smart material inspired by the structure of sea urchin spines. The biomimetic "mechanoelectrical" material is highly sensitive and durable, with potential applications in advanced sensors, medical devices, and sonar technology.
The research, published in the journal *Nature*, identified that the long-spined sea urchin (*Diadema setosum*) possesses a natural mechanoelectrical sense. This means its spines can generate a measurable voltage signal from the touch of a water droplet or the pressure of flowing water. This sensory 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, led by Professor Lu Jian, Dean of the College of Engineering at CityUHK, discovered that this capability is not biological but stems from the spine's intrinsic material structure. Microscopic analysis revealed the sea urchin's spine has a porous skeleton with a gradient in pore size from base to tip. The smaller pores and higher surface area at the spine's apex enhance the electrical charge separation at the solid-liquid interface, generating a streaming potential when water flows through. Using a 3D printing technique called vat photopolymerization, the researchers fabricated a biomimetic replica of the spine's gradient structure. This engineered material demonstrated a threefold increase in voltage output and an eightfold increase in signal amplitude compared to a version without the structural gradient. This breakthrough showcases that the material's sensory performance is governed by its topological structure rather than its chemical composition. The resulting smart material can detect underwater flow direction and intensity in real-time without needing an external power source or sensors. The project was a collaborative effort between City University of Hong Kong, The Hong Kong Polytechnic University, and Huazhong University of Science and Technology. This discovery challenges the conventional view of natural porous materials as having purely mechanical functions and opens new avenues for self-sensing intelligent materials. Potential applications for this technology are vast, including advancements in marine environmental monitoring, underwater exploration, and the development of a new class of integrated structural and functional materials for aerospace and biomedical engineering.
