Hong Kong Team 3D-Prints Smart Material

The research, led by Professor Lu Jian, Dean of the College of Engineering at CityU, was published in the journal *Nature*. His team discovered that the natural porous ceramic structure of sea urchin spines generates a measurable voltage when water flows over them. This response is incredibly fast, occurring within tens of milliseconds, which is over a thousand times faster than the sea urchin's own visual perception. The key to this phenomenon lies in the spine's unique microstructure. It has a gradient of pore sizes, with smaller pores near the tip. As water moves through these microchannels, it creates what is known as a streaming potential, effectively turning the spine into a natural micro-sensor without any living tissue involved. To replicate this, the Hong Kong team utilized a 3D printing technique called vat photopolymerization. This method allows for the creation of complex ceramic structures layer by layer. The 3D-printed versions with the biomimetic gradient structure showed a threefold increase in voltage output compared to those without the gradient. This new material offers a significant advantage for underwater applications. Current underwater communication and sensor technologies are often hampered by challenges like high signal attenuation, limited bandwidth, and large propagation delays of acoustic signals. A self-powered, highly sensitive material could lead to more efficient and reliable underwater monitoring systems. Beyond the ocean, this technology has significant potential in the biomedical field. The porous and biocompatible nature of ceramics makes them suitable for applications like bone tissue engineering. Electrically active scaffolds have been shown to promote bone regeneration by stimulating cell growth and differentiation. The ability to generate an electrical response to mechanical stress is a property of natural bone. This new material could be used to create "smart" implants that not only provide structural support but also actively stimulate the healing process by mimicking the body's own electrical signals. This breakthrough in biomimetic design provides a new platform for creating self-sensing intelligent materials. The research, a collaboration with The Hong Kong Polytechnic University and Huazhong University of Science and Technology, paves the way for next-generation devices in marine monitoring, resource management, and aerospace engineering.