Spine-inspired microstructures for advanced miniature devices
In work published in the journal Science Advances, a team of researchers led by Dr Yufeng Wang of the Department of Chemistry at The University of Hong Kong has developed a new method to create microscale superstructures called MicroSpine. Inspired by the human spine, these structures combine both soft and hard materials and can act as microactuators with shape-transforming properties.
The spine's essential architecture supports the human body while maintaining flexibility. Mimicking the soft-hard structure found in nature could lead to the design of artificial materials and devices like actuators and robots. However, creating such structures at the microscale level has proven extremely challenging due to limitations in material integration and manipulation.
Biological organisms contain structures of synergistically integrated soft and hard components that account for their mechanical functions. These structures have stimulated the creation of artificial materials and devices, such as actuators and robots, which change shape, move, or actuate according to external cues. While soft-hard structures are relatively easy to fabricate at the macroscale, they are difficult to achieve at the microscale due to the challenges of integrating and manipulating mechanically distinct components.
Traditional manufacturing methods, such as lithography, face several limitations when attempting to create small-scale components using top-down strategies. To address these challenges, Dr Wang and his team used colloidal assembly, a bottom-up approach that enables precise control over the creation of the desired structures from various building blocks, yielding higher results.
The team designed new particles derived from metal-organic frameworks (MOFs), an emerging material that can assemble with high directionality and specificity. These MOF particles combine with soft liquid droplets to form linear chains, with hard and soft components taking alternating positions in the chain to mimic the spine structure.
The researchers introduced a mechanism that enables the soft component of the chain to expand and shrink when heated or cooled, allowing MicroSpine to change shape reversibly. The MicroSpine system demonstrated various precise actuation modes when the soft parts of the chain were selectively modified. Furthermore, the chains were used for encapsulation and release of guest objects, controlled solely by temperature.
This development has significant implications for creating intelligent microrobots capable of performing sophisticated microscale tasks, such as drug delivery, localised sensing, and other applications. The highly uniform and precisely structured microscale components could lead to more effective drug delivery systems or sensors that can detect specific molecules with high sensitivity and accuracy.
Dr Wang believes this technology represents an important step towards creating complex microscale devices and machines. “If you think about modern machinery such as cars, they are assembled by tens of thousands of different parts. We aim to achieve the same level of complexity using different colloidal parts,” he said. By taking inspiration from nature, the research team hopes to design more biomimetic systems that can perform complex tasks at the microscale and beyond.
Dr Yufeng Wang is an Associate Professor in the Department of Chemistry at HKU. As a material chemist, Dr Wang and his team specialise in designing anisotropic particles, which are the essential components for creating mesoscale materials with applications in photonics, sensing, micro robotics, cargo delivery, and active matter. Dr Wang obtained his BSc degree from Peking University in 2008 and his PhD degree from New York University in 2013. Before joining HKU in 2016, he completed his postdoctoral training at MIT. Dr Wang received the Croucher Innovation Award in 2019. To view his Croucher profile click here.