Design and application of responsive hydrogel functionalized microspheres报告人:
College of Engineering, China Agricultural University
Zhang Wenqiang, Associate Professor, College of Engineering, China Agricultural University(CAU), China. Dr. Zhang received his Ph.D. from Beihang University in 2012. Dr. Zhang served as a full-time faculty in China Agricultural University from 2012 to 2021 and was promoted to Associate Professor in 2016 in the College of Engineering in CAU. Dr. Zhang’s research has been on Biofabrication, Biodetection, Agriculture Robotics, and Bio-MEMS. He established his research from Biofabrication to Micro-swimmer. Dr. Zhang has received 2 research grants from the National Natural Science Foundation of China (NSFC). He has published over 40 peer-reviewed journal papers, 10 authorized patents.
Responsive hydrogels have broad application prospects in the fields of smart wearable and tunable flexible sensing. Among them, hydrogel microspheres with enriched functions can be prepared by modification and structural design of temperature-sensitive hydrogels. Therefore, it is necessary to optimize their mechanical and physical response properties and precise fabrication.
Phase change microvalves in microfluidic chips are an interesting application scenario for temperature-sensitive hydrogel microspheres. We modified the mechanical properties of NIPAM temperature-sensitive hydrogel materials using Laponite RD. The dispersion efficiency of Fe3O4 nano photothermal material in the hydrogel matrix was also enhanced. The modified photo responsive microspheres were fabricated in large quantities by droplet generation microfluidic chips. Such modified microspheres can change their volume rapidly in response to the irradiation of infrared laser. Using this property, the phase change microvalves constructed on the microfluidic chip can be remotely controlled by the infrared laser. Benefiting from the Laponite RD modification, the microvalve can effectively close the flow channel. The microvalve can open the flow channel within 2s and close the channel within 16s under the control of the laser. The flow control of the fluid is realized in a small-scale microfluidic chip, which solves the problem of difficult integration of complex flow channels and microvalves in microfluidic chips.
In addition, temperature-sensitive color-changing microspheres with photonic crystal structure were prepared in NIPAM hydrogel matrix using the principle of electrostatic self-assembly of PS microspheres. The physical color of the thermochromic microspheres is related to the lattice constant and particle size of the PS spheres inside. The hydrogel matrix of the microspheres shrinks responsively when the temperature changes, resulting in a change in the surface color of the microspheres. By encapsulating the microspheres with PDMS, the color change of the microspheres in response to temperature change can effectively indicate the change of temperature heating system and the opening and closing characteristics of microvalves in microfluidic detection chips.