Dr. Yu Chai is an assistant professor in the physics department at the City University of Hong Kong. He joined CityU in April 2020. Before that, he worked as a postdoctoral researcher at the University of California, Berkeley, and Lawrence Berkeley National Laboratory. He got his Ph.D. in physics at the University of Waterloo, Canada, in 2016. Dr. Chai has a long-term research interest in soft matter with a particular focus on surfaces and interfaces. With the help of state-of-the-art in situ instruments, including atomic force microscopes, he and his group have discovered many interesting behaviors of various soft materials at the surfaces and interfaces. Over the past decade, Dr. Chai has published more than 30 peer-reviewed papers, most of which are in prestigious journals, including Science, Science Advances, Nature Communications, PNAS, Advanced Materials, Nano Letters, ACS Nano, etc.
Colloidal particles can assemble at liquid interfaces, thereby reducing the interfacial energy. Self-assembly of colloidal particles at liquid interfaces has attracted a lot of attention from academia and industry due to its complex energy landscape and potential application in various emerging fields. However, the small size of colloidal particles and the liquid environment make it challenging to explore the self-assembly of colloidal particles at liquid interfaces, especially for those at the nanoscale. In this talk, I will show our recent research advances in using atomic force microscopy (AFM) to study the self-assembly of nanometer-sized colloidal particles at liquid interfaces. With in situ AFM, we show for the first time real-space imaging of sub-20 nm silica particles assembled at the water-oil interface with the help of oppositely charged polymeric surfactants, and the adsorption events of individual silica particles to the water-oil interface, among others. The local packing and dynamic information of these small particles at liquid interfaces revealed by in situ AFM allow us to develop novel soft devices.
References:
[1] Chai, Y.; Hasnain, J.; Bahl, K.; Wong, M.; Li, D.; Geissler, P.; Kim, P. Y.; Jiang, Y.; Gu, P.; Li, S.; Lei, D.; Helms, B. A.; Russell, T. P.; Ashby, P. D., Direct observation of nanoparticle-surfactant assembly and jamming at the water-oil interface. Science Advances 2020, 6 (48), eabb8675.
[2] Chai, Y.; Lukito, A.; Jiang, Y.; Ashby, P. D.; Russell, T. P., Fine-Tuning Nanoparticle Packing at Water-Oil Interfaces Using Ionic Strength. Nano Letters 2017, 17 (10), 6453-6457.
[3] Zhao, S.; Zhang, J.-Y.; Fu, Y.; Zhu, S.; Shum, H. C.; Liu, X.; Wang, Z.; Ye, R.; Tang, B. Z.; Russell, T. P.; Chai, Y., Shape-Reconfigurable Ferrofluids. Nano Letters 2022, 22 (13), 5538-5543.