Physics

 

Research Interests:

My research interests encompass several areas of soft condensed matter physics, including dewetting instability of polymer thin films, dynamics of polymer nanometer films, wetting properties of textured surfaces, and control of particle trajectories in microfluidics. As atomic force microscopy (AFM) is a major tool in my research, I am also engaged in the development and application of various AFM techniques such as AFM mechanics, nanotribology and nanolithography.

Education:

University of Hong Kong, B. Sc. in Physics, First class honors Princeton University, Ph. D. in Physics

Representative publications:

• "Glass Transition Dynamics and Surface Layer Mobility in Unentangled Polystyrene Films", Z. Yang, Y. Fujii, F. K. Lee, C. -H. Lam, O. K. C. Tsui, Science, 328, 1676 (2010).
• "Wettability of End-Grafted Polymer Brush by Chemically Identical Polymer Films", X. Zhang, F. K. Lee, Ophelia K. C. Tsui, Macromolecules, 41, 8148 (2008).
• "Variable Liquid Crystal Pretilt Angles by Nanostructured Surfaces", F. S. Y. Yeung, J. Y. Ho, Y. W. Li, F. C. Xie, O. K. C. Tsui, P. Sheng, H. S. Kwok, Appl. Phys. Lett., 88, 051910 (2006).
• "Liquid Crystal Orientation Transition on Microtextured Substrates", Baoshe Zhang, Fuk Kay Lee, Ophelia K. C. Tsui, Ping Sheng, Phys. Rev. Lett., 91, 215501 (2003).
• "Study on the Origin of Inverted Phase in Drying Solution-Cast Block Copolymer Films", Haiying Huang, Fajun Zhang, Zhijun Hu, Binyang Du, Tianbai He, Fuk Kay Lee, Yongjian Wang, Ophelia K. C. Tsui, Macromolecules, 36, 4084 (2003).
• "Effect of C60 Molecular Rotation on Nanotribology", Qi Liang, O. K. C. Tsui, Yabo Xu, Hongnian Li, Xudong Xiao, Phys. Rev. Lett., 90, 146102 (2003).
• "Effect of Interfacial Interactions on the Glass Transition of Polymer Thin Films", O. K. C. Tsui, T. P. Russell, C.J. Hawker, Macromolecules, 34, 5535 (2001).
• "Studying Surface Glass-to-Rubber Transition Using Atomic Force Microscopic Adhesion Measurements" O.K.C. Tsui, X. P. Wang, Jacob Y. L. Ho, T. K. Ng, Xudong Xiao, Macromolecules, 33, 4198 (2000).
• "Sharp Magnetoabsorption Resonances in the Vortex State of Bi2Sr2CaCu2O8+d", Ophelia K. C. Tsui, N. P. Ong, Y. Matsuda, Y. F. Yan and J. B. Peterson, Phys. Rev. Lett. 73, 724 (1994).

 

In the news:

• Ophelia Tsui and collaborators published in Science Magazine

 

Research Descriptions:

Dewetting of Polymer Films

Dewetting is a phenomenon in which a liquid film of uniform thickness on a non-wetting substrate surface breaks up and develops into liquid beads. In some sense, this process can be viewed as a phase separation process, wherein a homogeneous polymer film phase separates into regions deficient of the polymer (i.e. holes) and regions rich in the polymer (i.e. polymer beads). Though simple as this analogy may sound, for a decade opinions have been divided between spinodal instability (which is tie to an unstable system) and heterogeneous nucleation (tie to a metastable system) being the major cause of the instability. We devise experiments to be able to make the distinction unambiguously and hence delineate applicability of the classical linear theory of spinodal decomposition in regimes close to metastable regions.

Besides studying the fundamentals, we also explore possibilities to make use of this spontaneous dewetting process to make useful mesoscopic structures in large areas. Figure 1 shows one kind of pattern that can be made by using this approach. It is interesting to note that the pattern contains features of sub-micron sizes. Normally, to make features with such sizes will require sophisticated techniques such as photo- or e-beam lithography. But with our approach, it is as simple as roasting the sample on a hot plate for a few minutes.