Personal Information and Interests

Academic Interests

Research Interests:
Thesis Advisor: Alan Hatton

Research Description

The active control of surface tension and self-assembling has been shown to be important in emerging high technologies, such as in the pumping and control of flow in microfluidic devices, micelle-based separation, and in the microchemical analysis of complex fluids, flow cytometry, rapid DNA screening, etc. The fine-tuning and control of these properties is made possible by the inherent nature of hydrophobic effect, which is the dominant driving force in self-assembling and surfactant adsorption, the latter actually determines the surface tension. The hydrophobic effect distinguishes itself from other interactions by two characteristics: the small energy scale (of the order of several kBTs,) and the sensitivity to molecular architecture. The first one implies the liability of hydrophobic-dominant processes to external stimuli and provides the possibility to control these processes; the second one actually indicates the method: tuning surface tension and self-assembling by control molecular architecture.

My research is focused on the photo-control of interfacial and self-assembling properties in surfactant solutions, which consists of three intervolving projects. Firstly, the new photo-responsive surfactants, which exhibit large changes in both surface tension and self-assembling behavior in response to different illuminations, need to be designed and synthesized. Secondly, the structures of self-assembled surfactant aggregates under need to be elucidated under different radiation conditions. At last, the structures of surfactant adsorbed layers under different illuminations need to be probed. The core inside all these projects is the molecular design of new photoresponsive surfactants. We have already demonstrated that, by careful and smart molecular design, it is possible to acquire azobenzene-based surfactants, which exhibit significant surface tension and self-assembling response to external illuminations. The self-assembling structures of these surfactants have been investigated by state-of -art technologies such as small angle neutron scattering, dynamic and static light scattering under different illumination conditions. The adsorbed layer structures of these surfactants under different radiation have also been elucidated by recently developed technology neutron reflection.

Figure 1. Photo-isomerization of azobenzene. The 3D structures show the planar trans and bent cis isomers.

Figure 2. Concentration dependence of the equilibrium surface tension for photoresponsive surfactants at 25 ºC under both visible (squares) and UV light (circles) illumination.