Process and Projects

The Willson research group has been focused on developing low viscosity photocurable material systems that reduce the time scale of pillar formation by orders of magnitude.  Replacing the polymeric film with a low viscosity liquid also removes the requirement for heat.  Pillars form rapidly at room temperature and are then locked into place via photopolymerization.  Images of thiol-ene pillar arrays are shown below. Figure.  Microscope image of pillars formed using photocurable thiol-ene liquids. In related work, we have demonstrated the use of pillars as sacrificial materials for the formation of porous membranes in collaboration with Professor Goujon Liu.  The interstitial region between the pillars is filled with a crosslinkable liquid.  The pillars are then selectively dissolved away, leaving behind a high porosity, low dispersity membrane [1]. In addition, our group has developed a method to surface treat Indium Tin Oxide (ITO) [2].  ITO is a transparent conducting oxide that is used as the upper electrode to form pillars.  ITO finds use in many applications including flat panel displays due to its unique ability to conduct electricity and transmit visible light.  The surface of ITO is covered by hydroxyl groups.  By modifying the surface chemistry, the ITO can be made “non-stick” by covalently binding fluorinated molecules.  This allows the pillars to selectively release at the upper electrode interface during separation of the electrodes.  The method is based on chlorosilane chemistry, which is often utilized to treat hydroxyl groups on quartz (ie glass).  We have found that the hydroxyl groups on ITO are less reactive than those of SiO2.  Consequently, we have developed a method that utilizes a base pretreatment of the surface to increase the reactivity. References

1. X. Yan, G. Liu, M.D. Dickey, and C.G. Willson. “Preparation of porous polymer membranes using nano- or micro-pillar arrays as templates.” Polymer, 2004. 45: p.8469-74.
2. T.W. Holcombe, M.D. Dickey, and C.G. Willson. “Durable fluorinated mono-layers for Indium-Tin Oxide” Langmuir (submit Feb 2006).