Symposium Sessions

CP06.04.09 : Dynamic Surface Topography in Micro-Objects and Films

5:00 PM–7:00 PM Apr 23, 2019 (US - Arizona)

PCC North, 300 Level, Exhibit Hall C-E

Mustafa Abdelrahman1 Hyun Kim1 Patrick Ondrusek1 Jimin Maeng1 Taylor Ware1

1, The University of Texas at Dallas, Richardson, Texas, United States

Strategies to induce dynamic surface topography may enable new engineering devices where friction, fluid flow, or cell attachment is a property that needs to be controlled on-demand. There are multiple ways to create polymeric materials where the surface topography can be induced to change in response to a stimulus. For example, shape memory polymers can switch from smooth to rough on heating, but require mechanical programming, limiting this effect to only objects that can be easily deformed such as films. Also, liquid crystalline networks could induce surface topography changes without a programming step; however, they require a constant energy source in order to keep the surface topography from returning to its original state. They also require an initial alignment step, which further confines this ability. Here we describe a versatile strategy to significantly and permanently alter the surface topography of films, microstructures and microspheres without any mechanical programming step or initial alignment. Specifically, we use a radical thiol-ene reaction to build semi-crystalline polymer networks from low molecular weight monomers. Crystallization of the network occurs concurrently with polymerization and produces a material with built-in stresses. On heating through the melting point of the network, these initially smooth materials, having an average roughness of 10nm, form peaks and valleys, reaching an average roughness of 500 nm. We have been able to produce this effect in films, micro-molded structures, and microspheres. The magnitude of the roughness can be controlled by altering either the melting point of the network, the crosslink density, and/or the polymerization temperature. For example, we show that the closer the polymerization temperature is to the substrate's melting temperature, the less rough the substrate becomes after being heated to its melting temperature. This allows us to pattern roughness by simply polymerizing different portions of the substrate under various temperatures. This control will allow us to tackle major engineering challenges in the areas of micro fluidics, self-cleaning films, bio-adhesion and cell growth.