This Broadening Participation Research Initiation Grant in Engineering (BRIGE) provides funding for the development of a novel nanoscale surface fabrication and patterning technique. This method utilizes the hindered diffusion of chemicals through a three-dimensional polymer mesh to create pseudo-grayscale functionalized surface patterns; the three-dimensional polymer substrate serves as a mask to control the diffusion path length of molecules from a liquid reservoir to the target patterning surface. In this manner, both the placement of surface-functionalized chemicals and the local density of these chemicals can be controlled. Experiments will be conducted in order to characterize mesh density and solute transport rates through polymers and this information will be used to derive predictive relationships correlating hindered diffusion rate to basic polymer and solute properties. These relationships will be used to generate numerical computer models of the described patterning mechanism, and the results will be validated experimentally. Finally, the combined numerical and experimental results will be used to create deterministic algorithms for selecting optimized polymer geometry and mesh density for any desired chemical/pattern combination.
Selective deposition of chemicals can be used to modify a number of surface properties, including binding affinity, manufacturability, hydrophobicity, and immune response. The current state-of-the-art in surface patterning only enables the user to make microscale binary patterns, where regions are either completely absent of chemical modification or contain a single uniform chemical density. If successful, this research will represent an inexpensive method for producing surface patterns in a highly accurate manner with a level of geometric complexity that is unattainable with current methods. The focus on low-cost, widely-available materials would make this process immediately accessible to a large number of manufacturers and researchers. Applications for grayscale surface patterning are numerous and varied, including high-throughput binding studies for pharmaceutical development, portable biosensors for medical testing, control of fluid movement for microfluidics and self assembly, and quantitative studies of cell behavior. In addition, the hindered-diffusion studies and analytical models developed in this research will provide invaluable tools in the large number of fields governed by this transport mechanism, including tissue engineering, targeted drug delivery, and medical diagnostics.
Miniaturization of sensors, actuators, electronics, and other systems offers a wide variety of benefits, from reduced weight and volume to decreased energy consumption. But successful miniaturization of complex systems is frequently hindered by lack of necessary fabrication methods. One important micro/nano fabrication method involves chemically modifying a surface in order to locally change its properties—making it water repellant or resistant to bacteria, for example. This same method can be used to print proteins or DNA on a surface, which is a necessary step in many bioscreening or biosensor applications. However, the techniques used to print these biomarkers are severely limited in the complexity of patterns they can produce. The goal of this project was to address this critical need in microfabrication by developing a new micromolding method capable of making 3D features as small as 10 micrometers with very high precision and throughput. And further, to use this micromolding method to create hydrogel masks that would allow accurate control of protein and DNA deposition on a target surface through controlled diffusion and electrodeposition. This work increases our understanding of how proteins move on the micro and nanoscale and also paves the way for two new high-throughput microfabrication methods. For many applications of microfabricated technology it is necessary to have microscale control over 3D geometry and over both the location and concentration of biochemical deposition. The methods developed as a result of this research could find application in many of these areas, such as high-throughput screening methods for pharmaceuticals, basic study of human cells and tissues, and platforms for artificial tissue engineering.