Flexible Microfluidic Systems for Cellular Analysis Using Low Cost Fabrication Technologies

Abstract

This dissertation presents the design, fabrication, and testing of a microfluidic system to be used for whole-cell analysis. The study of cellular function and structure is essential for disease diagnosis and treatment. Microsystems developed to perform these bioanalyses add benefits such as requiring smaller samples and reagents, testing multiple samples in parallel, and supporting point-of-care testing, all of which increases throughput and reduces cost-per-analysis. Traditional methods for designing a microsystem use standard materials and techniques such as silicon, glass, photolithography, and wet and dry etching. This research is focused on utilizing materials and techniques that require less infrastructure, allow for a faster design-to-prototype cycle, and can integrate electrical and fluidic functionality to address a variety of possible applications. The microfluidic system presented in this thesis is comprised of multiple layers of Kapton, a polyimide available from DuPont. Kapton provides a biocompatible substrate that is flexible while maintaining structural stability and can be used in high temperature and other harsh environments. Microchannels with widths of 400 m and thru-hole fluidic vias less than 5 m in diameter are laser ablated through the flexible polyimide sheets using excimer and CO2 lasers. Electrical traces and contact pads are defined on the substrate by vapor deposition through reusable microstencils rather than with photolithography. The patterned layers are bonded using heat staking and then packaged with the addition of wires and a fluidic interface. Validation of the system for whole-cell analysis was first performed with impedance spectroscopy measurements collected on air, DI water, phosphate buffered saline, clusters of human cancer cells, and human cancer tissue samples. This was followed by testing the ability to use the device to control the movement and position of 10 m diameter microbeads and dissociated cells. As a whole, this research demonstrates the realization of a microfluidic system for whole-cell analysis based on non-standard fabrication materials and techniques.