Electrostatically Actuated Microvalves Fabricated with Soft-Lithographic Techniques for Integrated Microfluidics

Complex chemical and biological microsystems have the potential to significantly impact point-of-care diagnostics, portable detection systems, and automated, high-throughput chemical processing. The implementation of these systems, however, requires the development of a microvalve that can effectively control connectivity between microfluidic components. Ideally, the valve should be fabricated with simple techniques at low temperature and ambient pressure to facilitate wide dissemination of the technology and also assure effective manufacturability. In addition, the valve should be easily integrated with controls in a portable format. In this work, I report the development of an electrostatic microvalve that is fabricated with simple, soft-lithographic techniques. An analytical model was developed to guide the fabrication process of the microvalves and also optimize the electrical potentials needed to actuate the microvalves. Several methods were investigated for conferring conductivity to elastomeric membranes, including the patterning of nanoparticle/elastomer composites, the airbrushing of conducting nanoparticle suspensions, and the microtransfer printing of nanoparticle films formed by vacuum filtration. The latter was used to integrate the conducting membranes into a fabrication process for microvalves, which included the incorporation of membrane support structures. The fabrication process was optimized by exploring the design space identified by the model, and the optimization yielded microvalves that actuated with electrical potentials as low as 5 V. The potentials required to operate the valve are low enough that the valve can be directly controlled by electrical integrated circuit chips. Finally, I report the pressures that the microvalves can effectively isolate and the actuation of the microvalves in different liquid media, including fluorinated oils and water