Inkjet printing of smart hydrogels and their response characterization
T h e U n i v e r s i t y o f U t a h G r a d u a t e S c h o o l STATEMENT OF THESIS APPROVAL The thesis of Vishal Bhola has been approved by the following supervisory committee members: Prashant Tathireddy , Chair ABSTRACT Hydrogels find extensive applications in biomedical research, process control in bioreactors, and metabolite monitoring in human/animal research. However, for commercial success of hydrogel-based products, there needs to be an easy technique or process to dispense
... dispense pre-polymerized hydrogel in a precise location, in precise microliter volumes. Moreover, the process should be inexpensive and repeatable. Microliters dispensing allows the fabrication of thinner hydrogel structures with large surface area to volume ratio, which translates to faster response times. There exists no technique at present that can produce these hydrogels with microscale precision commercially for these applications. In this project, we use the inkjet printing process for inexpensive, highly repeatable microscale patterning for synthesis of smart hydrogel arrays for various applications with a potential for commercial-scale synthesis. An Epson Artisan 50 inkjet printer printhead was employed for dispensing pregel solution that essentially comprises the monomer mixture and the initiators required for polymerization. We characterized this printer for the resultant size of the synthesized hydrogels under various conditions. The effect of oxygen plasma treatment duration on contact angle of water-glass substrate was obtained to control the spread of the pregel and height of the hydrogels. Magnetic field variation was chosen as the preferred transduction mechanism to translate the hydrogel swelling and deswelling. For this, the hydrogel sensors were equipped with either a magnetic sheet or embedded magnetic particles as the source iv of magnetic field. A set of COMSOL simulations were performed to understand the effect of particle density and magnetization of the magnetic particles and sheet on the magnetic field variation. The synthesized magnetic hydrogel sensors were characterized for their response time to varying analytes concentrations. Response times (τ90) of 6 minutes and 15 minutes were obtained for hydrogel sensors with magnetic sheet and magnetic particles, respectively.