This dissertation describes the development of simple and non-photolithographic techniques for patterning proteins. Protein patterns have relied mainly on conventional photolithography and photolithography-based soft lithography, which require sophisticated instruments and clean room facilities and therefore are expensive. As simple and cost-effective alternatives, the four techniques developed in this study allow protein patterning to be performed at bench top in any common laboratories.
The first technique utilizes the dewetting of a polystyrene (PS) thin film on a proteinresistant poly(ethylene glycol) (PEG)-modified substrate. The dewetted PS droplets allow the selective adsorption of proteins while the exposed PEG-modified substrate act as the non-fouling background. Micro- and nanoscale droplet patterns can easily be achieved by tuning the thickness of PS thin films.
The second technique is based on stepwisely contact printing octadecyltrichlorosilane (OTS) gradients by using a hemispherical poly(dimethylsiloxane) (PDMS) stamp. The stepwise OTS gradient is further backfilled by PEG-silane, resulting in an OTS-PEG mixed monolayer gradient. The amount of adsorbed proteins and cell density on the stepwise gradient decrease with the increasing surface coverage of PEG, which increases with the increasing contact printing time for each step.
The third and fourth techniques focus on using non-photolithographic approaches to fabricate masters for creating PDMS stamps. The masters in the third technique are porous PS films fabricated by using the ordered arrays of water droplets as templates, which result from Marangoni flow. The arrangement, size, and inter-pore distance of the porous films can be tuned. For the fourth technique, parallel PDMS strips are fabricated by peeling a PDMS sheet bonded onto a SiOx substrate. The periodicity and the coverage of the PDMS strips can be controlled by varying the bending strain applied during peeling and UV/Ozone oxidation time prior to bonding. By using the porous films and PDMS strips as masters, PDMS stamps with arrays of posts structures and strips can be fabricated respectively for contact printing OTS patterns, which are subsequently used for protein patterns.