Surfaces involve many different processes, ranging from protein adhesion to cell migration. Therefore, tailoring the surface properties such as wettability and surface potential are of great interest in a lot of technological, bio-medical and research applications. Spatial gradients have received a great attention in the past few decades as a novel means of studying the complex biochemical processes occur at the interfaces. A gradient surface provides the scope to interrogate the effect of rapidly changing surface properties on a biochemical process which is important for applications in drug delivery, tissue engineering and bio-sensor development. In the past few years, our group has developed a simple and robust method of fabricating functional gradients by sol-gel chemistry. The “Controlled Rate Infusion” method involves infusion of the precursor solution to the silica substrate by a programmable syringe pump. During infusion, the bottom of the substrate is exposed to the solution for the longest period of time whereas the top is exposed to the solution for the shortest period of time, thus producing a spatial variation of the density across the substrate. 1.5 x 3 cm2 silica gradient substrates functionalized with carboxylic acid functional groups show different surface wettability at different pH. The wettability also gradually decreases from the higly functionalized end to the less functionalized end. The FTIR spectra of the substrate also shows that the =CO streatching band intensity of carboxylic acid group at ~1712 cm-1 gradually decreases from the highly functionalized end to the less functionalized end. The zeta potential measurements show that the surface zeta potential decreases with the increase in the pH due to deprotonation of the carboxylic acid groups.

Fabrication and characterization pH-sensitive smart material gradients: A sol-gel approach

254th National Meeting (2017)

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