Stephen A. Morin
Date of this Version
Mazaltarim, Ali Jamal, "Harnessing Surface Chemistry and Instabilities in Silicone Elastomers to Synthesize Adaptive Systems with Mechanically Tunable Surface Properties and Functionality " (2021). ETD collection for University of Nebraska - Lincoln.
Material interfaces are of critical importance to numerous fields, including nanomaterials, electronics, microfluidics, synthesis, bioanalysis, pharmaceuticals, and catalysis, and they have been extensively researched. The materials used in these fields are often rigid/hard (such as silicon wafers) resulting in static surface properties. Consequently, the chemical/morphological properties of a surface may be modified using synthetic or mechanical means to tailor the interfacial properties of a material (i.e., surface energy, adhesion, topography, and reactivity). Recently, emphasis has been placed on designing dynamic materials with adaptive interfacial properties that respond to a variety of environmental stimuli. To this end, the surface chemistry and topography of common silicone elastomers (e.g., polydimethylsiloxane; PDMS) are rationally designed to afford systems with mechanically tunable surface properties. These adaptive surfaces are utilized towards the generation of wettability/topographical patterns, adaptive microdroplet transport, mechano-switchable adhesion, and mechanically triggered catalysis.
Silicone polymers are biocompatible elastic materials that are frequently used in adaptive technologies (e.g., soft robotics), medical/pharmaceutical applications, soft lithography, and microfluidics. Surface activation (i.e., oxidation) of silicone surfaces often results in the formation of an undesirable/mechanically unstable brittle silica layer that readily fractures following mechanical stimuli, limiting the application space of these materials. In this work, the effect of mechanical stimuli on silicone surface chemistry and topography is investigated. The surface chemistry and instabilities (i.e., cracking and wrinkling) are leveraged for: (i) fabricating wettability patterns and gradients, (ii) designing superhydrophobic surfaces with mechano-switchable droplet adhesion, (iii) generating hierarchically structured micro-/nanotopographies with tunable surface chemistry, (iv) creating mechanically switchable microdroplet transport, (v) designing advanced microdroplet transport systems, and (vi) achieving mechano-activated catalysis. The work presented here is relevant to the fields of soft robotics, microfluidics, bioanalysis, intelligent and adaptive materials, anti-icing, and catalysis. These results may find useful applications in printing technologies, liquid repellent surfaces and apparel, microfluidics, microreactors, water-harvesting technologies, heterogeneous catalysis, and the creation of interactive reaction vessels (i.e., reactionware).
Advisor: Stephen A. Morin