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Leveraging Silicone Elastomer Surface Chemistry and Mechanics towards the Rational Patterning of Micron-Scale Objects
The ability to rationally pattern or manipulate micron-scale objects has applications across a vast number of fields including energy storage, optics, sensing, and robotics. The methods used to accomplish these applications have relied on hard, rigid materials (such as silicon wafers) with predictable surface chemistry templates as the underlying substrate. The ability to use soft, elastic materials, specifically silicone elastomers, would enable the creation of dynamic surface chemical patterns through the introduction of stress from straining the elastomer which are imperative in new and upcoming fields like stretchable electronics or microactuation. The following studies detail how chemically modified surfaces of silicone elastomers were designed to drive the patterning of micron-scaled objects of varying sizes, shapes, and chemistries. Silicones are common elastomers used in numerous applications including soft lithography, microfluidics, and soft robotics. Surface modification of these elastomers follows a relatively straight forward process using an oxidation step followed by a silane coupling reaction which allows the attachment of almost any functional group onto the elastomer surface. Combining the surface modification of elastomers with the inherent elastic mechanical properties gives rise to dynamic surface chemical patterns which when strained decrease the density of the functional groups on the surface and lead to a surface chemical pattern that has a different shape then the initial pattern. The fabrication of these dynamic surface chemical patterns was used to: i) design a method to pattern polymeric microstructures or inorganic crystals using a new screening method whose effectiveness could be predicted using van der Waals interactions and surface mechanics, ii) drive the patterning of aqueous hydrogel precursor droplets that were loaded with various stimuli-responsive materials which would drive actuation in different environments when crosslinked, iii) enable the attachment of hydrogels to elastomeric surfaces for the creation of in situ actuators, iv) use the differences in van der Waals interactions between a functionalized elastomer and inorganic crystals to drive delamination and pattern creation, and v) utilize the strain of a substrate to control mass transport and nucleation of inorganic crystals. The projects herein have a broad application space including in optics, microactuation, forensics, and crystal engineering.
Rose, Mark A, "Leveraging Silicone Elastomer Surface Chemistry and Mechanics towards the Rational Patterning of Micron-Scale Objects" (2020). ETD collection for University of Nebraska-Lincoln. AAI27956775.