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Ali Mazaltarim1 Jay Taylor1 Abhiteja Konda1 Michael Stoller1 Stephen Morin1

1, University of Nebraska-Lincoln, Lincoln, Nebraska, United States

Silicone elastomers are widely used in “stretchable” technologies (e.g., wearable electronics) that require the elastomeric components to accommodate varying magnitudes of mechanical stress. Understanding how mechanical stress influences the surface chemistry of these elastomeric components is therefore critical to the performance of these materials. We treated silicone films (polydimethylsiloxane; PDMS) with oxygen plasma and systematically exposed these films to various magnitudes of tensile stress while studying the associated surface chemical changes using contact angle measurements, X-ray photoelectron spectroscopy, and gas chromatography-mass spectrometry. We discovered that mechanical stressing oxidized PDMS films resulted in the on-demand restoration of the film’s hydrophobicity due to: i) cracking of the brittle surface oxide layer, ii) migration of uncured monomers from the bulk towards the surface, and iii) surface rearrangement. We utilized these understandings to develop a facile method for the rapid, on-demand switching of surface wettability and the generation of surface wettability patterns and gradients. These findings are broadly applicable to the fields of microfluidics, soft robotics, printing, and to the design of adaptable materials and sensors.

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