Mechanically Induced Hydrophobic Recovery of Poly(dimethylsiloxane) (PDMS) for the Generation of Surfaces with Patterned Wettability

Abstract

Silicone elastomers are used in a variety of “stretchable” technologies (e.g., wearable electronics and soft robotics) that require the elastomeric components to accommodate varying magnitudes of mechanical stress during operation; however, there is limited understanding of how mechanical stress influences the surface chemistry of these elastomeric components despite the potential importance of this property with regards to overall function. In this study, plasma-oxidized silicone (poly­(dimethylsiloxane)) films were systematically subjected to various amounts of tensile stress and the resulting surface chemical changes were monitored using contact angle measurements, X-ray photoelectron spectroscopy, and gas chromatography–mass spectrometry. Understanding the influence of mechanical stress on these materials made possible the development of a facile method for the rapid, on-demand switching of surface wettability and the generation of surface wettability patterns and gradients. The use of mechanical stress to control surface wettability is broadly applicable to the fields of microfluidics, soft robotics, printing, and to the design of adaptable materials and sensors.

Janus Evaporators with Self-Recovering Hydrophobicity for Salt-Rejecting Interfacial Solar Desalination

“…Considering the temperature dependence of the recovery rate, we believe that the self-recovering hydrophobicity of PDMS was caused by the thermal movement of PDMS macromolecular segments, − as illustrated in Figure b. The glass transition temperature of PDMS is −123 °C, which indicates that the polymer chain was very flexible enough to move at the working temperature.…”

Dynamic manipulation of droplets using mechanically tunable microtextured chemical gradients

“…Previously, we demonstrated a method—one based on template-guided vapor diffusion—for the generation of periodic chemical gradients on soft surfaces 42 . Further, we have employed strain-induced, irreversible microtexture to synthesize wettability patterns and gradients 43 , and we have applied mechanical buckling to generate reversible microtexture for optical functionality 44 . We combined our unique expertize in the generation of periodic gradients and the generation of reversible microtextures to the synthesis and operation of chemical gradients with mechano-dynamic microtexture.…”

Hydrophobic stretchable polydimethylsiloxane films with wrinkle patterns prepared via a metal‐assisted chemical etching process using a Si master mold

“…Plasma and UVO treatments are an attractive technique to fabricate micro/nanostructures on flexible surfaces; however, they easily render the surface of polymer films hydrophilic 20–23 . Moreover, polymer films can be created by chemically modifying the surface of a polymeric substrate (oxidation by exposure to UV plasma) 24,25 . This process causes wrinkle instability because extrinsic or mechanical stress of the double‐layer system results in mismatch deformation due to heat shrinkage and mechanical stress, and wrinkles are subsequently generated through swelling caused by solvent exposure 26–28 .…”