Controllable Broadband Optical Transparency and Wettability Switching of Temperature-Activated Solid/Liquid-Infused Nanofibrous Membranes

Abstract

Inspired by biointerfaces, such as the surfaces of lotus leaves and pitcher plants, researchers have developed innovative strategies for controlling surface wettability and transparency. In particular, great success has been achieved in obtaining low adhesion and high transmittance via the introduction of a liquid layer to form liquid-infused surfaces. Furthermore, smart surfaces that can change their surface properties according to external stimuli have recently attracted substantial interest. As some of the best-performing smart surface materials, slippery liquid-infused porous surfaces (SLIPSs), which are super-repellent, demonstrate the successful achievement of switchable adhesion and tunable transparency that can be controlled by a graded mechanical stimulus. However, despite considerable efforts, producing temperature-responsive, super-repellent surfaces at ambient temperature and pressure remains difficult because of the use of nonreactive lubricant oil as a building block in previously investigated repellent surfaces. Therefore, the present study focused on developing multifunctional materials that dynamically adapt to temperature changes. Here, we demonstrate temperature-activated solidifiable/liquid paraffin-infused porous surfaces (TA-SLIPSs) whose transparency and control of water droplet movement at room temperature can be simultaneously controlled. The solidification of the paraffin changes the surface morphology and the size of the light-transmission inhibitor in the lubricant layer; as a result, the control over the droplet movement and the light transmittance at different temperatures is dependent on the solidifiable/liquid paraffin mixing ratio. Further study of such temperature-responsive, multifunctional systems would be valuable for antifouling applications and the development of surfaces with tunable optical transparency for innovative medical applications, intelligent windows, and other devices.

External‐Field‐Induced Gradient Wetting for Controllable Liquid Transport: From Movement on the Surface to Penetration into the Surface

“…[108][109][110] Water-droplet adhesion switching has been achieved by the thermoresponsive phase transition of the n-paraffin-swollen organogel surface for water-droplet movement control. [37,87] Similar results have been obtained on a side-chain liquid-crystal polymer surface by temperature, owing to the phase transition from the smectic A phase to the isotropic phase. [108] Furthermore, underwater oil and cell adhesion can also be reversibly controlled by temperatures lower or higher than the lower critical solution temperature at the water/solid interface containing PNIPAAm.…”

“…[81][82][83][84][85][86] For a thermoresponsive phase-change material (e.g., the n-paraffin-swollen organogel surface), a water droplet can switch between the slippery state and the pinning state by thermal activation, corresponding to the transition between the air/liquid 1 /liquid 2 /solid system and the air/liquid/solid system; [37] that is, a temperature-activated solidifiable/liquid paraffin-infused porous surface for water droplet movement control is created. [87] In addition to normal thermoresponsive surfaces, directional droplet transport has also been achieved on a tilted silicon nanowire surface at high temperature owing to its anisotropic wetting performance. [28] Furthermore, a thermoresponsive surface-tension gradient could be achieved based on light-heat conversion.…”

External Stimuli Responsive Liquid‐Infused Surfaces Switching between Slippery and Nonslippery States: Fabrications and Applications

“…According to the factors determine the lubricant's depletion, efforts also have been made to overcome the loss of lubricant as use time goes on. For example, selecting lubricants with higher viscosity and lower vapor pressure, increasing chemical affinity of lubricant and substrate, designing and fabricating materials with self‐healing or self‐replenishing, or self‐regulated liquid‐secretion, and so on . In the other hand, for most of the E‐LIS, the thickness of lubricant layer should be well controlled.…”

“…Achieving wettability switching of temperature E‐LIS at room temperature was desired. Manabe and co‐workers fabricated porous substrate through layer by layer method, and then introduced solidifiable/liquid paraffin mixture as lubricant, as shown in Figure b . By adjusting the ratio of solidifiable/liquid paraffin, the water droplet's motion behavior on this surface can be tuned between pinning and sliding under room temperature.…”

“…As a result, droplet switched from pinning to sliding when the environmental temperatures increased from 22 to 30 °C. Reproduced with permission . Copyright 2016, American Chemical Society.…”