Person:

Yao, Xi

Omniphobic fluorogel elastomers were prepared by photocuring perfluorinated acrylates and a perfluoropolyether crosslinker. By tuning either the chemical composition or the temperature that control the crystallinity of the resulting polymer chains, a broad range of optical and mechanical properties of the fluorogel can be achieved. After infusing with fluorinated lubricants, the fluorogels showed excellent resistance to wetting by various liquids and anti-biofouling behavior, while maintaining cytocompatiblity.

Materials that adapt dynamically to environmental changes are currently limited to two-state switching of single properties, and only a small number of strategies that may lead to materials with continuously adjustable characteristics have been reported1-3. Here we introduce adaptive surfaces made of a liquid film supported by a nanoporous elastic substrate. As the substrate deforms, the liquid flows within the pores causing the smooth and defect-free surface to roughen through a continuous range of topographies. We show that a graded mechanical stimulus can be directly translated into finely tuned, dynamic adjustments of optical transparency and wettability. In particular, we demonstrate simultaneous control of the film's transparency and its ability to continuously manipulate various low-surface-tension droplets from free-sliding to pinned. This strategy should make possible the rational design of tunable, multifunctional adaptive materials for a broad range of applications.

The emergence of stretchable electronics and its potential integration with textiles have highlighted a challenge: textiles are wearable and washable, but electronic devices are not. Many stretchable conductors have been developed to enable wearable active textiles, but little has been done to make them washable. Here we demonstrate a new class of stretchable conductors that can endure wearing and washing conditions commonly associated with textiles. Such a conductor consists of a hydrogel, a dissolved hygroscopic salt, and a butyl rubber coating. The hygroscopic salt enables ionic conduction, and matches the relative humidity of the hydrogel to the average ambient relative humidity. The butyl rubber coating prevents the loss and gain of water due to the daily fluctuation of ambient relative humidity. We develop the chemistry of dip coating the butyl rubber onto the hydrogel, using silanes to achieve both the crosslink of the butyl rubber and the adhesion between the butyl rubber and the hydrogel. We test the endurance of the conductor by soaking it in detergent while stretching it cyclically, and by machine-washing it. The loss of water and salt is minimal. It is hoped that these conductors open applications in healthcare, entertainment, and fashion.

The diffusion and transport of substances between a hydrogel and its environment have received tremendous research interest, due to the wide range of applications of hydrogel materials in fields related to drug carriers and drug delivery vehicles. To date, much research has been done to tailor the diffusion and transport of substances through hydrogels, where most efforts were focused on tuning the 3D network properties of the hydrogel including loop size, hydrophobicity of building blocks and the stimuli-responsive properties of backbones. These conventional strategies, however, usually suffer from complicated fabrication procedures and result in a homogeneous increase in hydrophobicity of the hydrogel network, leading to low efficiency control over the diffusion of substances through the hydrogel. Herein, a facile strategy that can functionalize the surfaces of hydrogels, while keeping the interior network unchanged, was reported, and is realized by quaternization reaction confined to the hydrogel/oil interface. Owing to the introduction of the photo-responsive molecule IBSP as a modifier, the surface wettability of the resulting hydrogel can be controlled by light both in air and underwater environments. Consequently, the diffusion rate of a substance through this modified hydrogel can be regulated by light, which brings convenience to the controlled release of hydrogels and other hydrogel-related fields.

A liquid jet can stably bounce off a sufficiently soft gel, by following the contour of the dimple created upon impact. This new phenomenon is insensitive to the wetting properties of the gels and was observed for different liquids over a wide range of surface tensions, γ = 24–72 mN/m. In contrast, other jet rebound phenomena are typically sensitive to γ: only high γ jet rebounds off a hard solid (e.g. superhydrophobic surface) and only low γ jet bounces off a liquid bath. This is because an air layer must be stabilized between the two interfaces. For a soft gel, no air layer is necessary and jet rebound remains stable even when there is direct liquid-gel contact.