Fabrication of a Bending-Insensitive In-Plane Strain Sensor from a Reversible Cross-Linker-Functionalized Silicone Polymer

Controllable hydrogen-bonded poly(dimethylsiloxane) (PDMS) membranes for ultrafast alcohol recovery

The lack of efficient separation membranes limits the development of bio-alcohol purification via a pervaporation process. In this work, novel controllable hydrogen-bonded poly(dimethylsiloxane) (PDMS) membranes are prepared from self-synthesized supramolecular elastomers for alcohol recovery. Different from the conventional covalently-bonded PDMS membranes, the hydrogen-bonding content and therefore the crosslinking degree in the as-synthesized PDMS membranes can be exactly regulated, by the suitable molecular design of the supramolecular elastomers. The effects of hydrogen-bonding content on the flexibility of the polymer chains and the separation performance of the resultant supramolecular membranes are investigated in detail. In comparison with the state-of-the-art polymeric membranes, the novel controllable hydrogen-bonded supramolecular PDMS membrane exhibits ultrahigh fluxes for ethanol (4.1 kg m-2 h-1) and n-butanol (7.7 kg m-2 h-1) recovery from 5 wt% alcohol aqueous solutions at 80 °C, with comparable separation factors. The designed supramolecular elastomer is therefore believed to provide valuable insights into the design of next-generation separation membrane materials for molecular separations.

Highly Stable Silver Nanowires/Biomaterial Transparent Electrodes for Flexible Electronics

Flexible transparent electrodes (FTEs) possess excellent optoelectrical properties, mechanical robustness, and environmental adaptability are important for the industrial scale development of flexible electronics. Silver nanowires (AgNWs) are widely used in FTEs owing to their excellent optoelectrical properties and mechanical flexibility. However, the high surface roughness and poor stability of AgNWs FTEs still limit their practical applications. Here, highly stable FTEs are demonstrated via combining AgNWs and biomaterial propolis which is eco-friendly and antioxidative. The AgNWs/propolis composite transparent electrodes exhibit excellent optoelectrical performance as well as a smooth surface (root-mean-square roughness ∼ 6.2 nm). Meanwhile, the composite electrodes possess high mechanical stability (10,000 bending cycles), thermal stability, and environmental adaptability (60 °C and 85 ± 3% humidity for 700 h). The versatile composite FTEs show great potential applications in organic light-emitting diodes and pressure sensors, which exhibit high performance, mechanical stability, and environmental adaptability. Our strategy of introducing biocompatible materials into metallic nanowires opens up new possibilities to achieve high-quality FTEs in a simple and eco-friendly way.

Silane-Functionalized Carbon Dots and Their Polymerized Hybrids: From Optoelectronics to Biotherapy

Nanomaterials usually manifest unique properties in solutions but will be undermined in the solid state. It is necessary to incorporate them into substrates or hybrid them with other functional materials for multiple devices and applications. Though there are a variety of methods to inherit their intrinsic properties like fluorescent and mechanical performance, most nanohybrid materials would lose their transparency irreversibly when construct solid-state devices. As a hot topic of nanomaterials in recent years, scientific works found a type of carbon dots using silane coupling agents as precursors that can overcome the shortcoming. These carbon dots, called silane-functionalized carbon dots (SiCDs), are catching increasing interest due to their versatility. Silane coupling agents endow SiCDs with the ability to disperse in solvents or polymerize with matrices by blending or covalent bonds without loss of transparency and decline of performance. The distinguishing features make SiCDs an ideal high transmittance, high doping concentration nanomaterial. The synergistic effect of SiCDs and hybridized sol-gel solid structures can not only hold the optical features of CDs but also enhance their original physical and chemical performance. This highlight focuses on the connection between SiCDs and organosilanes. Plus, preparation methods, applications, and prospective of SiCDs are mentioned.

Dynamic Covalent Polyurethane Network Materials: Synthesis and Self-Healability

Polyurethane (PU) has not only been widely used in the daily lives, but also extensively explored as an important class of the essential polymers for various applications. In recent years, significant efforts have been made on the development of self-healable PU materials that possess high performance, extended lifetime, great reliability, and recyclability. A promising approach is the incorporation of covalent dynamic bonds into the design of PU covalently crosslinked polymers and thermoplastic elastomers that can dissociate and reform indefinitely in response to external stimuli or autonomously. This review summarizes various strategies to synthesize self-healable, reprocessable, and recyclable PU materials integrated with dynamic (reversible) Diels-Alder cycloadduct, disulfide, diselenide, imine, boronic ester, and hindered urea bond. Furthermore, various approaches utilizing the combination of dynamic covalent chemistries with nanofiller surface chemistries are described for the fabrication of dynamic heterogeneous PU composites.

Fabrication of Flexible Electrode with Sub-Tenth Micron Thickness Using Heat-Induced Peelable Pressure-Sensitive Adhesive Containing Amide Groups

In response to the increasing demand for flexible devices, there is increasing effort to manufacture flexible electrodes. However, the difficulty of handling a thin film is an obstacle to the production of flexible electrodes. In this study, a heat-induced peelable pressure-sensitive adhesive (h-PSA) was fabricated and used to manufacture a flexible electrode with sub-tenth micron thickness. Unlike the control PSA, the incorporation of amide groups made the h-PSA fail through adhesive failure at temperatures ranging from 20 to 80 °C. Compared to the peeling adhesion (1719 gf/in) of h-PSA measured at 20 °C, the value (171 gf/in) measured at 80 °C was decreased by one order of magnitude. Next, the 8 μm thick polyethylene terephthalate (PET) film was attached on a thick substrate (50 μm) via h-PSA, and Mo/Al/Mol patterns were fabricated on the PET film through sputtering, photolithography, and wet-etching processes. The thick substrate alleviated the difficulty of handling the thin PET film during the electrode fabrication process. Thanks to the low peel force and clean separation of the h-PSA at 80 °C, the flexible electrode of metal patterns on the PET (8 μm) film was isolated from the substrate with little change (<1%) in electrical conductivity. Finally, the mechanical durability of the flexible electrode was evaluated by a U-shape folding test, and no cracking or delamination was observed after 10,000 test cycles.

A Highly Stretchable, Self-Healing Elastomer with Rate Sensing Capability Based on a Dynamic Dual Network

Flexible sensing materials have attracted tremendous attention in recent years because of their potential applications in the fields of health monitoring, artificial intelligence, and so on. However, the preparation of rate sensing materials with self-healing performance is always a huge challenge. Herein, we first report the design and synthesis of a highly stretchable, recyclable, self-healing polysiloxane elastomer with rate sensing capability. The elastomer is composed of a dynamic dual network with boron/oxygen dative bonds and hydrogen bonds, which overcomes the structural instability of conventional solid-liquid materials. It exhibits certain adhesion, satisfactory mechanical robustness, and superior elongation at break (up to 1171%). After heating treatment at 80 °C for 2-4 h, the mechanical properties of damaged materials can be almost completely restored. Because of the "solid-liquid" property of the elastomer, it has irreplaceable functions which can sense different rates by resistance change after blending with multiwalled carbon nanotubes, principally in the range of 10 mm/min-150 mm/min. Especially, this rate sensing elastomer can be personalized by 3D printing at room temperature. This rate sensing strategy coupled with the introduction of dynamic dual-network structure is expected to help design advanced wearable devices for human rhythmic movement.