Smart Superhydrophobic Textiles Utilizing a Long-Range Antenna Sensor for Hazardous Aqueous Droplet Detection plus Prevention

Large-Area Conductor-Loaded PDMS Flexible Composites for Wireless and Chipless Electromagnetic Multiplexed Temperature Sensors

Capacitive dielectric temperature sensors based on polydimethylsiloxane (PDMS) loaded with 10 vol% of inexpensive, commercially-available conductive fillers including copper, graphite, and milled carbon fiber (PDMS-CF) powders are reported. The sensors are tested in the range of 20-110 °C and from 0.5 to 200 MHz, with enhanced sensitivity from 20 to 60 °C, and a relative response of 85.5% at 200 MHz for PDMS-CF capacitors. PDMS-CF capacitors are interrogated as a sensing element in wirelessly coupled chipless resonant coils tuned to 6.78 MHz with a response in the resonant frequency (fr) of the sensor, demonstrating an average sensitivity of 0.38% °C-1, a 40x improvement over a pristine PDMS capacitive sensor and outperforms state-of-the-art frequency-domain radio frequency temperature sensors. Exploiting its high sensitivity, the wireless sensing platform is interrogated using a low-cost, portable, and open-source NanoVNA demonstrating a relative response in fr of 48.5%, good agreement with instrumentation-grade vector network analyzers (VNAs) and negligible change in performance at a range of reading distances and humidities. Finally, a wireless tag is demonstrated with rapid, reversible dynamic response to changes in temperature, as well as the in the first scalable, multiplexed array of chipless sensors for spatial temperature detection.

Carbon nanotube triaxial woven films with high mechanical properties for impacting protection

Fiber-based fabrics have great potential in impacting protection as composite materials. Herein, we proposed a novel nanostructure in which the (5,5) single-walled CNTs (SWCNTs) with a diameter d of ∼6.67 Å were employed to weave triaxial 2D films with an angle of adjacent CNTs as 60°. The bending angle of a single CNT in the structure unit length was set at 90°, while the bent length was 196.87 Å. The in-plane mechanical properties and impacting properties of triaxial woven films (TWFs) were investigated through a fully atomic molecular dynamics (MD) simulation. Experiments verified that the tensile mechanical properties of TWFs were related to the loading directions. The impacting test of single-layer films showed that the TWF possessed impacting protection and reached its force peak at the center of the sphere passing through the film. In addition, for bilayer composite films of TWFs and plain woven films, this combination developed a high strain with high stress. The impacting properties of the composite film in both directions (plain/triaxial and triaxial/plain) were investigated, and the percentages of absorbed energy were calculated to be 87.8% and 86.9% for the Plain/Triaxial and Triaxial/Plain films, respectively, indicating an outstanding impacting protection for the composite films. This work provides an in-depth understanding of the mechanical properties of TWFs and broadens the applications of CNT-based nanomaterials.

Recent Developments in the Fabrication and Application of Superhydrophobic Suraces

A superhydrophobic surface is defined as having a contact angle exceeding 150 °C, indicating a remarkable ability to repel water. Generally, superhydrophobicity originates from the utilization of low-surface-energy materials with unique micro- and nanostructures. Superhydrophobic surfaces have gained considerable recognition and are widely employed in diverse areas for anti-icing, oil-water separation, anticorrosion, self-cleaning, blood-repellent, and antibacterial applications. These surfaces can greatly enhance industrial processes by yielding significant performance improvements. In this review, we introduce the basic theories that provide a foundation for understanding the hydrophobic properties of superhydrophobic surfaces. We then discuss current techniques for fabricating superhydrophobic coatings, critically analyzing their strengths and limitations. Furthermore, we provide an overview of recent progress in the application of superhydrophobic materials. Finally, we summarize the challenges in developing superhydrophobic materials and future trends in this field. The insights provided by this review can help researchers understand the basic knowledge of superhydrophobic surfaces and obtain the latest progress and challenges in the application of superhydrophobic surfaces. It provides help for further research and practical application of superhydrophobic surfaces.

MXene Free Standing Films: Unlocking the Impact of Flake Sizes in Microwave Resonant Structures in Humid Environments

Microwave communication devices necessitate elements with high electrical conductivity, a property which was traditionally found in metals (e.g., copper). However, in applications such as satellite communications, metals prevent the payload from achieving lightweight and flexible characteristics. Here, we demonstrate the development of MXene film microwave resonators, leveraging MXene's high electrical conductivity and unique mechanical properties. To investigate resonant performance in humid conditions and study the effects of MXene's processing and treatment, MXene films with different flake sizes are prepared and exposed to cyclic humidity. For the large- and small-flake Ti3 C2 MXene films in cyclic humidity, the large-flake film demonstrates higher electrical conductivity, higher resonance quality factor (150 and 35 as unloaded, and loaded), and less fluctuation of performance (≈1.7% total shift in resonance frequency). Further, by implementing MXene films of two different diameters, the correlation between film size and resonant frequency is demonstrated. By introducing an active resonant configuration, the effect of MXene degradation and microwave losses can be compensated. This active feedback loop demonstrates a ≈300 times increase in the quality factor of MXene resonators. As a building block for terrestrial and satellite communication modules, MXene resonators potentiate the replacement of metals in achieving unique electrical and mechanical properties.

A facile approach to obtain super-hydrophobicity for cotton fiber fabrics

It is a challenging task to directly apply emulsified silicone oil to the surface of cotton fabric to obtain superhydrophobic properties. In this work, a temperature-responsive microgel was first synthesized and the particle size and distribution of the microgel, thermo-responsiveness, and hydrophobicity of the microgel membrane were investigated. Then, through an emulsifying PMHS/water system with microgels as a Pickering emulsifier, a series of Pickering emulsions were obtained. The results showed that the emulsion had the best stability when the microgel content was 2.14 wt% and the mass ratio of PMHS/water was 3/7. The optical microscopy showed that the oil phase could be uniformly dispersed in aqueous solution, and the liquid phase particle size was about 10-22 μm. And stratification of the Pickering emulsion did not occur when placed at room temperature for over one month. Finally, when the addition of Pickering emulsion is 50 g L-1 and the rolling rate is 80%, through a simple two-dip-two-padding treatment, a cotton fabric can obtain the superhydrophobic effect with a static contact angle of 149.6° at 25 °C and 156.4° at 45 °C. The development of this work provides a simple method to make cotton fabric obtain superhydrophobic effects.

Preparation of Stable POSS-Based Superhydrophobic Textiles Using Thiol–Ene Click Chemistry

In this study, a superhydrophobic fabric was synthesized by modifying the fiber’s surface with dopamine-containing hydroxyl functional groups. Furthermore, we introduced mercapto-based functional groups by the hydrolysis of mercaptopropylmethyldimethoxysilane (MPMDS) and finally grafted POSS and mercaptans using a thiol–ene click reaction. These processes generated a superhydrophobic fabric with a static contact and a sliding angle of 162° and 8°, respectively. The superhydrophobic fabric’s compact and regular micro-nano rough structure based on POSS and mercaptans provides stable fastness and durability, as well as high resistance to organic solvents, acid–base environments, mechanical abrasion, UV rays, and washing. Moreover, it can be used for self-cleaning and oil–water separation, and it has a wide range of applications in the coating industry.

Facile Preparation of Robust Superhydrophobic/Superoleophilic TiO2-Decorated Polyvinyl Alcohol Sponge for Efficient Oil/Water Separation

Oily wastewater and oil spills pose a threat to the environment and human health, and porous sponge materials are highly desired for oil/water separation. Herein, we design a new superhydrophobic/superoleophilic TiO₂-decorated polyvinyl alcohol (PVA) sponge material for efficient oil/water separation. The TiO₂-PVA sponge is obtained by firmly anchoring TiO₂ nanoparticles onto the skeleton surface of pristine PVA sponge via the cross-linking reactions between TiO₂ nanoparticles and H₃BO₃ and KH550, followed by the chemical modification of 1H,1H,2H,2H-perfluorodecyltrichlorosilane. The as-prepared TiO₂-PVA sponge shows a high water contact angle of 157° (a sliding angle of 5.5°) and an oil contact angle of ∼0°, showing excellent superhydrophobicity and superoleophilicity. The TiO₂-PVA sponge exhibits excellent chemical stability, thermal stability, and mechanical durability in terms of immersing it in the corrosive solutions and solvents, boiling it in water, and the sandpaper abrasion test. Moreover, the as-prepared TiO₂-PVA sponge possesses excellent absorption capacity of oils or organic solvents ranging from 4.3 to 13.6 times its own weight. More importantly, the as-prepared TiO₂-PVA sponge can separate carbon tetrachloride from the oil-water mixture with a separation efficiency of 97.8% with the aid of gravity and maintains a separation efficiency of 96.5% even after 15 cyclic oil/water separation processes. Therefore, the rationally designed superhydrophobic/superoleophilic TiO₂-PVA sponge shows great potential in practical applications of dealing with oily wastewater and oil spills.