Photo-crosslinked thiol-ene based hybrid polymeric sensor for humidity detection

Recent Sensing Technologies of Imperceptible Water in Atmosphere

Accurate detection and quantitative evaluation of environmental water in vapor and liquids state expressed as humidity and precipitation play key roles in industrial and scientific applications. However, the development of supporting tools and techniques remains a challenge. Although optical methods such as IR and LASER could detect environmental water in the air, their apparatus is relatively huge. Alternatively, solid detection field systems (SDFSs) could recently lead to a revolution in device downsizing and sensing abilities via advanced research, mainly for materials technology. Herein, we present an overview of several SDFS based sensing categories and their core materials mainly used to detect water in atmosphere, either in the vapor or liquid phase. We considered the governing mechanism in the detection process, such as adsorption/desorption, condensation/evaporation for the vapor phase, and surface attach/detach for the liquid phase. Sensing categories such as optical, chilled mirror, resistive, capacitive, gravimetric sensors were reviewed together with their designated tools such as acoustic wave, quartz crystal microbalance, IDT, and many others, giving typical examples of daily based real scientific applications.

Packaging materials and technologies for microwave applications: a review1

Packaging materials for microwave application should be generally designed based on products properties and processing conditions such as microwavability, susceptibility, processing condition, barrier properties, mechanical properties, storage condition, sustainability, convenience, and so on. Ready-to-eat products are packed in materials that can sustain thermal processing in an industrial oven and warming process in a household oven. In this context, high barrier polymers are versatile microwave packaging materials due to the microwave transparency (unlike metalized film) and high barrier. Additionally, microwave packaging materials used for ready-to-cook are intended to facilitate the microwave heating of the products in a domestic oven. The introduction of a functional feather to microwave packaging tends to improve the microwaving efficiency such as susceptor and shielding in the household oven or self-venting microwave packaging to safely release the internal steam. Furthermore, microwave-assisted thermal processing intends to control microbial contamination, requiring materials with adequate stability during processing and storage. The features of these materials are addressed in this review along with details on the basic requirements and advanced technologies for microwave packaging, microwave processing of prepackaged food, and migration testing. The prospects of microwave packaging materials in the near future are also discussed.

Polyimide-Based Capacitive Humidity Sensor

The development of humidity sensors with simple transduction principles attracts considerable interest by both scientific researchers and industrial companies. Capacitive humidity sensors, based on polyimide sensing material with different thickness and surface morphologies, are prepared. The surface morphology of the sensing layer is varied from flat to rough and then to nanostructure called nanograss by using an oxygen plasma etch process. The relative humidity (RH) sensor selectively responds to the presence of water vapor by a capacitance change. The interaction between polyimide and water molecules is studied by FTIR spectroscopy. The complete characterization of the prepared capacitive humidity sensor performance is realized using a gas mixing setup and an evaluation kit. A linear correlation is found between the measured capacitance and the RH level in the range of 5 to 85%. The morphology of the humidity sensing layer is revealed as an important parameter influencing the sensor performance. It is proved that a nanograss-like structure is the most effective for detecting RH, due to its rapid response and recovery times, which are comparable to or even better than the ones of commercial polymer-based sensors. This work demonstrates the readiness of the developed RH sensor technology for industrialization.

Facile Preparation of Crosslinked PAN Membranes Based on Thiol-Ene Photopolymerization

To improve the mechanical strength and antipollution properties of membranes, this research presents a facile method to prepare crosslinked polyacrylonitrile (PAN) membranes. This was achieved firstly by radical copolymerization with acrylonitrile, allyl methacrylate and sulfobetaine methacrylamide. Then, the copolymer was crosslinked by a thiol-ene click reaction under UV irradiation. Finally, the crosslinked membranes were prepared by traditional immersion precipitation phase inversion. These prepared membranes showed excellent water-pressure resistance and solvent swelling, owing to their crosslinked structure. This research will help in preparing crosslinked membranes through facile crosslinking under mild reaction conditions. The betaine structure also considerably improved the antifouling properties of the membranes.