Wearable flexible sensors face many harsh environments in practical applications. However, developing corrosion-resistant conductive hydrogel-based flexible sensing materials for applications under harsh conditions remains a formidable challenge because significant damages are caused by the inevitable solvent corrosion on the polymer network structure. Here, a novel conductive hydrogel with superior chemical stability and stretchability was intelligently designed and successfully fabricated by introducing a small amount of N,N′-methylenebis(acrylamide) (BIS) and graphene oxide (GO) as chemical and physical crosslinking agents into the polymer interpenetrating network formed by poly(N-isopropylacrylamide) (PNIPAM) and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS). Benefiting from the introduction of strong chemical bonds and GO nanosheets, the synthesized conductive hydrogel exhibited swelling resistance to strong alkali/polar solvents and surprising chemical structure stability to all solvents. Interestingly, the hydrogel-based sensor could even achieve an accurate and a stable mechanical sensing of tensile strain in a variety of solvents. Furthermore, the hydrogel sensor is featured by strong adhesion, high reliability, and wide sensing ranges for detecting and distinguishing various human motions. Therefore, such design strategy greatly extends the application range of conductive hydrogels in flexible electronic devices and shows great potential in the applications of electronic skins and soft robots in harsh environments (especially in various solvents).

The massive amount of water-soluble urea used leads to nutrient loss and environmental pollution in both water and soil. The aim of this study was to develop a novel lignin-based slow-release envelope material that has essential nitrogen and sulfur elements for plants. After the amination reaction with a hydrolysate of yak hair keratin, the coating formulation was obtained by adding different loadings (2, 5, 8, 14 wt%) of aminated lignin (AL) to 5% polyvinyl alcohol (PVA) solution. These formulations were cast into films and characterized for their structure, thermal stability, and mechanical and physicochemical properties. The results showed that the PVA-AL (8%) formulation had good physical and chemical properties in terms of water absorption and mechanical properties, and it showed good degradation in soil with 51% weight loss after 45 days. It is suitable for use as a coating material for fertilizers. Through high-pressure spraying technology, enveloped urea particles with a PVA-AL (8%) solution were obtained, which showed good morphology and slow-release performance. Compared with urea, the highest urea release was only 96.4% after 30 days, conforming to Higuchi model, Ritger–Peppas model, and second-order dynamic model. The continuous nitrogen supply of PVA-AL coated urea to Brassica napus was verified by potting experiments. Therefore, the lignin-based composite can be used as a coating material to produce a new slow-release nitrogen fertilizer for sustainable crop production.

A modified hydrothermal method for the synthesis of TiO₂material to achieve a more efficient visible light response.