Highly adhesive chitosan/poly(vinyl alcohol) hydrogels via the synergy of phytic acid and boric acid and their application as highly sensitive and widely linear strain sensors.

In recent years, flexible strain sensors have attracted increasing interest, and accurate sensing and comfortable wearables are highly demanded. However, current flexible strain sensors fail to have wide linearity and high sensitivity simultaneously, and their adhesion is insufficient for convenient wear and precise motion monitoring. Herein, chitosan/poly(vinyl alcohol) hydrogels with phytic acid (PA) and boric acid (BA) as crosslinkers (CS/PVA-PA-BA hydrogels) were fabricated. The synergy of phytic acid and boric acid not only improved the mechanical properties of the obtained hydrogels (1070% of fracture strain and 0.83 MPa of fracture stress), but also provided them with outstandingly strong adhesion. Their adhesive strength was up to 527 kPa for a variety of materials, including glass, silica rubber, steel, polytetrafluoroethylene (PTFE), and skin. In addition, the hydrogel-based strain sensor demonstrated high sensitivity (gauge factor = 4.61), a wide linear strain range (up to 1000%, R2 = 0.996), fast response time (90 ms), and good stability. A flexible strain sensor with such high sensitivity and wide linear range simultaneously, to the best of our knowledge, has never been reported before. The development of CS/PVA-PA-BA hydrogels is expected to inspire a novel method for high-adhesive and high-sensing-performance wearable electronics.

Conductive Hydrogels with Ultrastretchability and Adhesiveness for Flame- and Cold-Tolerant Strain Sensors.

Hydrogel strain sensors with extreme temperature tolerance have recently gained great attention. However, the sensing ability of these hydrogel strain sensors changes with temperature, resulting in the variety of output signals that causes signal distortion. In this study, double-network hydrogels comprising SiO2 nanoparticles composed of polyacrylamide and phytic acid-doped polypyrrole were prepared and applied on strain sensors with a wide sensing range, high adhesiveness, and invariable strain sensitivity under flame and cold environments. The hydrogels had stable conductivity, excellent adhesive strength of up to 79.7 kPa on various substrates, and high elongation of up to 1896% at subzero temperature and after heating. They also exhibited effective flame retardancy with low surface temperature (71.2 °C) after 1200 s of heating (200 °C) and antifreezing properties at a low temperature of -20 °C. Remarkably, even under cold temperature and heat treatment, the hydrogel-based strain sensor displayed consistent sensing behaviors in detecting human motions with a broad strain range (up to 500%) and steady gauge factor (GF, ∼2.90). Therefore, this work paves the way for the applications of hydrogel sensors in robotic skin, human-mechanical interfaces, and health monitoring devices under harsh operating environments.

Thalidomide as a treatment for inflammatory bowel disease in children and adolescents: A systematic review.

WHAT IS KNOWN AND OBJECTIVE: Thalidomide is used off-label for the treatment of inflammatory bowel disease (IBD) and not as a first-line treatment option. The instructions clearly state that thalidomide is contraindicated in children because its safety and effectiveness in children are unknown. In this article, we review the efficacy and safety of thalidomide as a treatment for IBD in children and adolescents. METHODS: We searched PubMed, Embase, the Cochrane Library, CNKI, WanFang Data, CBM database [from the date of database establishment to June 2019] and clinical trials [systematic review and meta-analysis, randomized controlled trials (RCTs), cohort studies, case-control studies and case series studies] for studies concerning the use of thalidomide as a treatment for IBD in children and adolescents. RESULTS AND DISCUSSION: Seven studies (two RCTs and five case series), which included 134 children and adolescents (32 with ulcerative colitis, 102 with Crohn's disease), met the inclusion criteria. The included studies showed that the clinical remission rate of thalidomide was 44%-100% and the steroid tapering rate was 50%-100% in children and adolescents with refractory IBD. Peripheral neuropathy was the most common major adverse reaction, and it appeared to be cumulative dose-dependent. WHAT IS NEW AND CONCLUSION: Thalidomide as a treatment for refractory IBD in children and adolescents can improve clinical remission and achieve longer-term maintenance of remission. Peripheral neuropathy is the main adverse drug reaction, and it can be monitored and prevented. It is necessary to fully communicate with parents and obtain informed consent before using this drug.