Fabrication and Characterization of Partially Conjugated Poly (Vinyl Alcohol) Based Resistive Humidity Sensor

Humidity sensors have been developed based on a wide variety of materials such as ceramic, semiconductors and polymers. However, slow recovery rates is one of the major ongoing concerns of flexible poly(vinyl alcohol) (PVA) based humidity sensors. In this study, a simple, cost effective, fast responding, fast recovering and high sensitive, resistive poly(vinyl alcohol) (PVA) based humidity sensor was developed through the development of controlled conjugation system in PVA polymer matrix by hydroiodic acid (HI) treatment. Changes in structural and morphological parameters on sensor performance were investigated. Resistance of the sensor increased from 10.2 kΩ to 4.5 MΩ when relative humidity (RH) decreased from 92% to 7% RH, while capacitance varied slightly from 70 nF to 100 nF. The response and recovery times of the sensor were measured to be 224.6 s and 56.3 s respectively at room temperature when switching between 50% and 90% RH, demonstrating excellent performance towards fluctuating humidity levels. The results indicate the sensor is capable of measuring humidity levels above 30% with full scale recovery by only consuming 25% of the sensing time. Cost-effective, flexible, fast recovery and resistive sensing can be recognized as the most effective potential applications for this sensor

Drug-Loaded Halloysite Nanotube-Reinforced Electrospun Alginate-Based Nanofibrous Scaffolds with Sustained Antimicrobial Protection

Halloysite nanotube (HNT)-reinforced alginate-based nanofibrous scaffolds were successfully fabricated by electrospinning to mimic the natural extracellular matrix (ECM) structure which is beneficial for tissue regeneration. An antiseptic drug, cephalexin (CEF)-loaded HNT, was incorporated into the alginate-based matrix to obtain sustained antimicrobial protection and robust mechanical properties, the key criteria for tissue engineering applications. Electron microscopic imaging and drug release studies revealed that CEF had penetrated into the lumen space of the HNT and also deposited on the outer walls, with a total loading capacity of 30 wt %. Moreover, the diameter of alginate-based nanofibers of the scaffolds ranged from 40 to 522 nm with well-aligned HNTs, resulting in superior mechanical properties. For instance, the addition of 5% (w/w) HNT improved the tensile strength (σ) and elastic modulus by 3-fold and 2-fold, respectively, compared to those of the alginate-based scaffolds without HNT. The fabricated scaffolds exhibited remarkable antimicrobial properties against both Gram-negative and Gram-positive bacteria, and the cytotoxicity studies confirmed the nontoxicity of the fabricated scaffolds. Drug release kinetics showed that CEF inside HNTs diffuses within 24 h and that the diffusion of the drug is delayed by 7 days once the CEF-loaded HNTs are incorporated into the alginate-based nanofibers. These fabricated alginate-based electrospun scaffolds with enhanced mechanical properties and sustained antimicrobial protection hold great potential to be used as artificial ECM scaffolds for tissue engineering applications