Hydrophobic and Stable MXene-Polymer Pressure Sensors for Wearable Electronics.

Ti3C2Tx MXene has exhibited great potential for use in wearable devices, especially as pressure sensors, due to its lamellar structure, which changes its resistance as a function of interlayer distance. Despite the good performance of the reported pure MXene pressure sensors, their practical applications are limited by moderate flexibility, excessively high MXene conductivity, and environmental effects. To address the above challenges, we incorporated multilayer MXene particles into hydrophobic poly(vinylidene fluoride) trifluoroethylene (P(VDF-TrFE)) and prepared freestanding, flexible, and stable films via spin-coating. These films were assembled into highly sensitive piezoresistive pressure sensors, which show a fast response time of 16 ms in addition to excellent long-term stability with no obvious responsivity attenuation when the sensor is exposed to air, even after 20 weeks. Moreover, the fabricated sensors could monitor human physiological signals such as knee bending and cheek bulging and could be used for speech recognition. The mapping spatial pressure distribution function was also demonstrated by the designed 10 × 10 integrated pressure sensor array platform.

On the Effect of Sweat on Sheet Resistance of Knitted Conductive Yarns in Wearable Antenna Design.

Researchers are looking for new methods to integrate sensing capabilities into textiles while maintaining the durability, flexibility, and comfort of the garment. One method for imparting sensing capabilities into garments is through coupling conductive yarns with the radio frequency identification (RFID) technology. These smart devices have exhibited promising results for short-term use. However, long-term studies of their performance are still needed to evaluate their performance over a longer period. Like all garments, wearable sensors are susceptible to environmental factors during use. These factors can lead to dielectric coupling and corrosion of conductive yarns, which has the potential to degrade the performance of the device. This letter analyzes the effect of sweat and moisture on silver-coated nylon yarn by extracting the sheet resistance at 913 MHz from transmission line measurements. HFSS simulation shows the level of perturbation in antenna performance as sheet resistance increased with each cycle of sweat-immersion, washing, and drying.

Investigation of nanoyarn preparation by modified electrospinning setup.

Higher ordered structures of nanofibers, including nanofiber-based yarns and cables, have a variety of potential applications, including wearable health monitoring systems, artificial tendons, and medical sutures. In this study, twisted assemblies of polyacrylonitrile (PAN), polyvinylidene fluoride trifluoroethylene (PVDF-TrFE), and polycaprolactone (PCL) nanofibers were fabricated via a modified electrospinning setup, consisting of a rotating cone-shaped copper collector, two syringe pumps, and two high voltage power supplies. The fiber diameters and twist angles varied as a function of the rotary speed of the collector. Mechanical testing of the yarns revealed that PVDF-TrFe and PCL yarns have a higher strain-to-failure than PAN yarns, reaching 307% for PCL nanoyarns. For the first time, the porosity of nanofiber yarns was studied as a function of twist angle, showing that PAN nanoyarns are more porous than PCL yarns.

Detection of diisocyanates in nesting material associated with mortality in pigeon chicks.

Diisocyanates, commonly used in the production of polyurethane foams, paints, elastomers, varnishes, and coatings, are considered among the most hazardous inhalation toxicants. The present report describes 2 unusual cases of mortality in pigeon chicks associated with nesting material contaminated by diisocyanates. Case 1 was submitted by a racing pigeon breeder who had lost all the hatchlings (n = 125) following replacement of the nesting material with a different lot. All adult birds appeared healthy, and hatchability was not significantly affected, but hatchlings became lethargic and dyspneic after a day of hatch. At necropsy, dark wet lungs were found in the hatchlings. Case 2 was submitted by a show-roller pigeon breeder. In this case, the owner reported lower hatchability, and all hatchlings (approximately 100) died within 2 days of hatching with clinical signs similar to the first case. Necropsy did not reveal any significant findings. For both cases, nesting materials were screened for toxic compounds using gas chromatography-mass spectrometry. Toluene-2,4-diisocyanate (approximately 190-290 ppm) and 4,4'-methylene diphenyl diisocyanate (unquantified) were detected in the nesting pads. While there is very limited information on toxicosis in birds, there are reports of inhalant exposure of diisocyanates causing pulmonary edema and death in various mammalian species. Although cause-effect relationship of mortality and the nesting material was not established in the present cases, the presence of toxic compounds in the nesting materials is a cause for concern. Further investigation is needed to determine the prevalence and toxicity of diisocyanates-contaminated nesting material in avian species.