Search

Selectivity and enhanced response remain an issue in gaseous acetone sensing. This report demonstrates MoS2 on MXene (Ti3C2Tx) contact based on a low-cost flexible sensor for selective detection of acetone using principle component analysis and binary logistic regression. The piezotronic effect enhances the response of the sensor. The fabricated acetone sensor exhibited an excellent response of ∼5.84% at lower concentrations of acetone ranging from 5 to 30 ppm at room temperature (25 °C). The sensor's response values with (5%) and without applied external strain were calculated to be approximately 5.84 and 7.21%, respectively. This suggested an increment in the sensing performance under the applied external strain with an improved response time (448 s). A detailed study is presented in terms of comparative performance of MoS2 and MXene/MoS2 under strained and unstrained conditions. Principle component analysis and binary logistic regression techniques were used to successfully selectively detect acetone among other eight VOC (volatile organic compound) (toluene, benzene, isopropyl alcohol, formaldehyde, hydrogen sulfide, dimethyl sulfide, ethanol, and methanol) gases. A real-time breath analyzer is presented wherein an artificial breath consisting of different humidities and acetone was created, and acetone was sensed using the fabricated sensor. Finally, a proof of concept for the flexible bracelet is presented for the on-site detection of acetone levels in human breath to monitor diabetes at the point-of-care setting. This successful demonstration of the acetone sensor presents future possible avenues for healthcare, food, and industrial research. [ABSTRACT FROM AUTHOR]

The design and implementation of a portable fluorescence-based vapor sensing system are described. The system incorporates previously developed microsensor array technology into a compact, low-power device capable of collecting and delivering ambient vapor samples to the array while monitoring and recording the fluorescent responses of the sensors. The sensors respond differentially when exposed to a sample vapor and, when processed using a support vector machine (SVM) pattern recognition algorithm, are shown to discriminate between three classes of petroleum distillates. The system was characterized using sample vapors prepared under several different conditions in three sensing scenarios. The first scenario demonstrates the basic operational capability of the device in the field by presenting high concentration vapors to the array. The second scenario introduces the potential for a greater degree of variability in both sample vapor concentration and composition in an effort to emulate real-world sensing conditions. The third scenario uses an on-board trained pattern recognition algorithm to identify unknown vapors as their responses are collected. The device demonstrated high classification accuracy throughout the field tests and is capable of improving its classification accuracy when challenged with samples presented under variable ambient conditions by enhancing the signal-to-noise ratio of the array response.

Deep eutectic solvent (DES) gel electrolytes have recently emerged as promising alternatives to ionic liquid- or water-based gels for "ionic skin" sensor applications. Researchers have also been exploring the effects that varying amounts of water may have on the local hydrogen bonding environment within a few model DES systems. In this study, the physical properties and ionic conductivities of biopolymer (gelatin)-supported gels featuring two established DESs and three DES/water mixture formulations are investigated and compared. The DES/water mixtures are formed by combining choline chloride with one of three organic hydrogen bond donors (HBDs), ethylene glycol, glycerol, or 1,2-propanediol, in a 1:2 molar ratio, together with a controlled amount of water, 25 mol % (approximately 5-6 wt % water). For the same fixed gelatin content (20 wt %), DES/water mixture gel Young's modulus values are found to be tunable based on the organic HBD identity, increasing 6-fold from 7 (1,2-propanediol) to 42 (glycerol) kPa. Furthermore, large differences are observed in the resulting gel properties when water has been intentionally added to well-studied DESs. Coformulation with water is found to increase ethylene glycol-based DES gel toughness, measured via tensile testing, from 23 to 68 kJ/m 3 while simultaneously boosting gel room temperature ionic conductivity from 3.3 to 5.2 mS/cm. These results highlight the multiple roles that controlled amounts of water in DES can play within gelatin-supported DES/mixture gel electrolytes, such as influencing gelatin self-assembly and reducing local viscosity to promote facile ion transport.

Oxygen is essential to cell survival and tissue function. Not surprisingly, ischemia resulting from myocardial infarction induces cell death and tissue necrosis. Attempts to regenerate myocardial tissue with cell based therapies exacerbate the hypoxic stress by further increasing the metabolic burden. In consequence, implanted tissue engineered cardiac tissues suffer from hypoxia-induced cell death. Here, we report on the generation of oxygen-generating hydrogels composed of calcium peroxide (CPO) laden gelatin methacryloyl (GelMA). CPO-GelMA hydrogels released significant amounts of oxygen for over a period of 5 days under hypoxic conditions (1% O 2 ). The released oxygen proved sufficient to relieve the metabolic stress of cardiac side population cells that were encapsulated within CPO-GelMA hydrogels. In particular, incorporation of CPO in GelMA hydrogels strongly enhanced cell viability as compared to GelMA-only hydrogels. Importantly, CPO-based oxygen generation reduced cell death by limiting hypoxia-induced necrosis. The current study demonstrates that CPO based oxygen-generating hydrogels could be used to transiently provide oxygen to cardiac cells under ischemic conditions. Therefore, oxygen generating materials such as CPO-GelMA can improve cell-based therapies aimed at treatment or regeneration of infarcted myocardial tissue.