Manipulating OH- -Mediated Anode-Cathode Cross-Communication Toward Long-Life Aqueous Zinc-Vanadium Batteries.

The anode-cathode interplay is an important but rarely considered factor that initiates the degradation of aqueous zinc ion batteries (AZIBs). Herein, to address the limited cyclability issue of V-based AZIBs, Al2 (SO4 )3 is proposed as decent electrolyte additive to manipulate OH- -mediated cross-communication between Zn anode and NaV3 O8 ⋅ 1.5H2 O (NVO) cathode. The hydrolysis of Al3+ creates a pH≈0.9 strong acidic environment, which unexpectedly prolongs the anode lifespan from 200 to 1000 h. Such impressive improvement is assigned to the alleviation of interfacial OH- accumulation by Al3+ adsorption and solid electrolyte interphase formation. Accordingly, the strongly acidified electrolyte, associated with the sedated crossover of anodic OH- toward NVO, remarkably mitigate its undesired dissolution and phase transition. The interrupted OH- -mediated communication between the two electrodes endows Zn||NVO batteries with superb cycling stability, at both low and high scan rates.

Gradient-Based Colorimetric Array Sensor for Continuous Monitoring of Multiple Gas Analytes.

Colorimetry is widely used in chemical sensing due to its high sensitivity and high selectivity. However, most colorimetric sensors are one-time use because the color-producing reactions or bindings are usually irreversible. In addition, traditional colorimetric sensors like the detection tubes are bulky and packed individually, making parallel sensing of multiple analytes difficult. Here, we demonstrate a gradient-based colorimetric array sensor (GCAS) to overcome these limitations. Different colorimetric sensing elements are inkjet-printed as parallel straight lines on a porous substrate. Lateral transport of analytes across the substrate creates color gradients on the sensing elements. The color gradients shift along the transport direction over time, and GCAS tracks the gradient shifts and converts them into analyte concentrations in real time. Using a low-cost complementary metal-oxide semiconductor imager, we show detection of three air pollutants using a single GCAS chip and 24 h continuous monitoring of ambient ozone.

A Miniaturized Particulate Matter Sensing Platform based on CMOS imager and Real Time Image Processing.

A miniaturized particulate matter (PM) sensing platform was developed. The platform uses a CMOS imager as sensor, electrostatic particle collector to collect ambient PM on an imaging substrate, and a laser diode as light source to scatter light from the particles. Image processing based PM sensing algorithm was developed to obtain particle number, size and size distribution in real time. The system is compact, power efficient, and low cost. The PM sensing platform is suitable for personal PM exposure monitoring with applications in environmental health, occupational and epidemiological studies.

Real-time Simutaneous Separation and Detection of Chemicals using Integrated Micro Column and Surface Plasmon Resonance Imaging Micro-GC.

An integrated and miniaturized Micro-Gas Chromatography with real-time imaging capability for simultaneous chemical separation and detection was developed. Surface Plasmon Resonance imaging (SPRi) was used as a sensitive and real-time imaging based detector for various gaseous chemical mixtures and good gas chromatographs were obtained. The system integrated a home-made miniaturized molecular sieve packed spiral micro-channel column with the SPRi imaging chip and real-time chemical separation and detection were demonstrated using alkanes. The chemical separation processes were simulated using COMSOL and matched well with experimental results. The system enabled the study of chemical separation processes in real-time by miniaturizing and integrating the Micro-GC separation and detection units. This approach can be expanded to multidimensional GC development.

Noncontact Monitoring of Blood Oxygen Saturation Using Camera and Dual-Wavelength Imaging System.

We present a noncontact method to monitor blood oxygen saturation (SpO2). The method uses a CMOS camera with a trigger control to allow recording of photoplethysmography (PPG) signals alternatively at two particular wavelengths, and determines the SpO2 from the measured ratios of the pulsatile to the nonpulsatile components of the PPG signals at these wavelengths. The signal-to-noise ratio (SNR) of the SpO2 value depends on the choice of the wavelengths. We found that the combination of orange (λ = 611 nm) and near infrared (λ = 880 nm) provides the best SNR for the noncontact video-based detection method. This combination is different from that used in traditional contact-based SpO 2 measurement since the PPG signal strengths and camera quantum efficiencies at these wavelengths are more amenable to SpO2 measurement using a noncontact method. We also conducted a small pilot study to validate the noncontact method over an SpO2 range of 83%-98%. This study results are consistent with those measured using a reference contact SpO2 device ( r = 0.936, ). The presented method is particularly suitable for tracking one's health and wellness at home under free-living conditions, and for those who cannot use traditional contact-based PPG devices.