High-Sensitivity, Quantified, Linear and Mediator-Free Resonator-Based Microwave Biosensor for Glucose Detection.

This article presents a high-sensitivity, quantified, linear, and mediator-free resonator-based microwave biosensor for glucose sensing application. The proposed biosensor comprises an air-bridge-type asymmetrical differential inductor (L) and a center-loaded circular finger-based inter-digital capacitor (C) fabricated on Gallium Arsenide (GaAs) substrate using advanced micro-fabrication technology. The intertwined asymmetrical differential inductor is used to achieve a high inductance value with a suitable Q-factor, and the centralized inter-digital capacitor is introduced to generate an intensified electric field. The designed microwave sensor is optimized to operate at a low resonating frequency that increases the electric field penetration depth and interaction area in the glucose sample. The microwave biosensor is tested with different glucose concentrations (0.3-5 mg/ml), under different ambient temperatures (10-50 °C). The involvement of advanced micro-fabrication technology effectively miniaturized the microwave biosensor (0.006λ0 × 0.005λ0) and enhanced its filling factor. The proposed microwave biosensor demonstrates a high sensitivity of 117.5 MHz/mgmL-1 with a linear response (r2 = 0.9987), good amplitude variation of 0.49 dB/mgmL-1 with a linear response (r2 = 0.9954), and maximum reproducibility of 0.78% at 2 mg/mL. Additionally, mathematical modelling was performed to estimate the dielectric value of the frequency-dependent glucose sample. The measured and analyzed results indicate that the proposed biosensor is suitable for real-time blood glucose detection measurements.

Coherently parallel fiber-optic distributed acoustic sensing using dual Kerr soliton microcombs.

Fiber-optic distributed acoustic sensing (DAS) has proven to be a revolutionary technology for the detection of seismic and acoustic waves with ultralarge scale and ultrahigh sensitivity, and is widely used in oil/gas industry and intrusion monitoring. Nowadays, the single-frequency laser source in DAS becomes one of the bottlenecks limiting its advance. Here, we report a dual-comb-based coherently parallel DAS concept, enabling linear superposition of sensing signals scaling with the comb-line number to result in unprecedented sensitivity enhancement, straightforward fading suppression, and high-power Brillouin-free transmission that can extend the detection distance considerably. Leveraging 10-line comb pairs, a world-class detection limit of 560 fε/√Hz@1 kHz with 5 m spatial resolution is achieved. Such a combination of dual-comb metrology and DAS technology may open an era of extremely sensitive DAS at the fε/√Hz level, leading to the creation of next-generation distributed geophones and sonars.

Ultrafast Detection and Discrimination of Methanol Gas Using a Polyindole-Embedded Substrate Integrated Waveguide Microwave Sensor.

The fast and sensitive detection of methanol gas using cost-effective sensors in the industry is a significant issue to be addressed. Herein, a polyindole (PIn)-deposited substrate integrated waveguide (SIW) has been introduced to perform quantitative and qualitative methanol gas sensing with quick response and recovery time at room temperature. First, PIn is synthesized and deposited in the microwell etched at the intensified electric field region of the microwave-based cavity resonator, which gives a sensing response through variation of PIn's high-frequency conductivity and dielectric property caused by the adsorption and desorption of methanol gas. Second, an enhanced filling factor and high Q factor have been attained using the proposed microwell etched SIW structure, which exhibits high sensitivity in terms of frequency shift (3.33 kHz/ppm), amplitude shift (0.005 dB/ppm), bandwidth broadening (3.66 kHz/ppm), and loaded Q factor (10.60 Q value/ppm). Third, the gas measurement results reveal excellent long-term stability with a relative standard deviation (RSD) of 0.02% for 7 days, excellent repeatability with an RSD of 0.004%, and desired response and recovery time of 95 and 120 s, respectively. The results indicate that the proposed microwave sensor has great potential to achieve high sensitivity and fast response toward methanol gas molecules at room temperature.

Neuroprotective effect of baicalin on focal cerebral ischemia in rats.

Baicalin, a flavonoid compound from the root of the herb Scutellaria baicalensis Georgi, has been widely used to treat patients with inflammatory disease. The aim of this study was to assess the efficacy of baicalin in a rat model of focal cerebral ischemia. Adult male Sprague-Dawley rat models of cerebral artery occlusion were established and then randomly and equally divided into three groups: ischemia (cerebral ischemia and reperfusion), valproic acid (cerebral ischemia and reperfusion + three intraperitoneal injections of valproic acid; positive control), and baicalin (cerebral ischemia and reperfusion + intraperitoneal injection of baicalin for 21 days). Neurological deficits were assessed using the postural reflex test and forelimb placing test at 3, 7, 14, and 21 days after ischemia. Rat cerebral infarct volume was measured using 2,3,5-triphenyltetrazolium chloride (TTC) staining method. Pathological change of ischemic brain tissue was assessed using hematoxylin-eosin staining. In the baicalin group, rat neurological function was obviously improved, cerebral infarct volume was obviously reduced, and the pathological impairment of ischemic brain tissue was obviously alleviated compared to the ischemia group. Cerebral infarct volume was similar in the valproic acid and baicalin groups. These findings suggest that baicalin has a neuroprotective effect on cerebral ischemia.