Tremendous demands for sensitive and reliable label-free biosensors have stimulated intensive research into developing miniaturized radiofrequency resonators for a wide range of biomedical applications. Here, we report the development of a robust, reusable radiofrequency resonator based integrated passive device biosensor chip fabricated on a gallium arsenide substrate for the detection of glucose in water-glucose solutions and sera. As a result of the highly concentrated electromagnetic energy between the two divisions of an intertwined spiral inductor coupled with an interdigital capacitor, the proposed glucose biosensor chip exhibits linear detection ranges with high sensitivity at center frequency. This biosensor, which has a sensitivity of up to 199[emsp14]MHz/mgmL-1 and a short response time of less than 2[emsp14]sec, exhibited an ultralow detection limit of 0.033[emsp14][mgr]M and a reproducibility of 0.61% relative standard deviation. In addition, the quantities derived from the measured S-parameters, such as the propagation constant ([ggr]), impedance (Z), resistance (R), inductance (L), conductance (G) and capacitance (C), enabled the effective multi-dimensional detection of glucose.

A reusable robust radio frequency (RF) biosensor with a rectangular meandered line (RML) resonator on a gallium arsenide substrate by integrated passive device (IPD) technology was designed, fabricated and tested to enable the real-time identification of the glucose level in human serum. The air-bridge structure fabricated by an IPD technology was applied to the RML resonator to improve its sensitivity by increasing the magnitude of the return loss (S21). The resonance behaviour, based on S21 characteristics of the biosensor, was analysed at 9.20 GHz with human serum containing different glucose concentration ranging from 148-268 mg dl(-1), 105-225 mg dl(-1) and at a deionised (D) water glucose concentration in the range of 25- 500 mg dl(-1) for seven different samples. A calibration analysis was performed for the human serum from two different subjects and for D-glucose at a response time of 60 s; the reproducibility, the minimum shift in resonance frequency and the long-term stability of the signal were investigated. The feature characteristics based on the resonance concept after the use of serum as an analyte are modelled as an inductor, capacitor and resistor. The findings support the development of resonance-based sensing with an excellent sensitivity of 1.08 MHz per 1 mg dl(-1), a detection limit of 8.01 mg dl(-1), and a limit of quantisation of 24.30 mg dl(-1).

We report the excellent sensing performance and health detecting applications of a flexible capacitive pressure sensor based on a Ti ₃ C ₂ T _x (MXene)/polyvinyl pyrrolidone (PVP) composite nanofiber membrane.

Self‐powered pressure detection using smart wearable devices is the subject of intense research attention, which is intended to address the critical need for prolonged and uninterrupted operations. Current piezoelectric and triboelectric sensors well respond to dynamic stimuli while overlooking static stimuli. This study proposes a dual‐response potentiometric pressure sensor that responds to both dynamic and static stimuli. The proposed sensor utilizes interdigital electrodes with MnO₂/carbon/polyvinyl alcohol (PVA) as the cathode and conductive silver paste as the anode. The electrolyte layer incorporates a mixed hydrogel of PVA and phosphoric acid. The optimized interdigital electrodes and sandpaper‐like microstructured surface of the hydrogel electrolyte contribute to enhanced performance by facilitating an increased contact area between the electrolyte and electrodes. The sensor features an open‐circuit voltage of 0.927 V, a short‐circuit current of 6 µA, a higher sensitivity of 14 mV/kPa, and outstanding cycling performance (>5000 cycles). It can accurately recognize letter writing and enable capacitor charging and LED lighting. Additionally, a data acquisition and display system employing the proposed sensor, which facilitates the monitoring of athletes’ rehabilitation training, and machine learning algorithms that effectively guide rehabilitation actions are presented. This study offers novel solutions for the future development of smart wearable devices.

In recent years, flexible pressure sensors have become an important part of soft electronics due to their tactile sensing abilities. However, manufacturing pressure sensors with high sensing performance and excellent applicability is still a great challenge. In this paper, we report the fabrication, sensing performance and applications of a flexible capacitive pressure sensor based on a polyvinyl pyrrolidone (PVP) nanofiber membrane (NM), which has a better biocompatibility and a wider applicability than the traditional dielectric layer materials. The cost-effective process of electrospinning and an ultra-violet (UV) photochemical aftertreatment are employed to prepare a PVP NM, which contribute to improving the performance of the sensor. The experimental results show that our sensor exhibits a fast response/recovery time (41/36 ms), a high sensitivity (0.278 kPa⁻¹ at 0–2 kPa), a wide pressure range (0–200 kPa), an ultra-low detection limit (∼50 Pa) and an excellent stability (8000 cycles). Thanks to its superior performance, the sensor can be used to monitor various subtle physiological and physical signals, such as pulse rate, respiration, mouse clicks, body movement and air flow. In addition, a 4 × 4 sensor array is fabricated that can map objects with various geometries, which demonstrates its ability to accurately identify the spatial pressure distribution. The developed high-performance and wide-applicative flexible sensor can provide new opportunities for innovative applications of advanced human–computer interface systems.