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.

This paper presents highly selective, low-loss and miniaturized balun devices fabricated using Integrated Passive Device (IPD) technique for GSM band (900/1800 MHz) and WiFi band (2400 MHz) in mobile applications. Balun devices were fabricated on a gallium arsenide (GaAs) substrate using IPD fabrication process to reduce the overall size (0.05 λg × 0.036 λg at 900 MHz). Each device is the combination of lattice lumped structure with a low pass filter (LPF) and a high pass filter (HPF) configuration. This structural formation of lumped elements helps to reduce the phase mismatch error in balun devices. For all balun devices, the measured results indicated a minimum amplitude imbalance (< 0.47 dB) and low phase imbalance (180 ± 2.6°). Mathematically calculated, calculated after considering parasitic effects, simulated and measured results exhibited a good correlation. The return loss is below 18 dB and insertion loss is below 0.25 dB for the entire fabricated devices. Balun device with a center frequency of 900 MHz has given the best results amongst all fabricated devices.

The inherent trade-off among the level of sensing electromagnetic (EM)-energy and the performance parameters, and consequently, the inevitable nonlinearity at high-sensitivity renders the performance-optimization of a micro-fabricated microwave resonant sensor very difficult. This paper presents a shunt capacitor-based EM-energy splitting technique to generate three distinct levels of coupled EM-energies in micro-fabricated microwave LC resonant ethanol sensors and investigate the quantitative correlation among the resulting energy level, sensitivity, linearity, and signal-to-noise ratio (SNR). Gallium arsenide (GaAs)-based micro-fabrication technique is used to implement the proposed microwave LC resonators employing an air-bridged circular spiral inductor and meandered-line coupling capacitors. The experimental results reveal that the performance-optimized sensor rapidly and accurately quantifies the wide range of nanoliter (200 nl) ethanol concentrations (5%–50% vol.) with a high-sensitivity (1.817 MHz/% vol.), good linearity, and SNR; thus, highlighting the significance of the proposed method to develop a high-performance ethanol sensor. In addition, ethanol-dependent complex permittivity, which is calculated using the measured central frequencies and loaded-quality factors, reveals a negative correlation between the real-permittivity and ethanol concentration of the aqueous solution.

High density electrocorticography (ECoG)-based microelectrode arrays (MEAs) are fabricated to timely record the neural activities to provide the fundamental understanding in neuroscience and biomedical engineering. This paper aims to introduce a device-based concept and wafer-scale fabrication process for MEAs. Flexible and biocompatible polyimide is applied on MEAs to bear all possible stress and strain. Detailed fabrication key techniques, including surface treatment, polyimide stability measurement, evaporation process, and curing conditions, have been discussed thoroughly. Moreover, the fabricated polyimide-based MEAs are surface-mounted on well-packaged printed circuit boards (PCBs) via a slot-type connector without any additional wire bonding to make the signal recording process easier. An absence seizure was recorded during the in vivo test, which shows the availability of signal recording based on the presented MEAs. The proposed MEAs could be remained at the skull, while the connector and PCBs can be disassembled apart. Therefore, the testing sample will get less suffering. To verify the robustness of the fabricated MEAs, the impedance properties were characterized using electrochemical impedance spectroscopy. The measured results indicate an average impedance of 12.3 ± 0.675 kΩ at 1 kHz. In total, 10 groups of MEAs were sample tested, and over 90% of the total 60 channels per 1-MEAs operated efficiently.