Nephrogenic diabetes insipidus (NDI), which can be congenital or acquired, results from the failure of the kidney to respond to the anti-diuretic hormone (ADH). This will lead to excessive water loss from the body in the form of urine. The kidney, therefore, has a crucial role in maintaining water balance and it is vital to restore this function in an artificial kidney. Herein, an ultrasensitive and highly selective aptameric graphene-based field-effect transistor (GFET) sensor for ADH detection was developed by directly immobilizing ADH-specific aptamer on a surface-modified suspended graphene channel. This direct immobilization of aptamer on the graphene surface is an attempt to mimic the functionality of collecting tube $V_2$ receptors in the ADH biosensor. This aptamer was then used as a probe to capture ADH peptide at the sensing area which leads to changes in the concentration of charge carriers in the graphene channel. The biosensor shows a significant increment in the relative change of current ratio from 5.76 to 22.60 with the increase of ADH concentration ranging from 10 ag/mL to 1 pg/mL. The ADH biosensor thus exhibits a sensitivity of 50.00 µA· ${\left(\mathrm{g}/\mathrm{mL}\right)}^{-1}$ with a limit of detection as low as 3.55 ag/mL. In specificity analysis, the ADH biosensor demonstrated a higher current value which is 338.64 µA for ADH-spiked in phosphate-buffered saline (PBS) and 557.89 µA for ADH-spiked in human serum in comparison with other biomolecules tested. This experimental evidence shows that the ADH biosensor is ultrasensitive and highly selective towards ADH in PBS buffer and ADH-spiked in human serum.

The unique monoatomic structure of graphene makes it as an enticing material to be used in sensitive detection of analytes in biosensing applications. Implementation of graphene as a conducting channel in graphene based field effect transistor (GFET) allows ultrasensitive detection of analytes in a targeted sample. Herein, we have investigated the transfer characteristics of GFET for biosensing applications. GFET was modelled and simulated using Lumerical DEVICE charge transport solver (DEVICE CT). The device shows ambipolar curve and achieved minimum conductivity of 0.00012 A at Dirac point. However, the Dirac point shifts to the right and introduces significant change in the minimum conductivity as drain voltage bias is increased. This shows that external factors such as doping can influence the surface charges of the GFET and this property of graphene is crucial in ultrasensitive detection of analytes in biosensing applications.

The race towards the development of user-friendly, portable, fast-detection, and low-cost devices for healthcare systems has become the focus of effective screening efforts since the pandemic attack in December 2019, which is known as the coronavirus disease 2019 (COVID-19) pandemic. Currently existing techniques such as RT-PCR, antigen–antibody-based detection, and CT scans are prompt solutions for diagnosing infected patients. However, the limitations of currently available indicators have enticed researchers to search for adjunct or additional solutions for COVID-19 diagnosis. Meanwhile, identifying biomarkers or indicators is necessary for understanding the severity of the disease and aids in developing efficient drugs and vaccines. Therefore, clinical studies on infected patients revealed that infection-mediated clinical biomarkers, especially pro-inflammatory cytokines and acute phase proteins, are highly associated with COVID-19. These biomarkers are undermined or overlooked in the context of diagnosis and prognosis evaluation of infected patients. Hence, this review discusses the potential implementation of these biomarkers for COVID-19 electrical biosensing platforms. The secretion range for each biomarker is reviewed based on clinical studies. Currently available electrical biosensors comprising electrochemical and electronic biosensors associated with these biomarkers are discussed, and insights into the use of infection-mediated clinical biomarkers as prognostic and adjunct diagnostic indicators in developing an electrical-based COVID-19 biosensor are provided.

The exclusive monoatomic framework of graphene makes it as an alluring material to be implemented in electronic devices. Thus, using graphene as charge carrying conducting channel material in Field Effect Transistors (FET) expedites the opportunities for production of ultrasensitive biosensors for future device applications. However, performance of GFET is influenced by various parameters, particularly by the length of conducting channel. Therefore, in this study we have investigated channel length scaling in performance of graphene field effect transistor (GFET) via simulation technique using Lumerical DEVICE software. The performance was analyzed based on electrical characterization of GFET with long and short conducting channels. It proves that conducting channel lengths have vast effect on ambipolar curve where short channel induces asymmetry in transfer characteristics curve where the n-branch is suppressed. Whereas for output characteristics, the performance of GFET heavily degraded as the channel length is reduced in short channels of GFET. Therefore, channel length scaling is a vital parameter in determining the performance of GFET in various fields, particularly in biosensing applications for ultrasensitive detection.

This paper investigates the effect of squeeze film damping on a micromechanical structure that oscillates due to the pressure distribution on moveable top plate that pair with perforated backplate. The damping characteristics are analytically evaluated to establish the optimum design that increase dynamics performance. The squeezed film damping governing equation, the Reynolds equation, is the fundamental equation of this work. The damping coefficient, air gap damping and viscous damping are calculated by using Skvor's formula. The size of perforation holes and air gap thickness that influencing the squeeze film damping were studied. Analytical solution with various holes structure are summarized. Overall, the 3μm of hole radius, 50μm of holes center-to-center distance and 4μm of air gap thickness were found to be the best in order to reduce squeeze film damping in capacitive microphone.