A review of bio-impedance devices.

Bio-impedance measurement analysis primarily refers to a safe and a non-invasive technique to analyze the electrical changes in living tissues on the application of low-value alternating current. It finds applications both in the biomedical and the agricultural fields. This paper concisely reviews the origin and measurement approaches for concepts and fundamentals of bio-impedance followed by a critical review on bio-impedance portable devices with main emphasis on the embedded system approach which is in demand due to its miniature size and present lifestyle preference of monitoring health in real time. The paper also provides a comprehensive review of various bio-impedance circuits with emphasis on the measurement and calibration techniques.

Dielectrically Modulated III-V Compound Semiconductor Based Pocket Doped Tunnel FET for Label Free Biosensing Applications.

In this paper, a novel structure of double gate tunnel FET has been proposed and simulated for biosensing applications. The device uses III-V compound semiconductors and an n+ doped pocket at the source channel junction. Biomolecules of different dielectric constants (K) with different charge densities (Nbio), both negative and positive, are inserted in the nano-gap cavities (15 nm ×1.5 nm) that have been created under gates near source channel junction to capture biomolecules. From extensive 2D simulations, ION sensitivity of 4.351 ×108/1.03 ×108/1.514 ×109 , subthreshold swing sensitivity of 15.67/20.21/18.57 mV/dec, and threshold voltage sensitivity of 18/12/23 mV for neutral (K = 12)/negatively charged biomolecules ( [Formula: see text] C/cm2, K = 12)/positively charged biomolecules ( [Formula: see text] C/cm2, K = 12) respectively has been observed. Also, transconductance sensitivity of 9.74 ×107 and ION/IOFF sensitivity of 5.255 ×108 for neutral biomolecules (K = 12) has been calculated. Furthermore, the device performance with one-third filled cavities, two-third filled cavities and fully filled cavities has also been studied. The performance of the proposed biosensor has been compared with the previously published work and it has been observed that the sensitivity of the proposed biosensor is 100 times better than the best reported biosensor.

L-Shaped High Performance Schottky Barrier FET as Dielectrically Modulated Label Free Biosensor.

In this work, we demonstrate the realization of L-Shaped Schottky Barrier FET as a biosensing device with improved sensitivity. The proposed device uses dual material gate with work functions of 4.2 eV (Al) and 4.8 eV (Cu) and Hafnium Oxide (HfO2) as the gate dielectric. In order to detect the biomolecule, a nano-gap cavity is created in the vertical gate (Gate1) by etching out the oxide. The electrical characteristics of biomolecules such as dielectric constant and charge density modulate the Schottky Barrier width, which in turn, changes the drive current of the device. Various sensitivity parameters have been thoroughly investigated at [Formula: see text] and a comparative analysis with the conventional device has been performed. The results so obtained reveal that [Formula: see text] sensitivity of the proposed device is much better for both neutral as well as charged biomolecules (maximum of 21x for neutral, at K = 12; 20x for charged biomolecules at ρ = -5×10 10cm-2, at K = 12). Besides this, the [Formula: see text] sensitivity, transconductance ( [Formula: see text]) sensitivity and selectivity show similar improvements. Further, the proposed device shows better sensitivity performance at low as well as at higher temperatures as compared to the state-of-the-art biosensing devices.