Fully integrated impedimetric deoxyribonucleic acid biosensor design using 0.18 um complementary metal oxide semiconductor technology

Abstract

Deoxyribonucleic acid (DNA) biosensor is a powerful tool that utilizes the DNA hybridization procedures to detect the presence of bacterial and virus diseases through the use of highly conserved DNA sequences. Label-free and fully integrated biosensor has favored the developing of a low cost Point-of-Care (POC) device. Recently several studies on electrical detection of biomolecules that is based on the changes in electrical double layer capacitance of the bio-functionalized electrode surface have been proposed. Such systems harness the unique impedance values i.e. permittivity of the biomolecules. However, this method does not present enough stable and accurate electrical signal since the double layer formed at the electrode-electrolyte interface is an imperfect insulator. In capacitive sensing, the occurrence of ion conduction through the permeable DNA layers can cause leakage by discharging the charge on the double layer capacitance. Therefore, a more efficient detection method is desirable. This work demonstrates an impedimetric DNA detection circuit using standard Complementary Metal-Oxide Semiconductor (CMOS) technology. In this approach, the electrical changes are defined by computing both capacitance and resistance of the electrode-electrolyte interface. A fully integrated biosensor circuit design consists of an on-chip microelectrode, a current-to-voltage converter (IVC) and two quadrature phase double-balanced Gilbert cell mixers using 0.18 µm Silterra CMOS process is carried out. The Direct Current (DC) output voltage of the detection circuit is used to estimate the magnitude and phase of the measured admittance. The IVC shows a transimpedance gain of 166 dB and an input referred noise current of 332 fA/vHz in 10 kHz bandwidth. The total power dissipation from 1.8 V DC supply is 97.2 µW and the size of the layout area is approximately 4485 µm2. The developed biosensor has great potential for future array integration due to its low power and flexibility in miniaturization.