Open AccessToward a Practical Impedimetric Biosensor: A Micro-Gap Parallel Plate Electrode Structure That Suppresses Unexpected Device-to-Device Variations
Author(s) -
Haruka Honda,
Yusuke Kusaka,
Haiyun Wu,
Hideki Endo,
Daiju Tsuya,
Hitoshi Ohnuki
Publication year - 2022
Publication title -
acs omega
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.779
H-Index - 40
ISSN - 2470-1343
DOI - 10.1021/acsomega.1c06942
Subject(s) - electrode , dielectric spectroscopy , biosensor , materials science , planar , electrical impedance , optoelectronics , electrode array , analytical chemistry (journal) , nanotechnology , electrochemistry , chemistry , electrical engineering , computer science , chromatography , computer graphics (images) , engineering
We propose a rational electrode design concept for affinity biosensors based on electrochemical impedance spectroscopy to substantially suppress unexpected device-to-device variations. On the basis that the uniformity of the current distribution affects the variation, a novel micro-gap parallel plate electrode (PPE) was developed, where two planar electrodes with edges covered with a SiO 2 layer were placed face to face. The structure provides a uniform current distribution over the planar electrode surface and maximizes the contribution of the planar electrode surface to sensing. For a comparative study, we also fabricated a micro-structured interdigitated electrode (IDE) that has been widely adopted for high-sensitivity measurement, although its current is highly concentrated on the electrode edge corner. Protein G (PrG) molecules were immobilized on both electrodes to prepare an immunoglobulin G (IgG) biosensor on which the specific binding of PrG-IgG can occur. We demonstrated that the IgG sensor with the PPE has small device-to-device variations, in strong contrast to the sensor with the IDE having large device-to-device variations. The results indicate that the current distribution on the electrode surface is important to fabricating electrochemical impedance spectroscopy biosensors with small device-to-device variations. Furthermore, it was found that the PPE allows ultrasensitive detection, that is, the sensor exhibited a linear range from 1 × 10 -13 to 1 × 10 -7 mol/L with a detection limit of 1 × 10 -14 mol/L, which is a record sensitivity at low concentrations for EIS-based IgG sensors.