Using nanogap in label-free impedance based electrical biosensors to overcome electrical double layer effect

Point-of-care biosensor applications require low-cost and low-power solutions. They offer being easily accessible at home site. They are usable without any complex sample handling or any kind of special expertise. Impedance spectroscopy has been utilized for point-of-care biosensor applications; however, electrical double layer formed due to ions in the solution of interest has been a challenge, due to shielding of the electric field used for sensing the target molecules. Here in this study, we demonstrate a nanogap based biosensor structure with a relatively low frequency (1–100 kHz) measurement technique, which not only eliminates the undesired shielding effect of electrical double layer but also helps in minimizing the measurement volume and enabling low concentration (µ molar level) detection of target molecules (streptavidin). Repeatability and sensitivity tests proved stable and reliable operation of the sensors. These biosensors might offer attributes such as low-cost label-free detection, fast measurement and monolithic chip integrability. © 2015, Springer-Verlag Berlin Heidelberg