An Electrical Model for Off-Plane Nano Needle Array Electrodes in Intracellular Signal Measurement in Biological Environments

Abstract

Electrical signals emanating from biological cells can convey clinical information on the functionality thereof. However, measurement of such small signals caused primarily by ionic activity inside the cell, known as action potential, poses a great challenge to biomedical scientists. The electrical signals of the biological cells result from exchange of ions through the cell membrane. The characteristics of action potentials may reveal a great deal of information about the causes and symptoms of abnormal cell behaviour. Hence, it is imperative to capture high quality action potentials through the use of nano-sensors from within the cell. Recently, developments in silicon nanowires (SiNW) fabrication techniques have demonstrated a great potential for them to be used as nano-electrodes. Largescale assembly and integration of addressable complementary silicon nanowires arrays have been demonstrated for multiplexed biosensor arrays. The fabrication process resulted in a high-yield, high performance devices arrays for chemical and biological detection. In this paper, we seek to model the electrical interface that is responsible for recording the biological signals. We present electrical equivalent circuits that model the boundary between the biological cell and the nanowire electrode. Impedance measurement curves of nanowires for various sizes of length and diameter have also been presented and discussed. The impedance graphs show a hyperbolic dependence of resistance on length and diameter of nanowires. This non-linear behaviour may be mitigated in software algorithms when interpreting the measured cell signals.