On the Sensitivity Increasing of a Capacitive Bio Disease Detector

Nowadays scientists are chasing the vision of making miniaturized MEMS based specifically designed and manufactured biochips based on an array of micro cantilevers, which can detect several routinely diagnosed diseases which are detected simultaneously in the clinical laboratory [1].Sensing of tip deflection of a micro-cantilever which is subjected to smoothly flow of infected blood is one of the concepts of the diagnosis. This deflection is related to the antigens concentration in blood. These sets have been employed in monitoring certain diseases such as cancer and detecting specific chemical and biological infections [1]. As specific binding of bio-molecules occurs on the surface of a micro-cantilever, intermolecular nano mechanical stress induces a bending effect on the cantilever. This is achieved by immobilizing a monolayer of receptor molecules on one side of the cantilever in a liquid environment [2]. Cancer detecting microchips, myoglobin detection sensors, glucose biosensors, and biosensors for coronary heart disease are some application of micro cantilever in the field of disease diagnosis.Some optical sensing methods are used in post designed and investigated samples, but there is a problem that deflection due to presence of antigens is very small (in nanometer) and the sensitivity is low. Therefore in this paper firstly has been tried to increase the sensitivity of the sensor into antigens by use of applying voltage and secondly to dispose a capacitive sensing. Capacitive sensing method [3] is based on the changes of capacity of a planar capacitance due to the adsorption of the antigens