Electrochemical sensors for detection of biomolecules

A novel electrochemical sensor for detection of biomolecules was investigated. The sensor was fabricated using micro electro mechanical system (MEMS) knowledge, and the sensor has the ability to transduce bimolecular signal directly into an electrical signal. The capacitor-based sensors with a nanogap in the range of (20~100 nm) was produced using SOI (silicon on insulator) wafer, and the insulator layer was the media layer of the capacitor. When the nanogap size is smaller than the electro double layer thickness, the dependence of the nanogap capacitance on the ionic strength is insignificant. This is critical in using the capacitance change as an indicator of the existence of target molecules. Filling the nanogap with biomolecules resulted in the change of capacitance. A C-V analyzer was used to measure the electrical (capacitance) property of the sensor. DNA immobilization technique was also carried out to immobilize double stranded DNA on the sensor and this result was used to understand the effect of plasma modification of silicon surface. This research can have important consequences in DNA-based molecular electronics and direct label-free detection of DNA digestion and hybridization.