SEM electron microscope images of: a) the silicon nanowire (SiNW)/CMOS hybrid biosensor; b) a SiNW biosensor in the first stage; c) a magnified view of it; d) SiNW channel region, showing a 35-nm width

a) TEM electron microscope images of the SiNW; b) photo of the fabricated chip; c) view of the experimental setup

Hybrid Nanowire/CMOS Biosensor: In the burgeoning field of genetic research, one thorny problem is how to accurately and cost-effectively detect DNA molecules in electrolyte solutions such as bodily fluids. Because DNA molecules are so small and because the background electrical “noise” inherent in ionic solutions tends to mask the presence of DNA, the usual way to detect DNA molecules is to label, or tag, them, with a variety of substances that can be detected by specialized probes. This adds cost and complexity, which a label-free direct detection system would avoid. Until now, a sensor to make that possible has been lacking, but researchers from Kookmin University in South Korea will describe a hybrid biosensor which, for the first time, integrates silicon nanowires and CMOS devices for such an application. It combines the exquisite sensitivity of nanowire surfaces with the noise-reduction and readout capabilities of CMOS logic circuitry, and does away with the need for DNA labeling. It demonstrated extremely impressive and consistent sensitivity, expressed as a change in output voltage of 1.2 V per 0.4 change in pH level, and as a 1.2 V change per 200 fM of DNA. (fM is a unit of length; 1 femtometer is 10⁻¹⁵ meter).

(Paper #14.5, “A Novel SiNW/CMOS Hybrid Biosensor for High Sensitivity/Low Noise,” J. Lee et al, Kookmin University)

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