Atomic force microscopy based nano manipulation towards CNT-ISFET pH sensing system

In this paper, we present a novel means by which nano manipulation can be realized on a field effect transistor (FET) surface. Using atomic force microscopy (AFM) tip as a manipulation tool, micro and nano scale channels are created between the gap of a pair of gold (Au) electrodes. Following a dielectrophoresis (DEP) process, carbon nanotubes (CNTs) are deposited and aligned perfectly inside the channels cut by the AFM. Then, the two electrodes are bridged and ready to be developed as an ion-selective field effect transistor (ISFET) structure that has the potential to work as a high-performance pH sensor. Owing to the unique electrical properties of CNTs, such as conductivity (either metallic or semiconducting) and great current carrying capacity (~1 TA/cm³), there is a huge possibility that this CNT-based ISFET system is a much better replacement for the existing ISFET-based pH sensors. The pH sensing system will be much more compact, cheaper and reproducible, and no longer need outside amplifier circuits, which will have huge benefits in industry, biology as well as medicine.