Microfluidic Design of Neuron-MOSFET Based on ISFET

In this Paper we suggest a device which combines the operation of a neuron- MOS (1) (3) and an ISFET (2) . An ISFET is an ion-sensitive field effect transistor used to measure ion concentrations in a solution; when the ion concentration changes, the current through the transistor will change accordingly. A voltage between substrate and the oxide surfaces arises due to an ions sheath. The surface concentration of the -OH groups of the gate materials varies in the aqueous solutions due to pH value. The neuron-MOSFET was first proposed by Shibata and Ohmi in 1991. It contains a conventional MOSFET and a gate electrode which is electrically floating and N-input gates capacitively coupled to the floating gate. The effective gate potential is a function of both the potentials applied and the coupling capacitances. More the coupling capacitance, more the effect of the applied potential on the gate and the output potential. The suggested device contains multiple microchannels that are of varying size and are used to induce a potential on the floating gate. The microchannels (which act as multiple gates) can be arranged to cause flow of charge between the drain and the source of the MOSFET similar to a logic 'and' and logic 'or' operation. Using COMSOL Multiphysics TM simulation tool the suggested device was simulated.