Interdigited Electrodes with Nanoporous Insulator for Sensitive, Selective and Affordable Biosensing System

The ability to detect single molecule passing through a nano-sized pore holds the potential to serve as a valuable process in the world of nanotechnology. The molecules which translocate or cause a blockade at the pore orifice leads to a resistive spike and hence a sharp change in current, which is shape and size dependent and can be used as the sensing criteria. To understand the functioning of a nanopore better, it is of utmost importance to understand electrokinetics that govern the motion of a molecule in the vicinity of the pore. In this paper a nanoporous layer of a PDMS film has been adhered onto the surface of the interdigited electrodes. Hepatitis B surface antigen (HBsAg) functionalization is done on the sensor surface where the electrodes are exposed in nanometer range. Thus, even if the electrode dimensions and spacing are of the order of hundreds of microns, electric field lines percolate only through the nanopores of the PDMS located on the surface of the electrodes. The resistance of the buffer solution usually being lower than that associated with the electrical double layer at the electrode-electrolyte interface, it is expected that the measured resistance between the pair of electrodes will be dominated by the latter. Thus, the problem of fabricating nanometer or micrometer spaced electrodes can be addressed by this unique method of exposing the electrodes through the nanoporous insulator. Further, the selectivity is also expected to improve significantly, since the non-specifically adsorbed molecules on the surface of the insulator will not interfere with the electrical measurements. The detection limit has been lowered to 1fM by incorporating electrokinetic capture of the target molecules.