Researchers from the AMM&NS programme are collaborating on a research project on Advanced Materials and Nanotechnology on a Silicon Platform.  The project is being undertaken by an SMA PhD student, Ms Zhang Huijuan, who is jointly supervised by the Principal Investigators Prof John Thong from NUS, and Prof Francesco Stellacci from MIT.  The team has made significant progress, having filed for a patent on ‘Insulated Nanogap Devices and Methods of Use Thereof’ on 24 January 2008. The patent covers two techniques that the team developed to fabricate the device.

SMA Connect found out from Prof Thong that the project attempts to fabricate a electrical nanogap device that can be used to detect DNA molecules rapidly and inexpensively, which may be useful for researchers in the medical and life sciences fields. In most medically relevant cases, such devices have to be operated in aqueous solutions, under physiological conditions, which presents a major problem due to the presence of large ionic currents.  These parasitic currents normally mask the minute signal from the DNA being detected.

The unique device the team created is built with a small gap between two electrodes. A polymer layer is overlaid above the gold electrodes to insulate them from the solution.  The key to the invention is the ability to create a tiny hole in the polymer layer in a one-step process alongside the nanogap fabrication, as shown in the schematic diagram below.

Schematic diagram of an insulated nanogap device that comprises sub-2nm nanogap
and self-aligned hole in overlying polymer layer

The device allows nanoparticles coated with DNA to be assembled in the gap. Single-stranded DNA are assembled to the exposed gold electrodes within the hole.  Binding occurs when DNA strands (attached to a gold nanoparticle) with the complementary sequence hybridize with the DNA on the electrodes, and this event can be detected as a miniscule current signal against the background of ultralow ionic currents.

The team believes that they have solved the problem of high parasitic ionic currents and that the method they devised is promising because it is easily reproduced for commercial use.  The researchers are currently cooperating with Prof Liu Xiaogang from the Department of Chemistry, NUS to work on further applications of the devices.

Research Team