Graphene-based lab-on-a-chip device for microfluidic sensing

Nan Lei

Carbon-based materials, such as graphene and carbon nanotubes (CNT), have received enormous attention since their discovery, due to their unique physical and electrical properties. It is believed that they hold great promise for the next generation of sensing devices for microfluidic and lab-on-a-chip applications. However, the inherent difficulties in handling and fabricating graphene and carbon nanotubes devices have been a major barrier in developing low-cost, high throughput graphenebased nanosensors. In this research, we developed two graphene-based sensors using different novel fabrication approaches, where graphene is configured as a planar chemiresistor. For the first approach, we use a lithography free technique via a focused ion beam. In more detail, the graphene sheets are made by mechanical exfoliation. Platinum contact electrodes are fabricated with a mask-free process using focused ion beam, and then expanded by silver paint. Annealing is used to improve the electrical contact. The experiment on the fabricated graphene device shows that the resistance of the device decreases linearly with increasing pH values in the surrounding liquid environment. For the second approach, graphene sheets were deposited onto the prefabricated electrodes with dielectrophoresis. With a comb-shaped electrode design, graphene sheets can be actively captured between electrodes. Dielectrophoresis proves effective in depositing a large-scale array of graphene on desired locations. The dielectrophoretically deposited graphene is used as the semiconducting material in a liquid-gated field-effect transistor (FET), and it demonstrates p-type characteristics with holes as the majority charge carriers. When used in two-terminal chemiresistors, the deposited graphene demonstrates high sensitivity towards pH values in liquid. In the above two approaches, the shape of graphene is always pre-determined. It would be very important to have the ability to engineer the shape of graphene, because the electrical properties of graphene are greatly affected by its shape. As the last section of this thesis, we demonstrate our preliminary study on modifying the shape of grahene using focused ion beam technique. An annealing process followed to improve the property of graphene and enhance the clean cut. We believe the method proposed here will have a great impact on the development of full-graphene electronics.

Graphene-based lab-on-a-chip device for microfluidic sensing

Files and links (1)

Abstract

Metrics

Details