Abstract
The many unique properties of graphene, such as the tunable optical, electrical, and plasmonic response make it ideally suited for applications such as biosensing. As with other surface-based biosensors, however, the performance is limited by the diffusive transport of target molecules to the surface. Here we show that atomically sharp edges of monolayer graphene can generate singular electrical field gradients for trapping biomolecules via dielectrophoresis. Graphene-edge dielectrophoresis pushes the physical limit of gradient-force-based trapping by creating atomically sharp tweezers. We have fabricated locally backgated devices with an 8-nm-thick HfO2 dielectric layer and chemical-vapor-deposited graphene to generate 10× higher gradient forces as compared to metal electrodes. We further demonstrate near-100% position-controlled particle trapping at voltages as low as 0.45 V with nanodiamonds, nanobeads, and DNA from bulk solution within seconds. This trapping scheme can be seamlessly integrated with sensors utilizing graphene as well as other two-dimensional materials.
Highlights
The many unique properties of graphene, such as the tunable optical, electrical, and plasmonic response make it ideally suited for applications such as biosensing
Biomolecules in viscous media is generally governed by diffusive transport, and the placement of target molecules at the region of highest sensitivity is a key prerequisite to biosensing
The entire wafer surface, including the Pd electrode, was coated with 8-nm-thick HfO2 deposited by atomic layer deposition (ALD)
Summary
The many unique properties of graphene, such as the tunable optical, electrical, and plasmonic response make it ideally suited for applications such as biosensing. Graphene[1] is an excellent alternative to noble metals for constructing a wide range of sensors due to its electrical tunability[2], high quantum efficiency for light-matter interactions[3], quantum capacitance effects[4, 5], and tightly confined mid-infrared plasmons[6,7,8,9,10] Unlike noble metals, such as gold or silver, the carrier concentration in graphene can be tuned, enabling the possibility of electrically reconfigurable biosensing[11]. The ability to precisely position and concentrate target molecules onto the edge of patterned graphene nanostructures is highly desirable yet is not extensively studied Besides biosensing, such capability can benefit nanophotonic applications for integrating quantum emitters and plasmonic antennas with tunable optoelectronic properties of graphene[14, 15]. In this case as our model system is based on nanoscale particles, we assumed a dipole approximation
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