Graphene is a sheet of carbon atoms just one atom thick that has many unique properties, including the fact that its optical, electrical and plasmonic properties can be tuned. These make it ideal for applications such as biosensing.

The researchers, led by Sang-Hyun Oh of the University of Minnesota at Minneapolis, made their tweezers by sandwiching an 8 nm-thick hafnium oxide (HfO2) dielectric layer between single-layer graphene, grown in a process called chemical vapour deposition, and a metal layer. HfO2 is an insulating material commonly employed in microelectronics.

“The tweezers work thanks to dielectrophoresis, which is a process that attracts polarized particles using a large electric field gradient,” explains Oh. “These types of gradients can be created at the edges of electrodes when a voltage is applied between them. Since graphene is only a single atom thick, it has the sharpest edge that can be realized, and so creates the largest gradient fields.”

The researchers found that their device can trap a large number of different types of nanoparticles, including polystyrene, nanobeads, nanodiamonds and DNA. Trapping is fast and can be performed at very low voltages.

“Since graphene electronic tweezers can rapidly trap biomolecules with less than 1 V of applied voltage, a key application could be a handheld disease diagnostic system that could be operated with a smart phone,” Oh tells nanotechweb.org. “The platform might also be used to study the biophysics of single molecules in a confined space. In particular, we are very interested in studying conformational changes of biomolecules trapped along the atomically sharp edges of graphene, where the local electric field is extremely high.”

The team, reporting its work in Nature Communications doi:10.1038/s41467-017-01635-9, is now busy turning the nanotweezer into a sensor. “In our present work, we used the graphene to grab biomolecules and we then observed these in a microscope. The ultimate goal, however, is to sense the biomolecules electrically. For these studies, we are collaborating with Steven Koester and his colleagues at Minnesota, who have been working for many years on using this same device structure to create sensitive sensors for glucose and other biologically relevant molecules.”

The other researchers on the team are Avijit Barik, Yao Zhang, Roberto Grassi and Tony Low, all at the University of Minnesota, and Joshua Edel and Binoy Paulose Nadappuram from Imperial College London.