Researchers from the University of Minnesota have developed tiny electronic 'tweezers' that can grab biomolecules floating in water with incredible efficiency. They believe this capability could lead to a revolutionary handheld disease diagnostic system that could be run on a smartphone.
The physical principle of tweezing or trapping nanometer-scale objects, known as dielectrophoresis, has been known for a long time and is typically practiced by using a pair of metal electrodes. However, metal electrodes lack the 'sharpness' to pick up and control nanometer-scale objects.
“Graphene is the thinnest material ever discovered, and it is this property that allows us to make these tweezers so efficient. No other material can come close,” said Professor Sang-Hyun Oh from the University's Department of Electrical and Computer Engineering.
“To build efficient electronic tweezers to grab biomolecules, basically we need to create miniaturized lightning rods and concentrate huge amount of electrical flux on the sharp tip. The edges of graphene are the sharpest lightning rods.”
The graphene tweezers were created using a sandwich structure where a thin layer of insulating material hafnium dioxide was sandwiched between a metal electrode on one side and graphene on the other.
The team also showed that the graphene tweezers could be used for a wide range of physical and biological applications by trapping semiconductor nanocrystals, nanodiamond particles, and even DNA molecules. Normally this type of trapping would require high voltages, restricting it to a laboratory environment, but graphene tweezers can trap small DNA molecules at around 1 Volt, meaning that this could work on portable devices such as mobile phones.
“Besides graphene, we can utilise a large variety of other two-dimensional materials to build atomically sharp tweezers combined with unusual optical or electronic properties,” said Oh.
“It is really exciting to think of atomically sharp tweezers that can be used to trap, sense, and release biomolecules electronically. This could have huge potential for point-of-care diagnostics, which is our ultimate goal for this powerful device.”
[An illustration of how the nano 'tweezers' trap biomolecules. Image: In-Ho Lee, University of Minnesota]