Penn researchers are first to study how 2-D nanopores react to light

Penn researchers are investigating a new technology that, if proven, could lead to small, chip-size sensors capable of sensing molecules and detecting illnesses, or even possibly the presence of viruses.

This technology is focused on nanopores, which are tiny holes typically just a few nanometers across—100,000 times smaller than the width of a single strand of human hair. Threading a strand of DNA, which in its single strand form has a diameter of 1.1 nanometers, through these nanopores allows scientists to sequence the bases of the DNA due to their different sizes.

The Penn researchers are testing nanopores in a novel 2-D material called tungsten disulfide, which may provide a few advantages over graphene, including the optical properties of this class of metal dichalcogenide materials. In addition to realizing nanopores in this material and proving that these nanopores work in salt solution, the researchers found a surprising twist—the nanopores responded to light, expanding when laser light was shined on them, with an expansion rate that increased as the laser power was increased.

“What I was expecting was that by shining light, we could affect some aspect of DNA motion through the pore,” says Marija Drndić, the Fay R. and Eugene L. Langberg Professor of Physics in the School of Arts & Sciences. “But when we shined the light, we saw that the pores expanded.”

The research was led by Drndić and Penn graduate students Gopinath Danda and Paul Masih Das. A.T. Charlie Johnson, a physics professor in the School of Arts & Sciences, and Mauricio Terrones, a professor of physics at Penn State, also contributed to the research.

Not only is this the first time research has been done on nanopores in this particular material, it is also one of the first times researchers have studied how nanopores react to light.

It’s possible that this finding may provide researchers with a faster, less expensive technique for making and growing nanopores. If there is a tiny defect in the material and they shine light on it, it may provide a starting point for pore formation and growth.

“We’d like to see if we can use this phenomenon, this chemical reaction, to actually make pores with light,” Drndić says. “That’s one direction that could really benefit this whole technology because then you can imagine shining light and creating pores, which would be very fast and inexpensive.”

Although nanopore technology is still in its developmental stage, researchers hope it can be used for DNA or protein sequencing, biomarker detecting, and the quick detection of illnesses.

“Frequently, we learn about some illnesses once they spread enough that you see symptoms,” Drndić says. “But if you could detect the presence of viruses quickly by looking at their DNA, then you could map out how things are spreading.”

The researchers hope to harness this phenomenon to create nanopore sensors with dynamic size control.

“We can use the same nanopore device to separate a solution of particles of different sizes because we can control the nanopore size,” Danda says.

This would allow them to analyze biomolecules such as DNA and viruses using just one device by starting with a small nanopore, allowing all the small molecules to pass through it, and then using light to expand the nanopore and pass bigger particles through.

“As scientists at a university, we have the luxury of playing around a little bit to see what works better,” Drndić says. “We’re able to explore, which can lead to some new ideas. We’re laying down the fundamental basis behind how nanopores work so that one day engineers can continue the technology.”