Marvin White, director of Lehigh’s Sherman Fairchild Center for Solid State Studies, designs, simulates, fabricates and tests devices tinier than a virus that could find application in digital technologies, the study of cells and DNA sequencing.
In one project, White and his students are investigating the electronic properties of biological cells.
“We have fabricated nanopores and electronic circuitry on a silicon chip to form a planar ‘patch-clamp’ measurement system to study ion-channel currents,” says White. “Cells are surrounded by ion channels, which permit various ions, such as sodium, potassium and calcium, to move in and out of the cells. This ion-channel behavior is linked to more than 40% of human diseases, including multiple sclerosis, Alzheimer’s and cardiac arrhythmias.”
White’s group has formed a gigaseal to study individual ion-channels and is now developing a current amplifier to measure picoampere ion-channel currents that fluctuate several thousand times per second.
“One long-term goal of this project,” he says, “is to sequence DNA electronically in an hour or less. The sequencing is done now using a chemical process that can take several years. This is far into the future, but I think we are putting the basic building blocks in place.”
White’s group also models the behavior of nanoelectronic CMOS transistors used in advanced microprocessors and logic circuits. The dimensions of the dielectric films in these devices, says White, is a mere 5 angstroms – only an order of magnitude greater than the typical distance between a proton and electron in a hydrogen atom.
“This means we are exploring the quantum world, where electrons ‘tunnel’ through barriers and are no longer confined to spatial regions within a device. This raises questions about the extent to which we can scale down the size of transistors. We are exploring these limitations in terms of performance and reliability.”
