In 1999, Rice University chemist Jim Tour co-founded Molecular Electronics Corporation, a company that aimed to use single molecules to make a new type of electronic memory. But Tour had even bigger dreams. In a 2000 story in Wired, he foretold a future in which molecular electronics would leapfrog silicon-based circuitry, allowing computer chips to keep getting denser and more powerful. This vision was short-lived: five years later, flash had cornered the memory market, silicon continued to dominate chip technology, and Tour left the molecular electronics business. The once well-funded field nearly collapsed. 

Now, the San Diego-based startup Roswell Biotechnologies is hoping to give molecular electronics a second life, and Tour, who sits on Roswell’s scientific advisory board, is ready to stand up for it again. “I’ve been saying all along that this thing can work,” he says.

Instead of taking aim at computing circuitry, Roswell is focusing on integrating single molecules into electronic biosensor circuits, an approach it hopes will soon provide a cheap and convenient way to detect viruses, pick up on environmental toxins, and evaluate the effects of pharmaceuticals in real time. 

In January, the company reported a crucial advance in the journal PNAS: a set of 16,000 functional molecular biosensors fully integrated with the circuitry of a semiconductor chip. This shows that these chips can be made using existing fabrication methods at a commercial scale and, according to Barry Merriman, Roswell’s co-founder and chief science officer, they could cost as little as a few dollars per unit.

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“It’s a great concept. I think it’s long overdue for chip manufacturers to do something for us in biosciences,” says Nils Walter, a chemist at the University of Michigan and co-founder of aLight Sciences, a company that is also developing single molecules as biosensors, except its approach is to use fluorescence, or the emission of light, rather than electric signals to read out the results. 

Roswell is not the only company pursuing chip-based biosensors. For instance, Dynamic Biosensors, based in Munich, offers chips with DNA-based sensors that use light. But Roswell’s manufacturing approach produces precise sensors that are flexible enough to envision a “universal biosensor” that can be mass produced with modern chip-making techniques, Merriman says. 

The centerpiece of Roswell’s circuits is a molecular wire made from a chain of amino acids that is connected to the rest of the chip just as a regular metallic wire would be. To create a sensor, the lab attaches a molecule to the other end of the wire. When this molecule interacts with its intended target—which can be a strand of DNA, an antibody, or any of a number of other biologically relevant molecules—its electrical conductivity changes. The chip records this change, and software extracts the corresponding interaction details. 


To assemble thousands of sensors, Roswell starts with a silicon chip studded with prefabricated nanoelectrodes, then uses electric voltage to pull molecules out of solution and onto the chip. This part of the assembly process takes under 10 seconds; in the past, similar molecular processes took hours or even days.

Roswell’s approach could revive some of the hopes molecular electronics researchers had 20 years ago. At that time, it seemed like the small size of molecules could help make circuit components tinier and computational chips denser. Intriguingly, a molecular chipmaker could, in principle, “self-assemble” circuits, adding molecules under highly controlled conditions and letting them assemble into the desired structures all by themselves, explains George Church, a Harvard geneticist and a member of Roswell’s scientific advisory board.

Excitement about such molecular properties led to a rapid growth of the molecular electronics field in the late 1990s. It seemed like the perfect moment. “There were all these predictions all through the ’80s and ’90s, about how silicon was going to hit a brick wall,” Tour recalls. But it didn’t; engineers kept pushing ahead. “We were not shooting at a static target. Silicon just

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By: Karmela Padavic-Callaghan
Title: This startup wants to kick-start a molecular electronics revival
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Published Date: Thu, 31 Mar 2022 09:00:00 +0000

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