Students team with tech company to study the physics of friction
This summer a team of researchers at St. Olaf College partnered with hard disk drive manufacturing company Western Digital to investigate the underpinnings of friction at the molecular and even atomic level.
The project, part of the college’s Collaborative Undergraduate Research and Inquiry (CURI) program, was led by Associate Professor of Physics and Department Chair Brian Borovsky ’94.
Along with student researchers Lucas Sletten ’15 and Emily Johnson ’16, Borovsky worked with Western Digital to research ways of minimizing the impact of friction on micromachines.
“Micromechanics and even nanomechanics is a broad area of technology that is in a developmental phase right now,” Borovsky says. “There are certain kinds of micromachines that are now ubiquitous, and they’re around us every day even if we don’t know it.”
“Like the accelerometer in your smartphone,” Sletten adds, “or in the motion sensors that trigger the airbags in your car.”
But, Borovsky explains, accelerometers are relatively simple machines, with few moving parts that rub together. In order to build more complex micromachines, friction — or rather, the wear that it causes — is still a significant obstacle to be overcome.
“There has been no micromachine commercialized that allows for rubbing contacts,” he says. “Those tend to be very high friction, very high wear, and the machines don’t tend to last more than a day or two on the bench.”
Bridging the gap between theory and practicality
In larger-scale mechanics, mitigating the effects of friction is as simple as ensuring that the machine is well lubricated. But when the scale is measured in micrometers or even nanometers and space is at a premium, there simply isn’t enough room for a traditional lubricant.
To find a way around this design problem, companies like Western Digital are researching experimental lubricants that can efficiently minimize the effects of friction even when only the thickness of a single molecule. This summer Borovsky and his students worked to test the different experimental lubricants that Western Digital has been developing for its hard drives.
“Hard disk drive manufacturers are at a key point in their technology where they have gotten them to be so small and have so much data on them by reducing the distance between the reader and the disk,” Borovsky says. “But they’re at this key point where they can’t get much closer without actually starting to rub the reader against the disk. Yet they may need to do that if they’re going to compete with other memory storage technologies, like flash storage. So they’re seriously trying to figure out, ‘How do I get a fraction of a nanometer closer?’ Every fraction of a nanometer can really count for a competitive industry like this.”
In this summer’s research project, the St. Olaf team used a machine called a probe-quartz resonator apparatus to simulate the amount of friction that is created when very small contacts rub at high speeds — a technique used by only a few other research groups in the world. This enabled them not only to test the different lubricants being developed by Western Digital, but also to collect data that may lead to a greater understanding of the way friction works on such small scales, bridging the gap between theory and practicality.
“Ever since the modern study of friction began in the 1980s, researchers have been revealing surprising ways in which the simple laws of friction for everyday objects fail to describe the physics of ultra-small machines,” Borovsky says.
This is because, he explains, when an object is small enough, nearly all of its atoms are on the surface. With relatively few atoms stored inside, the machine has almost no bulk (inertia and cohesive strength) that could allow it to withstand the destructive effects of surface forces. Machines this small simply don’t behave the way much bigger objects do, and this creates an opportunity for scientific understanding to help guide the development of new technologies.
Paving the way for future research
The results of this summer’s work are promising, Borovsky says.
“We’ve had an excellent summer in the lab,” he says. “We upgraded our equipment for improved ease of use. Lucas and Emily automated our data acquisition scheme, and now we see data coming in faster than ever. More data means better statistics and ultimately better science. The first fruits of all this is a very large data set on the frictional behavior of two hard drive coatings provided by Western Digital.”
Borovsky says that although the experimental lubricants showed high levels of friction, they did exhibit less friction per area than uncoated control surfaces. The group’s next step, he says, is to use the frictional data they gathered to find ways of modifying the lubricants to cut down on friction even more.
“We are at the beginning of our collaborative effort here,” Borovsky says, “and it will be interesting to see how hard drive technology develops to stay competitive with other high-density storage media in the future.”