A Groundbreaking Engine Uses Information as Fuel

A 150-year-old thought experiment inspired a group of scientists from the Simon Fraser University (SFU) in Canada to create a surprisingly fast engine that runs on a unique fuel -- information.

The engine, described in a paper published in the Proceedings of the National Academy of Sciences, turns the random jiggling of tiny particles into stored energy and has the potential to significantly improve the speed and affordability of computers and bio-nano technologies.

What is an information-fueled engine?

We are used to thinking of engines as contraptions that eat up fuel and help us drive our cars, so an information-fueled engine might not ring any bells. This idea is actually the descendant of a thought experiment by the notable scientist James Clerk Maxwell 150 years ago. Maxwell wondered what would happen if you could see a system so small and so accurately that you could see its tiny fluctuations as it moved due to the air or the water molecules around it. Could we use that motion and harness it in such a way that we could convert information into 'work'?

"That's the kind of information that we're using," explained SFU physics professor and senior author Prof. John Bechoefer in an SFU video. "We wanted to find out how fast an information engine can go and how much energy it can extract, so we made one."

It can generate power 'comparable to molecular machinery in living cells'

A microscopic particle 'bead' immersed in water serves as their information engine. It's connected to a spring that's attached to a movable stage. Since a particle is too small to be attached to a spring, the researchers utilized an optical trap, which uses a laser to create a force on the particle that imitates the spring and stage, according to a press release by the university.

Thermal motion causes the particle to bounce up and down, and the researchers observe, playing the role of Maxwell's demon. In Maxwell's thought experiment, a demon would control a door between two gas chambers, with the goal of sending fast-moving gas particles into one compartment and slow ones into another. In their study, when researchers saw an upward bounce, they moved the stage up in response, and they waited if there was a downward bounce. 

They raised the particle without having to directly pull on it by repeating this action, thus storing a significant amount of gravitational energy. According to Ph.D. student Tushar Saha who partake in the study, "This ends up lifting the entire system using only information about the particle's position."

The researchers also discovered a fascinating trade-off between the particle mass and the average time it takes for a particle to bounce up. "While heavier particles can store more gravitational energy, they generally also take longer to move up," said Joseph Lucero, a Master of Science student.

The researchers were able to get the system to generate enough power that is "comparable to molecular machinery in living cells," with "speeds comparable to fast-swimming bacteria," said postdoctoral fellow Jannik Ehrich, and the extracted power and velocity has outperformed previously reported engines by being at least an order of magnitude higher.

From a thought experiment devised 150 years ago to actually seeing it in practice, it'll be interesting to see the types of applications that will emerge from information-fueled engines in the future, especially in computers and bio-nano technologies.