Scientists develop a microscopic motor that accomplishes what seemed impossible

Scientists develop a microscopic heat engine that achieves 100% efficiency, accomplishing what seemed impossible.

A new theoretical design describes a tiny heat engine that can convert all of the heat it absorbs into useful work under tightly defined conditions. The claim is laid out in a study led from Italy.

Researchers at the Abdus Salam International Centre for Theoretical Physics (ICTP) say their model reaches 100 percent efficiency by timing interventions to natural thermal motion.

When 100% is not 100%

The result applies to a Carnot efficiency, the ideal heat engine limit, measured only for the strictly thermal part of the cycle. That choice isolates heat in and work out while keeping separate the accounting for information and control tasks.

The authors show that this thermal fraction can hit one, or 100 percent, in the slow operating limit without breaking the second law. The total ledger still balances once the energy cost of measuring and processing information is counted.

The work was led by Édgar Roldán, physicist, at ICTP. His research focuses on non equilibrium fluctuations and information thermodynamics.

At the heart of the approach is an information engine, a device that uses measurements to extract work from randomness. The main loop follows a four step cycle with a twist during compression.

Demon in the machine

The controller is modeled on Maxwell’s demon, a thought experiment about sorting particles to extract work, that chooses moments to act based on measurements. In practice, the demon is a fast detector and computer.

That strategy builds on earlier demonstrations that information can be turned into energy at the microscale. One landmark study showed that real time feedback on a Brownian particle can raise its energy.

Engine plays blackjack with heat

The working substance is a colloidal particle, a plastic bead suspended in water. It is confined in a laser trap.

The trap is adjusted by optical tweezers, laser beams that hold and move tiny objects. The particle jitters because of Brownian motion, random jostling from molecules in the fluid.

During isothermal compression, the setup watches for a first passage condition, when a wandering particle first hits a target location. If the bead crosses the trap center before a set deadline, the trap stiffness jumps instantly to the final value at zero work cost.

In this protocol, the decision rule echoes a blackjack tactic. The timing rule is enforced by feedback control, using measurements to change system inputs.

Information is part of the bill

The clean separation of thermal efficiency and total energy cost hinges on Landauer’s principle, the minimum energy required to erase one bit of information. This principle links information processing to heat generation in any physical device.

In an interview, the researchers explained that when the energy cost of erasing information about each particle’s position is included in the calculations, the overall efficiency aligns once again with the Carnot limit.

This distinction underscores the importance of accounting for the energetic cost of information processing.

Decades of work back that point up. A classic experiment confirmed that erasing a single bit dumps a predictable amount of heat in the slow limit.

From theory to lab

The model is rooted in stochastic thermodynamics, the physics of small fluctuating systems, and tested with numerical simulations that match predictions. The team uses parameters from optical tweezer studies of Brownian engines.

“We are confident that our theoretical idea can be realized in the lab very quickly,” said Roldán. The group notes that sampling above 100 kilohertz is important for timely decisions and avoiding performance loss.

Those laboratory roots run deep. An earlier experiment built a Carnot style cycle with a single optically trapped particle and mapped its energy flows.

There is also prior theory showing how stopping rules drawn from card games can guide nanoscale control. A research established thermodynamic bounds for gambling style demons and tested ideas in a single electron device.

Nanoscale tools and heat engines

Engines that can time their moves to random motion may waste less energy than devices that push on a fixed schedule. That could matter for sensors that harvest tiny amounts of heat or for lab tools that need precise, gentle actuation.

Any practical device would still pay for detectors, memory, and computation. The theoretical win appears when you focus on the heat to work step and treat those overheads as separate modules that can be improved.

The idea sets a test bed for learning how information and energy trade off. Sampling limits, measurement noise, and delays will define what is achievable when the theory meets hardware.

The researchers noted that their ideas, along with others in the emerging field of stochastic thermodynamics, serve as proof of concept efforts that could eventually inspire realistic designs of efficient nanomachines capable of pushing beyond classical thermodynamic limits.

They added that the work establishes clear expectations for upcoming experimental tests.

The study is published in Physical Review Letters.

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