Laser-Held Silica Sphere Measures Single-Particle Pressure

A device that suspends a 100-nanometre silica sphere in a laser beam has measured pressure exerted by single particles for the first time. The sphere is held in place through electromagnetic interactions with the laser. When a particle strikes the sphere, the resulting change in reflected light is recorded and used to calculate pressure.

Researchers placed the device in an ultra-high vacuum and introduced particles from three different gases. Measurements of the sphere’s motion matched mathematical predictions for each gas.

The same approach could define extremely high vacuum conditions where conventional sensors register zero. Counting individual collisions would provide a direct pressure estimate in those regimes. The device may also detect hypothetical sterile neutrinos.

Such particles could address long-standing anomalies in particle-physics data and serve as a candidate for dark matter. Similar designs are being explored for measuring low-pressure regions between stars, where gas particles are difficult to observe with existing instruments.