Device Measures Pressure from Single Particle Collisions Using Levitated Silica Sphere

Researchers have built the first device capable of measuring the pressure produced by a single particle, using a 100-nanometre silica sphere held in place by laser light. Yu-Han Tseng at Yale University and his colleagues created the instrument, whose central component is a tiny silica sphere half the size of some viruses.

The sphere is held in place with a laser beam thanks to electromagnetic interactions between the two.

Whenever a particle hits the sphere, it reflects light which the researchers can then detect. The team placed the device into an ultra-high vacuum then systematically sent in particles of three different gases. They measured the device’s motion when hit by these particles, then calculated pressure from those measurements.

The calculated pressure showed good agreement with mathematical predictions. “You need to get everything right to get this measurement working,” said Yu-Han Tseng. ” Clarke Hardy, also at Yale University, said the new device could be used to establish a new definition for what counts as an extremely high vacuum where standard pressure sensors would simply read zero by counting the number of collisions.

Joseph Kelly at King’s College London said individual molecular collisions are rarely observed in real time. Traditionally their effects are only seen on average, like how a fast-moving object appears blurred in a long-exposure photograph. Animesh Datta at the University of Warwick in the UK said that similar device designs could be used in astronomy to detect gas particles in low pressure spaces between stars.

The team aims to use the device to detect hypothetical sterile neutrino particles. 18371. @NewScientist reported that the ultra-sensitive pressure sensor could help find elusive new particles, such as those that could make up dark matter.

Pressure is caused by particles hitting an object and collectively exerting a force across its area. Researchers typically think of it as an average effect rather than zooming in on each particle. When pressure is extremely low, such as in experiments conducted in near-perfect vacuum, tracking every particle is needed to properly account for its effects.