Chip that measures gases in vacuum

Vacuum chip

Vacuums are a vital part of the processes – such as freeze-drying – used to make and preserve countless everyday items and must be measured with precision.

An EPFL spin-off, Hexisense, is bringing to market a gallium nitride-based chip that can measure the quantity of certain gas molecules cheaply and with unrivalled precision.

The small 0.4 cm2 chip developed and soon to be marketed by the EPFL spin-off aims to offer an affordable way of measuring individual gases in all vacuum systems.

The mini-sensor harnesses two physical characteristics of its main component, gallium nitride: its reactivity to light and its status as a semiconductor. In a vacuum vessel, when gas molecules become less numerous, they move towards the walls and stick there. Gallium nitride, when exposed to a light source, repels certain gas molecules, like oxygen. So an LED is placed on the chip, which unsticks molecules from the walls. Once the light goes off, gallium nitride’s semiconductor properties allow the chip to measure how quickly gas molecules return to the walls. Specific algorithms then analyze the number of molecules on the surface along with the partial pressure of each gas. These tiny chips boast excellent efficiency: for example, they can detect oxygen within nitrogen at a concentration of less than 0.5%.

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Credit: “A chip to measure vacuums”, Cecilia Carron, EPFL