Two researchers from the USA have developed a thermometer that listens to objects to take their temperature.
Warm objects glow and softly hum. This humming is caused by rapid jitters of particles that make up the hot object. Human ears are not strong enough to hear this noise, but if they were, “it would sound like radio static. The hotter [an object] gets, the louder it gets,” explained Thomas Purdy of the University of Pittsburgh.
The acoustic thermometer, created by Purdy and Robinjeet Singh of the University of Maryland in College Park, detects the intensity of heat-generated sound coming from nearby objects. The core of the device is a sheet of silicon nitride, measuring at one-square-millimeter. That sheet is situated within a window cut at the center of a silicon chip, conveying sound waves better than air.
In lab experiments, the team dropped blobs of an epoxy substance on the chip’s surface, encircling the silicon nitride sheet. When they applied heat with a laser, each epoxy blob gave off sound waves that flowed through the chip to the sheet, causing it to vibrate. As they continued to apply heat, the epoxy blobs became hotter, creating stronger sound waves and more intense vibrations on the sheet.
Purdy and Singh were able to track the sheet’s motion and temperatures of the epoxy blobs by bouncing a laser beam off the sheet and measuring the beam’s angle of reflection.
Purdy envisions this new thermometer being used in quantum computing devices, which need to operate at very low temperatures. The pair published their findings on September 15 in the journal Physical Review Letters.
