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26 May 2017

Microscopic Heater-Thermometer Created at University of Nebraska-Lincoln

Tucked away within the walls of the University of Nebraska-Lincoln, a small team led by engineer Ming Han has made quite an incredible breakthrough. They have managed to create a laser-heated, silicon-tipped fibre optic combination device which serves as both a heater and thermometer capable of operating in temperatures approaching 2,000°F (1,093.3°C). The device, which Han describes as “like a tiny furnace”, climbs from room temperature to 300°F (148.8°C) in fractions of a second.

Img: University of Nebraska-Lincoln
According to Han the new device has quite the wide-spanning range of potential applications, and could find use in contexts such as monitoring greenhouse gases, prepping specimens for biological research, or the production of micro-bubbles used in medical and industrial applications. He further touted the heater-thermometer’s spectacular performance at high temperatures, which could allow it to be used in demanding environments such as engines and power plants.

Given the miniscule size of the device, which has a diameter of just one-tenth of a millimetre, its capabilities are truly astounding.

“We have an elegant sensor structure with a very efficient heating mechanism,” said Han. “In other devices, the heating element and the temperature-sensing element are generally two different elements. Here, we've integrated both into the same tiny structure.”

The design of the new device actually evolved from a previous project of Han’s, in which he was attempting to create a fibre optic sensor suitable for use in the field of oceanography. This sensor, much like the new device, incorporated a tiny silicon pillar attached to fibre optics. The project was hampered however as the glue used to bond the component would soften at around 200°F (93.3°C). This rendered it unusable at higher temperatures.

Then, a breakthrough somewhat changed the game.

After initially bonding the fibre optics and silicon pillar using glue, the team then passed a hot arc of electric current through the device, which fused another fibre optic strand to the other side of the silicon pillar. The heat generated by the process simultaneously softened the glue thereby detaching the original strand, leaving the newly-fused device intact.

The device actually works in quite an ingenious way. Two different wavelengths of light are fed through the fibre optic in the form of lasers, one at a wavelength of 980-nanometres, and the other at 1550-nanometres. The 980-nanometre wavelength is absorbed by the silicon, generating heat in the process. By manipulating the power provided to the remote-controlled laser, the team can effectively dictate the temperature of the device. The broader wavelengths are reflected at each end of the pillar rather than being absorbed, interfering with each other in the process. As the silicon’s temperature changes, so too do these interference patterns. This allows the device to be used as a highly precise thermometer.

Han asserts that the device’s ability to gauge and adjust its temperature grants it a level of functional versatility not offered by existing micro-heaters.

“We still have a lot of work to do to make it better, but this is a very promising technology that has a lot of exciting applications,” concluded Han.

Sam Bonson

Sam is an aspiring novelist with a passion for fantasy and crime thrillers. He is currently working as a content writer, journalist & editor in an attempt to expand his horizons.