University of Minnesota mechanical engineering PhD students Yingying Zhang (left) and Chi Zhang (right) use a home-built system involving ultrafast laser pulses to conduct measurements of the lanthanum strontium cobaltite devices. Photo: Dingbin Huang, University of Minnesota.A team led by scientists and engineers at the University of Minnesota has discovered a new method for tuning the thermal conductivity of materials to control heat flow ‘on the fly’. Their tuning range is the highest ever recorded among one-step processes in the field and will open the door to developing more energy-efficient and durable electronic devices. They report their work in a paper in Nature Communications.
Just as electrical conductivity determines how well a material can transport electricity, thermal conductivity describes how well a material can transport heat. For example, many of the metals used to make frying pans have a high thermal conductivity so they can transport heat efficiently to cook food.
Typically, the thermal conductivity of a material is a constant, unchanging value. However, the University of Minnesota team has discovered a simple process for ‘tuning’ this value in lanthanum strontium cobaltite, a material often used in fuel cells. Similar to the way a switch controls the flow of electricity to a light bulb, the researchers’ method provides a way to turn heat flow on and off in devices.
“Controlling how well a material can transfer heat is of great importance in daily life and in industry,” said Xiaojia Wang, co-corresponding author of the paper and an associate professor in the University of Minnesota Department of Mechanical Engineering. “With this research, we have achieved a record-high tuning of thermal conductivity, showing promise for effective thermal management and energy consumption in the electronic devices people use every day. A well-designed and functioning thermal management system would enable better user experience and make devices more durable.”
Wang’s team worked in tandem with Chris Leighton, a professor in the University of Minnesota Department of Chemical Engineering and Materials Science, whose lab specializes in materials synthesis. Leighton’s team fabricated the lanthanum strontium cobaltite devices using a process called electrolyte gating, in which ions are driven to the surface of the material. This allowed Wang and her research team to manipulate the material by applying a low voltage to it.
“Electrolyte gating is a tremendously powerful technique for controlling the properties of materials and is well established for voltage-control of electronic, magnetic and optical behavior,” said Leighton, co-corresponding author of the paper. “This new work applies this approach in the realm of thermal properties, where voltage-control of physical behavior is less explored. Our results establish low-power, continuously tunable thermal conductivity over an impressive range, opening up some pretty exciting potential device applications.”
“Although it was challenging to measure the thermal conductivity of lanthanum strontium cobaltite films because they are so ultrathin, it was quite exciting when we finally got the experiments to work,” said Yingying Zhang, first author of the paper and a University of Minnesota mechanical engineering PhD alumnus. “This project not only provides a promising example of tuning materials’ thermal conductivity but also demonstrates the powerful approaches we use in our lab to push the experimental limit for challenging measurements.”
This story is adapted from material from the University of Minnesota, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.