Electronics Finalist: Thin-Film Thermoelectric Cooling Device - Tech Briefs

Physical touch plays a crucial role in a person’s ability to communicate and perceive the world around them. Researchers have long sought to develop state-of-the-art prosthetic limbs that can restore near-natural hand and arm control for people living with loss of limb and limb differences. The ability to restore that sense of touch is possible through skin stimulation, but delivering thermal sensations in a fast, energy-efficient, and comfortable manner was yet to be realized — until now.

Developed by the Johns Hopkins Applied Physics Laboratory (APL) researchers, the wearable thin-film thermoelectric cooling (TFTEC) device is one of the world’s lightest, thinnest, and fastest refrigeration devices. In a form-factor similar to an adhesive bandage, TFTEC has a high-speed and cooling power density capable of matching the human body’s ability to rapidly sense temperature change, and thus providing intuitive thermal perceptions for those with missing limbs and prostheses. The device can also be applied to deliver temperature sensations to users in augmented reality situations to create more realistic and complex perceptions of touch for surgical and gaming applications.

The idea for TFTEC originated in 2000 while working on Office of Naval Research and Defense Advanced Research Projects Agency (DARPA) programs, when Rama Venkatasubramanian, at that time a semiconductor device engineer and currently Chief Technologist for APL’s thermoelectrics research, identified that thin-film nano-scale materials called superlattices can be designed to conduct electricity well, while being engineered to be poor conductors of heat — for the first time translating to a high thermoelectric performance at room temperatures.

After joining the APL, Venkatasubramanian continued development of superlattice structures that enabled an entirely new set of transduction capabilities for several Department of Defense applications, including cooling computer chips and engine components, and eventually facilitating temperature sensation in phantom limbs of amputees.

“Development of high performing, efficient N-type semiconductors remained a challenge until 2016 when the APL team was funded by DARPA to create the next generation of superlattice materials called Controlled Hierarchically Engineered Superlattice Structures (CHESS),” said Venkatasubramanian. “These structures enabled considerable progress in N-type materials development and device level innovations, and ultimately led to the invention of APL’s wearable TFTEC device.”

TFTEC was tested in trials with amputees and elicited cooling sensations in the phantom limbs of all participants during a cold detection task, whereas traditional thermoelectric technology only did so in half of them — and the TFTEC did so eight times faster and with three times the intensity. Additionally, TFTEC used half the energy compared to current thermoelectric devices.

At roughly 1 millimeter thick, TFTEC weighs only 0.05 grams, and uses almost 1/600th of the material commonly used in today’s commercial devices. These attributes deliver twice the energy efficiency found in other thermoelectric devices, enabling improved battery life — a critical capability for ease of use in wearable thermoelectric devices.

The TFTEC is manufactured using conventional semiconductor fabrication tools like those used in solid-state light emitting diode arrays, ideal for scaling production to manufacture large volumes of the devices for electronics, photonics, healthcare and augmented reality applications.

“In addition to demonstrating the TFTEC’s effectiveness in facilitating temperature sensation in phantom limbs of amputees for improved prostheses, the device enables new capabilities for a variety of applications, such as haptics for new modalities in augmented reality (AR) and thermally modulated therapeutics for pain management. The technology also has a variety of potential industrial and research use cases, such as cooling electronics and lasers and energy harvesting in satellites,” added Venkatasubramanian.

According to him, APL is engaged with several companies to license this technology for energy-harvesting wearable electronics and solid-state refrigeration applications as well as continues to consider and identify new licensing and partnership opportunities.

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This article first appeared in the November, 2024 issue of Tech Briefs Magazine (Vol. 48 No. 11).

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