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Former student publishes research on wearable thermoelectric generators

Published Jan 07, 2018

Former student Akanksha Menon has showcased the possibility of wearable thermoelectric generators using polymers.

“Because these materials (polymers) are lightweight and flexible, we can target applications like flexible and wearable electronics for self-powered sensors and body heat harvesting,” said Menon who is currently a Ph.D. student in the Woodruff School of Mechanical Engineering at the Georgia Institute of Technology.

The research is sponsored by PepsiCo, Inc. and the Air Force Office of Scientific Research and was reported online in the Journal of Applied Physics on 28 Sept.

The concept of thermoelectric generators has been in existence for years. However, previous research has incorporated inflexible and toxic materials that are unsuitable for wearable devices. These designs have also proven to create temperature fluctuation and contain internal resistance that minimizes power output when applied from a small contact area of the skin.

To create a model that is feasible for a wearable generator, Menon and her collaborators at the laboratory of Assistant Professor Shannon Yee developed a model using wiring patterns based on symmetrical fractals as opposed to traditional serpentine wiring. The circuit pattern depended on alternating p-type and n-type polymer dots in a closely packed sequence facilitated by inkjet printers. This enables larger heat conversion and lower total resistance which results in higher output.

Additionally, the design allows the components to be cut between symmetric areas, allowing users to generate energy from surface area according to the voltage and power needed. This feature removed the need for power converters that reduces total power output. Moreover, the use of symmetrical fractals patterns allow for surface conformation and self-localization, which results in more uniform temperature across the device.

“This is valuable in the context of wearables, where you want as few components as possible,” Menon said. ,”“As mechanical engineers, we are designing completely new device architectures for these applications with the goal of improving the performance while maintaining low costs.”

As of now, the circuit has been printed on ordinary paper but Menon and her fellow researchers are looking to explore the incorporation of the devices into fabrics used in commercial, daily clothes.

“People would feel comfortable wearing these fabrics, but they would be able to power something with just the heat from their bodies,” Menon said. The electricity harvested from the generated body heat is expected to be able to power simple biosensors, in the range of microwatts to milliwatts, for measuring various factors such as heart rate and respiration. There is also a possibility that the power from these wearable generators can supplement and prolong battery-operated devices. However, some of the challenges ahead are finding ways to protect the generators from moistures and determining their distance to the skin to transfer heat energy.

Menon, who graduated from Texas A&M at Qatar in 2013, is a Qatar Foundation fellowship recipient. After she completes her studies, Menon hopes to be able to gain postdoctoral experiences to enhance her expertise in heat transfer and energy systems. She plans to bring these advanced skill sets back to Qatar in research initiatives at Qatar Environment & Energy Research Institute (QEERI) or at Texas A&M at Qatar.

“The process of going through a Ph.D. gives you a skill set to solve a variety of research challenges,” said Menon, “I hope to be able to apply my background in thermal systems and polymer-based materials to address challenges within the energy-water nexus.”