Hot Bodies: The Future of Wearable Technology
By Jason M. Denoncourt, Chemical Engineering and Biochemistry, 2023
Wearable technology has emerged as the newest hot trend. Whether it be the newest Apple Watch, Google Glasses, or virtual reality headset, one common annoyance remains: batteries. Despite technological innovations over the past few decades, there is still no solution to dead smartwatches or fitness trackers. Thermoelectric generators, which harness energy from body heat, integrated into clothing could be a solution.
The current iteration of wearable thermoelectric generators has numerous flaws. Many have oversized, bulky components that inhibit range of motion. Others reach thermal equilibrium with the human body too fast to generate useful amounts of energy. These products also commonly contain rare materials that are effective conductors but are toxic and of limited availability.
The role of toxic semiconductors in traditional thermoelectric generators can be mimicked by a vapor–printed, thin coat of a compound known as PEDOT-Cl.
The Wearable Electronics (WE) Lab, led by Dr. Trisha L. Andrew of the University of Massachusetts, Amherst, has developed all-fabric wearable thermoelectric generators that resolve many of the issues encountered with current models. To tackle biocompatibility and toxicity, her team applied vapor printing — a complex process of layering thin organic films onto a surface. The role of toxic semiconductors in traditional thermoelectric generators can be mimicked by a vapor–printed, thin coat of a compound known as PEDOT-Cl. This alternative is much more versatile, as Andrew’s focus on fabric meets the need for flexibility in the generators.
After vapor-printing the cotton samples, Andrew tested the effectiveness of the cotton by a series of experiments. Since Andrew emphasizes the development of physical, wearable garments, she studied the cotton’s conductivity and thermoelectric energy generation in parts of the body. With the use of a thermal camera, Andrew focused on the upper arms, palms, and wrists, which demonstrate the greatest radiation of heat. Another factor the team considered was exercise; perspiration significantly increased the thermovoltage output of a thermoelectric generator armband. The PEDOT-Cl coating also turned out to be very durable; the electrical conductivity remained essentially unchanged after vigorous rubbing and cleaning of the fabric.
The PEDOT-Cl coating also turned out to be very durable; the electrical conductivity remained essentially unchanged after vigorous rubbing.
Though the PEDOT-Cl coating is much more practical and has far improved applications in wearable garments, the models developed by Andrew and her team were only able to output a stable thermovoltage as high as 23 mV. Considering it takes upwards to 120 V to power a lightbulb, the release of a mass-market product remains far into the distant future.
Sources
Adv. Mater. Technol. (2019). DOI: https://doi.org/10.1002/admt.201800615
