Research team develops wearable device for fashionable personal thermal comfort

Imagine adjusting your clothes to beat the summer heat or winter cold simply by changing the temperature of your clothes, on the go. This is exactly what wearable thermal control devices promise, providing portable personal thermal comfort. Not only that, but these devices also have other applications such as providing temperature feedback in virtual and augmented reality and thermotherapy for heat issues, among others.

Therefore, researchers have explored different types of wearable thermal devices in depth. In particular, soft robotic clothing and liquid-cooling clothing are distinguished by their ability to naturally adapt to the human body.

Liquid cooling clothing, already used by race car drivers, surgeons, chemotherapy patients, multiple sclerosis patients and athletes, uses tubes built into clothing to circulate cold or hot liquids via a pump to change body temperature. However, powering these systems requires bulky and noisy equipment, making them cumbersome.

Recently, the electrohydrodynamic (EHD) pump, which pumps liquids by injecting charges inside a liquid and moving them using an electric field, has attracted the attention of portable devices. The EHD pump is quiet, lightweight and offers higher flow rates than other pumps.

The combination of an EHD pump with flexible tubing, which easily adapts to the human body, provides a unique opportunity for compact and quiet portable thermal control devices. However, these flexible tubes can experience blockages due to bending, requiring real-time flow monitoring and thus requiring additional equipment and power sources.

To solve this problem, a team of Japanese researchers, led by Ph.D. Yu Kuwajima, a student from the Department of Engineering Sciences and Mechanics at Shibaura Institute of Technology, developed a new electrohydrodynamic pump ( PSEP) innovative, pocket-sized and smart, for clothing.

“Our innovative device, with its compact, sleek design, breaks the size and appearance constraints associated with traditional portable cooling and heating devices, while its self-sensing capability to monitor flow rates improves system reliability without requiring additional equipment. » explains Kuwajima.

The team included Yuhei Yamada and Shingo Maeda from the Tokyo Institute of Technology, Naoki Hosoya from the Shibaura Institute of Technology, and Yasuaki Kakehi from the University of Tokyo. Their study is published in ACS Applied Materials and Interfaces.

A key innovation from PSEP is the self-sensing model of flow rates in EHD pumps. This self-sensing model uses current changes between the electrodes of the PSEP to measure flow. If a load changes the flow rate, the current through the electrodes changes. This change in current can then be used to measure the flow inside the device itself.

The team experimentally validated their model and found that the results were consistent with their theoretical calculations. Additionally, their tests revealed that the PSEP can adjust the temperature by up to 3°C, significantly improving personal comfort.

Using this model, the team built a compact PSEP device that fits into a regular shirt pocket, providing sleek and unobtrusive thermal control. Additionally, it features an intuitive smartphone interface for seamless wireless control and monitoring. In addition, its ability to detect and warn users of blockages, thanks to auto-detection, guarantees efficient operation and a long lifespan. In the future, the team plans to integrate technologies such as self-healing liquids and advanced materials into the PSEP to improve its resilience.

“Next-generation wearable technology has the potential to go beyond simple gadgets and truly transform our lives,” says Kuwajima. “The key lies in achieving both miniaturization and advanced functionality. Our research marks the start of this exciting journey, paving the way for a future where technology will seamlessly integrate into our daily routines, making them richer and more comfortable.”