Traditional wearable thermal control devices use bulky and noisy components. New developments such as miniaturized electrohydrodynamic pumps and soft tubes offer a promising avenue for such devices. However, they require real-time flow rate monitoring, requiring additional equipment. Now, a team of researchers has developed a new device that uses self-sensing technology to monitor flow rate, resulting in a compact personal thermal control device, a breakthrough in wearable device research. It is an important step.

Imagine adjusting your clothing to beat the summer heat or winter chill by changing the temperature of your clothing on the go. Wearable thermal control devices promise just that, offering portable personal thermal comfort. Not only this, but these devices also have other applications such as providing temperature feedback in virtual and augmented reality and offering thermotherapy for heat problems. As a result, researchers are thoroughly exploring a variety of wearable thermal devices. In particular, soft robotics and liquid-cooled garments stand out for their ability to naturally conform to the human body.

Liquid cooling garments, already used by race car drivers, surgeons, chemotherapy, multiple sclerosis patients and athletes, circulate cold or warm fluids through a pump to alter body temperature. For this, tubes embedded in the fabric are used. However, these systems require heavy and noisy equipment to power them, making them cumbersome. Recently, the electrohydrodynamic (EHD) pump, which pumps liquids by placing charges inside the liquid and moving them using an electric field, is gaining attention for wearable devices. The EHD pump is quiet, lightweight, and offers higher flow rates than other pumps. Combining EHD pumps with soft tubes, which easily conform to the human body, provides a unique opportunity for compact and silent wearable thermal control devices. However, these flexible tubes can experience bottlenecks due to bending, requiring real-time flow rate monitoring and thus requiring additional equipment and power sources.

Addressing this problem, a team of researchers in Japan, led by Ph.D. Yu Kawajima, a student at Shibora Institute of Technology’s Department of Engineering Science and Mechanics, has developed an innovative pocketable and smart electrohydrodynamic pump (PSEP) for clothing. “Our innovative device, with its compact and stylish design, breaks down the size and appearance barriers associated with traditional wearable cooling and heating devices, while its self-sensing ability to monitor flow rates Increases system reliability without requiring any additional equipment.” Mr. Kuwajima explains. The team included Yuhei Yamada and Shingo Maeda from the Tokyo Institute of Technology, Noki Hosuya from the Shibora Institute of Technology, and Yasuke Kakihi from the University of Tokyo. Their study was made available online on December 14, 2023, and was published in the journal Volume 16, Issue 1. ACS Applied Materials and Interfaces On 10 January 2024.

A key innovation of PSEP is the self-sensing model of flow rates in EHD pumps. This self-sensing model uses changes in current between the electrodes of the PSEP to measure flow rate. 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 rate within the device itself. The team experimentally validated their model and found that the results were consistent with their theoretical calculations. Moreover, their testing revealed that PSEP can adjust the temperature up to 3 OC, significantly increase personal comfort.

Using this model, the team created a compact PSEP device that fits in a regular shirt pocket, offering stylish and discreet thermal control. Additionally, it features an intuitive smartphone interface for wireless control and monitoring. Additionally, its ability to detect and notify users of blockages through self-sensing ensures efficient operation and long life. In the future, the team plans to integrate technologies such as self-healing fluids and advanced materials into the PSEP to improve its flexibility.

“Next-generation wearable technology has the potential to go beyond mere gadgets and truly transform our lives,” says Mr. Kawajima, emphasizing the importance of this study. “The key lies in achieving both miniaturization and advanced functionality. Our research marks the beginning of this exciting journey, paving the way for a future where technology seamlessly integrates into our daily routines.” goes, and makes them richer and more comfortable.”