Fashion's Coolest Trend

Technology has advanced at such a rapid pace that it is often noted that today, most of us live more comfortable lives than even the kings of years long past. There is a lot of truth in this — consider the air conditioning that keeps us cool in scorching summers and the cozy embrace of central heating during the bitter cold of winter. And then there is the indoor plumbing that ensures we always have clean water at our fingertips, and also the convenience of electric lighting that banishes the darkness at will. Transportation has similarly been transformed, with cars, trains, and airplanes whisking us across vast distances in mere fractions of the time it once took.

The list of technological advancements goes on and on, but even still, there are persistent problems that just do not seem like they should exist any longer. For example, given the pervasiveness of indoor climate control, one might wonder why we cannot take this comfort with us on the go. Yet heating and cooling systems are not exactly standard features that we expect to find when shopping for a new T-shirt.

Liquid-cooling of garments has been explored extensively, and some systems have been developed, but they are highly impractical for normal, daily use. Existing solutions are tailored to special use cases, like for race car drivers spending hours on the track or surgeons performing lengthy procedures in the operating room. This is because, despite the flexibility and comfort of the tubing required for a liquid-cooled garment, bulky and noisy pumps and control systems are also needed for operation.

The dream of practical thermally-controlled clothing is now closer to reality, thanks to a team of researchers at the Shibaura Institute of Technology in Japan. They have built a lightweight and silent personal heating and cooling system that is small enough to fit in a shirt pocket. The innovative pump and monitoring system moves a liquid through soft tubes that easily conform to the shape of the body and induce temperature differences of approximately 5.4 degrees Fahrenheit.

The device utilizes an electrohydrodynamic pump, which injects electric charges inside of a liquid to create an electric field, which in turn sets the liquid in motion. Not only are these types of pumps light and silent, but they also offer high flow rates. However, a pump alone is insufficient to build a practical system. The flexible tubing is prone to being bent and creating blockages, which necessitates the presence of a monitoring system.

To avoid the bulk associated with traditional monitoring equipment, the team took a novel approach that allows the pump to effectively monitor itself. Under normal conditions, electrical current flows between electrodes in an electrohydrodynamic pump. When the flow rate changes — perhaps due to an obstruction — it causes the current flowing through the electrodes to also change. The researchers realized that by simply measuring the flow of current between the electrodes, they could efficiently monitor the flow of liquid through the system without any additional external components.

Using their techniques, the team built a personal, wearable cooling system that weighed just ten grams, with dimensions of 10 x 2 x 1.05 centimeters. It was demonstrated that this device could fit in a pocket and provide meaningful levels of both cooling and heating. Given the simplicity of the design, and the built-in monitoring system, it is anticipated that the device will have a long lifespan. But to extend the potential lifespan of the system even further, the researchers are presently experimenting with the idea of integrating self-healing liquids into the device in the future.