While there are already garments which cool or warm their wearer via circulating liquids, those garments tend to be equipped with cumbersome, noisy pumps. An experimental new system, on the other hand, uses interwoven tubular fibers as pumps.
Created by scientists at Switzerland’s EPFL research institute, the technology incorporates 2-mm-wide fibers which can be woven into conventional yarn. Each hollow fiber is produced by first winding polyurethane threads and two copper wires around a steel rod, heating the threads and wires so that they fuse together, then sliding out the rod.
When the resulting tube is filled with a special non-conductive liquid and connected to a small wearable power supply, the two helically wound wires act as electrodes, ionizing and accelerating the liquid’s molecules. This in turn generates a completely silent net forward flow of the fluid, based on a principle known as charge injection electrohydrodynamics.
The pressure of the liquid within the tubular fibers varies with each fiber’s length – the shorter the fiber, the higher the pressure.
Additionally, if a network of the fibers were to circulate their liquid through a small heated or cooled wearable reservoir, they could heat or cool the wearer accordingly. Not only could such a system simply keep people comfortable, but it might also be used to reduce inflammation or to enhance the performance of athletes. The fibers could even be incorporated into artificial muscles utilized in assistive exoskeletons.
And what’s more, the materials used in the technology are inexpensive, plus the fiber pumps can withstand being machine-washed with detergent.
“The pumps already perform well, and we’re confident that with more work, we can continue to make improvements in areas like efficiency and lifetime,” said postdoctoral researcher Michael Smith, lead author of the study.
A paper on the research was recently published in the journal Science.