Researchers at Stanford University have developed a reversible smart textile that, without any energy expenses, can either warm up or cool down the wearer depending on which side faces out.
The team, led by Yi Cui, Professor of Materials, Science and Engineering, believes the fabric could be a groundbreaking advancement for energy efficiency. Rather than warming or cooling entire buildings, individual people’s temperature could be adjusted according to their needs, with rippling effects on energy consumption.
Turning the temperature up or down by just a few degrees may not seem like a big deal; however, for every 1 degree Celsius a thermostat is turned down, a building can save 10 percent of its heating energy.
Human tactics of regulating temperature can only help within a restricted range of degrees. Taken beyond such temperatures our body is incapable of adapting, and that’s when technology comes into play.
The team had witnessed its first success in 2016 with the development of a permeable smart fabric that enables the body to expel and discharge its heat, cooling down the skin. This first plastic-based textile was inspired by transparent kitchen film; unlike cling film however, it was breathable, opaque and could protect the body from infrared radiation. Compared to a cotton sample, the fabric kept artificial skin 2°C cooler in a laboratory test, theoretically saving up to 20%-30% of a building’s total energy budget.
This year the team was able to solve the opposite problem, thanks to postdoctoral team fellow Po-Chun Hsu, who found that infrared radiation worked both ways. Hsu created a sandwich-like layer system, where two materials with a different heat-release ability and two layers of their own cooling polyethene. On one side, a copper coating traps the heat between a polyethene layer and the wearer’s skin; on the other, a carbon coating releases heat under another layer of polyethene. Worn with the copper layer facing out, the material is able to trap the heat and warm the skin in cold conditions.
At this stage, this smart textile is not ready to wear yet; the team’s goal is to make it into a fibre woven structure, more flexible and comfortable to wear in contact with skin.