The patch — which serves as a personal thermostat — provides personalized cooling and heating at home, work, or on the go by cooling or warming the user's skin to a comfortable temperature and keeping it there as the ambient temperature changes.
The soft, lightweight, stretchy patch is powered by a flexible, stretchable battery pack and can be easily integrated into clothing. The device physically cools or heats the skin to a temperature that the wearer chooses. The patch was built by taking small pillars of thermoelectric materials (made of bismuth telluride alloys), soldering them to thin copper electrode strips, and sandwiching them between two elastomer sheets. The sheets were created by mixing a rubber material called Ecoflex with aluminum nitride powder, a material with high thermal conductivity. The patch uses an electric current to move heat from one elastomer sheet to the other. As the current flows across the bismuth telluride pillars, it drives heat along with it, causing one side of the patch to heat up and the other to cool down. To provide cooling, the current pumps heat from the skin side to the layer facing outside; to provide heating, the current is reversed so heat pumps in the other direction. The flexible battery pack is made of an array of coin cells all connected by spring-shaped copper wires and embedded in a stretchable material. The system also includes a stretchable circuit board. One patch measures 5 × 5 centimeters in size and uses up to 0.2 Watt of power; it would take 144 patches to create a cooling vest.
University of California San Diego, Jacobs School of Engineering
The team is now working on patches that could be built into a prototype cooling and heating vest and hopes to commercialize the technology.
The patch is more energy-efficient than heating or cooling a large room. It can improve personal thermal comfort whether the user is commuting on a hot day or feeling too cold in the office.