A new fabric, developed by a team at the University of Maryland, is the first to automatically warm wearers up or cool them down as needed.
It was created using specially-engineered yarn created with fibers made of two different synthetic materials: one that absorbs water and one that repels it.
The strands are coated with carbon nanotubes. Each fiber expands or contracts when the temperature changes.
A team at Stanford created a similar fabric in 2017, but you had to reverse the garment to feel the effect.
To be useful, it would have to respond to the wearer, not the out-side temp. We respond to humidity and wind speed, for our sense of a comfortable temperature. the weather reports always give a temp. but forgo telling you the humidity is 90o. and wind speed at 2 mph.