Researchers have developed an innovative smart fabric capable of increasing its temperature by up to 54°F (30°C) using only sunlight. This fabric incorporates specialized nanoparticles within its fibers that are most commonly found in waterproof sportswear today. 

These nanoparticles absorb sunlight and convert it into heat. In tests, a small sweater knitted from this material reached approximately 128.3°F (53.5°C) after just 10 minutes of sun exposure.

The fabric features temperature-responsive dyes that change color as it warms, providing a visual indicator of temperature changes. I can see some instances where this has benefit (life saving rescue equipment, perhaps) but I'm not sure I'd want to walk around with a tell-tale sign that I just might be starting to break into a sweat.

Unlike traditional heated clothing that relies on battery packs or metal heating elements, this smart heating fabric is self-sustaining, lightweight, and durable. It retains its elasticity, can stretch up to five times its original size, and maintains both its heating efficiency and color-changing properties even after multiple washes. 

Potential applications include outdoor gear, rescue equipment, military apparel, and pet clothing designed for cold climates. The researchers aim to reduce production costs and simplify manufacturing processes to facilitate the integration of this material into future clothing lines.