Phase-change materials (PCMs) show promise for this, and now engineers at Texas A&M have developed a new PCM composite that can be 3D printed.

The name "phase-change materials" is pretty self-explanatory – these materials will switch between phases of matter as the temperature changes. One of the most promising applications for this technology is insulation: the PCM melts into a liquid as it absorbs heat, cooling its surroundings. As the ambient temperature cools, the material will solidify again, releasing its stored heat.

In the past, PCMs have been used in coffee cups to keep hot drinks hot, fabrics that keep wearers warm or cool as needed, liquid coatings that prevent frost build-up, and in building materials that better regulate indoor temperature. It's that last one that the researchers on the new study wanted to improve.

Previous PCMs have been rather inefficient and costly, because they need a shell to contain their liquid form. That means pellets of PCMs need to be embedded into a building material, but fewer of them can fit in that form, and it can be difficult to scale that production.

For the new study, the Texas A&M researchers looked to mix a PCM directly into a building material. They mixed paraffin wax, as the PCM, with liquid resin as the supporting structure, creating a soft, paste-like material that can be shaped as needed. Once it's in the desired shape, it can be cured with UV light to harden the resin.