A new approach to the passive heating and cooling of buildings, cars and consumer devices is being advanced at the University of Melbourne, Australia. control temperature in everyday environments. Proof-of-concept phase change inks have been formulated to adjust the amount of radiation that can pass through them, based on the surrounding conditions.

To supply heating needs in winter, the inks applied on a building façade could automatically transform to allow increased solar radiation to pass through during the day, and greater insulation to keep warmth in at night. In summer, the vanadium oxide-based materials could transform to form a barrier to block heat radiation from the sun.

Phase change materials typically must be heated to very high temperatures to provide the energy required to transform under stress. The researchers bypassed this thermal requirement: “We used our understanding of how these materials are put together to test how we could trigger the insulator to metal reaction, where the material basically acts as a switch to block heat beyond a particular temperature — near-room temperature.”

The inks described in The Royal Society of Chemistry's Journal of Materials Chemistry A can be laminated, sprayed or added to paints and building materials. The novel materials could also be incorporated into clothing, regulating body temperature in extreme environments, or in the design of large-scale, flexible and wearable electronic devices like bendable circuits, cameras and detectors, and gas and temperature sensors.