On a hot summer day, many of us are fortunate enough to have access to a refrigerator stocked with ice-cold drinks in a comfortable, humidity-controlled room. From domestic appliances to stadium-sized central air-conditioning systems, cooling and air-conditioning today are often seen as basic necessities. Indeed, HVAC (heating, ventilation, and air-conditioning) is a multibillion-dollar industry. There is always a demand for more efficient, inexpensive, and versatile cooling equipment.

Vapor compression technology has been around since the early 19th century, and it continues almost unchallenged as the dominant means of cooling. In a vapor compression cycle, as seen in figure 1a, pressure converts the refrigerant gas to a liquid state and latent heat associated with the phase transition is unleashed. When the pressure is released and the refrigerant changes back to the gaseous state, the latent heat is reabsorbed, drawn in from the environment to be cooled.

Our ability to cool...

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