A Solid State “Air Conditioner” for You and Your Smartphone

Electronic devices and systems have seen tremendous technological growth on two main fronts: increased functionality on a single device unit and miniaturization of each unit. But these advances pose challenges, as well. Both of these developments have increased the need for thermal management technologies.

Researchers have developed a flexible polymer film that can be adapted for devices with complex curvature or with moving surfaces. The film’s flexibility could be used in wearable electronics, robotic systems and new types of personalized cooling systems.

The application is the first solid state cooling device based on the electrocaloric effect, a phenomenon in which a material’s temperature changes when an electric field is applied to it. Developed by engineers and scientists from the UCLA Henry Samueli School of Engineering and Applied Science and SRI International, the device could also prevent smartphones and laptop computers that use power-intensive applications from overheating.

Solid-state cooling requires changing an external field to drive cooling, but current devices have proved inefficient for practical applications. The researchers constructed a lightweight and flexible device using a thin electrocaloric polymer film, where toggling it in an electric field between a heat source and “heat sink” drives the cooling process.

They found the device rapidly cools an overheated smartphone battery, demonstrating potential application for developing compact, low-profile electronics. Solid-state refrigeration offers potential advantages over traditional cooling systems, but few devices offer high specific cooling power with a high coefficient of performance (COP) and the ability to be applied directly to surfaces.

“We were motivated by the idea of devising a personalized cooling system,” said UCLA professor Qibing Pei, the study’s principal investigator. “For example, an active cooling pad could keep a person comfortable in a hot office and thus lower the electricity consumption for building air conditioning. Or it could be placed in a shoe insole or in a hat to keep a runner comfortable in the hot Southern California sun. It’s like a personal air conditioner.”

That tendency for electronic devices to overheat remains a key challenge. The cooling systems in larger devices like air conditioners and refrigerators, which use a process called vapor compression, are simply too large for mobile electronics. They are also impractical for smartphones and wearable technology because they use a chemical coolant that is an environmental hazard.

“The development of practical efficient cooling systems that do not use chemical coolants that are potent greenhouse gases is becoming even more important as developing nations increase their use of air conditioning,” says Roy Kornbluh, an SRI research engineer.

The UCLA–SRI system also has certain advantages over another advanced type of cooling system, called thermoelectric coolers, which require expensive ceramic materials and whose cooling capabilities don’t yet measure up to vapor compression systems.

The researchers have submitted a U.S. patent application for the device.

The research was published in Science.

In its August report, Thermal Management Technologies for Semiconductor Microchips, BCC Research projects the global market to reach nearly $4.7 billion and $6.3 billion in 2017 and 2022, respectively, with a 6.0% CAGR.

For detailed market forecasts on thermal management in microchip technologies, an overview of thermal management interface materials and segments, including heat sinks, fans and blowers, fan sinks, heat pipes, cold plates and thermoelectric technologies, download the free report overview.