HRL Laboratories’ Ultrathin Heat Exchangers Could Pave the Way for Artificial Organs

Penguins count on heat exchange to keep their feet warm. Cars rely on heat exchange to keep their engines cool. Researchers at HRL Laboratories, LLC, have announced that they have developed a miniaturized, high-performance heat exchange method that could be the first breakthrough in creating artificial organs.

According to Dr. Christopher Roper, HRL senior research staff engineer and project leader, both natural and engineered systems depend on the efficient exchange and transfer of heat and material to function. “In nature, blood vessels in penguin legs facilitate the transfer of heat from penguin arteries to penguin veins, preventing heat loss from a penguin’s feet to the ice,” he said. “In an engineered system, a radiator transfers heat from engine coolant to outside air, removing heat from a car’s engine.”

HRL’s groundbreaking process starts with 3D printing or additive manufacturing methods, which use lasers to build up the object one ultrathin layer at a time. “Typically, these 3D printed walls are limited by each layer’s resolution constraints,” said Roper. “We were able to overcome these limits by adding a coating step followed by mold removal step, creating walls measuring less than 1 micron – potentially 100 times thinner than a human hair.”

Overcoming the resolution limits of previous additive manufacturing methods was key to making high-performance heat exchangers from thermally insulating polymers. “By making the walls of the exchangers as thin as a sheet of paper, heat conduction through the walls does not limit the heat exchange,” said Dr. Roper.

The HRL method uses hundreds to thousands of self-aligned fluid connections to separate and combine fluids. “These bicontinuous fluid networks enable mass and heat transfer without fluid mixing and without the need to separate all components of each stream after the exchange,” said Roper. This is similar to the functions performed by cardiopulmonary bypass and hemodialysis machines outside the body, he noted.

The team’s findings, “Scalable 3D Bicontinuous Fluid Networks: Polymer Heat Exchangers Toward Artificial Organs,” published in the journal Advanced Materials, have enormous potential for applications ranging from lightweight radiators for more fuel efficient cars and aircraft, to compact artificial organs – like lungs and kidneys – that exchange mass.

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HRL Laboratories, LLC, Malibu, California ( is a corporate research-and-development laboratory owned by The Boeing Company and General Motors specializing in research into sensors and materials, information and systems sciences, applied electromagnetics, and microelectronics. HRL provides custom research and development and performs additional R&D contract services for its LLC member companies, the U.S. government, and other commercial companies.

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