A miniaturized heat-exchange technology developed by HRL Laboratories (Malibu, CA) may represent a breakthrough in the creation of artificial organs, according to researchers. HRL, which is jointly owned by The Boeing Co. and General Motors, used 3D printing to build paper-thin walls for the heat exchanger that allow heat conduction without limiting heat exchange.
|Dr. Christopher Roper, HRL
The novel heat exchange system developed by HRL uses "stereolithography to generate sacrificial scaffolds from a photopolymer," Roper explained to PlasticsToday. "We then uniformly coat these photopolymer scaffolds with parylene. Finally, we selectively remove the sacrificial photopolymer to leave a pure parylene heat exchanger," said Roper.
Parylene polymers are applied by chemical vapor deposition and are used extensively in electronics, aerospace and medical applications. The thin, conformal coating material typically is pinhole-free and withstands exposure to organic solvents, inorganic reagents and acids.
The 3D-printed walls typically are limited by each layer's resolution constraints, noted Roper in a news release. By adding a coating step followed by a mold removal step, the researchers were able to create walls measuring less than 1 micron, potentially 100 times thinner than a human hair, he added.
Other methods besides 3D printing can be used to generate the sacrificial scaffold, Roper told PlasticsToday. "For instance, we used HRL's photopolymer waveguide process as an alternate method in some cases. However, 3D printing allows a wider variety of features, which can be good for improving heat and mass transfer performance."
The HRL method uses hundreds to thousands of self-aligned fluid connections to separate and combine fluids. The 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, explained Roper. This is similar to the functions performed by cardiopulmonary bypass and hemodialysis machines outside the body, he noted.
The potential wide-ranging applications of the technology include lightweight radiators for fuel-efficient cars and aircraft and compact artificial organs, such as lungs and kidneys, that exchange mass.
The team's findings have been published in the journal Advanced Materials under the title, "Scalable 3D Bicontinuous Fluid Networks: Polymer Heat Exchangers Toward Artificial Organs."