NASA’s Langley Research Center has extensively studied self-metallized polyimide films for aerospace applications. These thin films have shown promise not only as reflective coatings, but also conductive coatings. NASA believes that its technology may offer advantages to sensor companies, especially thermocouples as the conductive films show a volume resistivity approaching the pure metal. Specifically, NASA offers a process for producing metallized polymer films with thick conductive metal coatings.
Work to date has been performed with polyimides, but the technology is expected to work with a variety of solvent castable polymers, as well as a variety of metal coatings, including silver, palladium, copper, and aluminum. The process is simple, readily scalable, does not employ vacuum processing, does not require a separate step for surface preparation or deposition of a tie-coat, and provides excellent adhesion. Functionally, the invention creates a metal tie-coat as part of the plastic film casting and curing process. The as-processed self-metallized film is then subjected to electroplating using the self-metallized layer as an electrode in order to build up substantial thickness of high-quality metal film. It is believed that the entire process of film formation and electroplating could be run in a continuous fashion.
The use of polyimide film substrate makes the resulting sensor flexible and conformable. In addition, it has increased conductivity and better heat transfer because the polyimide substrate has metal particles embedded in it. The technology can be tailored for applications based on the potential to use varied materials in bi-layers, enabling manufacture of thermocouples with improved performance at extended temperatures.
The conformable nature of this sensor enables it to be located in tight spaces, and also around complex shapes where monitoring would otherwise be difficult. In automotive applications, it could apply to under-the-hood sensing; in aeronautics, it could offer benefit on structures and areas of high thermal load; and in industrial monitoring, it lends itself to extreme environments. Other applications might include capacitors, flexible circuit boards (flex circuits), varied sensors, antennas, and EMI shielding.