This innovation has two main parts — a wireless, flexible film heater containing multi-walled carbon nanotubes (MWCNTs) to convert radiated microwave energy into heat, and a radio frequency identification (RFID) temperature sensor to provide wireless temperature feedback.

The MWCNTs have been demonstrated to convert microwave energy directly to heat, thus providing a wireless heating mechanism. This mechanism can be used to produce flexible composite materials that can serve as wireless heater elements. The addition of a surface acoustic wave (SAW) RFID temperature sensor in direct contact with the flexible wireless heater elements permits sensing of the resulting temperature response, wirelessly, using RFID technology. The manufacture of the flexible heaters with MWCNT, and the use of radiated microwave energy as a source for the heaters, has been successfully demonstrated during a proof-of-concept development phase. This use of SAW RFID technology in conjunction with the film heater has also been demonstrated.

The innovation comprises a flexible wireless heater element consisting of MWCNT sandwiched into various flexible substrates (such as polyurethane or Teflon FEP), and an integral SAW RFID temperature sensor in direct contact with the wireless heater. The microwave source, the RFID reader, and the associated computer equipment are not considered part of this innovation, but are required for operation; the software required to provide temperature data to start/stop microwave broadcasting is part of this innovation.

A flexible wireless heater with an integral RFID temperature sensor is affixed to a component/system requiring heat. An external microwave source, providing the required microwave power flux density at the desired frequency, is energized to beam microwave energy to the heater element. The flexible wireless heater absorbs the incoming microwave radiation and, consequently, converts this energy to heat.

Periodic wireless interrogation of the RFID temperature sensor allows temperature monitoring of the heater element or the component to be heated. The temperature interrogation unit, when connected to a computer that controls the microwave energy, may be programmed to terminate the microwave energy when a specified cutoff temperature is sensed. Upon cooling to a specified temperature, the microwave energy is restored, allowing the heater to resume operation. Through this closed-loop feedback, a wireless heater with thermostatic control is possible.

This work was done by Phong Ngo, Patrick Fink, and Steven Rickman of Johnson Space Center, and Edward Sosa of ERC Inc. MSC-24962-1

NASA Tech Briefs Magazine

This article first appeared in the February, 2016 issue of NASA Tech Briefs Magazine.

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