Tech Briefs

Enhanced sensing and/or actuation functionalities are imparted to solid surfaces.

"Smart” skin materials based, variously, on polymers, dendrimers, carbon nanotubes, and/or other tailored molecular components are being developed for use as conformal coating surfaces of mechanical structures, including those of aircraft, to impart enhanced functionality to the coated surfaces. As used here, “smart” signifies that a material so characterized exhibits a useful physical response (e.g., a change in color) to a change in some aspect of its environment (e.g., temperature or pressure) or to a control or actuation signal. It is envisioned that smart skin materials could be used for diverse purposes, including sensing surface flow conditions and altering surface optical properties to enable detection, concealment, or display. It is further envisioned that smart skin materials could be integrated with microscopic electronic, optoelectronic, electro-optical, and microelectromechanical devices to obtain smart skins exhibiting even more varieties and higher degrees of functionality.

The scope of this development effort is so broad and deep as to preclude a detailed description within the space of this article. The accomplishments thus far can be summarized as follows:

  • State-of-the-art pressure- and temperature- sensing luminescent paints have been developed and applied to models used in wind tunnel testing. Progress has also been made in incorporating other functionalities into paints to be used for diagnosis of aircraft, groundvehicle, and ship surfaces.
  • Substantial progress has been made in developing light-harvesting and frequency- conversion coatings and improving the efficiency of metals by exploiting the site isolation afforded by the cores of dendrimers. Significant progress has been made in developing new photonic-bandgap materials. The state of the art of polymeric, dendritic, and dendronized-polymer electro-optical materials has advanced to the point where the performances of these materials, as measured in terms of bandwidths and required drive voltages, now significantly exceed those of such inorganic materials as lithium niobate.
  • New materials have been incorporated into such novel thin-film device structures as those of ring microresonators, enabling manipulation of light in novel ways, including active wavelength- division multiplexing (time and wavelength information encoding) and voltage-controlled wavelength selective filtering.
  • A variety of new sensors, notably including microresonator-based strain and temperature sensors, has been developed.
  • Flexible polymeric electro-optical devices have been fabricated and evaluated.
  • Significant advances have been made toward realizing the potential of carbon nanotubes for smart-skin applications, including the potential use of carbonnanotube- containing smart skins as radar-absorbing materials and as microelectromechanical systems (MEMS).
  • Advances have been made in polymeric thin films for light-emitting, electronic, and photovoltaic applications.

This work was done by Larry Dalton of the University of Washington for the Air Force Research Laboratory. For more information, download the Technical Support Package (free white paper) at www.defensetechbriefs.com/tsp under the Materials category. AFRL-0014

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Polymeric “Smart” Skin Materials (reference AFRL-0014) is currently available for download from the TSP library.

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