Project Title:

Thin Film Sensing Elements for Skin Friction Imaging Arrays (7 124- 570)

  	  94-1	02.08	0003

  	  Thin Film Sensing Elements for Skin Friction Imaging Arrays 
  (7 124-
  	  570)

Abstract:

Physical Sciences Inc. (PSI) herein proposes to continue 
engineering development of a new skin friction imaging 
measurement 
technique suitable for aerodynamic and hydrodynamic flow 
fields. A 
previous NASA-sponsored effort has demonstrated the key 
component 
technologies for a new approach to skin friction and surface 

contamination measurement which offers the potential of high 

resolution readout and display in real time for wind tunnel 
instrumentation and aeronautical applications. The Phase I 
program 
will demonstrate the feasibility of manufacturing integrated 

sensing elements. A single prototype skin friction sensor 
with 
integrated thin film transistor, i.e., a "unit cell" of the 
proposed arrays, will be developed, and tested in the Phase I 
program. Ultimately, the device would consist of an array of a skin 
friction sensors integrated into a thin, flexible sheet or "skin". 
High sensitivity, flexible pyroelectric sensors which accumulate 
charge in proportion to local temperature changes, can monitor 
local surface cooling rates after known heat pulses are delivered 
by heating films. This cooling rate has a simple relationship to 
the skin friction. In principle, temperature changes, and thus the 
skin friction, can be sampled and read out with hard-wired dynamic 
and analog shift registers, similar to CCD arrays. As a 
prerequisite to actual TFT switch fabrication, the ability to 
deposit semiconductor grade amorphous hydrogenated silicon on 
polymers such as polyimide has been previously demonstrated. Such 
a sheet could be readily attached to any surface and the skin 
friction monitored and displayed continuously in, for example, RGB 
video format.

A non-intrusive skin friction `camera' has the potential to become 
a commercial product usable on commercial aircraft and in fluid 
dynamics laboratories around the world including several NASA 
facilities. These distributed sensor arrays could be installed on 
aircraft wings with outputs coupled to control system which improve 
aerodynamic performance. Because they readily detect surface ice 
contamination, such sensors could also serve as the basis for 
efficient, adaptive anti-icing techniques with significant 
commercial potential.

Key Words

Physical Sciences Inc.
20 New England Business Center
Andover, MA 01810-1077