Probe is sufficiently flexible so that it can be worn comfortably for long periods of time, but relatively rigid to permit easy insertion. Body and electrical leads of small thermistor are imbedded in flexible fluorosilicone matrix contained in vinyl plastic tubing

Beljan, J. R.

Haro, P. J.

Winget, C.

English

NASA Technical Reports Server

B73-10498 
NASA TECH BRIEF 
Ames Research Center 	
-im 
Dece'mber 1973
NASA Tech Briefs announce new technology derived from the U. S. space program. They are issued to encourage 
commercial application. Tech Briefs are available on a subscription basis from the National Technical Information 
Service, Springfield, Virginia 22151. Requests for individual copies or questions relating to the Tech Brief program may 
be directed to the Technology Utilization Office, NASA, Code KT, Washington, D.C. 20546. 
Flexible Temperature Probe for Biological Systems 
S
The problem: 
To construct a small probe for sensing rectal tem-
perature in human subjects; the probe must be suffi-
ciently flexible so that it can be worn comfortably for 
long periods of time, but relatively rigid to permit 
easy insertion. 
The solution: 
Imbed the body and electrical leads of a small 
thermistor in a flexible fluorosiicone matrix contained 
in vinyl plastic tubing. 
How it's done: 
The electrical leads of a small thermistor are cut at 
staggered lengths, the longest at 25.4 mm, and then 
soldered to polytetrafluoroethylene-coated wire (29 
AWG, 51 strands) of appropriate length. The wires 
are twist-braided and inserted into a long sheath 
made of fluorosilicone rubber tubing (1.6-mm I. D. x 
2.4-mm 0. D.) up to the thermistor tip. To strengthen 
the cable while maintaining flexibility, the tubing is 
filled with liquid fluorosiicone rubber and allowed 
to cure for 24 hours; interconnected ties made with 
surgical silk above and below the solder joints act as 
a strain relief. The thermistor, leads, solder joints, and 
part of the cable are inserted into a 50-mm length of 
vinyl plastic sleeve so that the sensitive end of the 
thermistor extends about 1.6 mm beyond the sleeve.
Finally, the exposed thermistor, sleeve, and part of 
the attached cable assembly is encapsulated for a 
length of about 125 mm by dipping it in a white, 
room-temperature-vulcanizable silicone rubber com-
position that has been diluted with a light solvent so 
that thin coatings can be applied. The encapsulant is 
allowed to dry somewhat; then another coat is ap-
plied and allowed to cure for 24 hours prior to use. 
Note: 
No additional documentation is available. Specific 
questions, however, may be directed to: 
Technology Utilization Officer 
Ames Research Center 
Moffett Field, California 94035 
Reference: B73-10498 
Patent status: 
NASA has decided not to apply for a patent. 
Source: Peter J
.
 Haro and Charles Winget 
Ames Research Center 
with John R. Beljan of 
University of California at Davis 
under contract to 
Ames Research Center 
(ARC-10796) 
Category 05 
This document was prepared under the sponsorship of the National 	 Government assumes any liability resulting from the use of the 
Aeronautics and Space Administration. Neither the United States 	 information contained in this document, or warrants that such use 
Government nor any person acting on behalf of the United States 	 will be free from privately owned rights.
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Flexible temperature probe for biological systems

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