A pressure transducer is described in which the sensing element is a crystal of the monomeric charge transfer complex of pyrene and tetracyanoethylene

Rembaum, A.

English

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FROM:
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Counsel for Patent Matters
SUBJECT: Announcement of NASA-Owned U.S. Patents in ST7-VR
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In accordance with the procedures agreed upon by Code GP-4
and Code NI-IB , the enclosed NASA-owned U.S. Patent is being
forwarded for abstracting and announcment in NASA STAR.
The following information is provided:
U . S . Patent No. : 3,641.470 _
or
Corporate Employee
Supplementary Corporate
Source (if applicable)
NASA Patent Case No.
California Institute of
Technology, Pasadena, CA
JPL
NPO-11,150
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NOTE - Is this an invention made by a corporate employee
of a NASA contractor? YES (
 y | NO
If "YES" is checked, the following is applicable: Pursuant
to Section 305 (a) of the National Aeronautics and Space 7\ct,
the name of the Administrator of NASA appears on the first
page of the patent; however, the name of the actual inventor
(author) appears at the heading of column No. 1 of the
Specification, following the words "...with respect to an
invention of ..."
Elizabeth A. Carter/-v
Enclosure
https://ntrs.nasa.gov/search.jsp?R=19780009416 2020-03-20T12:51:47+00:00Z
• United States Patent
RembscmetsL
(15) 3,641,470
Feb. 8, 1972
[54] PRESSURE TRANSDUCER
• [72] Inventorc Abn Beeboxa, Ahadoa, C*Kf.; Aba H.
Kenans, New Orfeam, La.
{731 AMgnoe: CaEfonda festftafe of Tcctacfaor.
. li
UNTIED STATES PATENTS
(221 Filed: Styt.lt, 19*9
'[21] AppLNo.: 658^ 50
(56]
2,951,817 9/l<*0 Myen
3,451,032 6/1969 Tempel
Primary Examiner— Rodney D. Bennett, Jr.
Assistant Ezamintr—R. Ktoberg
Attonvy—Sokoiski & Wohigemuth
338/100 X
338/114
I57J ABSTRACT
(52J U&CL
[5!) Lsi.O
[58]
J38/99,338/36,338/100
„ HCltS/06
338/36,99.100.1 U.47
Crystals at a monorotric charge-traiafer complex of
pyTenst:c^cy83octh)-ltna are found to hsve ea e?sctricai coft-
ductivity that fe wstrenseJ? cresgure dcpsaJeRt, fuch dist tbete
crystals can form the £=ndr.g etement of s t»vd ptessure
6 Gstea, 2 DrtwSsg F%BNS
PATENTEOFEB 81972 3.641,470
PRESSURE DEPENDENCE OF THE RESISTIVITY OF PYROiE -TCNE
CHARGE-TRANSFER COMPLEX
100
J0£
I I
Q QlA,_.Of CONTACT AREA = '/"
~~ '"~ " ~" " " — - — • ! by
Q CHA. OFCONTACT AREA* i£
8 12 16 20
PRESSURE — Kbar
!\ 1 /
II
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19
32 36
FIG. 2
PIG. I
ALAN REM3AUM
ALLEN M. HERMANN
, » 3,641,470
1 2
PRESSURE TRANSDUCER The complex of pyrene and TCNE is prepared by preferably
r»n-n«nFTWPivvEwnnM dissolving approximately equal portions of these material in a
ORIGIN OF THE INVENTION suitable solvent such as ethytacetate. Additiorud rther surubie
The invention described hereir. was made in the per- solvents will include, for example, benzene, toluene.
fbrmance of work under a NASA contract and is subject to the 5 tetrahydrofiirtn and the like.
provisions of Section 305 of the National Aeronautics and The two components can be dissolved in a large excess of
Space Act of 1958, Public Law 83-568 (72 StaL 435; 42 USC solvent without heating. However, it is preferable to dissolve
24S7). each component in solvent and heat same to between about
in 50° and 80° Cor up to the boiling poi".t of the solvent. The in-
BACKGROUNDOFTHE INVENTION '0 dividual heated solutions are then mixed together. Tlie solu-
1. Field of the Invention - tion °* pyrene and TCNE may be evaporated in a beaker
This invention is in the field of pressure transducer*. More under a hood or in a flask by applying a tow vacuum. The size
particularly, the invention relates to the novel utilization of a of the resulting crystals depends on the time period of
particular rooBomeric charge-transfer complex as a sensing 15 evaporation The slower the rate the evaporation the larger
etement in a pressure transducer and the resulting transducer *« crystals obtained. After formation of the crystals, they are
which possesses high-pressure sensitivity. filtered from the remaining solvent in the rcactioa vessel.
2. Description oT the Prior An . It is often desirable to provide the rexuiring compiest in the
Prior to the herein invention, several studies have been coa- f«m of a single crystal to which conductive plates could be
ducted relating to the pt essare dopendecce of the conductivi- 20 adequately bonded. Th; process to obtain a sing-* crystal is
ty of organic semiconductors. Tie studies have included the same as previously described for several crystals, however
materials such as polycyciic aromatic hydrocarbons, the solvent is evaporated much slower. A typicsl crystal on the
polymers, charge-transfer complexes, free radicals polymers order to 3X4 millimeters/2 millimeters thick can thus be
such as poiyvinyi-anthrscene-iodine and monomeric charge- formed upon slow evaporation over, for example, a several
transfer complexes. From the studies of these various materi- 25 day period. This slow evaporation might occur, for example,
ab, it was found that their electrical conductivity increased by under a nitrogen gas atmosphere.
a tactOT of from 10 to 10,000 for a tenfold increase of pres- In addition to providing a single relatively large crystal, *
sure. In other words, the maximum sensitivity of the prior art pellet of many smaU crystals can be used. It has been found
organic semiconductor devices was a three order magnitude that ground or crushed crystals of the complex can be pressed
increase in conductivity for a tenfold increase in pressure. -° into a coherent pellet mass; this pellet can be utilized in the
This range of sensitivity was not sufficient to provide same manner as a single crystal v/ith good results. As can be
widespread utilization of these materials for pressure traradu- appreciated, the formation of such a pellet enables one to con-
cen. trol the size of th; sensing element formed from the complex.
OB^ANDSUMMARVOPTHEtKVENTION 35
Thus, an object of this invention is to provide a pressure crystal are bonded conductive plates 13 which can be formed
transducer utilizing a novel sensing element of silver or other suitable highly conductive material. The
A fu.thtr object of this invention is to provide a sensing ele- plates can be bonded to the crystal by silver paste, soWer or
ment for a pressure transducer which possesses a significantly 40 other like conductive adhesive-type material.
greaser sensitivity to increase in pressure than similar prioi art Individual kads IS arc aSixed to each of the plats 13 and
tnslerials. ' are directed to both a power source 17 and a meter 19 forming
The above and other objects of the invention are derived a circuit such that the variance in conductivity of the complex
from the utilization of the monomeric charge-transfer com- 1 ! can be adequately measured with changes in external pres-
ptex pyrene-t£tracyanaethy!ene as the sensing element in a 45 sure upon the plates 13. The power source can supply virtually
pressure transducer. This charge-transfer complex can be pro- any voltage up to 100 volts. Above this excessive heating will
vided in the form of a polycrystsliine powder comprised of a occur. Voltages as low as microvolts can be used provided the
plurality of crystals, or preferably one relatively large single current is sufficient to achieve the desired results.
cryscii to which eaii be attached conductive .Jectrodes. l.iads For many applications it is particularly de^rabie that the
from these electrodes then wiBntfiect the changed condurtivi- 50 crystalline complex II, together widi its associated plates 13
ty of the complex when subjected to a impression in a be isolated from the surrounding environment. This is paiticu-
direction normal to uVp!:ites. Further, the >5em can be encap- lady so when the device would be utilized in underwater en-
suiaied in a flexible protective housing .<aich tha* it can be util- vironments. Thus, the crystal end plates may be encapsulated
bed in underwater enviranmer.tt and the tike, to obtain depth by with a suitable material 21 which can be a flexible resin
measaretoenK and other destrafcie pressure data. As will be 55 j^^nai such gg ^ poxy resins, alkyd resins and other known
shown, the charge-transfer cotnpte* has an electroconductivi- coatings. Additionally, a rubber base :naerii j can be used.
ty which is much more sensitive to pressure other than other The main requirements of the encapsulating material 21, of
charge-transfer ccmple.xe*. course, is that it be flexible and sJlow ,*nection of the plates
BWEFDESCRIPT10NOFTHEDRAWINCS 60 21 t°j™^a compressor, of thecrystal H.VYhen pressure is
exerted in the direction of the arrcw shown.
FK3. 1 is a schematic diagram of a technical pressure trana- It sftould be pointed out that tte -esulting pleasure trans-
ducer of the invcntk*), together with a circuit in which it ducer 23 shown in F1O. 1 is not ef nn inheiei.Uy novel con-
•jiaaid be utilized. struction and that wide latitude can be utilized in designing
FKJ. 2 is « chart disclosing the change in resistivity of the
 6j such a transducer. The novelty of t'» transducer, however,
complex of the material in relation to pressure. lies in the partJc-Jar use of the corny i '.• sx of pyrene and TCNE
DE^RimONOFr.iEPriEFERR£DEMBODIMENTS 1^ ""
Prior to the herein invention, the ccmpiex of psrene and Though the specific embodiment shown discloses cnnduc-
tetracyanoethytene. hereiiuifter referred to at TCNE, was 70 tive piates affixed to the crystal complex maier.al, mere etee-
k-x.vm. bical leads can be bonded to the surfaces cf a single crystal or
Unexpectedly, however, in the courts of the development pellet snd uic desired result: obtaitted. Thus, any suhabte con-
of the herein invention, i> has been found that this complex ductive electrode material is contemplated.
lies an electrical resistivity thai is much mare sensitive to pres- It is believed that the invention will be better t ica-itood
sure than avty other known material of a siatilar nature. 75 from the following detailed example:
3
EXAMPLE
3,641,470
Equal molar portions of pyrene and TCNE were dissolved in
ethylaceiate. Specifically. 2.02 g. of pyrene was dissolved in
SO ml. of ethylacetate and the mixture heatsd until the pyrene
'dissolved. 1.28 g. cf TCNE was dissolved in SO ml. of
ethylacetate and mixture heated until the TCNE dissolved.
The two hot solutions were then mixed together in a glass ves-
sel. After the solution wat achieved, th: mixture was then al-
lowed to ctand under a hood end the solvent slowly
evaporated over a period of 12 hours. Remaining in the bot-
tom of the vessel were dark blue crystals of the complex of
pyrene tnd TCNE. The crystals were then filtersd from the
remaining solvent
The resulting crystals were then ground in a motar. This was 15
done to prevent the crystals from exploding out of the pres-
sure apparatus used, as we!) as insuring a high density of the
crystals per volume within the pressure apparatus.
The giound crystals were then placed in a pressure ap-
paratus which utiliredtv^oopTiosed vanadium alloy steel anvils 20
having a ammeter of one-fourth of an inch. The anvils were
connected by itais to s Kcithey Electrometer such that re-
sistivity determinations could be made. This test arrangement
is described on page 82 of Progress in Dielectrics, Vol. 6,
Academic Press, Inc., (1965). The anvils were placed in a 25 comprised of a single crystal.
the squares.
When the game example was repeated utttranj one-half
inch diameter anvils the results obtained were ta indicated on
ths graph of FIG. 2 is indicated by the circles. As can be seen,
5 the resistivity of the crystals decreases by a factor of 7 order*
of magnitude between 3.5 and 33 kilnbara. This is believed to
be the largest reported decrease in resistivity for any known
charge transfer complexes and polymers over such a pressure
range. Although the results shown in FIG. 2 are with regard to
10 plurality of fine crystels between conductive plates, it should
be pointed out that essentially the same results will be
achieved from a single large crystal.
What is claimed is: . • .
1. A pressure transducer comprising:
two spacerf-apart electrically conductive electrode surfaces,
and
a sensing element disposed between said surfaces formed of
the charge-transfer complex of pyrcRe-tetra-
cyancsthylene.
2. The transducer of claim 1 wherein said sensing etenent is
comprised of a plurality of crystals,
3. The transducer of claim 1 wherein said sensing dement is
a pellet formed from z plurality cf pressed crystals.
4. The transducer of claim 1 wherein the sensing element is
hydraulic press type of pressure epparnt'.is so list various
pressures could be applied between them. Care was taken to
ensure that any spurious voltages across the samples were a
factor of 100 or greater less than the applied voltage. All the
measurements resulting from varying the pressure on the
crystals between the anvils was made at room temperature.
The results are shown in the graph of FIG. 2 as indicated by
30
5. Th; tnjr&iucei of ciiiin 4 wherein:
said electrically conductive electrode surfaces are bonded
to opposite sines of said crystal.
6. The transducer of claim 4 further comprising:
encapsulating sjid sensing element and electrode surfaces
in a flexible housing.
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