BiosensorsandTransducers2

RoomP，Friday，Dec6，17：00−18：30

APPLICATIONOFQUARTZCRYSTALOSCILLATO鱒■TOATMOSPHERIC
MOLECULESENSOR

・S．Hashimotol，T．Senoul，K．％madal，T・Saharal，T・Sekiyamal，H．Okul，YMorit
1BiomedicalSystems，Dept・OfElectronics，InformationandCommunicationEngineerlng，
hasimoto
elc．oit．ac．
OsakaInstituteofTbclm0logy，Osaka，Japan，
2InstituteforFrontierMedicalSciences，KyotoUniversity，Kyoto，Japan
the chamberwith the vapor of chemicals：aCetOne，ethanol，undecan01，anammOniasolution，benzylacetate，anisaldehyde，Citral，Water，methylacetate，andoctanol．
Acup（1ml）ofeachchemicalin■theliquidstatewas

AbstT・aCt：ThequartzcrystaloscillatoI；Whichhasa
Stable naturalfrequency，has been app）ied to an
atmospheric mo）eculesenson Thefrequencyshif（SWith the micro−Weight−Change of crystalwith
adsorbed molecu）es．Experiments wereperformed

placedinthecornerofthechamber，inwhichthevapor

With variollS COmbinations ofthe coated membrane

WaS Stirredwithafan．At25degrees C，theshi免of

andthevaporchemicals．Thedesignedsystemhas
enoughsensitivitytodetectatmosphericmolect］］esin

naturalfrequencyoftheoscillatorwasmeasuredfor15
minutes exposure to the vapor，andfor successive5

thevapoI二

minutesinthefreshair．

Kq7WOrゐ： Quartz crystal osci11ator；Nattlral
frequency，Adsorption，Membrane，Coating
IntrQdⅥCtion﹂．山︺ムJぅ∵↑トキ∵■一−：＼︑∴︑．︽⁚ぐ

The quartz crystal［1］has been applied to an
OSCillator，Which has a stable natural倉equency．The
丘equency shiRs with the micro−Weight−Change of
CryStal．In this study，a SenSOr SyStem WaS designed

withthequartzcrystaltodetectatmosphericmolecules，and experiments were perfbrmed with various
COmbinationsOfthe coated membrane and the vapor
Chemicals．
MaterialsandMethods

The quartz crystal oscillators．with a natural

Figure．1：Thequartzcrystaloscillator

freq？enCyOflO・7386MHz（Fig・1）wereappliedtothe

SenSlng SyStem．The oscillator was vibrated withan

Results

electriccircuit．Thes11rfacesofcrystalweremod漬ed
to hydrophilicwiththe silane−COuPling reaction，OrtO
The naturalfrequencylinearly decreasedwith thehydrophobicwithozonation．Anelectriccounte；was numberofaccumulatedmembranelayers，WhentheLB
designedtomeasurethevibrating丘・equenCy，SOthatthe membrane was accumulated on the quartz crystal
variationoflHzcanbedetected．
OSCillator・ Figure 2 exempl浦es the relationship

The surfhces of the crystals were coated with

Various organic molecule membraneS：palmitic acid，
Stearicacid，araChidicacid，Japaneselacqller，POlyvlnyl
alcohol，Or Cellulose acetate．The Langmur−Brodget（LB）techniquewasappliedtothecoatingofpalmitic
acid，Stearic acid，and arachidic acid，andtherelations
between the shi氏of the naturalfrequency and the

between number：OfLBlayers ofpalmitic acid and丘equencyshiR．：Theresultsweresimilaraboutstearicacid and arachidic acid．The rate ofdecreasein thenaturalfrequencywasproportionaltomolecularweight
oftheacid．

membraneofJapaneselacquerwasnxedonthecrystal

In the▲eXperiment with the chamber，the natural
丘equency decreased with adsorptlOn Of atmospheric・mOleculesandsaturatedwithin15minutes．Figures3
and4exemplifythe丘equencytracingswith arachidic
acid．and withJapaneselacquer． The shi鮎 of丘equencyvariedupto700Hz．Theshi鮎depended
OnCOmbinationofthecoatedmembraneandthe＼′aPOr

in130degreesCfbr30minutes・

ofchemicals．

number of thelayers coated on the crystalwere
measuredduringLBcoatlngprOCeSS．Thedippedand
dried method was applied to the coating of Japaneselacquer，POlyvlnylalcohol，andce11uloseacetate．Thel

Thecoatedcrystalwasputinacubicchamberof20

Cm・Thevariationsweremadeabouttheatmospherein

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1FMBEProc20023（1）堅RoomP，Friday，Dec6，17二00−18‥30

BiosensorsandTransducers2

Discussion
5

●
●

0

2

LB technique had been applied to modify surface

15

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0

OSCillatortendstoreturntoorlglnalvaluea且erremoval

丁ン二

0
0
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0
︵VU O

7十三

frequency with the decrease of mass of o5Cillatlng
quartzcrystal．Thenaturalfrequencyofquartzcrystal

●

／hU

0

4

．

0

＼

Chemicalpropertiesin biosensors［2］・The technique
WaS efftctive to certify the proportionalsh拍 of

0

0

4

0

0

1

2

Ofvapor．TherecoverymeansreversibleadsorptlOnOf
chemicalmolecules to thesurface ofquartz crystal
OSCillator．ThecoatlngOfJapaneselacquerwas most1

effE：Ctive to galn wider sh沌 of 丘equency withadsorptlOn Of atmospheric molecules・The selective

adsorptlOnCanbeappliedtosmellsensors．
NumberofLBlayers
Conclusions

The designed system has enough sensitivlty tO

Figure 2：The relationship between number ofLangmurTBrodgetlayersofpalmiticacidandftequency

detect atmospheric moleculesin the vapor・ The

SenSitivltyCanbecontrolledwiththecoatedmembrane．
The present study shows the availability of quartz
crystal oscillators for the sensor for atmosphericshiftoftheoscillator

004

molecules．

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0
2
0

＞ ThisworkwassupportedinpartbyaGrant−in−Aid
for Scientinc Research危・Om theJapanese Ministry of
Education，Culture，Sports，ScienceandTechnology・

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2
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／hU OONHピコSトUuUコb巴﹄

Acknowledgements

REFERENCES

だ臣賢レ巨1李転炉町臣紆ぎ妄▲㌻﹁㌻い主≡［1］S．Hashimoto，T．Nakamura，0．Hasegawa，M．
Yasaka， Thrombus fbrmation on ultrasonically

Exposuretime，SVibrating surface ，inPfT）C．抒brld肋／ticoT痴nnce
O〃伽Je／〃fc∫qムer〃eJブc∫β〃dJゆr／〃β〟c∫，VOl・10，
Orlando，201〕1，pp．448−451●Ammoniasolution▲Acetone［2］M．Ohnishi，T．Ishibashi，M．AokiandC．Ishimoto，Gassensitivlty Ofmodined surfaces of a surface
acoustic wave d弓vice by chemicaladsorpt10n
technique andLangmuirTBlodgetttechnique ，Japn・J．Appl．Phys．，VOl．33，PP・598l−5986・Partl，No・

Figure3：The舟equency shift ofthe oscillator coatedwiththreelayersofarachidicacid︑ ．亡三′︑；⊇ニ一ンこ

10，Oct．1994，

Exposuretime，S●Ethanol

OMethyl acetatee▲Acetone△Benzylacetate

Figure4：The丘equency shift ofthe oscillator coated
WithJapaneselacquer

lFMBEProc20023（1）305

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