Póster presentado al 1st Senspol Workshop: SENSPOL European Thematic Network (EC Environmental and
Climate Programma) Sensing Technologies for Contaminated Sites and Groundwater celebrado en Alcala de Henares (Madrid-España) en 2001.Peer reviewe

Humphris, A. D. L.

Lechuga, Laura M.

Miles, M. J.

Tamayo de Miguel, Francisco Javier

Digital.CSIC

" " , .~ 1"15 · ·CHEMICAL SENSORSAND BIOSE'NSORS IN LIQUIDENVIRONMENTBASED· 	 . ' . . - . .. ' . .' " ON M1CROCANTILEVERS WITH AMPLlFiED QUALITY FACTOR ' . ' . : .' , . . .. "... . ' . ". ' . o··· :. ' : ". '. ' . ' .. ' . J. Tamayo1, AD.L. Humphris2,M.J. Miles2 and L Lechuga1 . . . ' . .' .... " ' . ' . 11nstüuto de .' Microelectrónica ' de ' Madrid ' (CSIC), . Jsaac Newton 8, 287.60 Tres Cantos, Madrid,Spain. 2H.H. Wills Physics Laboratory, lJniversity otBristol, TyndaU · Avenue, Bristol B881 TL,UK . .'.In an atomic force ' microscope ' (AFM), a micrometer~sized lever (transducer) bends as consequenceofthe interatomic force between avery sharp tip (sensing surface) .ah.d a sample(target). The cantilever ·d'eflection is measured withsub-áhgstromresolution by a ·	detector that typically consistsof a laser beam reflecting off íhe cantilever into a segmented photodiode. Thus~ forces of the order of 10 picone~ons can be measur~d . AFM provídes . .."... .'.the topography of Or~anic and inorgamc surfáces átatomic arid nanOmeterscrue in air, ultra · . high' vaéuum . and in líquid's.. The large 'ex~ansion of AFM technique~ has widely benefited' · íTam the commercializationof microfabricated wafers composed ofcantilevers of silicon or · silicem ·nitride.This has brought abaut the ' birth of a ' new c1asS of chemicaIsensorsand . . 	 . '. ' . . biosensors based on microéantilevers . . ,. . , ". . . " " ' . ". " .. "'. ".' . . . " . ' .,' .. . . '.' In sensors based on mícrocantilevers, th~ cantilever is coated with a sensing~ím oÍ' receptor molecules. Asa gaseoUs or liquid sample$olution is flowed ' ~verthe cantilever, the target molecuIesattach to the sensitizedsurfáce. The cantilever itself works like él . '. transducer, ~hus inthemicrobalance~ethod, thetarget substanceis detected by a change of '. . the cantilever mass, tbatgivesrise toachange in tlle. resonance frequency oi the cantilever · (AC-detection), In the surface stress method, onIy onesideof thecantileveris coated with the senSing molecules . The"surface stress o(~his sidechangesas thetarget substan.ce adheres '. to the surface, producing a cantÍlever bend'ing as thé 'surface Qf this side expands or contracts . 	 . ' · to balance the surface energy chang~. Thebendif\gi~ measured bydetecting the cantilever deflection(DC-detection). Sensors based ·on microcan~ijevers' have been tnainly developecÍ for <ietection ina gas environment, giving a resoludon ID rnass of -1 pg~ and aresolution in surface stress of ~1 mJ/m2 •. -245- . PiS · .. . '. A ·. new technique ....IS . preSented for. bio/chemical sensors, based on microcantilevers, for ' detection iil liquid environment. . The 'low ,quality factor ' of the cantilever inliquid isincreased upto three orders of magnitude by using Q-control. '.' Ihisenables AC detection that isirnmune to the long-terro drift of the DC cantilever . response inliquids, andlotemperature variations. Thistechniquehasbeen applied fór . . the detection of ethanQl in aqueoussolution byusing the nUcrObalaIlce method, and ... foi" . antibody!antigen recognitionby~ the . surfice stress method . . The . results . show the. feasibilityand very highsensitivity ofthese noveldevices . . l· - 246­I 

Chemical sensors and biosensors in liquid environment based on microcantilevers with amplified quality factors

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