TDO0213 PUB Piezoelectric Foil Sensors and Actuators · The direct piezoelectric effect is used in...
3
Piezoelectric Foil Sensors and Actuators Category: Sensors & Measuring Techniques Reference: TDO0213 Broker Company Name: cesah GmbH Broker Name: Frank Zimmermann Telephone: +49 (0)6151 392156-12 Email: [email protected] Abstract Piezoelectric films made of PVDF (Polyvinylidene fluoride) are very thin and flexible active electromechanical transducers. They can convert about 12% of mechanical energy into electrical energy, and vice versa. Thus they are useful as a sensor as well as an actuator. Description The piezo foil technique allows the design of extremely flexible and thin sensors as well as actuators, which may be placed on 3D-contoured surfaces or inserted in small gaps as well as embedded in GRP/CRP structures. Due to the piezo-active measurement principle only very small contact wires are required, allowing the integration of a high number of sensors with a spatial resolution down to sub-mm scales. Due to anisotropic properties of mono-axial oriented foils the charge produced by different strain components is amplified or dampened, resulting in a multitude of specific sensor applications. Several multi- layer and multi-element actuators can be realized, producing longitudinal or torsional motion or traveling waves in beam elements. Further Information The piezofilm is a transparent film of highly polar poly-vinylidene-fluoride (PVDF). In proportion to the influence of mechanical stress or strain the film develops an electrical charge that could be shunted over the metal-coated surfaces. Otherwise the application of electric current leads to a proportional mechanic deformation. The direct piezoelectric effect is used in sensor applications and the inverse piezoelectric effect in actuator applications. Fig. 1: Numerical classification of axes (1- length, 2-width, 3-thickness)
Transcript of TDO0213 PUB Piezoelectric Foil Sensors and Actuators · The direct piezoelectric effect is used in...
PiezoelectricFoilSensorsandActuators
Category:Sensors&MeasuringTechniquesReference:TDO0213BrokerCompanyName:cesahGmbHBrokerName:FrankZimmermannTelephone:+49(0)6151392156-12Email:[email protected]
AbstractPiezoelectric films made of PVDF(Polyvinylidene fluoride) are very thin andflexibleactiveelectromechanicaltransducers.They can convert about 12%ofmechanical energy into electrical energy, and viceversa.Thustheyareusefulasasensoraswellasanactuator.
DescriptionThepiezofoiltechniqueallowsthedesignofextremelyflexibleandthinsensorsaswell as actuators, which may be placed on 3D-contoured surfaces or inserted insmallgapsaswellasembeddedinGRP/CRPstructures.
Due to the piezo-active measurement principle only very small contact wires arerequired, allowing the integration of a high number of sensors with a spatialresolution down to sub-mm scales. Due to anisotropic properties of mono-axialoriented foils the charge produced by different strain components is amplified ordampened, resulting in a multitude of specific sensor applications. Several multi-layer and multi-element actuators can be realized, producing longitudinal ortorsionalmotionortravelingwavesinbeamelements.
FurtherInformation
Thepiezofilmisatransparentfilmofhighlypolarpoly-vinylidene-fluoride(PVDF).Inproportion to the influence of mechanical stress or strain the film develops an
electrical charge that could be shuntedover the metal-coated surfaces.Otherwise the application of electriccurrent leads to a proportionalmechanicdeformation.The direct piezoelectric effect is used insensor applications and the inversepiezoelectric effect in actuatorapplications.
Fig.1:Numericalclassificationofaxes(1-length,2-width,3-thickness)
Inelectronictermsthepiezofilmisacapacitorthatreactswithachangeinelectriccharge proportional to the change of applied force. Piezoelectric materials areanisotropic.Thismeans,thattheirelectricalandmechanicalpropertiesvarywiththedirectionofappliedforce,strainorelectricalfield.Thefilm´saxesareidentifiedbythenumeralsindicatedinfig.1.ThesymbolslistedinTechnicalData forstrain-andstressconstantdiiandgiiaredeclaredas follows.Thefirstindexidentifiesthedirectionofappliedelectricalfield(alwaysthedirectionofthethicknessofthefilmwhenusingpiezoelectricfilms).Thesecondindexreferstotheaxisofinducedmechanicalstrainorappliedstress.UsagePiezofilm sensors are well qualified for detecting dynamic events, like pressurefluctuations,vibrationsor forcechanges.Especiallyunderspace-limitedconditions,theextremethinsensormaterialisadvantageous.Becauseofthehighdynamic range, the greatbandwidthandthehighflexibility,manymeasurementproblemscanbe solved, which is impossible todowithothertechniques.SensorandactuatordesignThepiezofilmcouldbedesignedasa single- or multi sensor array innearly any form and dimension.Single point sensors with aminimum diameter of 0.25 mmcould be realized. Multi layersensorswithdifferentorientationscould be used as filters forseparatingspecificforcedirectionsorforscreeningthesensorsignals.Actingasanactuator, really complex bending-torsion motions could be realized, i.e. foradjustablemirrors.Thepiezofilmmetalcoatusuallyconsistsofaluminiumornickel.Othermetallizationsuchas copper, goldor silver couldbedeliveredon special request. Thepiezofilmsensor signals are enhanced by special adapted amplifiers for specific measuringtasksandcanbestoredandcomputedwithcommondatarecordingandprocessingunits.ApplicationThesensorfoilsaresuitableforapplicationsintheareasofdynamicforce,pressure,motion and temperature measurements up to high frequencies. Some realizedexamples are: fluid, IR, vibration and pulse pressure sensors, keyboards, robotics,tactile and ultrasonic sensors. Piezoelectric actuators are suitable for largedisplacements with small forces as for example the damping or amplification of
oscillationsof lightweightstructures,opticalcomponentsandminiaturepositioningdevicesorfans.
DescriptionofSpaceHeritagePiezofilmsensorswithamplifiersareusedinspaceapplicationsforthedetectionofstructurevibrationsonanaerodynamictestbody,foractivevibrationdampingandstimulating.Furtherspaceapplicationsare:
- Development and construction of piezofilm sensor arrays with amplifiersystemsforflowsensing inairplanewingresearch,pressurefluctuationsonwingparts.
- Aerodynamicmeasurementsinwindtunnele.g.simulationofre-entry
ThisTechnologyDescriptionwasdownloadedfromwww.esa-tec.eu
