Piezoelectric actuators and sensors

Transcription

1 Lecture 9 Piezoelectric actuators and sensors

2 Piezoelectric equations Equations E Sij = sijkltkl + dkijek T Dj = dikltkl + ε jkek E Tij = cijkls e E S Dj = eiklskl + ε jke s E ijkl c ε E ijkl kl kij k k i,j,k,l = 1 to 3 D Sij = sijkltkl + gkij Dk T Ej = gikltkl + β jkd D Tij = cijklskl hkij Dk S Ej = hiklskl + β jk D D, s elastic compliance at constant electrical field and constant ijkl electrical displacement conditions D, c elastic stiffness at constant electrical field and constant ijkl electric displacement conditions S T jk, ε jk dielectric permittivity at constant strain and constant stress conditions S β jk T, β jk dielectric impermittivity at constant strain and constant stress conditions k k

3 Piezoelectric equations Equations dijk, eijk, gijk, and hikl E d = e s = g ε ijk ilm lmjk ljk E e = d c = h ε ijk ilm lmjk ljk S il D g = h s = d β ijk ilm lmjk ljk D h = g c = e β ijk ilm lmjk ljk T il T il S il piezoelectric coefficients which represent piezoelectric coupling between the electrical and mechanical variables For a particular problem, the choice of which coefficient to use becomes clear when the boundary conditions of the materials are considered. In compressed matrix notation, ij and kl is replaced by p and q with 11 1; 22 2, 33 3; 23, 32 4; 13, 31 5; 12, 21 6; thus p, q = 1 to 6.

4 Piezo-Micropumps Pump structures A micro diaphragm pump with active valves (a) (b) Principle set-up of a "piston type" micropump. Schematic set-up of the saliva dispensing micropump of "Graphosoma lineatum".

5 Piezo-Micropumps Pump structures A planar peristaltic micropump Micro diaphragm pump with piezoelectric actuation Electrostatically actuated micro diaphragm pump

6 Piezo-Micropumps Pump structures Valve-less micro diaphragm pump with piezoelectric actuation: schematic diagram, and pumping principle

7 Piezo-Micropumps Pump structures A compact pump and integrated microvalves Li et al, 1 of 2 Sensors and Actuators A: Physical Volume 11, 2005, pp

8 Piezoelectric accelerometers Accelerometer structures A Schematic piezoelectric thin film micro-accelerometer Piezoelectric thin film elements are connected in (a) series or (b) in parallel.

9 Piezoelectric accelerometers Accelerometer structures When subjected to applied acceleration Applying an acceleration along the z direction, one piezoelectric layer is compressed while the other is extended due to the intrinsic mass of each device. (a) parallel and (b) serial connection of the two sensing elements When subjected to the temperature change

10 Piezoelectric accelerometers Accelerometer structures When subjected to the temperature change An aluminum case containing the sensing elements and the electronics

11 Piezoelectric shear stress sensor Sensor structures

12 Piezoelectric devices Optical beam deflector Schematic of the optical beam deflector. Big arrows indicate the direction of the polarization of the piezoceramics.

13 Piezoelectric resonator Beam resonators Sensors and Actuators A: Physical Volume 118, 2005, pp Ferguson and DeVoe Fundamental resonator mode shapes from composite ANSYS analysis: (a) free free flexural beam, and (b) torsional anchor. Theoretical, finite element, and experimental resonance frequencies for fabricated free free resonator structures

14 Thin film resonators Thin film resonator Principle of BAW resonator operation: A longitudinal standing acoustic wave is excited electrically in a thin piezoelectric film. The layer thickness of the piezoelectric film and of the electrodes determines the resonance frequency of the BAW resonator.

15 Thin film acoustic wave resonators AlN FBAR XRD pattern of AlN film Micro-machined FBAR fabrication process flow

16 Thin film acoustic wave resonators Thin film resonator

17 Thin film resonator and filter Thin film resonator and filter BAW filter principle: the electrical impedance curve of the parallel resonator p is shifted in frequency relative to the series resonator s by f=fa fr. This creates a band-pass filter characteristics in S21

18 Acoustic wave sensors QCM for sensors NO 2 gas sensor BVD equivalent circuit for an unperturbed AT-cut quartz resonator (a) or modified BVD equivalent circuit for a loaded ATcut quartz crystal resonator (b).

19 Piezoelectric devices Bimorph beam splitter Unimorph pressure sensor

20 Piezoelectric devices Vibration sensor

21 Piezoelectric devices For surface roughness

22 Piezoelectric devices For AFM cantilever

23 Piezoelectric devices Scanning tunneling microscopy

24 Piezoelectric devices Data read/write cantilever

25 Piezoelectric devices Multilayer actuators

26 Piezoelectric devices Mechanical amplifier

27 Piezoelectric devices Mechanical amplifier

28 Piezoelectric devices Impact drive mechanism using piezoelectric actuator

29 Piezoelectric devices

30 Piezoelectric devices A micro gripper using unimorph actuator Swimming device

31 Piezoelectric devices A dynamic focusing lens

32 Piezoelectric devices A dynamic focusing lens