Electromechanical Sensitivity Research Articles

A study of Love wave devices in ZnO/Quartz and ZnO/LiTaO 3 structures

Love wave devices are very promising for sensing applications because of high sensitivity. In this paper, ZnO thin films doped with lithium (Li) and magnesium (Mg) were deposited on the 42°45′ ST-cut quartz and 36° YX-LiTaO 3 substrates by RF magnetron sputtering technique. XRD, SEM, and AFM measurements investigated characteristics of the films. Under different conditions such as doping content, layer thickness, and substrate temperature, the phase velocity, temperature coefficient of frequency, electromechanical coupling coefficient and sensitivity of Love wave devices in ZnO/Quartz and ZnO/LiTaO 3 structures are presented. The maximum sensitivities of ZnO/Quartz and ZnO/LiTaO 3 are much higher than the SiO 2/Quartz and SiO 2/LiTaO 3 structures reported.

Topology optimization of electrostatically actuated microsystems

This study addresses the design of electrostatically actuated microelectromechanical systems by topology optimization. The layout of the structure and the electrode are simultaneously optimized. A novel, continuous, material-based description of the interface between the structural and electrostatic domains is presented that allows the optimization of the interface topology. The resulting topology optimization problem is solved by a gradient-based algorithm. The electromechanical system response is determined by a coupled high-fidelity finite element model and a staggered solution procedure. An adjoint formulation of the coupled electromechanical design sensitivity analysis is introduced, and the global sensitivity equations are solved by a staggered method. The proposed topology optimization method is applied to the design of mechanisms. The optimization results show the significant advantages of varying the interface topology and the layout of the electrode versus conventional approaches optimizing the structural layout only.

Effect of an ultralow-frequency electric field on the explosive instability threshold of ice

It is found that a weak (103–105 times lower than breakdown fields) ultralow-frequency (1<ω<1000 Hz) electric field has a strong effect on the explosive instability threshold of ice uniaxially compressed by high pressures in the temperature range 210–240 K. The explanation for the high electromechanical sensitivity of ice is based on the concept that ice undergoing structure modifications due to highly nonuniform compression is a heterogeneous system with cooperative phenomena in space-bounded sets of dipoles. The dipoles form around new-phase nuclei, defects, or air microbubbles and occupy domains with a typical size of 10−2–10−5 mm. When exposed to ultralow-frequency electric fields, such systems may exhibit resonant bursts of polarization, causing the ice stability to drastically drop because of dipole compression or microbreakdowns.

Measurements on micromachined silicon accelerometers with piezoelectric sensor action

In this paper, the results of electrical, mechanical (vibration) and electromechanical (sensitivity) measurements on micromachined accelerometer devices with four piezoelectric read-out capacitors are presented. The average capacitance at 1 kHz is 1.2 nF with a Q-factor of 62. The resonance frequencies (in vacuum) of the first two bending modes and the first torsional mode are 12.35 kHz, 26.38 kHz and 17.95 kHz, respectively. The Q-factor of the first bending mode decreases from about 50 in vacuum (0.1 mbar) to 25 at atmospheric pressure. With a sinusoidal excitation at 1.26 kHz, the average accelerometer sensitivity is around 0.1 mV/g; a slight increase of the sensitivity is found in the range from 1 kHz to 6 kHz.

Improving the bandwidth of 1-3 connectivity composite receivers using mode coupling

Temporal resolution in an ultrasonic system may be enhanced by the application of mechanical damping to the transducer rear face, thereby reducing internal reverberation and increasing effective bandwidth. However, for thickness drive transducers, this is accompanied inevitably by a reduction in sensitivity and, moreover, manufacture of suitable damping blocks can be difficult, particularly for lower frequency, small signal applications such as the detection of gas coupled ultrasound. This work describes an interesting alternative approach that utilizes the relatively strong coupling between the fundamental thickness mode and first lateral mode in 1-3 connectivity piezocomposite transducers. Finite element modeling is used to evaluate the influence of mode interaction on electromechanical coupling efficiency, surface displacement, sensitivity, and bandwidth as functions of the ceramic pillar dimensions for operation into both water and air load media. A range of composite devices was constructed and close agreement between theory and experiment is demonstrated, with a measured device bandwidth of 130% centered at 1.15 MHz. An example of using such a device within a gas-coupled ultrasonic system is presented and the response is shown to compare favorably with alternative transducer configurations.