Bimorph

About: Bimorph is a research topic. Over the lifetime, 3339 publications have been published within this topic receiving 51880 citations.

Fabrication and operation of polyimide bimorph actuators for a ciliary motion system

Abstract: In order to extract macroscopic mechanical work out of microelectromechanical systems, we have proposed the concept of distributed micromotion systems (DMMS). The key idea of DMMS is to coordinate simple motions of many microactuators in order to perform a task. Design, fabrication, and operation of a type of DMMS, called a ciliary motion system, are presented. A bimorph thermal actuator using two types of polyimides with different thermal expansion coefficients and a metallic microheater in between them was fabricated. The cantilever-shaped actuator curled up from the substrate owing to the residual stress in polyimides which built up during the cooling process after they were cured at 350 degrees C. It flattened and moved downward by flowing current in the heater. The dimensions of the cantilever were 500 mu m in length, 100 mu m in width, and 6 mu m in thickness. The tip of the cantilever moved 150 mu m in the direction vertical to the substrate and 80 mu m in the horizontal direction; these were the maximum displacements obtained with 33 mW dissipated in the heater. The cut-off frequency was 10 Hz. On a 1-cm-square substrate, 512 cantilevers were fabricated to form an array. Two sets of cantilevers were placed opposing to each other. We operated them in coordination to mimic the motion and function of cilia and carried a small piece of a silicon wafer (2.4 mg) at 27-500 mu m/s with 4-mW input power to each actuator. >

Piezoelectric multifrequency energy converter for power harvesting in autonomous microsystems

Abstract: A multifrequency mechanoelectrical piezoelectric converter intended for powering autonomous sensors from background vibrations is presented. The converter is composed of multiple bimorph cantilevers with different natural frequencies, whose rectified outputs are fed to a single storage capacitor. The structure of the converter, description of the operation, and measurement data on the performances are reported. Experimental results show the possibility of using the converter with input vibrations across a wideband frequency spectrum, improving the effectiveness of the overall energy conversion over the case of a single converter. The converter was used to supply power to a battery-less sensor module that intermittently reads the signal from a passive sensor and sends the measurement information via RF transmission, in this way forming an autonomous sensor system with improved measure-and-transmit rate.

The constituent equations of piezoelectric bimorphs

Abstract: A brief review of applications of piezoelectric bimorphs is presented. The constituent equations which describe the behavior of piezoelectric bimorphs for various mechanical boundary conditions are derived. The internal energy density of infinitesimally small volume elements in thermodynamic equilibrium is calculated in the presence of a voltage on the electrodes, a clamped cantilever beam condition on one side of the beam and a set of three different classical boundary conditions on the other side of the beam. These are a mechanical moment M at the end of the beam, a force F perpendicular to the beam, applied at its tip, and a uniformly distributed body force p. The total internal energy content is calculated by integrating over the entire volume of the beam. Two different beam configurations are considered: parallel polarizations of the two adjoining elements of the beam with an internal electrode; and antiparallel orientation without an internal electrode. The canonical conjugate of the moment is calculated as the angular deflection at the tip of the beam α, while that of the force at the tip is the local vertical deflection δ. The canonical conjugate of the uniform load on the beam is found to be the volume displacement V of the beam. The canonical conjugate of the voltage across the electrodes is the charge on the electrodes. The equations are given in the direct form, with external parameters (M, V), (F, V), and (p, V) as independent variables and also in a linear combination with (M, F, p, V) as variables. These constituent equations can be used to calculate the behavior of the bimorph under any condition that can be described as a linear combination of forces at the tip, moments at the tip and uniform loads on the entire beam. This allows us to use the bimorph as a black box, without having to consider its internal movement or charges.

Detection of pico-Tesla magnetic fields using magneto-electric sensors at room temperature

Abstract: The measurement of low-frequency (10−2–103Hz) minute magnetic field variations (10−12Tesla) at room temperature in a passive mode of operation would be critically enabling for deployable neurological signal interfacing and magnetic anomaly detection applications. However, there is presently no magnetic field sensor capable of meeting all of these requirements. Here, we present new bimorph and push-pull magneto-electric laminate composites, which incorporate a charge compensation mechanism (or bridge) that dramatically enhances noise rejection, enabling achievement of such requirements.

Modeling of electric energy harvesting using piezoelectric windmill

Abstract: This letter reports a theoretical model for determination of generated electric power from piezoelectric bimorph transducers in low frequency range far from the piezoelectric resonance. The model is divided into two parts. In the first part the open circuit voltage response of the transducer under the ac stress is computed based on the bending beam theory for bimorph. In the second part, this open circuit voltage acts as the input to the equivalent circuit of the capacitor connected across a pure resistive load. The results of the theoretical model were verified by comparing it with the measured response of a prototype windmill. The prototype piezoelectric windmill consisting of ten piezoelectric bimorph transducers was operated in the wind speed of 1–12 mph. A power of 7.5 mW at the wind speed of 10 mph was measured across a matching load of 6.7kΩ. The theoretical model was found to give very accurate prediction of the generated power and matching load and an excellent matching was found with the experim...