Bimorph

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

Snap-through buckling behavior of piezoelectric bimorph beams: I. Analytical and numerical modeling

Abstract: Piezoelectric structures are used in a variety of applications where instant response, high energy conversion efficiency and accurate control are required. However, it is widely known that piezoelectric structures suffer from a series of drawbacks, among which the most important is the small displacement capacity. A number of techniques have been used in order to transform the micron-scale displacements of PZT layers into meaningful millimeter-scale ones. Non-linear mechanics belong to this category, providing the possibility to transform a traditional bimorph linear output structure into a non-linear high displacement actuator with increased combination of force/displacement output. In the present work the analytical modeling and the subsequent analysis of non-linear actuators with enhanced characteristics in terms of displacement is presented. The piezoelectric structure that is studied is a traditional bimorph structure with two piezoelectric layers and an aluminum substrate. The main concept is to leverage non-linear mechanics, and more specifically snap-through buckling, so that large displacements can be achieved with the transition of the structure from one equilibrium position to another. During the development process the importance of boundary conditions has been revealed and thus special attention has been provided to this issue. A modified analytical model was elaborated in order to come up with a closed form solution including relaxed boundary conditions. The experimental verification of the analytical and numerical model is presented in part II.

Time constant and lateral resonances of thermal vertical bimorph actuators

Abstract: Thermal vertical bimorph actuators consist of silicon beams side-coated with aluminium. Upon heating they bend like a bimetal and produce movement in the wafer plane. We have measured the time constant describing the deflection response of the actuator to input pulses. Depending on the dimensions of the actuator, the time constant ranges from 0.5 ms to 3.8 ms. Lateral resonances of the first mode have been measured using thermal excitation and are found to be between 20 and 85 kHz.

A concept for energy harvesting from quasi-static structural deformations through axially loaded bilaterally constrained columns with multiple bifurcation points

Abstract: A major obstacle limiting the development of deployable sensing and actuation solutions is the scarcity of power. Converted energy from ambient loading using piezoelectric scavengers is a possible solution. Most of the previously developed research focused on vibration-based piezoelectric harvesters which are typically characterized by a response with a narrow natural frequency range. Several techniques were used to improve their effectiveness. These methods focus only on the transducer?s properties and configurations, but do little to improve the stimuli from the source. In contrast, this work proposes to focus on the input deformations generated within the structure, and the induction of an amplified amplitude and up-converted frequency toward the harvesters? natural spectrum. This paper introduces the concept of using mechanically-equivalent energy converters and frequency modulators that can transform low-amplitude and low-rate service deformations into an amplified vibration input to the piezoelectric transducer. The introduced concept allows energy conversion within the unexplored quasi-static frequency range (?1?Hz). The post-buckling behavior of bilaterally constrained columns is used as the mechanism for frequency up-conversion. A bimorph cantilever polyvinylidene fluoride (PVDF) piezoelectric beam is used for energy conversion. Experimental prototypes were built and tested to validate the introduced concept and the levels of extractable power were evaluated for different cases under varying input frequencies. Finally, finite element simulations are reported to provide insight into the scalability and performance of the developed concept.

Polarization-Modulated Multidirectional Photothermal Actuators.

Abstract: Photothermal actuators have attracted increasing attention due to their ability to convert light energy into mechanical deformation and locomotion. This work reports a freestanding, multidirectional photothermal robot that can walk along a predesigned pathway by modulating laser polarization and on-off switching. Magnetic-plasmonic hybrid Fe3 O4 /Ag nanorods are synthesized using an unconventional templating approach. The coupled magnetic and plasmonic anisotropy allows control of the rod orientation, plasmonic excitation, and photothermal conversion by simply applying a magnetic field. Once the rods are fixed with desirable orientations in a bimorph actuator by magnetic-field-assisted lithography, the bending of the actuator can be controlled by switching the laser polarization. A bipedal robot is created by coupling the rod orientation with the alternating actuation of its two legs. Irradiating the robot by a laser with alternating or fixed polarization synergistically results in basic movement (backward and forward) and turning (including left-, right-, and U-turn), respectively. A complex walk along predesigned pathways can be potentially programmed by combining the movement and turning modes of the robots. This strategy provides an alternative driving mechanism for preparing functional soft robots, thus breaking through the limitations in the existing systems in terms of light sources and actuation manners.