Bimorph

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

Actuating Single Wall Carbon Nanotube-Polymer Composites: Intrinsic Unimorphs**

Abstract: Electromechanical coupling effects in polymers have been routinely employed to create an array of sensors and actuators. The most dominant coupling effects originate from piezoelectric, electrostrictive, and electrostatic (also known as the Maxwell effect) mechanisms. To generate high displacements, electrostrictive and Maxwell effects are typically exploited because the strain in such polymers is a quadratic function of the applied electric field, whereas it is linear for piezoelectrics. However, the high compliance of most electrostrictive and electrostatic polymers limits their durability and output force and reduces their applicability. Owing to their low dielectric constants relative to ceramics, polymers typically require large applied electric fields to actuate. For strain amplification, several actuator concepts have been demonstrated including multilayer and bender designs. Most commercial actuators integrate design concepts, including unimorph, bimorph, and multimorph. These designs require extra processing steps and introduce extraneous layers such as adhesives and inactive, so-called ‘‘dummy’’, layers to convert longitudinal to bending strain. The incorporation of these adhesive and inactive layers reduces the magnitude of the actuation of a given actuation system significantly and often causes delamination. Furthermore, mismatches in the thermal expansion coefficients and mechanical properties among the adhesive, inactive, and active layers can cause additional adverse effects on the actuation performance. Here we introduce a novel electroactive single-walled carbon nanotube (SWNT)–polymer composite, an intrinsic unimorph, which can actuate to a large strain (2.6%) at relatively low driving voltages (<1 MV m ) while maintaining

Five-port equivalent electric circuit of piezoelectric bimorph beam

Abstract: Electromechanical behavior of a three-layered piezoelectric bimorph beam is represented by an electrically equivalent circuit with impedance elements. Each impedance is determined from the components of the electrically equivalent 5×5 impedance matrix. The derivation of the impedance matrix is based on a bimorph beam theory where vertical and angular displacements at each end of the beam are considered. The impedance matrix thus consist of one electrical, four mechanical and one electromechanical coupling loops. Entire electromechanical flows and efforts accordingly have one electrical and four mechanical ports. For an electromechanical system where other mechanical or electrical components are attached to the bimorph, an equivalent electric circuit of the system can be thus generated by connecting the electrically equivalent impedances to the circuit according to the mechanical boundary conditions or external mechanical components. The characteristics of the electromechanical system, e.g., an electrical admittance, can be obtained from the equivalent circuit. As examples, three different types of mechanical boundary conditions — free, simply supported and cantilevered — are considered, and the equivalent circuits are drawn with each port opened or closed according to the boundary conditions. Two examples of external mechanical systems attached to the bimorph are also shown, i.e., a cantilevered bimorph beam with a mass–spring–damper system attached to its free end, and a segmented piezoelectric bimorph beam with an extended substrate arm. In each case, an equivalent circuit is also drawn and the electrical admittance is directly derived from the circuit. The resonance and antiresonance frequencies are accordingly calculated, and it is found that the five-port equivalent electric circuit of the piezoelectric bimorph beam presented in this paper yields an exact expression for the vibration of the piezoelectric bimorph.

Utilisation of smart polymers and ceramic based piezoelectric materials for scavenging wasted energy

Abstract: Piezoelectric smart polymer and ceramic materials can be deployed as a mechanism to transform mechanical energy into electrical energy that can be stored and used to power portable devices. This paper focuses on the development and comparison of a micropower based harvesting generator using piezoelectric PZT (lead zirconate titanate) ceramic, PVDF (polyvinylidene fluoride) membrane and PP (polypropylene) foam polymer with the intention of establishing power output from temperature fluctuations. Unimorph and bimorph strips of various sizes were prepared and subjected to vibration and impact experiments in order to directly compare the voltage output. The effect of the ceramic fibre diameter, laminate thickness, impact area, weight of the free falling mass, vibration frequency and temperature on the voltage output were studied. Experiments are outlined detailing the performance characteristics of such piezoelectric fibre laminates. Results show voltage outputs of nearly 40 V which is considered sufficient for potential applications in powering microsystems.

A Novel Piezoelectric Based Wind Energy Harvester for Low-power Autonomous Wind Speed Sensor

Abstract: In this paper, a novel method to harvest wind energy using PZT piezoelectric material for a low power autonomous wind speed sensor has been proposed. The conversion of wind energy into electrical energy is based on direct piezoelectric effect and utilizes the bimorph piezoelectric actuator. Combined with the wireless transmission, this technology provides a practical solution to meet the electrical energy supply need of remote sensors and communication devices. Energy harvested from the piezoelectric based wind harvester is first accumulated in a capacitor and when sufficient energy is harvested to power the wireless radio frequency (RF) transmitter, a trigger signal is initiated to release the stored energy in the capacitor to the RF transmitter. Experimental results obtained show that the harvested stored energy of 917 muJ is able to power the RF transmitter to transmit 5 digital words of 12-bit information during the transmission period of 100 msec. The proposed piezoelectric based wind energy harvester is used to detect wind speed beyond a certain threshold level in an early warning of storm detection system.

Self-Locomotive Soft Actuator Based on Asymmetric Microstructural Ti3C2Tx MXene Film Driven by Natural Sunlight Fluctuation.

Abstract: Soft actuators and microrobots that can move spontaneously and continuously without artificial energy supply and intervention have great potential in industrial, environmental, and military applications, but still remain a challenge. Here, a bioinspired MXene-based bimorph actuator with an asymmetric layered microstructure is reported, which can harness natural sunlight to achieve directional self-locomotion. We fabricate a freestanding MXene film with an increased and asymmetric layered microstructure through the graft of coupling agents into the MXene nanosheets. Owing to the excellent photothermal effect of MXene nanosheets, increased interlayer spacing favoring intercalation/deintercalation of water molecules and its caused reversible volume change, and the asymmetric microstructure, this film exhibits light-driven deformation with a macroscopic and fast response. Based on it, a soft bimorph actuator with ultrahigh response to solar energy is fabricated, showing natural sunlight-driven actuation with ultralarge amplitude and fast response (346° in 1 s). By utilizing continuous bending deformation of the bimorph actuator in response to the change of natural sunlight intensity and biomimetic design of an inchworm to rectify the repeated bending deformation, an inchwormlike soft robot is constructed, achieving directional self-locomotion without any artificial energy and control. Moreover, soft arms for lifting objects driven by natural sunlight and wearable smart ornaments that are combined with clothing and produce three-dimensional deformation under natural sunlight are also developed. These results provide a strategy for developing natural sunlight-driven soft actuators and reveal great application prospects of this photoactuator in sunlight-driven soft biomimetic robots, intelligent solar-energy-driven devices in space, and wearable clothing.