Lead-Free LiNbO3 Thick Film MEMS Kinetic Cantilever Beam Sensor/Energy Harvester

In this paper, we present integrated lead-free energy converters based on a suitable MEMS fabrication process with an embedded layer of LiNbO3. The fabrication technology has been developed to realize micromachined self-generating transducers to convert kinetic energy into electrical energy. The process proposed presents several interesting features with the possibility of realizing smaller scale devices, integrated systems, miniaturized mechanical and electromechanical sensors, and transducers with an active layer used as the main conversion element. When the system is fabricated in the typical cantilever configuration, it can produce a peak-to-peak open-circuit output voltage of 0.208 V, due to flexural deformation, and a power density of 1.9 nW·mm−3·g−2 at resonance, with values of acceleration and frequency of 2.4 g and 4096 Hz, respectively. The electromechanical transduction capability is exploited for sensing and power generation/energy harvesting applications. Theoretical considerations, simulations, numerical analyses, and experiments are presented to show the proposed LiNbO3-based MEMS fabrication process suitability. This paper presents substantial contributions to the state-of-the-art, proposing an integral solution regarding the design, modelling, simulation, realization, and characterization of a novel transducer.

Hybrid Piezo/Magnetic Electromechanical Transformer

This paper presents a hybrid electromechanical transformer that passively transfers electrical power between galvanically isolated ports by coupling electrodynamic and piezoelectric transducers. The use of these two complementary electromechanical transduction methods along with a high-Q mechanical resonance affords very large transformations of voltage, current, or impedance at particular electrical frequencies. A chip-size prototype is designed, simulated, fabricated, and experimentally characterized. The 7.6 mm 7.6 mm 1.65 mm device achieves an open-circuit voltage gain of 31.4 and 48.7 when operating as a step-up transformer at 729.5 Hz and 1015 Hz resonance frequencies, respectively. When operating as a step-down transformer, the resonance frequencies and the corresponding voltage gains are 728 Hz, 1002 Hz, and 0.0097, 0.0128, respectively. In one operational mode, the system shows a minimum power dissipation of only 0.9 µW corresponding to a power conversion efficiency of 11.8%.

An enhanced hybrid piezoelectric–electromagnetic energy harvester using dual-mass system for vortex-induced vibrations

This article proposes a novel hybrid piezoelectric–electromagnetic vortex-induced vibration energy harvester from flow of water inside of a pipe. The piezoelectric energy harvester was modeled with a macro-fiber composite P2-type while the electromechanical transduction was modeled by an elastic magnet coupled to the bluff body movement. A dual-mass configuration was proposed to increase the energy harvesting efficiency. Theoretical models and the submerged natural frequencies of the hybrid energy harvesters were outlined. Computational fluid dynamics and finite element analysis with ANSYS were used to visualize the response in synchronization and output the voltage extracted from the harvesting mechanisms. The addition of a secondary system improves the amount of harvestable energy and outputs more energy than just a single system. This demonstrates the superiority of a dual-mass hybrid system. A tuned secondary beam was used for L-body configurations to make use of inline oscillations, and the secondary piezoelectric output improved for all configurations. Secondary beam tuning also improved the performance of the harvester by any amount between 21% and 52% when compared against a single-mass hybrid energy harvester. A comparative study showed that the L-vertical and vertical bluff-body-tuned was the best performing hybrid-PE energy harvester based on total voltage output.

Enhancement of the Piezoelectric Cantilever Beam Performance via Vortex-Induced Vibration to Harvest Ocean Wave Energy

Renewable and sustainable energies exhibit promising performance while serving as the power supply of a wireless sensor especially located in marine waters. Various microgenerators have been developed to harvest wave energy. However, the conversion ability from a dynamic oscillating source of wave is crucial to enhance their effectiveness in practical applications. In this paper, a new piezoelectric converter system is proposed to harvest the kinetic energy from ocean waves. The vortex-induced effect in an air channel enhances the vibration performance, improving the energy harvesting efficiency. The system comprises an oscillating water column (OWC) air chamber, a bluff body, and a piezoelectric piece for electromechanical transduction. The fluid–solid–electric coupling finite element method was used to investigate the relation between the output voltage and geometrical parameters, including the size and position of the piezoelectric cantilever beam, which is based on the user-defined function of the ANSYS. It is found that the bluff body in the outlet channel above the air chamber induced high-frequency vortex shedding vibration. The regular wave rushed into the air chamber with a frequency of 0.285 Hz and extruded the air across the bluff body in the outlet channel. This incurred the fluctuation of the air pressure and excited the piezoelectric cantilever beam vibration with a high frequency of 233 Hz in the wake region. Furthermore, a continuous electrical output with a peak voltage of 6.11 V is generated, which has potential applications for the wireless sensors on the marine buoy.

Ionoelastomer junctions between polymer networks of fixed anions and cations

Soft ionic conductors have enabled stretchable and transparent devices, but liquids in such devices tend to leak and evaporate. In this study, we demonstrate diodes and transistors using liquid-free ionoelastomers, in which either anions or cations are fixed to an elastomer network and the other ionic species are mobile. The junction of the two ionoelastomers of opposite polarity yields an ionic double layer, which is capable of rectifying and switching ionic currents without electrochemical reactions. The entropically driven depletion of mobile ions creates a junction of tough adhesion, and the stretchability of the junction enables electromechanical transduction.

Design of a Command-Shaping Scheme for Mitigating Residual Vibrations in Dielectric Elastomer Actuators

Dielectric elastomers (DEs) are a class of highly deformable electroactive polymers (EAPs) employed for electromechanical transduction technology. When electrostatically actuated dielectric elastomer actuators (DEAs) are subjected to an input signal comprising multiple Heaviside voltage steps, the emerging inherent residual vibrations may limit their motion accuracy in practical applications. In this paper, the systematic development of a command-shaping scheme is proposed for controlling residual vibrations in an electrically driven planar DEA. The proposed scheme relies on invoking the force balance at the point of maximum lateral stretch in an oscillation cycle to bring the actuator to a stagnation state followed by the application of an additional electric input signal of predetermined magnitude at a specific time. The underlying concept of the proposed control scheme is articulated for a single Heaviside step input-driven actuator and further extended to the actuator subjected to the multistep input signal. The equation governing the dynamic motion of the actuator is derived using the principle of virtual work. The devised dynamic model of the actuator incorporates the effects of strain stiffening of elastomer and viscous energy dissipation. The nonlinear dynamic governing equation is solved using matlab ode solver for extracting the dynamic response of the actuator. The applicability of the devised command-shaping control scheme is illustrated by taking a wide range of parameters including variations in the extent of equilibrium state sequences, damping, and polymer chain extensibility. The proposed scheme is found to be adaptable in controlling the vibrations of the actuator for any desired equilibrium state. The results presented in this paper can find its potential application in the design of an open-loop control system for DEAs.

Investigation on Electromechanical Properties of Solid Silicone Rubber Composites with Conductive Carbon Filler

Dielectric elastomers belonging to the class of electroactive polymers are promising materials for electromechanical transduction. They are used as actuators, capacitive sensors and energy harvesters. In the present study solid silicone rubber-super conducting carbon black composites are prepared through compression moulding process and evaluated for their mechanical and dielectric properties. Electromechanical sensitivity is estimated and discussed using Taguchi orthogonal arrays for the factors, such as content of active filler and curing agent, mixing time in roll mill, curing temperature. Permittivity of the composites increased 6 times when compared with the sample without active filler. Electromechanical sensitivity of the composite improved 2 times, thus highlighting that this approach could lead to development of newer dielectric elastomer transducer materials.