AC Actuation Research Articles

INFLUENCE OF THE POLES SHAPE OF DC ELECTROMAGNETIC ACTUATOR ON ITS THRUST CHARACTERISTIC

Many technical objects use the electromagnetic DC actuators, which, unlike AC actuators, are more reliable, simpler in terms of manufacturing technology and have greater wear resistance. The listed advantages are the reason for the significant use of DC actuators in various industries including application as drive mechanisms of electrical devices. The DC actuator as a part of any technical object almost always plays one of the main roles from the point of view of reliable operation of entire device. Therefore the question of studying the designs of actuators and their characteristics is a rather topical task. Three designs of forward-moving electromagnetic DC actuators with the same overall dimensions and winding data are studied. They differ in the shapes of the supporting surfaces of poles, in other words, the surfaces with flat, conical and cut-conical shapes. As established, the shape of the supporting surfaces of poles has a significant impact on the thrust characteristics of the actuator and depending on the length of air gap this effect has a different character. The patterns of magnetic field of the studied actuators with an attracted armature are constructed, and the nature of magnetic field distribution and magnetic flux density distribution in operated gap are evaluated. The nature of the influence of cutting angle on static thrust characteristic for actuators with conical and cut-conical pole shapes is studied too. References 21, table 1, figures 7.

Smart electro-magneto-viscoelastomer minimum energy structures with particle-reinforcements: Theoretical equilibrium and nonlinear dynamics of actuated configurations

Soft transduction technology is rapidly adopting soft active elastomer-based minimum energy structures because of their distinctive programmable shape-morphing characteristics. For effective device design, an understanding of the nonlinear dynamic behavior is crucial as they often experience time-dependent motion while operating. Moreover, there has been an increasing scientific interest in enhancing the actuation performance of soft active elastomers by imparting particle reinforcements. This article provides a theoretical framework for investigating the nonlinear dynamics of smart composite elastomer-based minimum energy structures (SCEMES) with the provision of non-aligned electric and magnetic fields, leading to an actively programmable pre-stretch paradigm. Unlike conventional actuators, the proposed SCEMES is made up of a polymer that has electro-magnetic properties and is filled with appropriate fillers with specific volume fractions. An electromagneto-viscoelastic model is developed here to predict actuator behavior and investigate the effects of particle reinforcement on equilibrium and actuated configurations. Besides strengthening the polymer, particle reinforcement is observed to enhance the equilibrium angle achieved by the structure with enhanced functionality. The proposed nonlinear dynamic model is extended to investigate a number of critically influential parameters, including shear modulus ratio of fiber to matrix, frame bending stiffness, membrane pre-stretching, and electro-magnetic loading with time-dependent DC and AC modes of actuation. The results reveal that the combined electro-magnetic actuation enhances the actuation range significantly. The attained tip angle of the actuator increases appreciably when the magnetic and electric fields are applied mutually perpendicular to each other, indicating that the direction of applied magnetic field governs the attained actuated configuration. Further, particle reinforcement enrichments result in a depletion in oscillation amplitudes and an increase in excitation frequencies under the AC actuation mode. The efficient semi-analytical framework presented here would be crucial in developing new actuators, smart devices and soft robots for a variety of advanced engineering and medical applications.

Dynamic control of high-voltage actuator arrays by light-pattern projection on photoconductive switches

The ability to control high-voltage actuator arrays relies, to date, on expensive microelectronic processes or on individual wiring of each actuator to a single off-chip high-voltage switch. Here we present an alternative approach that uses on-chip photoconductive switches together with a light projection system to individually address high-voltage actuators. Each actuator is connected to one or more switches that are nominally OFF unless turned ON using direct light illumination. We selected hydrogenated amorphous silicon (a-Si:H) as our photoconductive material, and we provide a complete characterization of its light to dark conductance, breakdown field, and spectral response. The resulting switches are very robust, and we provide full details of their fabrication processes. We demonstrate that the switches can be integrated into different architectures to support both AC and DC-driven actuators and provide engineering guidelines for their functional design. To demonstrate the versatility of our approach, we demonstrate the use of the photoconductive switches in two distinctly different applications—control of µm-sized gate electrodes for patterning flow fields in a microfluidic chamber and control of cm-sized electrostatic actuators for creating mechanical deformations for haptic displays.

HZO-based FerroNEMS MAC for in-memory computing

This paper demonstrates a hafnium zirconium oxide (HZO)-based ferroelectric NEMS unimorph as the fundamental building block for very low-energy capacitive readout in-memory computing. The reported device consists of a 250×30 μm2 unimorph cantilever with 20-nm-thick ferroelectric HZO on 1 μm SiO2. Partial ferroelectric switching in HZO achieves analog programmable control of the piezoelectric coefficient (d31), which serves as the computational weight for multiply accumulate (MAC) operations. The displacement of the piezoelectric unimorph was recorded by actuating the device with different input voltages Vin. The resulting displacement was measured as a function of the ferroelectric programming/poling voltage VP. The slopes of central beam displacement (δmax) vs Vin were measured to be between 182.9 nm/V (for −8 Vp) and −90.5 nm/V (for 8 Vp), which corresponds to displacement proportionality constant β of 68 nm/V2 for +ve Vp and 47 nm/V2 for −ve Vp, demonstrating linear behavior of the multiplier unit. The resultant δmax from AC actuation is in the range of −18 to 36 nm and is a scaled product of Vin and programmed d31 (governed by the Vp). The multiplication function serves as the fundamental unit for MAC operations with the ferroelectric NEMS unimorph. The displacement from many such beams can be added by summing the capacitance changes, providing a pathway to implement a multi-input and multi-weight neuron. A scaling and fabrication analysis suggests that this device can be CMOS compatible, achieving high in-memory computational throughput.

Numerical Analysis of Magnetic Soliton Excited on Nonlinear LC Ladder Circuit Array Using Permanent Magnet Flux Biased Inductor

A soliton is a unique wave that maintains its shape and constant velocity. It has been observed widely in natural nonlinear systems. In particular, a magnetic soliton has been observed experimentally on a nonlinear <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> ladder circuit array. The aim of this article is to excite a magnetic soliton on the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> ladder circuit array using a permanent-magnet-flux-biased (PMFB) inductor. Electromagnetic analysis reveals that the PMFB inductor has exponential inductance characteristics due to the effective use of magnetic saturation in the stator core. Four PMFB inductors with different magnetic circuit topologies are analyzed and compared, to decrease the inductor current. Finally, this article numerically solves the loop equation for the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">LC</i> ladder circuit array and shows that the magnetic soliton is successfully excited and propagates without changing its shape and velocity. This technique is equivalent to a rotating magnetic field and has a great potential in developing new ac motors or actuators.

Nonlinear analysis and effectiveness of weakly coupled microbeams for mass sensing applications

In this work, we develop a general model of a mass sensor made of N weakly mechanically coupled microbeams subject to electric actuation. The developed model is verified by comparing the simulated pull-in voltages, natural frequencies, and frequency response of a two-weakly coupled beam system against their experimental counterparts reported in the literature. The sensitivity of the mass sensor in terms of frequency shift is observed to significantly increase when enlarging the size of the beams array. The simulation results reveal a clear transformation of the frequency response from a nearly linear to nonlinear behavior as result of the deposition of a small mass on the coupled system. As such, we show the potential use of bifurcations that result in an abrupt jump to a large-amplitude motion for sensing purposes. Furthermore, by exploiting the mode localization effect, the nonlinear response can be triggered on one of the beams when an added masses is introduced, allowing for an amplitude-based mass detection mechanism of the device. The proposed sensing method has the possibility to operate in bifurcation mode for mass threshold detection that can be tuned using the AC actuation or in continuous mode based on extracting the added mass from the amplitude of the sensing beam’s oscillations.

Dynamics Characterization of a U-Shaped Micro-Resonator Portal Frame

We present a study of the natural (resonance) frequencies of a tunable in-plane Microelectromechanical portal frame (U-shape) under DC electrostatic loads. The structure is designed and fabricated to excite the in-plane anti-symmetric (sway, first) and the symmetric (second) modes. Experimental results show high tunability of the resonance frequencies of both modes due to the electrostatic forces. Finite element simulations show good agreement with the experimental measurements. Further simulations are presented for the tunability of the natural frequencies of other higher-order modes using various electrode configurations. Frequency-response curves are presented for pure AC actuation of the first two modes showing strong nonlinear softening behavior due to the geometric nonlinearities of the portal frame. [2020-0269]

X-ray Photoelectron Spectroscopy with Electrical Modulation Can Be Used to Probe Electrical Properties of Liquids and Their Interfaces at Different Stages.

Operando X-ray photoelectron spectroscopy (o-XPS) has been used to record the binding energy shifts in the C 1s peak of a pristine poly(ethylene glycol) (PEG) liquid drop in an electrowetting on dielectric (EWOD) geometry and after exposing it to several high-voltage breakdown processes. This was achieved by recording XPS data while the samples were subjected to 10 V dc and ac (square-wave modulation) actuations to extract electrical information related to the liquid and its interface with the dielectric. Through analysis of the XPS data under ac actuation, a critical frequency of 170 Hz is extracted for the pristine PEG, which is translated to a resistance value of 14 MΩ for the liquid and a capacitance value of 60 pF for the dielectric, by the help of simulations using an equivalent circuit model and also by XPS analyses of a mimicking device under similar conditions. The same measurements yield an increased value of 23 MΩ for the resistance of the liquid after the breakdown by assuming that the capacitance of the dielectric stays constant. In addition, an asymmetry in polarity dependence is observed with respect to both the onset of the breakdown voltage and also the leakage behavior of the deteriorated (PEG + dielectric) system such that deviations are more pronounced at positive voltages. Both dc and ac behaviors of the postbreakdown system can also be simulated, but only by introducing an additional element, a diode or a polarity- and magnitude-dependent voltage source (VCVS), which might be attributed to negative charge accumulation at the interface. Measurements for a liquid mixture of PEG with 8% ionic liquid yields an almost 2 orders of magnitude smaller resistance for the drop as a result of the enhanced conductivity by the ions. Coupled with modeling, XPS measurements under dc and ac modulations enable probing unique electrochemical properties of liquid/solid interfaces.

P.325 Reward anticipation processing in major depressive disorder and prediction of treatment response - a functional magnetic resonance imaging study

DNA hybridization kinetics has been playing a critical role in molecular diagnostics for binding discrimination, but its study on digital microfluidic (DMF) systems is ultimately restrained by the laminar flow condition. The kinetic mixing technique is widely employed to ensure a fast reaction rate, but poses intrinsic risk in cross contamination and exhibits instable fluorescence intensity during the droplet transportation. While the electrothermal technique can provide stationary droplet mixing through the established thermal gradient within the hybridization solution, the significant increase in the droplet temperature will inevitably undermine the hybridization equilibrium and jeopardize the binding discrimination. To enhance the hybridization efficiency while ensuring a stable droplet temperature (within ±0.1℃), this paper presents a DMF platform that can perform isothermal hydrodynamic-flow-enhanced droplet mixing. Specifically, with a single electrode, droplet-boundary oscillation under a slow AC actuation is studied for improving the reaction rate. The dependencies between the mixing efficiency and the actuation voltage, actuation frequency and the spacer thickness are also systematically studied. Reliable mixing efficiency improvement is further validated over a wide range of solute concentrations. The results from real-time on-chip DNA hybridization kinetics with stationary droplets using the complete sandwiched DMF system shows that the proposed rapid mixer can achieve the same hybridization equilibrium with >13 times faster reaction rate when compared to the reference one through pure diffusion, while preventing biased hybridization kinetics as demonstrated in the electrothermal technique.

Sistem Kendali dan Akuisisi Data Suhu Serta Kelembaban Ruang Budidaya Jamur Tiram (Pleurotus Ostreatus) Berbasis Internet Of Things (IOT)

This study aims to determine the performance of temperature and humidity control technology of the Internet of Things (IoT) automatic oyster mushroom cultivation space. The stages of device development consist of analysis, design, assembly and testing. The design developed combines hardware control, software, and cloud server. This tool consists of 3 main processes, namely input using DHT11 sensors, process and output, namely 220 V AC actuators. There are two tests namely technical and effectiveness. The test results that have been carried out are: (1) the performance test results obtained an average error of 1.44% and a mean humidity of 3.35%, so that it can be used properly in the process of oyster mushroom cultivation; (2) the actuator will turn on if the temperature is more than 28oC or the humidity is less than 70%. The results of the transmission and storage of hardware data to the software on the database function properly, testing the effectiveness which shows the tools developed are more effective 5 hours compared to the manual method, (3) The advantages of this tool are that it can work automatically with IoT technology, there is realtime data recording, and features that are easy to use, so that it can help farmers in the care of oyster mushrooms.

Carbon Nanostructures for Actuators: An Overview of Recent Developments

In recent decades, micro and nanoscale technologies have become cutting-edge frontiers in material science and device developments. This worldwide trend has induced further improvements in actuator production with enhanced performance. A main role has been played by nanostructured carbon-based materials, i.e., carbon nanotubes and graphene, due to their intrinsic properties and easy functionalization. Moreover, the nanoscale decoration of these materials has led to the design of doped and decorated carbon-based devices effectively used as actuators incorporating metals and metal-based structures. This review provides an overview and discussion of the overall process for producing AC actuators using nanostructured, doped, and decorated carbon materials. It highlights the differences and common aspects that make carbon materials one of the most promising resources in the field of actuators.

Hydrodynamic-flow-enhanced rapid mixer for isothermal DNA hybridization kinetics analysis on digital microfluidics platform

DNA hybridization kinetics has been playing a critical role in molecular diagnostics for binding discrimination, but its study on digital microfluidic (DMF) systems is ultimately restrained by the laminar flow condition. The kinetic mixing technique is widely employed to ensure a fast reaction rate, but poses intrinsic risk in cross contamination and exhibits instable fluorescence intensity during the droplet transportation. While the electrothermal technique can provide stationary droplet mixing through the established thermal gradient within the hybridization solution, the significant increase in the droplet temperature will inevitably undermine the hybridization equilibrium and jeopardize the binding discrimination. To enhance the hybridization efficiency while ensuring a stable droplet temperature (within ±0.1℃), this paper presents a DMF platform that can perform isothermal hydrodynamic-flow-enhanced droplet mixing. Specifically, with a single electrode, droplet-boundary oscillation under a slow AC actuation is studied for improving the reaction rate. The dependencies between the mixing efficiency and the actuation voltage, actuation frequency and the spacer thickness are also systematically studied. Reliable mixing efficiency improvement is further validated over a wide range of solute concentrations. The results from real-time on-chip DNA hybridization kinetics with stationary droplets using the complete sandwiched DMF system shows that the proposed rapid mixer can achieve the same hybridization equilibrium with >13 times faster reaction rate when compared to the reference one through pure diffusion, while preventing biased hybridization kinetics as demonstrated in the electrothermal technique.

AC Electrowetting Modulation of Low-Volatile Liquids Probed by XPS: Dipolar vs Ionic Screening.

X-ray photoelectron spectroscopic (XPS) data have been recorded for a low-molecular-weight poly(ethylene glycol) microliter-sized sessile liquid drops sitting on a dielectric covered planar electrode while imposing a ±6 V square-wave actuation with varying frequencies between 10-1 and 105 Hz to tap into the information derivable from (AC) electrowetting. We show that this time-varying XPS spectra reveal two distinct behaviors of the device under investigation, below and above a critical frequency, measured as ∼70 Hz for the liquid poly(ethylene glycol) with a 600 Da molecular weight. Below the critical frequency, the liquid complies faithfully to the applied bias, as determined by the constant shift in the binding energy position of the XPS peaks representative of the liquid throughout its entire surface. The liquid completely screens the applied electrical field and the entire potential drop takes place at the liquid/dielectric interface. However, for frequencies above the critical value, the resistive component of the system dominates, resulting in the formation of equipotential surface contours, which are derived from the differences in the positions of the twinned O 1s peaks under AC application. This critical frequency is independent of the size of the liquid drop, and the amplitude of the excitation, but increases when ionic moieties are introduced. The XP spectra under AC actuation is also faithfully simulated using an equivalent circuit model consisting of only resistors and capacitors and using an electrical circuit simulation software. Moreover, a mimicking device is fabricated and its XP spectra are recorded using the Sn 3d peaks of the solder joints at different points on the circuit to confirm the reliability of the measured and simulated AC behaviors of the liquid. These new findings indicate that in contrast to direct current case, XPS measurements under variable frequency AC actuation reveal (through differences in the frequency response) information related to the chemical makeup of the liquid(s) and brings the laboratory-based XPS as a powerful complimentary arsenal to electrochemical analyses of liquids and their interfaces.

A 141-&lt;inline-formula&gt; &lt;tex-math notation="LaTeX"&gt;$\mu$ &lt;/tex-math&gt; &lt;/inline-formula&gt;W High-Voltage MEMS Gyroscope Drive Interface Circuit Based on Flying Capacitors

Electronic readout circuits for microelectromechanical gyroscopes suffer from high power consumption caused by the electrostatic sensor actuation with signals above the standard chip supply voltage. This paper presents an electronic circuit principle and implementation, which exploits the fact that ac actuation signals in the range of the chip supply voltage are sufficient, if they are combined with a high-voltage (HV) dc biasing. Therefore, the developed system performs the generation of the time-varying signal in the low-voltage domain and uses precharged flying capacitors to efficiently add a high dc biasing voltage. The circuit consists of a closed-loop low ripple charge pump, low-voltage driver amplifier, and an HV common frame biasing amplifier. The fully on-chip implementation occupies an area of 0.58 mm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> and reduces the power consumption to 141 μW.

Dynamics and vibration analysis of an electrostatically actuated FGM microresonator involving flexural and torsional modes

In this paper a nonlinear pedal like microresonator made of Functionally Graded material is introduced and modeled. Using Lagrangian formulation nonlinear equations of motion of the system are derived and the natural frequencies and mode shapes are extracted by linear analysis. The effects of various parameters such as geometry, FG material index and DC voltages on the natural frequencies and mode shapes are investigated. Static pull-in voltages of the system are obtained and it is found that depending on the type of actuation, both softening and hardening behaviors can be observed in the system. The results are compared with previous studies and finite element method where a good agreement is achieved. A two-mode reduced order model along with first-order averaging technique is implemented to derive the asymptotic dynamic equations of motion. The effects of different parameters including AC actuation level, damping and material power index on the dynamic response of the system are studied around resonance conditions. It is observed that when the system parameters are adjusted properly, the directly excited in-plane mode, in turn excites the out-of-plane torsional mode of the structure through internal resonance of 1:2 ratio within a specific frequency bandwidth. A wide range of frequency will be available by changing only the power index of the material and the system can be manipulated to be used in various MEMS applications such as mass sensors and RF filter-mixer devices.

Electromagnetic Control of Nonlinear Behavior of an Excited Cantilever Beam in a Single Mode Approximation

The effects of combined DC and fast AC electromagnetic actuations on the dynamic behavior of an excited cantilever beam is studied considering a single mode approximation. Analytical investigation is performed to extract the equation of motion describing the slow dynamic of the system. The influence of the fast AC actuation and the air gap on the nonlinear behavior of the system is examined. It is shown that the nonlinear characteristic of the system can be controlled by appropriately tuning the AC actuation or the air gap. This can be useful in certain engineering applications where the operating frequency range includes one or several critical frequencies that should be avoided.

Chaos prediction in nano-resonators based on nonlocal elasticity theory

By decreasing the thickness of micro- and nano- beams, classical continuum theory is not accurate to predict the static and dynamic response due to the absence of length scale parameter. In this paper, nonlocal elasticity theory is used to detect chaos in nano-resonators. In this way, first mode shape of the nano-beam is found and Galerkin method is used to convert the governing partial differential equation to an ordinary differential equation. Melnikov method is used to determine the critical value of AC actuation voltage resulting chaotic motion. Effects of nonlocal parameter and beam thickness on the stability region of the resonator are investigated. It will be shown that increasing the nonlocal parameter and decreasing the beam thickness increases the difference between stability regions obtained by classical and nonlocal theories. Moreover, increasing the nonlocal parameter decreases the nonlinear stiffness and increases the critical actuation voltage which may lead to chaotic motion.

Study on the influence of actuation parameter of SDBD on induced jet in low-pressure air

Surface dielectric barrier discharge (SDBD) is an important form of atmospheric discharge. The present study uses particle image velocimetry to investigate the influence of the duty cycle and pulse frequency on the flow field of plasma-induced jets and turbulent flow features for high-frequency high-voltage AC actuation under a low pressure of 7 kPa. The results prove that the SDBD plasma induces a suction flow and a horizontal tangential flow. Both the duty cycle and the pulse frequency have significant effects on the induced flow field. With the increasing duty cycle, the length and velocity of the jets increase linearly, the exit angle increases, and the Reynolds number of the tangential jet increases. The tangential jet transitions from turbulent to laminar flow as the duty cycle increases. As the pulse frequency increases, both the length of the tangential jet and the exit angle decrease gradually, and this trend accelerated near 30 Hz. The Reynolds number of the tangential jet increases to a maximum and then decreases with the increasing pulse frequency, with a peak near 50 Hz. The pulse frequency has little effect on the velocity of the jets or the turbulent flow characteristics of the tangential jet. A low duty cycle and a low pulse frequency should be adopted to increase the turbulent flow area and jet size to achieve a better actuation effect.

Size Effect Impact on the Mechanical Behavior of an Electrically Actuated Polysilicon Nanobeam based NEMS Resonator

In this paper, the dynamic response of resonating nano-beams is investigated using a strain gradient elasticity theory. A nonlinear model is obtained based on the Galerkin decomposition method to find the dynamic response of the investigated beam around its statically deflected position. The mid-plane stretching, axial residual stress and nonlinear interaction due to the electrostatic force on the deflected beam are included in the proposed nonlinear beam model. Comparing the beam natural frequency using strain gradient theory with experimental data shows an excellent agreement among both approaches. The normalized natural frequency is shown to be increasing nonlinearly with the decrease of the applied DC voltage as well as beam thickness. The results also reveal that increasing the tension axial stress increases the natural frequency; however its influence decreases when decreasing the beam thickness. To investigate the effect of AC actuation voltage on the beam resonant frequency, a Lindstedt-Poincare based perturbation method is utilized and validated by comparison with experimental data. The results show that increasing the AC actuation voltage makes the beam stiffer by increasing its resonant frequency.

AC actuation contribution to the induced electromotive force in the miniaturized inductive planar microphone

In this paper, we aim to analyze the gain ratio in the output induced voltage of a CMOS-compatible miniaturized electrodynamic microphone which is based on the use of two coplanar concentric inductors. These latter are comparable to a concentric transformer with a secondary situated on the microphone diaphragm top. The study has been applied when the outer inductor is actuated using an AC bias instead of DC leading to a time-variable B-field. The induced output voltage expression has been evaluated using two distinct analytic methods: the magnetic field derivation and the electric field approach. When an AC current with frequency above that of the acoustic band is used to bias the primary, results show that the induced voltage increases and becomes independent from the incident pressure wave frequency. The paper demonstrates also that with an AC bias, the microphone induced voltage values can reach the order of hundreds of µVs, as opposed to only few µVs when applying a DC bias. The gain in the induced voltage has been investigated and it is shown that it can be correlated to the AC current frequency, ?c, and the inner inductor fluctuation frequency, ?p. Moreover, this has been quantified analytically and it is shown that it equals ?c/8?p. This result will not only enhance the overall performance of the microphone, but will also make the preamplification design less complicated by increasing the SNR ratio.