Cantilever Actuator Research Articles

Polyisobutylene Encapsulated PEDOT: Pss Electrode Honeycomb Skeleton Electrolyte for Moisture Resistant Electro‐Ionic Soft Artificial Muscles

AbstractAdvances in electro‐ionic soft actuators hold significant potential as next‐generation bioelectronic interfaces due to mechanical compliance and operation in agreement with soft biological tissues and low voltages. However, current devices call for encapsulation strategies to accommodate high mechanical demands and long‐term stability in environmental changes. In this study, a durability of polyvinylidene‐fluoride‐co‐hexafluoropropylene (PVDF‐co‐HFP) honeycomb skeleton electrolyte encapsulated with a biocompatible polyisobutylene (PIB) thin film is being investigated. A low water vapor transmission rate (0.61 g m−2 day−1) and elastic modulus (10 kPa) are measured from a 7.5 µm‐thick thin‐modified PIB‐encapsulation layer. The PIB‐encapsulated soft actuator maintains 68% of its mechanical durability after 40 000 cycles of zero‐to‐tension fatigue loading at room temperature. A cantilever actuation test of the PIB‐encapsulated 3mm‐wide 30mm‐long actuator film shows a large tip displacement (15.90 mm) at a low voltage (±1.5 V) under 0.1 Hz, 37 °C, 50% relative humidity (RH). Most importantly, while the unencapsulated actuator immediately degrades in a few cycles at 37 °C, 50%RH, and 0.1% applied strain, PIB‐encapsulated soft actuator performs up to 6500 dynamic actuation cycles without any functionality degradation. Exceptional durability against mechanical fatigue and stability at elevated temperature and humidity meet the prerequisite for future soft biomedical robots that enable long‐lasting safe operations.

Dynamic Response of Paper-Based Bi-Material Cantilever Actuator

This work presents a dynamic modeling approach for analyzing the behavior of a bi-material cantilever actuator structure, consisting of a strip of filter paper bonded to a strip of tape. The actuator’s response is induced by a mismatch strain generated upon wetting, leading to the bending of the cantilever. The study delves into a comprehensive exploration of the dynamic deflection characteristics of the bilayer structure. It untangles the intricate connections among the saturation, modulus, hygro-expansion strain, and deflection, while uniquely addressing the challenges stemming from fluid–structure coupling. To solve the coupled fluid–solid differential equations, a combined numerical method is employed. This involves the application of the Highly Simplified Marker and Cell (HSMAC) technique for fluid flow analysis and the Finite Difference Method (FDM) for response deflection computation. In terms of the capillary flow model, the Computational Fluid Dynamics (CFD) simulations closely align with the classical Washburn relationship, depicting the wetted front’s evolution over time. Furthermore, the numerical findings demonstrate that heightened saturation levels trigger an increase in hygro-expansion strain, consequently leading to a rapid rise in response deflection until a static equilibrium is achieved. This phenomenon underscores the pivotal interplay among saturation, hygro-expansion strain, and deflection within the system. Additionally, the actuator’s response sensitivity to material characteristics is highlighted. As the mismatch strain evolving from paper hygro-expansion diminishes, a corresponding reduction in the axial strain causes a decrease in response deflection. The dynamic parameter demonstrates that the deflection response of the bilayer actuator diminishes as dynamic pressure decreases, reaching a minimal level beyond which further changes are negligible. This intricate correlation underscores the device’s responsiveness to specific material traits, offering prospects for precise behavior tuning. The dependence of paper modulus on saturation levels is revealed to significantly influence bilayer actuator deflection. With higher saturation content, the modulus decreases, resulting in amplified deflection. Finally, strong concordance is observed among the present fluidically coupled model, the static model, and empirical data—a testament to the accuracy of the numerical formulation and results presented in this study.

Sparse Lissajous scanning reflectance confocal microscope with an adjustable field of view and fast iterative Fourier filtering reconstruction.

Medical imaging devices are becoming increasingly compact, necessitating optimization research into different methods of actuation. Actuation influences important parameters of the imaging device such as size, weight, frame rate, field of view (FOV), and image reconstruction for imaging devices point scanning techniques. Current literature around piezoelectric fiber cantilever actuators focuses on device optimization with a fixed FOV but neglects adjustability. In this paper, we introduce an adjustable FOV piezoelectric fiber cantilever microscope and provide a characterization and optimization procedure. To overcome calibration challenges, we utilize a position sensitive detector (PSD) and address trade-offs between FOV and sparsity with a novel inpainting technique. Our work demonstrates the potential for scanner operation when sparsity and distortion dominate the FOV, extending the usable FOV for this form of actuation and others that currently only operate under ideal imaging conditions.

Pilot Study: Magnetic Motion Analysis for Swallowing Detection Using MEMS Cantilever Actuators.

The swallowing process involves complex muscle coordination mechanisms. When alterations in such mechanisms are produced by neurological conditions or diseases, a swallowing disorder known as dysphagia occurs. The instrumental evaluation of dysphagia is currently performed by invasive and experience-dependent techniques. Otherwise, non-invasive magnetic methods have proven to be suitable for various biomedical applications and might also be applicable for an objective swallowing assessment. In this pilot study, we performed a novel approach for deglutition evaluation based on active magnetic motion sensing with permanent magnet cantilever actuators. During the intake of liquids with different consistency, we recorded magnetic signals of relative movements between a stationary sensor and a body-worn actuator on the cricoid cartilage. Our results indicate the detection capability of swallowing-related movements in terms of a characteristic pattern. Consequently, the proposed technique offers the potential for dysphagia screening and biofeedback-based therapies.

A reconfigurable ladder-shaped THz metamaterial integrated with a microelectromechanical cantilever array

We experimentally demonstrate a microelectromechanically reconfigurable ladder-shaped metamaterial (LS-MM) operating in a terahertz (THz) range. Ultrasmall cantilever actuators with a beam length of 14 μm are employed to independently reshape each unit cell of the LS-MM, correspondingly switching the transmission response of THz waves. The microelectromechanically driven LS-MM achieves a tuning contrast of 60.1% in transmittance at 0.78 THz and a 0.9-rad delay in the transmission phase shift at 1.35 THz through the off-to-on reconfiguration. In particular, the cantilever actuator has a high mechanical resonant frequency of 585 kHz owing to its small size. The microelectromechanically driven LS-MM advantageously offers a pathway for applications requiring fast tunable transmission modulations, such as high-resolution THz imaging and wireless communications.

Importance of Three-Dimensional Piezoelectric Coupling Modeling in Quantitative Analysis of Piezoelectric Actuators

This paper demonstrates the importance of three-dimensional (3-D) piezoelectric coupling in the electromechanical behavior of piezoelectric devices using three-dimensional finite element analyses based on weak and strong coupling models for a thin cantilevered piezoelectric bimorph actuator. It is found that there is a significant difference between the strong and weak coupling solutions given by coupling direct and inverse piezoelectric effects (i.e., piezoelectric coupling effect). In addition, there is significant longitudinal bending caused by the constraint of the inverse piezoelectric effect in the width direction at the fixed end (i.e., 3-D effect). Hence, modeling of these effects or 3-D piezoelectric coupling modeling is an electromechanical basis for the piezoelectric devices, which contributes to the accurate prediction of their behavior.

Carbon nanotubes enhanced bimorph effect of U-shaped flexure cantilever beam actuators made from polyethylene terephthalate and polymethyl methacrylate

U-shaped cantilever actuators made from PET and PMMA exhibit a bimorph effect upon radiation heating and beam always moves toward PMMA side with maximum displacement and displacing rate measured to be 2100 μm and 35 μm s−1. This number increases to 3300 μm and 55 μm s−1 while PET surfaces are coated with single-walled carbon nanotubes acting as heat reservoir. Actuations can be further improved by carbon nanotube resistive heating and improvement reaches two-fold (4100 μm and 68.3 μm s−1). Coated beam actuators exhibit an excellent stability over 2 h intermittent operations where the maximum displacement varies only in ±1%.

Design and Fabrication of Millimeter-Wave Frequency-Tunable Metamaterial Absorber Using MEMS Cantilever Actuators.

In this paper, a MEMS (Micro Electro Mechanical Systems)-based frequency-tunable metamaterial absorber for millimeter-wave application was demonstrated. To achieve the resonant-frequency tunability of the absorber, the unit cell of the proposed metamaterial was designed to be a symmetric split-ring resonator with a stress-induced MEMS cantilever array having initial out-of-plane deflections, and the cantilevers were electrostatically actuated to generate a capacitance change. The dimensional parameters of the absorber were determined via impedance matching using a full electromagnetic simulation. The designed absorber was fabricated on a glass wafer with surface micromachining processes using a photoresist sacrificial layer and the oxygen-plasma-ashing process to release the cantilevers. The performance of the fabricated absorber was experimentally validated using a waveguide measurement setup. The absorption frequency shifted down according to the applied DC (direct current) bias voltage from 28 GHz in the initial off state to 25.5 GHz in the pull-down state with the applied voltage of 15 V. The measured reflection coefficients at those frequencies were −5.68 dB and −33.60 dB, corresponding to the peak absorptivity rates of 72.9 and 99.9%, respectively.

ZIF-Based Metal-Organic Frameworks for Cantilever Gas Sensors

Among the different gas sensing platforms, cantilever-based sensors have attracted considerable interest in recent years thanks to their ultra-sensitivity and high-speed response. The gas sensing mechanism in a dynamic cantilever sensor is based on its resonance frequency shift upon adsorption of a gas molecule on the sensor. In order to sensitize the surface of a cantilever, a sensitive receptor material with large surface area is required. Metal-organic frameworks (MOFs) are a class of nanoporous crystalline materials composed of metal ions coordinated to organic linkers. MOFs are promising for gas sensing applications as they have large surface area, rich porosity with adjustable pore size and excellent selective adsorption capability for various gasses.[1] Zeolite imidazole frameworks (ZIFs) are a class of MOFs where metals with tetrahedral coordination (i.e. Zn, Co, Fe, Cu) are the central node and the ligands are imidazolate-based organic molecules.In this work, we developed a ZIF-based thin film for dynamic cantilever gas-sensing applications. We employed a novel atmospheric pressure spatial atomic layer deposition (AP-SALD)[2][3] technique to deposit a ZnO sacrificial layer on the silicon cantilevers. This technique allows the deposition of high-quality films at atmospheric pressure, faster than conventional ALD. The ZnO layer was then converted to a particular ZIF film with desired porosity and size, through a MOF-CVD process.[4] A gas-sensing bench setup was developed for the cantilever actuation and read-out. We present the chemical and morphological properties of the ZIF, as well as the frequency response of the sensor to various gases. The device showed reliable sensitivity to humidity, CO2 and several VOCs.

Design of Shape Memory Micro-Actuator Modules with Sequential Actuation

Shape memory alloy film-based micro-actuators have their behaviour controlled by a change in the thermomechanical stress that occurs in the bimorph - shape memory alloy film plus substrate assembly. The modification of the composition of the shape memory alloy leads to a change of the transformation temperature and implicitly of the temperature at which the stress change takes place in the bimorph. The design of micro-actuator blocks in which the composition and/or the temperature control mode of each micro-actuator in the block allows to obtain successive or sequential transformation sequences. The paper analyses the case of cantilever actuator modules with films of different compositions, deposited on the same substrate. It is highlighted how the composition of the alloy film with shape memory influences the modification of the curvature of bimorph cantilever type actuators in the studied block.

The Staircase Drive-A Novel Actuator Design Optimised for Daisy-Chaining and Minimum Stress Load Coupling.

This work presents a novel type of actuator that improves over the standard cantilever by permitting daisy-chaining while minimising stress to the joint connecting to the load. A detailed structural and functional comparison of the proposed device against the cantilever actuator as a baseline is given, led by a brief revision of the cantilever actuator as the state-of-the-art that highlights its limitations with respect to daisy-chaining and the stress it inherently creates within the joint connecting to the load when attempting out-of-plane displacement without rotation. Simulations of both devices’ performance confirm that the newly proposed device yields the targeted displacement profile that both enables the daisy-chaining of such a device into a higher-order actuator for increased displacement and reduce stress in the joint with the load. This comes at the cost of reduced maximum displacement compared to the cantilever, which can be overcome by daisy-chaining. The proposed device’s performance is further evaluated on the basis of manufactured prototypes measured by means of a laser scanning vibrometer. The prototype was manufactured on a 150 m alumina substrate, and both electrodes and piezoelectric layer were deposited in a thick-film printing process.

Theoretical Modeling of Piezoelectric Cantilever MEMS Loudspeakers

Piezoelectric microelectromechanical system (MEMS) loudspeakers have received extensive attention in recent years. In particular, the piezoelectric cantilever MEMS loudspeaker, which uses multilayer piezoelectric cantilever actuators (MPCAs), has attracted attention because of its small size, low cost, ease of manufacture, and desirable piston movement. However, owing to the complex driving principles of MPCAs, no adequately efficient and appropriate method currently exists that can be used to analyze and predict the performance of piezoelectric cantilever MEMS loudspeakers. In this study, the equivalent circuit method (ECM) is adopted to theoretically model piezoelectric cantilever MEMS loudspeakers, and an ECM model with a special MPCA transformer for electromechanical conversion is proposed. With the proposed ECM model, the performance characteristics of piezoelectric cantilever MEMS loudspeakers, such as the displacement and sound pressure response, can be calculated efficiently and conveniently. To verify the accuracy of the ECM model, the finite element method is adopted for simulation, and the simulated results are compared with those of the ECM models. A satisfactory agreement was found, which verifies the accuracy of the proposed ECM model.

Magnetophoresis-Assisted Capillary Assembly: A Versatile Approach for Fabricating Tailored 3D Magnetic Supercrystals.

The fabrication and integration of sub-millimeter magnetic materials into predefined circuits is of major importance for the realization of portable devices designed for telecommunications, automotive, biomedical, and space applications but remains highly challenging. We report here a versatile approach for the fabrication and direct integration of nanostructured magnetic materials of controlled shaped at specific locations onto silicon substrates. The magnetophoresis-assisted capillary assembly of magnetic nanoparticles, either spherical or anisotropic, leads to the fabrication of high-performance Co-based permanent magnets and Fe-based supercrystals. Integrated sub-millimeter magnets as well as millimeter self-standing magnets exhibiting magnetic properties competing with NdFeB-based composites were obtained through this cost- and time-efficient process. The proof-of-concept of electromagnetic actuation of a micro-electromechanical system cantilever by means of these supercrystals highlights their potentiality as efficient integrated magnetic materials within nomadic devices.

Integration of SMP with PVDF Unimorph for Bending Enhancement.

Heat generation in active/passive layer-based piezoelectric actuators is unavoidable due to the mechanical, dielectric, and resistive losses in the material. In this work, a polyvinylidene fluoride (PVDF)-based unimorph cantilever actuator is developed with simulation and experimental studies on the effect of DC high voltages on heat production in the PVDF layer. A layer of one-way shape memory polymers (1W-SMPs) is integrated in the actuator to exploit the heat produced to increase the bending angle. The length and mounting location of the SMP layer impacts the bending of the actuator; by using an SMP layer with a length equal to half of the PVDF layer at the center of the unimorph actuator, the absolute bending angle is increased to 40° compared to the base piezo bending angle of 4° at 20 V/µm.

Force control of electro-active polymer actuators using model-free intelligent control

In this paper, a model-free control framework is proposed to control the tip force of a cantilevered trilayer CPA and similar cantilevered smart actuators. The proposed control method eliminates the requirement of modeling the CPAs in controller design for each application, and it is based on the online local estimation of the actuator dynamics. Due to the fact that the controller has few parameters to tune, this control method provides a relatively easy design and implementation process for the CPAs as compared to other model-free controllers. Although it is not vital, in order to optimize the controller performance, a meta-heuristic particle swarm optimization (PSO) algorithm, which utilizes an initial baseline model that approximates the CPAs dynamics, is used. The performance of the optimized controller is investigated in simulation and experimentally. Successful results are obtained with the proposed controller in terms of control performance, robustness, and repeatability as compared with a conventional optimized PI controller.

Distributed transfer function-based unified static solutions for piezoelectric short/open-circuit sensing and voltage/charge actuation of beam cantilevers

Closed-form unified solutions using the distributed transfer functions (DTFs) method are presented for the first time for the static short/open-circuit sensing and voltage/charge actuation of moderately thick beam cantilevers with co-localized surface-bonded piezoelectric patches. For this purpose, the smart beam is divided into three segments, of which the clamp and free sides parts are elastic, while the middle one is made of an elastic core sandwiched between two electroded piezoelectric patches. The latter can be different in material properties and thickness but should have the same length, and their widths can be different from the host elastic beam. The theoretical formulation is based on Timoshenko’s first-order shear deformation theory for the kinematics and piezoelectric constitutive equations and the principle of virtual works for the variational equations. The latter integrate explicitly the physical equipotential constraints on the patches electrodes. The balance equations and boundary conditions are derived for the three segments independently and then connected at their interfaces by the equilibrium equations and continuity conditions. The unified static solutions for the resulting four problems are derived analytically in closed form using the DTF approach. These are validated against only open literature benchmarks having tabulated results or analytical formulas in order to avoid curves induced inherent additional deviations. Very good correlations were obtained in comparison with the found reference two-dimensional (2D) plane strain/stress analytical and 2D plane strain/stress and three-dimensional finite element results.

Two-frequency parametric excitation and combination resonance of a nanocomposite laminated piezoelectric trapezoidal plate in subsonic airflow

In this study, an analytical approach is presented to analyze the bifurcations and nonlinear dynamics of a cantilevered piezoelectric nanocomposite trapezoidal actuator subjected to two-frequency parametric excitations in the presence of subsonic airflow. The assumption of uniformly distributed single-walled carbon nanotubes along the thickness is taken into the consideration. The governing equations are built by the von-Karman nonlinear strain-displacement relations to consider the geometrical nonlinearity and the linear potential flow theory. The present study focuses on a specific resonance case deals with the occurrence of simultaneous resonances in the principal parametric resonance of the first mode and combination of the parametric resonance of the difference type involving two modes. The multiple scales method is employed to obtain the four nonlinear averaged equations which are solved by using the Runge-Kutta method. Moreover, the frequency-response curves, bifurcation diagrams, time history responses, and phase portrait are obtained to find the nonlinear dynamic responses of the plate. The effects of the amplitude of piezoelectric excitation, piezoelectric detuning parameter, and aerodynamic pressure are also studied. The results indicate that, the chaotic, quasi-periodic and periodic motions of the plate exist under certain conditions and the variation of controlling parameters can change the form of motions of the nanocomposite piezoelectric trapezoidal thin plate.

Investigation on Actuation Performance of Continuous Fiber Reinforced Piezoelectric Composite Actuator

ABSTRACTIn this paper, a novel continuous fiber reinforced piezoelectric composite (CFRPC) actuator is proposed to improve the stability and reliability of piezoelectric actuators. A piezoelectric driving structure composed of a cantilever beam and the CFRPC actuator is utilized to research the actuation performance of the CFRPC actuator. The expression of the equivalent moment for the CFRPC actuator is obtained using the equivalent load method and electro-mechanical coupling theory. Based on Euler-Bernoulli beam theory, the analytical expression of the deflection for the cantilever beam is derived. The accuracy of the obtained analytical expressions is demonstrated by finite element simulation as well as published experimental results. The actuation performance of the CFRPC actuator is investigated through the analytical expressions of the equivalent moment and deflection. The results show that the key parameters such as driving voltage, fiber volume fraction, cantilever beam height, actuator height, actuator length and actuator position have great influence on the actuation performance of the CFRPC actuator. The CFRPC actuator has good mechanical and electrical properties, and has a wide application prospect in the field of structural shape control.

Investigation of Deformation in Bimorph Piezoelectric Actuator: Analytical, Numerical and Experimental Approach

Piezoelectric actuators are widely used in many fields such as medical instruments, optics, and aerospace due to their small size and high reliability. Piezoelectric cantilever actuators are used in different configurations such as unimorph and bimorph. In this paper, a 3-D lead zirconate titanate (PZT) bimorph was modeled in COMSOL Multiphysics software for investigation of series and parallel configuration. Theoretical analysis has been developed for the measurement of deformation of a piezoelectric cantilever in inverse piezoelectric effect. The experiment was also performed to examine the deformation of piezoelectric bimorph cantilever. It is found that under a constant applied electric field of 100 V bimorph piezoelectric actuator produces maximum deformation at 100 mm length, 30 mm width, and 20 mm thickness. It is also found that piezoelectric series benders have relatively less deformation than piezoelectric parallel benders. Experimental results show good agreement with theoretical and Numerical results.

A laminar fluid flow model for study of ventilation systems in micro-electromechanical systems (MEMS) clean room

This paper reports the simulation based analysis results of air flow in a MEMS clean room aimed at predicting the air borne distribution of 0.5 μm particles as per the ISO standard. These particulate contaminants, if not flushed by proper design of the ventilation system of the clean room can get deposited and accumulated on the MEMS devices under fabrication, contributing possibly to the affected functionality of the device, particularly high precision devices such as single cantilever type precision MEMS sensors and actuators. The results of computational fluid dynamics (CFD) based flow analysis done in COMSOL™ estimated for adverse conditions such as a desired ISO-5 cleanliness degrading to ISO-8 cleanliness due to poor maintenance have been presented. Based on the flow conditions, conclusions on the particle accumulation have been drawn.