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International audience; Recent progress in the field of microsystems on flexible substrates raises the need for alternatives to the stiffness of classical actuation technologies. This paper reports a top-down process to microfabricate soft conducting polymer actuators on substrates on which they ultimately operate. The bending microactuators were fabricated by sequentially stacking layers using a layer polymerization by layer polymerization of conducting polymer electrodes and a solid polymer electrolyte. Standalone microbeams thinner than 10 μm were fabricated on SU-8 substrates associated with a bottom gold electrical contact. The operation of microactuators was demonstrated in air and at low voltage (±4 V).

This paper reports the development of a new two-axis micromechanical scanning transducer for handheld 3D ultrasound imaging. It consists of a miniaturized single-element ultrasound transducer driven by a unique 2-axis liquid-immersible electromagnetic microactuator. With a mechanical scanning frequency of 19.532 Hz and an ultrasound pulse repetition rate of 5 kHz, the scanning transducer was scanned along 60 concentric paths with 256 detection points on each to simulate a physical 2D ultrasound transducer array of 60 × 256 elements. Using the scanning transducer, 3D pulse-echo ultrasound imaging of two silicon discs immersed in water as the imaging target was successfully conducted. The lateral resolution of the 3D ultrasound image was further improved with the synthetic aperture focusing technique (SAFT). The new two-axis micromechanical scanning transducer does not require complex and expensive multi-channel data acquisition (DAQ) electronics. Therefore, it could provide a new approach to achieve compact and low-cost 3D ultrasound imaging systems, especially for handheld operations.

A chevron thermal actuator has been implemented as a constant velocity puller in a multiasperity frictional test platform. This platform enables a wide variation of puller velocity (1– $3100~\mu \text{m}$ /s, 3.5 decades), normal load (2– $4500~\mu \text{N}$ , 3.4 decades), and spring constant (0.06– $100~\mu \text{N}/\mu \text{m}$ , 3.2 decades). These characteristics are achieved by leveraging the actuator thermal time constant, which is long compared with the mechanical time constant, in combination with iterative learning control. Good thermal isolation between the actuator and the friction block is achieved by shunting heat to the substrate. Uncoated and FOTAS [tridecafluorotris(dimethylamino)silane, CF3(CF2)5(CH2)2Si(N(CH3)2)3]-coated devices were tested, and normal load induced a transition from steady sliding to stick-slip. This platform could have several important uses for mapping microscale kinetic friction phase diagrams, including determining the stick-slip to steady sliding bifurcation line, performing start-stop tests and instantaneous velocity change tests, and inferring information on wear performance of coatings as a function of load and velocity. [2015-0123]

Flexible beams of variable effective length, serve both transmission and actuation functionalities in compliant mechanisms, have been employed in many devices, e.g., thermal actuators and continuum robots. This difunctional feature is favorable when utilized for operations in confined space. However, the length variation introduces modeling difficulties, which poses a new challenge to designers. To accurate model flexible beams of variable effective length and characterize the behaviors of associated compliant mechanisms form the primary objectives of this study. The chained beam constraint model is revisited and extended to model beams of variable effective length. Modeling of a chevron shape thermal in-plane microactuator and a continuum mechanism are provided to demonstrate the effectiveness of the proposed method. The predicted results have a high degree of accuracy as compared to experimental results and nonlinear finite element results.

This paper proposes and studies the characteristics of a laser-driven optothermal microactuator (OTMA) directly operated in water. A theoretical model of optothermal temperature rise and expansion is established, and simulations on a 1000 µm long OTMA are conducted, revealing that its arm is able to expand and contract in response to the laser pulses in a water environment. Microactuating experiments are further carried out using a microfabricated OTMA. The results demonstrate that the OTMA can be practically actuated in water by a 650 nm laser beam and that the OTMA’s deflection amplitude increases linearly with laser power. When irradiated by laser pulses with 9.9 mW power and 0.9–25.6 Hz frequencies, the OTMA achieves deflection amplitude ranging from 3.9 to 3.2 µm, respectively. The experimental results match well with theoretical model when taking the damping effect of water into account. This research may be conducive to developing particular micro-electromechanical systems or micro-optoelectromechanical devices such as underwater optothermal micromotors, micro-pumps, micro-robots, and other underwater microactuators.

Light-driven micro/nano-actuators are one of the most important topics in the biomedical micro-electromechanical systems (MEMS) field. Currently, their development is hampered due to the difficulties in designing and fabricating biocompatible light-driven microactuators with the dimensions less than one hundred micrometres and a response time in the order of seconds. In this work, gel photoresists were prepared by embedding photothermal surface-modified Fe3O4 nanoparticles (NPs) into a mixture that included a photoinitiator, photosensitizer, monomers, crosslinkers and solvents. Macroscopic poly(N-isopropylacrylamide) (PNIPAM)/nano-Fe3O4 hydrogels were prepared by ultraviolet photopolymerization of gel photoresists, which showed good temperature-responsive volume changes and light-triggered bending deformation. Then the two-photon polymerization (TPP) microfabrication properties of gel photoresists with 0, 0.48 and 0.95 wt% Fe3O4 NPs were investigated in detail. Importantly, after the TPP microfabrication and subsequent solvent-exchange procedure, a double-armed near-infrared (NIR)-light-driven three-dimensional (3D) hydrogel microcantilever with a size of ∼26 μm was successfully fabricated. The hydrogel microactuator had a fast response time of ∼0.033 s in water under NIR radiation and showed good reversibility. Furthermore, the distance between the two arms of the hydrogel microcantilever could be manipulated by controlling the laser focus and incident laser power.

This work develops the first tubular microactuator functionalized by ferrofluid that enables both rotational and axial motions in a simultaneous or selective manner for endoscopic imaging and spectroscopy catheter applications. A layer of ferrofluid attracted on the magnetic rotor/slider lifts it off the inner walls of the catheter tube, offering a near friction-less electromagnetic revolution of the rotor and/or its sliding motion along the catheter's axis controlled by a fluidic pressure. A device prototype coupled with a prism mirror is microfabricated and evaluated to verify the effectiveness of the device design for 3-dimesnional (3D) scanning of a probing laser beam. Measurements show a superior revolving stability along its axis compared to the preceding design without axial motion function. An application of angle-resolved endoscopic Raman spectroscopy is experimentally demonstrated through an ex-vivo test using mouse tissue. The study suggests a promising potential of the microactuator for 3D endoscopic applications with Raman spectroscopy and likely with other modalities including ultrasound and optical coherence tomography.

In the ever advancing field of minimally invasive surgery, flexible instruments with local degrees of freedom are needed to navigate through the intricate topologies of the human body. Although cable or concentric tube driven solutions have proven their merits in this field, they are inadequate for realizing small bending radii and suffer from friction, which is detrimental when automation is envisioned. Soft robotic actuators with locally actuated degrees of freedom are foreseen to fill in this void, where elastic inflatable actuators are very promising due to their S3-principle, being Small, Soft and Safe. This paper reports on the characterization of a chip-on-tip endoscope, consisting out of a soft robotic pneumatic bending microactuator equipped with a 1.1 × 1.1 mm2 CMOS camera. As such, the total diameter of the endoscope measures 1.66 mm. To show the feasibility of using this system in a surgical environment, a preliminary test on an eye mock-up is conducted. ispartof: Biomedical Microdevices vol:20 issue:3 ispartof: location:United States status: published

Here we describe development of a microfluidic viscometer based on arrays of magnetically actuated micro-posts. Quantitative viscosities over a range of three orders of magnitude were determined for samples of less than 20 μL. This represents the first demonstration of quantitative viscometry using driven flexible micropost arrays. Critical to the success of our system is a comprehensive analytical model that includes the mechanical and magnetic properties of the actuating posts, the optical readout, and fluid-structure interactions. We found that alterations of the actuator beat shape as parameterized by the dimensionless "sperm number" must be taken into account to determine the fluid properties from the measured actuator dynamics. Beyond our particular system, the model described here can provide dynamics predictions for a broad class of flexible microactuator designs. We also show how the model can guide the design of new arrays that expand the accessible range of measurements.

Tunable THz metamaterials has shown great potential to solve the material challenge due to the so called “THz gap”. However, the tunable mechanism of current designs relies on using semiconductors insertions, which inevitably results in high ohmic loss, and thereby significantly degrades the performance of metamaterials. In this work, we demonstrate a novel tunable mechanism based on polymetric microactuators. Our metamaterials are fabricated on the surface of patterned pillar array of flexible polymers embedded with magnetic nanoparticles. The transmission spectrum of the metamaterial can be tuned as the pillars are mechanically deformed though applied magnetic field. Compared to previous semiconductor based tunable mechanism, our structure has shown much lower loss.

This paper reports on a piezoresistive strain sensor that uses vertically aligned carbon nanotube (CNT) filler elements which are embedded in a rubber matrix. Compared to previously used conductive filler elements, vertical CNTs can be patterned using lithography, making it possible to scale down the sensor footprint into the micrometer range. This technological advancement is instrumental for developing intelligent soft microrobots with embedded flexible sensors. We compare vertical CNTs and carbon black as filler elements, where newly developed lithographic production techniques are applied to shape a generic strain sensor topology that is compatible with the majority of planar inflatable microactuators. This research shows a significant improvement in sensor linearity by using vertical CNTs as filler elements over carbon black. Further, a lithographically fabricated strain sensor has been successfully embedded in an elastic inflatable bending microactuator with outer dimensions of 5.5×1×0.06mm3. The full lithographic production process to create this actuator is described in this paper, together with its characterization under a static pressure input.

Use of a thin-film piezoelectric microactuator for axial scanning during multi-photon vertical cross-sectional imaging is described. The actuator uses thin-film lead-zirconate-titanate to generate the upward displacement of a central mirror platform micro-machined from a silicon-on-insulator wafer to dimensions compatible with endoscopic imaging instruments. Device modeling in this paper focuses on the existence of frequencies near device resonance producing vertical motion with minimal off-axis tilt, even in the presence of multiple vibration modes and non-uniformity in fabrication outcomes. Operation near rear resonance permits large stroke lengths at low voltages relative to other vertical microactuators. Highly uniform vertical motion of the mirror platform is a key requirement for vertical cross-sectional imaging in the remote scan architecture being used for multi-photon instrument prototyping. The stage is installed in a benchtop testbed in combination with an electrostatic mirror that performs in-plane scanning. Vertical sectional images are acquired from 15- $\mu \text{m}$ diameter beads and excised mouse colon tissue. [2017-0073]

In this paper, a bent beam thermal microactuator’s performance is presented. Displacement of this thermal actuator has been compared for different materials. The proposed bent beam microactuator operates on the code of Joule’s heating effect with the able guidance of thermal expansion which brings into play the advantage of the profile (chevron) to augment the cumulative effect of thermal expansion so that it can produce large in-plane displacement with minimum operating voltage. This revision is done by considering the basic benefit in the design of a bent beam microactuator system and thereby simulating this bent beam thermal microactuator using COMSOL Multiphysics5.1 to analyze the response. The behavior of this thermal bent beam microactuator is premeditatedly decided for different materials such as aluminum, gold, argentum, cuprum and nickel and observations are recorded for the displacement response for an applied electric potential 0.2 V between two anchors.

Fourier transform infrared spectroscopy is a widely used instrument to analyze and test different materials including organic and inorganic. Most of current commercial Fourier transform infrared spectrometers are limited in miniaturization and scanning velocity by their macroscopic components. MEMS FTIR spectroscopy is one of the important applications of translational actuator-driven systems by using MEMS technology. The critical component in MEMS FTIRs is the large displacement translating micromirror and its actuator. The paper presents a large displacement and high-surface quality micromirror. The micromirror consists of a micromagnetic actuator and a micromirror plate. The mirror plate and the actuator are fabricated separately and bonded together afterwards, and its size is 3.6 × 3.6 mm2 high-surface quality square mirror plate and a 1cm2 moving part. The microactuator’s moving part is fabricated using MetalMUMPS, and its fixed part includes a ring permanent magnet and a solenoid to realize a large displacement. The mirror plate is fabricated using polished silicon coated with metal layer with high-surface prototypes that are fabricated and experimentally tested. A maximum stroke of 400 μm has been achieved in pull-in whereas only 140 μm stroke have been measured for a 4 to 5-volt DC-controlled displacement, and the resonance frequency is 10 Hz.

In connection with the developments of information technology (IT), thick electronic ceramic films have become important constitutive materials for various IT devices and systems. For instance, good piezoelectric or ferromagnetic thick films having thickness from several microns to several hundreds microns are required in MEMS microactuator devices, optical devices, and high-frequency devices. It is well known that good electronic ceramic films whose thickness is approximately less than 1 μm can be formed by means of physical or chemical methods including sputtering and CVD. On the other hand, ceramic bulks with good electrical or magnetic properties are obtained by sintering.

This paper presents the overall design and implementation of a microactuator which is wirelessly powered and driven by electropermanent magnets. Electropermanent magnet based actuation allows for the actuator to consume power merely during actuation with zero power consumption in between actuations. This has significantly reduced the energy requirement of the actuator, making it easier to be powered wirelessly using inductive power transfer technologies. The wireless power system is designed to host the primary power track on the main control platform with the secondary pickup connected to the microactuator. Power is delivered wirelessly to charge the onboard supercapacitor energy buffer which facilitates the peak power requirement during actuation, which cannot be easily met by a low power wireless power system. Experimental results have shown that the actuator uses 2.5mJ of energy per actuation with the peak power requirement of 40W during the 120μ« actuation period, while the wireless power supply is rated up to 1.12W at steady state. The actuator is capable of generating a maximum holding force up to 220mN and deflections up to 2.5mm.

For maintenance microrobots for small diameter pipes in power plants and so on, a novel microgripper using divided-electrode type flexible electro-rheological valves (DE-FERVs) was proposed and developed. Each bendable finger consisted of the DE-FERV and a hydraulic rubber actuator and was several millimeters long. The DE-FERV had an axially divided parallel plate electrode pairs in a flexible tube. Each parallel plate electrode pair controlled the electro-rheological fluid (ERF) flow by changing the viscosity with the electric field. The DE-FERV had both high flexibility and sufficient pressure control range. The hydraulic rubber actuator had plural integrated walls inside to restrict its radial expansion and axially extended by the inner pressure controlled by the DE-FERV. A finger large model was fabricated and experimentally characterized. Then, a gripper having two fingers was constructed and the object handling was demonstrated.

In this study, a new piezoactuator-based prototype microactuator is proposed with a hydraulic displacement amplification system. A piezoactuator is used to deflect a diaphragm which displaces a certain volume of hydraulic fluid into a smaller-diameter piston chamber, thereby amplifying the displacement at the other end of the piston. An electro-mechanical model is implemented to estimate the displacement of a multilayer piezoelectric actuator for the applied input voltage considering the hysteresis behavior. The displacement characteristics of the proposed microactuator are studied for triangular actuation voltage signal. Results of the experiments and simulation of the displacement behavior of the stacked piezoactuator and the amplified displacement of the prototype actuator were compared. Experimental results suggest that the mathematical model developed for the new piezoactuator-based prototype actuator is capable of estimating its displacement behavior accurately, within an error of 1.2%.

This paper illustrates both thermal and mechanical analysis methods for displacement and contact force calculating of a novel sensing silicon-polymer microgripper when heat sources are applied by an electric current via its actuators. Thermal analysis is used to obtain temperature profile by figuring out a heat conductions and convections model. Temperature profile is then applied into the mechanical structure of the gripper's actuators to form the final equation of displacement and contact force of the jaws. Finally, the comparison among the calculation, simulation and actual measurement concludes that materialization methods are appropriate. Achieving the final equation of gripper's jaws displacement and contact force is a major step to optimize or reform this novel structure for different sizes to meet specific applications.

An ionic polymer microactuator driven by an organic photoelectric proton pump transducer is described in this paper. The light responsive transducer is fabricated by using molecular self-assembly to immobilize oriented bacteriorhodopsin purple membrane (PM) patches on a bio-functionalized porous anodic alumina (PAA) substrate. When exposed to visible light, the PM proton pumps produce a unidirectional flow of ions through the structure’s nano-pores and alter the pH of the working solution in a microfluidic device. The change in pH is sufficient to generate an osmotic pressure difference across a hydroxyethyl methacrylate-acrylic acid (HEMA-AA) actuator shell and induce volume expansion or contraction. Experiments show that the transducer can generate an ionic gradient of 2.5 μM and ionic potential of 25 mV, producing a pH increase of 0.42 in the working solution. The ΔpH is sufficient to increase the volume of the HEMA-AA microactuator by 80%. The volumetric transformation of the hydrogel can be used as a valve to close a fluid transport micro-channel or apply minute force to a mechanically flexible microcantilever beam.

A sensing estimation scheme is presented that combines analog and threshold sensing on a piezoelectric microactuator for calibration of microscale inertial sensors. Using a variation of the Kalman filter, an asynchronous threshold sensor improves state estimates obtained from less reliable analog sensor measurements of microactuator motion. The resulting velocity estimates are compared with estimates without threshold sensing, and related to feasible calibration performance for gyroscopes. Results show that incorporating threshold sensors in a projected low-noise environment based on capacitive sensing will produce high-accuracy velocity measurements at certain fixed angles, with an approximately 80% reduction in angular velocity estimation error. Experimental testing with noisier, more variable piezoelectric sensing shows improved estimation accuracy at all velocities and positions when threshold detections are added. In simulation, the addition of feedback control is shown to further improve estimation accuracy.

To further decrease feature sizes, the semiconductor industry heavily improved the photolithography. Photoresist layers are exposed through photomasks and structured accordingly. The underlying substrate is then selectively altered by adding or subtracting material. The unrivaled precision, resolution, and accuracy allow an unmatched level of miniaturization, and several thousand electrical components can be processed simultaneously. This technology was expanded to the fabrication of sensors and actuators, creating microelectromechanical systems. With silicon, the possibilities of further expanding this technology to new dimensions and applications are limited. Reasons are the stiffness, 2.5-D fabrication, and lack of optical transparency. To enable new applications, we present the successful translation of wafer-level fabrication to millimeter-scale actuators. This was achieved by changing the material to ultraviolet (UV)-curable polymers. Based on the electrostatic zipper actuator, avoiding the common pull-in-effect is essential for the successful realization of an acceptable microactuator. Therefore, the bottom electrodes are split and shaped to adjust the generated electrostatic forces, balancing the mechanical restoring forces. Besides the theoretical design, the fabrication technology based on classic photolithography is explained. Experimental results include voltage-dependent deflection measurements, achieving 110- $\mu $ m deflection with 70 V driving voltage. The dynamic response measurements show resonance frequencies of 1.89 kHz. [2014-0181]

An out-of-plane electrostatic microactuator delivering exceptionally high vertical displacements is described. The devices, based on an electrostatic zipper actuator design, employ composite Si/SiO2 beams with engineered stress gradients that result in large and controllable beam curvatures. The microactuators are fabricated in a silicon-on-insulator/deep reactive-ion etching process, with an additional oxidized silicon wafer serving as a bonded ground electrode. Simple cantilever Si/SiO2 zipper actuators are investigated and extended to a meander configuration with regions of variable curvature able to produce large tip deflections in a small on-chip footprint. An analytic model is presented and used to optimize deflection of the meander-shaped zipper actuators, followed by the implementation of a full microstage actuator employing parallel meanders connected to a moving silicon stage. Using this configuration, purely vertical actuation is realized. The static deflections of various actuator designs are characterized and shown to be in a good agreement with analytical predictions. Fabricated microstage actuators achieving deflections up to 60% of their in-plane dimensions are described, and reliable actuation over nearly $10^{6}$ Hz is demonstrated. [2013-0397]

The displacement of the central shuttle of a Z-shape chevron actuator can be calculated using a developed approach from other authors. Who demonstrated that the actuators with this geometry offer a larger displacement compared with V-shape actuators. Z-shape offers a larger stiffness and output force for the case of only one arm. This paper is focused on the optimization of the Z-shaped beams of a chevron actuator of eight beams, which seeks to increase the previously described response. The structure is designed in parametric solid modeling 3D software Autodesk Inventor, and simulated by finite element method in Ansys 15.0. These simulations were implemented considering several modifications on the length of the Z-shaped beams in order to choose the most appropriate length. The electric potential applied in all cases was from 0.2 V up to 5 V. The Z-shape length of the arms for the case of the optimized Z-shape actuator increases the shuttle’s displacement in approximately 50% compared to V-shape actuator, and 38% compare to the original Z-shape. Analytical adjusted approach is extremely matched with the simulations results. Length of the Z-shape beam is the determinant factor of the displacement. The low stiffness of the optimized Z-shape actuator (89% lower than the original V-shape and 58% compared to Z-shape) can allow its use as load sensor.

Micromachining of microelectromechanical systems which is similar to other fabrication processes has inherent variation that leads to uncertain dimensional and material properties. Methods for optimization under uncertainty analysis can be used to reduce microdevice sensitivity to these uncertainties in order to create a more robust design, thereby increasing reliability and yield. In this paper, approaches for uncertainty and sensitivity analysis, and robust optimization of an electro-thermal microactuator are applied to take into account the influence of dimensional and material property uncertainties on microactuator tip deflection. These uncertainties include variation of thickness, length and width of cold and hot arms, gap, Young modulus and thermal expansion coefficient. A simple and efficient uncertainty analysis method is performed by creating second-order metamodel through Box-Behnken design and Monte Carlo simulation. Also, the influence of uncertainties has been examined using direct Monte Carlo Simulation method. The results show that the standard deviations of tip deflection generated by these uncertainty analysis methods are very close to each other. Simulation results of tip deflection have been validated by a comparison with experimental results in literature. The analysis is performed at multiple input voltages to estimate uncertainty bands around the deflection curve. Experimental data fall within 95 % confidence boundary obtained by simulation results. Also, the sensitivity analysis results demonstrate that microactuator performance has been affected more by thermal expansion coefficient and microactuator gap uncertainties. Finally, approaches for robust optimization to achieve the optimal designs for microactuator are used. The proposed robust microactuators are less sensitive to uncertainties. For this goal, two methods including Genetic Algorithm and Non-dominated Sorting Genetic Algorithm are employed to find the robust designs for microactuator.

Shape memory alloys (SMAs) are a class of smart materials characterized by shape memory effect and pseudo-elastic behavior. They have the capability to retain their original form when subjected to certain stimuli, such as heat or a magnetic field. These unique properties have attracted many researchers to seek their application in various fields including transportation, aerospace, and biomedical. The ease process adaption from semiconductor manufacturing technology provides many opportunities for designing micro-scale devices using this material. This paper gives an overview of the fabrication and manufacturing technique of thin-film and bulk micromachined SMAs. Key features such as material properties, transformation temperature, material composition, and actuation method are also presented. The application and micromechanism for both thin-film and bulk SMA are described. Finally, the microactuator devices emphasized for biomedical applications such as microgrippers and micropumps are highlighted. The presented review will provide information for researchers who are actively working on the development of SMA-based microscale biomedical devices.

In an electrowetting-based liquid microactuator, two types of insulating materials are used for device operation: an dielectric material to provide capacitance between the liquid and conductor, and a hydrophobic coating at the interface of liquid and insulator. This paper investigates important physical properties for the insulating materials. Several alternative dielectric materials are compared for application in EW chips, breakdown phenomenon of insulating layers with different thicknesses is tested before and after droplet actuation. It appears that the used EW devices have lower breakdown voltages than unused devices, probably due to the locally trapped charges in the insulating layer.

Aiming to improve the displacement of the piezoelectric membrane microactuators, controllable in-plane tensile stress was introduced by applying a bias voltage on the idle part of PZT. The stress generated by the bias voltage was calculated by an analytical model based on the theory of plates and shells. Analytical result shows that tensile stress with a magnitude of 10 MPa can be generated under 100 V bias voltage. The stress is large enough to cause the change of piezoelectric coefficient d31 as well as the displacement of the actuator. Then the experimental results on the PZT thick film actuators demonstrated that d31 was remarkable increased for both the disc actuator and the ring actuator under an appropriate bias voltage, improving the displacement by 6% and 42%, respectively. Furthermore, the resonance frequency shifts were observed as a result of Young's modulus change under the bias voltage.

Pneumatic piston–cylinder actuators are commonly used in industry for a variety of automation and robotics applications. In order to suppress leakage, these actuators comprise seal rings which unfortunately introduce friction and affect the positioning accuracy and output force. This article investigates vibrations of the seal generated by integrated piezo actuators to reduce friction force. For this, two piezoelectric stacks are integrated in the cylinder and used to excite vibration modes. This concept was studied in a compact cylinder pneumatic actuator with a bore diameter of 5 mm and a stroke of 10 mm. Dry friction measurement shows a 52% reduction from the original friction force at a driving frequency of 18.29 kHz and vibration amplitude of 0.05 μm. In the wet friction experiments, the friction force can be reduced by 54% from the original wet friction with vibrations at amplitude of 0.04 μm.

This paper reports of a micromachined shape-memory-alloy (SMA) actuator in the shape of a rectangular spiral coil that is designed to perform cantilever-like actuation. The SMA-coil actuator itself forms a passive resonant circuit that functions as a wireless heat source activated using external radio-frequency (RF) electromagnetic fields for frequency-selective control of the actuation. The SiO 2 stress layers are selectively patterned on the actuator structure of nickel–titanium SMA, or Nitinol, to manipulate the cantilever profile at the nominal cold state. RF radiation with varying field frequencies shows strong frequency dependence of wireless heating, actuation displacement, and force generation by microfabricated actuators with resonant frequencies of 170–245 MHz. The actuators excited at resonance exhibit maximum out-of-plane displacement and force of 215 μm and 71 mN, respectively. The developed wireless SMA actuator not only provides >2× the force and 2× more power-efficient response compared to the preceding design with similar self-heating mechanism but also offers broader potential applications brought by its commonly adopted cantilever-based actuation.

Polyurethane shape memory polymers (SMPs) with tunable thermomechanical properties and advanced processing capabilities are synthesized, characterized, and implemented in the design of a microactuator medical device prototype. The ability to manipulate glass transition temperature (Tg ) and crosslink density in low-molecular weight aliphatic thermoplastic polyurethane SMPs is demonstrated using a synthetic approach that employs UV catalyzed thiol-ene "click" reactions to achieve postpolymerization crosslinking. Polyurethanes containing varying C=C functionalization are synthesized, solution blended with polythiol crosslinking agents and photoinitiator and subjected to UV irradiation, and the effects of number of synthetic parameters on crosslink density are reported. Thermomechanical properties are highly tunable, including glass transitions tailorable between 30 and 105 °C and rubbery moduli tailorable between 0.4 and 20 MPa. This new SMP system exhibits high toughness for many formulations, especially in the case of low crosslink density materials, for which toughness exceeds 90 MJ m(-3) at select straining temperatures. To demonstrate the advanced processing capability and synthetic versatility of this new SMP system, a laser-actuated SMP microgripper device for minimally invasive delivery of endovascular devices is fabricated, shown to exhibit an average gripping force of 1.43 ± 0.37 N and successfully deployed in an in vitro experimental setup under simulated physiological conditions.

A dual-stage piezoelectric shear-mode actuation scheme aiming at high-density hard disk drive applications is designed, simulated, and experimentally evaluated. In this actuation scheme, a shear-mode piezoelectric single-crystal microactuator is installed between a suspension and a slider for realizing magnetic head nanopositioning in hard disk drives. The piezoelectric single-crystal-based shear-mode microactuator is dedicatedly designed and made of ( $1\,-\,x$ )Pb(Zn1/3Nb2/3)O3PbTiO3 ( $x=0.06$ –0.07) material to meet the technical specifications of servo control for 10 Tbit/in $^{2}$ hard disk drives. The shear displacement of this microactuator under a constant voltage is independent of the dimensions of the microactuator, which has the great promise for further miniaturization and excellent performance consistency control. Theoretical analysis shows that the first intrinsic resonance of the microactuator is around 143 kHz. The shear-mode microactuator has a displacement of 25.4–30.7 nm at 12 V at frequencies up to 60 kHz. After it is installed between a suspension and a slider, and tested on a spin stand, the shear-mode microactuator exhibits a working frequency of 39.1 kHz and a displacement of more than 22 nm at 12 V under the disk flying condition. The technical feature and performance as achieved show that the dual-stage nanopositioning scheme using a shear-mode piezoelectric single-crystal microactuator is promising to meet the requirements of servo control for 10 Tbit/in $^{2}$ hard disk drives.

This paper proposes a sequential optimization methodology for designing an electrothermal polysilicon actuator in the presence of a fabrication tolerance. In the proposed method, a deterministic optimum is first sought from an initial design, and then a reliability-based robust design is obtained launching at the deterministic point. This serial design strategy can enhance numerical efficiency through minimizing the use of computationally expensive reliability-based design optimization. To effectively perform the robust design of very complex multiphysics problems, elaborate surrogate models based on the local window concept are exploited comprehensively. The proposed method is applied to an electrothermal polysilicon actuator with seven design random variables, and then three different nominal designs are examined in terms of maximum deflection, consumed power, and confidence level.

In this letter, we present a novel approach for integrating an electrostatic microactuator with a spiral thin-film resistor on a coplanar silicon substrate. We demonstrate a technique for fabricating large arrays of silicon nitride microactuators using low-stress plasma-enhanced chemical vapor deposition films. The process for integrating thin-film resistors spiraled around these actuators using sputtered films of tantalum nitride (sheet resistivity up to 1.4 k $\Omega $ per square) is then presented. We discuss a key application of this technology in optically addressable adaptive optics micromirror arrays.

A three-stage actuation control system is proposed to enable high servo bandwidth track-following and possibly for small skew angle actuation system of hard disk drives. It involves a voice coil motor actuator as a primary actuator and a PZT actuated milliactuator as a secondary actuator. Both of them have the first dominant resonance mode at 5 kHz and the milliactuator has 200 nm stroke. A thermal microactuator having 50 nm stroke is used as a third actuator for a high servo bandwidth. A control strategy with controller design method is proposed to meet the performance requirement of each actuator's control loop and the overall control system. More than 6 kHz servo bandwidth is achieved and 430 nm external vibration can be covered by the three-stage actuation system. Simulation and experimental results demonstrate the control performance of the three-stage closed-loop system.

This paper presents the design, assembly and testing of a hydrogel-based thermal microactuator. N-isopropylacrylamide (NIPAAm) with 3-acrylamidopropionic acid is synthesized as a temperature-sensitive poly (NIPAAm-co-AAmPA). To control the actuation, a temperature control system based on thermoelectrical cooling (TEC) was built up with both a fast response time of 146 s and a high resolution of 0.1 °C. A miniaturized prototype was assembled and tested: the response time amounts to 12.2 min, just half of that of an actuator being heated up by a temperature chamber. The response time reduces with increasing temperature from 35 to 45 °C.

This paper proposes and develops a multiple ER microactuator system using an alternating pressure source for in-pipe working micromachines, medical microrobots, and so on. A hydraulic microactuator is known to have high power density but also has the drawback of requiring large piping space for the supply and return of the working fluid. In this study, an alternating pressure system with synchronized control valves and a single pipe was proposed. As the control valves, simple ER microvalves were employed. The ER microvalves control an electro-rheological fluid (ERF) flow through its apparent viscosity change due to the applied electric field. In addition, a pressure transmitter is inserted between the pressure source and the ER valves, and low viscosity fluid such as water is used to transmit the alternating pressure. The use of the low viscosity fluid can reduce the diameter of the connecting pipe due to the low pressure loss. The proposed set-up is composed of multiple ER microactuators and an alternating pressure source; each ER microactuator consists of a pressure transmitter, two ER microvalves and a hydraulic microactuator. As the proposed system has half the number of pipes, of smaller diameter, compared with conventional hydraulic microactuator systems, it is suitable for a multiple actuator system. In this study, for verification of the working principle of the proposed system, we fabricated a large model of the system which consists of an ER finger 13 mm × 10 mm × 33 mm in size as a kind of ER microactuator and an alternating pressure source using a voice coil motor. Through experiments, we confirmed the tip displacement of 17 mm for the 16 mm-long movable part of the finger. Then, we fabricated a gripper using two ER fingers and confirmed its independent motion.

The purpose of this paper is to presents the conception, achievements, measurement and data analysis regarding the connecting and the assembling of the components of a MEMS electromagnetic microactuator, cantilever type.

In the paper, the optimization of an electro-thermo-elastic microactuator is proposed. In particular, the maximum temperature of the actuator is to be minimized, while the total displacement is to be maximized. For solving this problem, the Adaptive Gaussian Process-Assisted Differential Evolution AGDEMO method is applied.

The spatial filter is capable of splitting the original desired trajectory of the dual-stage actuator (DSA) into two segments with arbitrary range, controlled by a linear motor (LM) actuator and a piezoelectric actuator (PZT) microactuator, respectively. Backstepping nonsingular terminal sliding mode control law with error transformation is designed to allow the tracking error of the actuator to converge and remain stable for a limited time, and reach the expected properties. Meanwhile, the adaptive exponential reaching law is added to the control law, which effectively improves the approach speed. An experiment is provided to demonstrate the effectiveness of the backstepping nonsingular terminal sliding mode control with error transformation in the DSA system and has a good trajectory tracking performance.