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Actuator is a mechatronic system that transforms one type of energy into mechanical displacement and mechanical force. Nowadays, these actuators can be made of Functionally Graded Materials (FGM) to ensure the simple shape of the actuator and to improve its effectiveness, particularly for microsystems. FGM is built as a mixture of two or more constituents, which have almost the same geometry and dimensions. The variation of macroscopic material properties can be induced by variation of both the volume fractions and material properties of the FGM constituents. The paper deals with a new approach in analysing of the systems made of FGM using our new beam finite elements. Multiphysical analysis (weak coupled electro-thermo-mechanical analysis) and spatial continuous variation of material properties are supported. The analysis of the microactuator with a constant cross section made of FGM is presented in the paper. This simple-shaped actuator is supplied by electric current and the efficiency of the actuator is optimized. The solution results will be compared with those obtained by using solid elements of a FEM commercial program.

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This paper presents the design, fabrication and performance of origami-based folding microactuators based on a cold-rolled NiTi foil of 20 µm thickness showing the one-way shape memory effect. Origami refers to a variety of techniques of transforming planar sheets into three-dimensional (3D) structures by folding, which has been introduced in science and engineering for, e.g., assembly and robotics. Here, NiTi microactuators are interconnected to rigid sections (tiles) forming an initial planar system that self-folds into a set of predetermined 3D shapes upon heating. While this concept has been demonstrated at the macro scale, we intend to transfer this concept into microtechnology by combining state-of-the art methods of micromachining. NiTi foils are micromachined by laser cutting or photolithography to achieve double-beam structures allowing for direct Joule heating with an electrical current. A thermo-mechanical treatment is used for shape setting of as-received specimens to reach a maximum folding angle of 180°. The bending moments, bending radii and load-dependent folding angles upon Joule heating are evaluated. The shape setting process is particularly effective for small bending radii, which, however generates residual plastic strain. After shape setting, unloaded beam structures show recoverable bending deflection between 0° and 140° for a maximum heating power of 900 mW. By introducing additional loads to account for the effect of the tiles, the smooth folding characteristic evolves into a sharp transition, whereby full deflection up to 180° is reached. The achieved results are an important step towards the development of cooperative multistable microactuator systems for 3D self-assembly.

Forging customizable compounds into arbitrary shapes and structures has the potential to revolutionize functional materials, where independent control over shape and composition is essential. Current self-assembly strategies allow impressive levels of control over either shape or composition, but not both, as self-assembly inherently entangles shape and composition. Herein, independent control over shape and composition is achieved by chemical conversion reactions on nanocrystals, which are first self-assembled in nanocomposites with programmable microscopic shapes. The multiscale character of nanocomposites is crucial: nanocrystals (5-50 nm) offer enhanced chemical reactivity, while the composite layout accommodates volume changes of the nanocrystals (approximate to 25, which together leads to complete chemical conversion with full shape preservation. These reactions are surprisingly materials agnostic, allowing a large diversity of chemical pathways, and development of conversion pathways yielding a wide selection of shape-controlled transition metal chalcogenides (cadmium, manganese, iron, and nickel oxides and sulfides). Finally, the versatility and application potential of this strategy is demonstrated by assembling: 1) a scalable and highly reactive nickel catalyst for the dry reforming of butane, 2) an agile magnetic-controlled particle, and 3) an electron-beam-controlled reversible microactuator with sub-micrometer precision. Previously unimaginable customization of shape and composition is now achievable for assembling advanced functional components.

The improvement of soft inflatable microactuators using an actuation conversion mechanism is presented in terms of high-output generation; a bending inflatable microactuator with the conversion mechanism is designed to generate high-output bending motion. The designed microactuator consists of a pneumatic balloon on a base film and a conversion film over the balloon and ribs on the backside of the base film. A conversion film converts the inflating motion of a pneumatic balloon into a bending motion. The fabricated microactuator with a pneumatic balloon of 13 mm in diameter is 16 mm × 40 mm × 850 μm. A 25 μm thick polyimide film is used as a conversion film over the pneumatic balloon because polyimide film is both non-stretchable and flexible. An array of Si ribs (15 mm × 40 mm × 400 μm) is integrated on the backside of the base film. Analysis of the microactuators with and without the conversion mechanism indicates that the output performance is improved with the addition of the conversion mechanism, as designed. As a result, the microactuator with the conversion film generates a maximum force of 1.72 N at 80 kPa, whereas the microactuator without the conversion film generates a maximum force of 0.15 N at 40 kPa. The improved microactuator can provide 4.2 mN/mm3 as the force density. In addition to fundamental characterization, the performance characteristics of the actuators are examined by combining the fundamental results.

ChevBot is a novel microrobot for operation in dry environments driven by focused energy from a Nd:YAG laser. The microrobot operates using stick-slip locomotion by converting opto-thermal energy from the focused laser source into mechanical energy using “chevron-style” actuators. ChevBot’s body components are fabricated using Micro-Electro-Mechanical-System (MEMS) technology and completed using a microassembly process. In this paper, we investigate the effect of laser parameters such as pulse frequency, beam intensity and position to the maneuverability of the robot on planar substrates. The average microrobot forward speed could be varied between $1-134\mu m/s$ by sweeping the laser pulse frequency from 900-1500 Hz. Experiments also suggest that the average speed of the ChevBot can also be controlled by varying the number of pulses and laser drive current. Furthermore, the ChevBot could be steered in both the clockwise and counterclockwise directions by positioning the laser spot in various locations on the ChevBot’s microactuator.

A new type of microactuator incorporates free flight phases to overcome the lack of ball bearings in microsystems. These designs employ electromagnets to manipulate the flying projectile. A precise and fast control of this system requires an accurate and computationally efficient compact model of the electromagnetic interaction. This work proposes a compact model that couples the system matrices of a finite element model with the Maxwell stress tensor to compute the force as an alternative to a commonly used lookup table. Both system-level models are evaluated in terms of accuracy and speed compared to a reference finite element model.

Fiber microactuators are interesting in wide variety of emerging fields, including artificial muscles, biosensors, and wearable devices. In the present study, a robust, fast‐responsive, and humidity‐induced silk fiber microactuator is developed by integrating force‐reeling and yarn‐spinning techniques. The shape gradient, together with hierarchical rough surface, allows these silk fiber microactuators to respond rapidly to humidity. The silk fiber microactuator can reach maximum rotation speed of 6179.3° s−1 in 4.8 s. Such a response speed (1030 rotations per minute) is comparable with the most advanced microactuators. Moreover, this microactuator generates 2.1 W kg−1 of average actuation power, which is twice higher than fiber actuators constructed by cocoon silks. The actuating powers of silk fiber microactuators can be precisely programmed by controlling the number of fibers used. Lastly, theory predicts the observed performance merits of silk fiber microactuators toward inspiring the rational design of water‐induced microactuators., A new kind of robust and fast‐responsive silk microactuators, by integrating experimental and theoretical designs, are presented. These microactuators feature an ultrafast response speed for humidity change with performance that can compare with the most advanced microactuator systems.

Fourier transform spectrometers (FTS), mostly working in infrared (IR) or near infrared (NIR) range, provide a variety of chemical or material analysis with high sensitivity and accuracy and are widely used in public safety, environmental monitoring and national border security, such as explosive detection. However, because of being bulky and expensive, they are usually used in test centers and research laboratories. Miniaturized FTS have been developed rapidly in recent years, due to the increasing demands. Using micro-electromechanical system (MEMS) micromirrors to replace the movable mirror in a conventional FTS system becomes a new realm. This paper first introduces the principles and common applications of conventional FTS, and then reviews various MEMS based FTS devices.

We present a driving method for on-chip hydrogel microactuators developed to be used for single-cell manipulations. The hydrogel actuator is composed of a temperature-responsive gel coated on a glass substrate with light-absorbing micropatterning. The actuator is driven by light irradiation, which increases its temperature. The advantage of this driving method is two-fold: allowing local heating of the actuator while decreasing heat dissipation to the substrate and its environment. The local heating induced by light irradiation improves the response characteristics of the hydrogel microactuator because the slight increase in environmental temperature aids cooling of the microactuator when the light is turned off. Furthermore, local heating enables multiple actuators to be located in close proximity without unintentionally actuating neighboring actuators through heat dissipation. In addition, the heating induced by the light irradiation does not require wiring on the chip. Therefore, the developed driving method enables the integration of a large number of actuators that can be independently driven on a single chip.

Microvalves are important flow-control devices in many standalone and integrated microfluidic applications. Polydimethylsiloxane (PDMS)-based pneumatic microvalves are commonly used but they generally require large peripheral connections that decrease portability. There are many alternatives found in the literature that use Si-based microvalves, but variants that can throttle even moderate pressures (1) tend to be bulky (cm-range) or consume high power. This paper details the development of a low-power, normally-open piezoelectric microvalve to control flows with a maximum driving pressure of 1, but also retain a small effective form-factor of 5x5x1.8. A novel combination of rapid prototyping methods like stereolithography and laser-cutting have been used to realize this device. The maximum displacement of the fabricated piezoelectric microactuator was measured to be 8.5 at 150. The fabricated microvalve has a flow range of 0&ndash, 90 at 1 inlet pressure. When fully closed, a leakage of 0.8 open-flow was observed with a power-consumption of 37.5. A flow resolution of 0.2&mdash, De-ionized (DI) water was measured at 0.5 pressure.

We aim to develop the soft microactuator device that allows manipulating microscale objects by the interfacial force between the liquid crystal and isotropic phases. In previous work, the interfacial force between the nematic and isotropic phases is 1.4nN. To extend the application of the device, we focus on the interfacial force between the smectic and isotropic phases. From the experiments, the smectic-isotropic interfacial force is found to be more than 30 times stronger than the nematic-isotropic interfacial force. The results show that potential usage of this micro-actuator device that enables the manipulation of biological cells without damage.

The high work density and beneficial downscaling of shape memory alloy (SMA) actuation performance provide a basis for the development of actuators and systems at microscales. Here, we report a novel monolithic fabrication approach for the co-integration of SMA and Si microstructures to enable SMA-Si bimorph microactuation. Double-beam cantilevers are chosen for the actuator layout to enable electrothermal actuation by Joule heating. The SMA materials under investigation are NiMnGa and NiTi(Hf) films with tunable phase transformation temperatures. We show that Joule heating of the cantilevers generates increasing temperature gradients for decreasing cantilever size, which hampers actuation performance. In order to cope with this problem, a new method for design optimization is presented based on finite element modeling (FEM) simulations. We demonstrate that temperature homogenization can be achieved by the design of additional folded beams in the perpendicular direction to the active beam cantilevers. Thereby, power consumption can be reduced by more than 35 % and maximum deflection can be increased up to a factor of 2 depending on the cantilever geometry.

A current goal in microsystem research is to overcome small working ranges, typically resulting from mechanical connections and restoring forces such as for cantilevers. In the case of predefined resting positions and unidirectional motion, pseudo-levitation as in magnetic bearings is a promising solution. In order to investigate concepts for energy efficient, cooperative microactuators, which allow free motion of small objects, we present a bistable levitation setup. The system consists of a magnetic proof mass within a glass tube, a piezoelectric staple actuator, two permanent magnets and a solenoid used as an electromagnet. The movable mass is mechanically unconstrained in its upper vertical motion and is intended to switch between two predefined equilibrium positions, namely on the staple actuator and levitating at a defined upper position. The transition is accomplished by an impulse-like kick force by the staple actuator, and subsequent feedback controlled following of a trajectory via electromagnetic actuation. The goal of this work consists of both adapting the system parameters, guaranteeing stable and preferably robust equilibrium positions for the unactuated system, and finding optimal trajectories with a short settling time and minimum input effort for the controlled transition. These design and control objectives are combined within a co-design. In this approach, the system and controller optimizations are not performed consecutively, but within a single optimization, taking into account the coupling between the design and control. Here, we apply flatness-based control combined with feedback linearization, allowing for trajectories to be tracked without error in case of the undisturbed system. Thus, the controller is solely used for disturbance compensation and the problem can be simplified by optimizing only the trajectory without the controller parameters. We show that the combined optimization process is of advantage in comparison to the sequential approach and proficiently exploits the design parameters to improve the generated trajectories.

The paper introduces a modified version of a Proportional Integral Derivative (PID)-type iterative learning algorithm, which is very simple to implement on a digital control device for tracking control of a continuous-time system. The simulative application of it is for controlling a V-shaped electrothermal microactuator (VEM) and is carried out by using a Simscape model of VEM for the purpose that the asymptotic tracking behavior of system output to desired trajectory will be verified in a virtually real environment. Obtained simulation results confirm that the introduced iterative learning algorithm has not only provided a good output tracking behavior, as expected, but also is robust in the sense of reducing external disturbance effects.

Conductive polymers, particularly poly(3,4-ethylenedioxythiophene) (PEDOT) and its complex with poly(styrene sulfonate) (PSS) (i.e., PEDOT:PSS), provide a promising platform to developing for soft actuators or artificial muscles. To date, PEDOT-based actuators are available in the field of bionics or biomedicine, smart textiles, microactuator and other functional applications. In comparison to other conducting polymers, PEDOT provides higher conductivity and chemical stability, lower density and operating voltages, and by dispersing of PEDOT with PSS is further enriches performances in solubility, hygroscopicity, processability and flexibility making them is advance in actuator areas. In our view, nevertheless, the actuator fabricated by PEDOT and PEDOT:PSS is still in its infancy with many unknowns and challenges that requested more comprehensive understanding for their current and future developments. This review is aimed to provide a comprehensive understanding in the actuation mechanisms, performance evaluation criteria, processing technologies and configurations, and the recent progress of materials development and applications, as well as future opportunities for improving and exploiting of PEDOT-based actuators are also elaborated.

The integration of a flexible temperature sensor with a soft microactuator (a pneumatic balloon actuator) for a functional microfinger is presented herein. A sensor integrated with a microactuator can actively approach a target for contact detection when a distance exists from the target or when the target moves. This paper presents a microfinger with temperature sensing functionality. Moreover, thermocouples, which detect temperature based on the Seebeck effect, are designed for use as flexible temperature sensors. Thermocouples are formed by a pair of dissimilar metals or alloys, such as copper and constantan. Thin-film metals or alloys are patterned and integrated in the microfinger. Two typical thermocouples (K-type and T-type) are designed in this study. A 2.0 mm × 2.0 mm sensing area is designed on the microfinger (3.0 mm × 12 mm × 400 μm). Characterization indicates that the output voltage of the sensor is proportional to temperature, as designed. It is important to guarantee the performance of the sensor against actuation effects. Therefore, in addition to the fundamental characterization of the temperature sensors, the effect of bending deformation on the characteristics of the temperature sensors is examined with a repeated bending test consisting of 1000 cycles.

This paper proposed a micro-optical wavelength splitting element, which is controlled by the length of the Fabry-Perot optical cavity to select the wavelength range of the required interference filtering, and by means of a microactuator. Make a planar chip based optical spectrometer with ultra small in size and more suitable for developing into customer end product.

This paper presents a new microactuator using a phase change material (PCM) composite with induction heating. The PCM composite is consisting of paraffin wax, expanded graphite and nickel particle, which was used as an electrical conductive phase change material with improved magnetic permeability. Expanded graphite was used as an electrical conductive porous matrix absorbed with paraffin wax and nickel particle. This work relies on induction heating generated in the PCM composite with eddy current, rather than using external resistive heater. Experiments show that about 140 μ m actuation height was realized in 5 s with the input power of 1.42 W at excitation frequency of 1 kHz. Since an induction heating method is adopted with electrical conductive PCM composite, which means the new microactuator has no wire or electrodes to connect with the conductive PCM composite. The new PCM-composite-based microactuator has some advantages, such as ease of fabrication, small-sized, low cost, and eases of integration into Micro-Electro-Mechanical Systems (MEMS).

Samples of microactuators are made of a bimorph composite of Ti2NiCu alloy with a thermoelastic martensitic transition and the shape memory effect, and their response rate is investigated. The active layer of the composite actuator is a layer of the rapidly quenched Ti2NiCu alloy, pseudoplastically prestretched, and an amorphous layer of the same alloy is used as an elastic layer. Typical sizes of the microactuator are 30 × 2 × 2 μm. The controlled amplitude of the displacement of the microactuator tip is approximately 1 μm. The response rate of the microactuator was investigated by scanning electron microscopy. Activation of the microactuator was achieved by heating when electric pulses were passed through it. Full activation of the microactuator at frequencies up to 1 kHz was demonstrated; partial activation was observed at frequencies up to 8 kHz. The possibility of operating the device in a self-oscillating mode at frequencies of the order of 100 kHz is demonstrated.

Magneto-active elastomer is widely used for microactuator/microsensor application. For optimization of the actuation performance of the magneto-active elastomer, it is crucial to characterize its magnetic field distribution and mechanical behavior. By a novel multiphysics model, this paper thus investigates the transition between the uniform and non-uniform magnetic fields and the field-induced nonlinear deformation, due to reversible variation of the geometric size of the magneto-active elastomer from infinite to finite one. In this paper, both the elastomer and its surrounding medium are covered in the computational domain, where the Maxwell stress over the elastomer-surrounding interface is considered as an additional mechanical boundary, and the nonlinear magnetization included in a proposed free energy density. After validation of the present model with both the published theoretical and experimental works, it is concluded that increasing the geometric size of the magneto-active elastomer leads to a more uniform magnetic field, and thus the elastomer undergoes the transition from the non-uniform to uniform magnetic fields, if its size increases to a critical point, such as aspect ratio of 12.4 for the present cylindrical magneto-active elastomer. [2017-0232]

In this work, a Chevron electrothermal actuator is designed and its analytical model is developed. Chevron actuator works on the principle of Joules heating effect and thermal expansion. Aluminum is chosen as a material for actuator because of its good electrical and thermal properties and also it produces large displacement of about 10.94 µm with lower operating temperature of 448 °C for single beam. The Chevron based electrothermal actuator holds good when compared to the other conversion based conventional microactuators in terms of applied voltage vs displacement achieved. The analytical model is validated by comparing with 3D finite element model. The mathematical modeling is derived and the analytical calculations were performed over the mathematical model. The displacement and temperature results obtained from simulation and analytical models are in good agreement. The comparative results provides the proof for having a better performance in simulation which is again validated by the 0.3% of error with the analytical modeling of the Chevron based electrothermal microactuator.

For conventional open-loop hydrogel-based pH sensors, the sensor performance is often limited by the slow cooperative diffusion process of hydrogels. To overcome this drawback, a pH sensor with force compensation is developed. This new sensor concept capitalizes on the fact that a compensation pressure arising from an actuator can suppress the hydrogel’s swelling, accelerate the diffusion process within the hydrogel and, eventually, improve the sensor’s dynamic behaviour. To further miniaturize this force-compensated sensor, a microactuator with a high energy density is applied to replace the previous macroscopic actuator. It is the first time to present miniaturized force-compensated sensors, where both sensor elements and actuators are manufactured by microfabrication technologies. Following tests reveal that this sensor offers a wide operating pH range 4…10, a maximum sensitivity of −4.4 K/pH, and an average response time of 44 min, which is 5.8%…27.4% shorter than that of conventional open-loop sensors. Those experimental results clearly demonstrate that the sensor performance of hydrogel-based sensors can be improved by means of the force compensation approach.

Electromagnetic microactuators offer several advantages for robotic applications such as relatively large stroke and low input voltage requirements. Micro coils are significant components for electromagnetic microactuators for generating force required for micro robots. Non-spiral planar microcoils of square and circular geometries are analyzed here considering the fabrication easiness and low power consumption of non-spiral planar coils. Microfabrication of non-spiral planar coil is simpler and requires a single mask process only. Comparison between non-spiral coils and conventional spiral coils are also discussed. Series resistance of non-spiral coil is found out to be lesser than that of spiral coils though magnetic field is slightly lesser for non-spiral coils. The fabrication advantages and low power dissipation of non-spiral structures make them a strong alternative for conventional spiral planar microcoils. Comparison of different planar microcoils shows that the circular non-spiral coil gives better performance than other coil geometries considered here for robotic applications. Circular coil is found to provide a uniform field with lesser parasitic resistance. Electromagnetic microactuator using non-spiral planar circular and square microcoils are also analyzed to compare the performance between the two coil types. The results show that the force generated using non-spiral circular microcoil in the microactuator is adequate for microrobotic applications with an added advantage of uniform magnetic field provided by the circular coils.

© 2001-2012 IEEE. Terahertz (THz) tunable filter plays a significant role for miniaturization and multifunction in application systems. The frequency of existing schemes for tunable waveguide filter can only reach up to the W-band. The selection of tuning and assembly solution for THz band is significant and challenging. In this letter, we investigate the design of bimorph microactuator which uses microelectromechanical system (MEMS) technology. Based on this microactuator, we propose a THz tunable waveguide bandpass filter, whose center frequency can be tuned from 247 to 260 GHz. It is the first time to extend the center frequency of tunable waveguide bandpass filter to over 220 GHz while using MEMS bimorph microactuators to tune. The tuning ratio of the filter is 5.26%, and the measured insertion loss is better than 6 dB in the passband.

A miniature self-mixing interferometer based on microsphere superlens (MSSL) for the displacement measurement of microactuators is proposed. The interferometer is composed of a taper multimode fiber (TMMF) and MSSL with diameter D = 5 μ m . When the MSSL is irradiated by plane wave from the TMMF, the phenomenon of photonic nanojet (PNJ) occurs. The PNJ can focus on the surface of the microactuator. It can also enhance the scattered light from the surface of the microactuator, and enable the scattered light to return to the laser cavity to generate self-mixing interference phenomenon, which can be used to retrieve the displacement detection of the microactuator. Experimental results show that the relative errors are more accurate than 1% by using the proposed method

Thin hydrogel layers, based on a negatively charged cross-linked polymeric network, were deposited on conducting surfaces by means of an electrochemically induced free-radical polymerization method. The presence of ionized carboxylic groups in the polymer network allowed for the effective accumulation of Cu(II) cations in the hydrogel layer; these Cu(II) cations acted as an additional electroactive cross-linker and caused a substantial shrinking of the layer. It was found that the Cu(II) complexed by the polymer network could be electrochemically reduced to Cu(I) and that led to substantial swelling of the layer. Subsequent electrooxidation of Cu(I) led to the reformation of the crosslinking complexes, and again the shrinking of the layer was observed. The electrochemically active hydrogel layer deposited on the electrode surface was able to act as a microactuator due to its fast action, high stability, and reversibility of the shrinking/swelling transformation. The changes in hydrogel layer thickness were monitored by an electrochemical quartz crystal microbalance and confirmed by electron microscopy.

The development of lab-on-chip (LoC) devices has led to a demand of new microactuator technologies. Light-responsive hydrogels are promising candidates as actuator materials for this type of applications. These are polymers that change their water content and volume significantly upon illumination with a light source. For proper operation, the spatial resolution of the stimulation process is an important parameter. To investigate this resolution, poly(N-isopropylacrylamide) (PNIPAAm) hydrogels with incorporated graphene oxide (GO) were monitored with an infrared (IR) camera during illumination with a laser source. The GO nanoparticles convert the absorbed light energy into heat and for temperatures above the lower critical solution temperature (LCST), the polymer collapses. Therefore, the desired actuated area has to have a temperature above the LCST. A mathematical model was used to fit the recorded spatial temperature profiles in order to obtain the width at the LCST and to evaluate the temporal progression of the stimulated area. The results enable the development of new stimulation strategies and enhance the understanding of the spatial resolution of light-addressable hydrogels. Furthermore, the required stimulation time for different laser powers is presented.

This paper presents a wearable microsystem for minimally invasive, autonomous, and pseudo-continuous blood glucose monitoring, addressing a growing demand for replacing tedious fingerpricking tests for diabetic patients. Unlike prevalent solutions which estimate blood glucose levels from interstitial fluids or tears, our design extracts a whole blood sample from a small lanced skin wound using a novel shape memory alloy (SMA)-based microactuator and directly measures the blood glucose level from the sample. In vitro characterization determined that the SMA microactuator produced penetration force of 225 gf, penetration depth of 3.55 mm, and consumed approximately 5.56 mW·h for triggering. The microactuation mechanism was also evaluated by extracting blood samples from the wrist of four human volunteers. A total of 19 out of 23 actuations successfully reached capillary vessels below the wrists producing blood droplets on the surface of the skin. The integrated potentiostat-based glucose sensing circuit of our e-Mosquito device also showed a good linear correlation ( R 2 = 0.9733) with measurements using standard blood glucose monitoring technology. These proof-of-concept studies demonstrate the feasibility of the e-Mosquito microsystem for autonomous intermittent blood glucose monitoring.

Dual-stage actuation is an important technology enabler for advancing hard disk drive capacity and performance. This thesis describes the ongoing trend of decreasing track pitches required for areal density growth and increasing disturbances arising from rising spindle speeds, demonstrating that future dual-stage actuators will need to overcome the bandwidth limitations faced by the current suspension-based devices. First, the state of the art for dual-stage actuation is presented in the form of a literature review. This is followed by an overview of a new servo-mechanical design and analysis technique which is a hybrid of Galerkin beam elements and optimal linear quadratic Gaussian control analysis. This new technique is used to demonstrate the potential performance benefits of head-based actuation over suspension-based actuation. With the driving goal of designing a new head-based actuator, the constraints posed by industry are presented and discussed in detail. This is followed by an overview of the various actuation mechanisms evaluated, including several electrostatic and piezoelectric devices. The two most significant challenges identified through this analysis are the introduction of a gap at the trailing edge of the air-bearing and the necessity to actuate traces with sufficiently high actuation force.A quasi-shear mode piezoelectric actuator is proposed as a cost-effective head-based actuator which meets the given criteria and can be implemented at the wafer-scale. A new prototype was fabricated at the Berkeley Nanofabrication Laboratory with a measured bandwidth above 50 kHz. Since the proposed head-based actuation scheme requires a gap in the air-bearing surface, a second actuation mode is also presented. It is shown that the gap width between the slider body and read/write head can be controlled independently of track-following displacement in order to minimize pressure loss at the air-bearing surface. It is also shown that the directionality along each actuation mode of this device is greater that 1:10, although the resolution of measurement tools makes it difficult to determine how much greater the directionality is.The two key figures of merit for this project are microactuator bandwidth and static displacement gain. For the prototype presented herein, the bandwidth is shown to be greater than 50 kHz, which is the highest frequency measurable by the available equipment. The static gain is measured to be approximately 1 nm/V. With sol-gel based stacking methods, however, the static gain could be scaled as high as 20 nm/V or more, although this will require further investigation by industry to develop. The intellectual merits of this project include a newly developed servo-mechanical design tool, modified beam equations with piezoelectric energy taken into account, and several new fabrication methods. The new fabrication methods include chemical mechanical polishing of PMN-PT, eutectic bonding of PMN-PT to silicon, scribing high aspect-ratio geometry in PMN-PT with a dicing blade, epoxy drop deposition with flipchip bonding, and fabrication of tall MEMS structures with sacrificial copper plating with a wet etch release.

We present the design, fabrication, and characterization of single and antagonistic SMA microactuators allowing for uni- and bi-directional self-folding of origami-inspired devices, respectively. Test devices consist of two triangular tiles that are interconnected by double-beam-shaped SMA microactuators fabricated from thin SMA foils of 20 µm thickness with memory shapes set to a 180° folding angle. Bi-directional self-folding is achieved by combining two counteracting SMA microactuators. We present a macromodel to describe the engineering stress–strain characteristics of the SMA foil and to perform FEM simulations on the characteristics of self-folding and the corresponding local evolution of phase transformation. Experiments on single-SMA microactuators demonstrate the uni-directional self-folding and tunability of bending angles up to 180°. The finite element simulations qualitatively describe the main features of the observed torque-folding angle characteristics and provide further insights into the angular dependence of the local profiles of the stress and martensite phase fraction. The first antagonistic SMA microactuators reveal bi-directional self-folding in the range of −44° to +40°, which remains well below the predicted limit of ±100°.