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The self-sensing technology of microactuators utilizes a smart material to concurrently actuate and sense in a closed-loop control system. This work aimed to develop a position feedback-control system of nickel electrothermal microactuators using a resistivity self-sensing technique. The system utilizes the change in heating/sensing elements' resistance, due to the Joule heat, as the control parameter. Using this technique, the heating/sensing elements would concurrently sense and actuate in a closed loop control making the structures of microactuators simple. From a series of experiments, the proposed self-sensing feedback control system was successfully demonstrated. The tip's displacement error was smaller than 3 µm out of the displacement span of 60 µm. In addition, the system was less sensitive to the abrupt temperature change in surroundings as it was able to displace the microactuator's tip back to the desired position within 5 s, which was much faster than a feed-forward control system. [ABSTRACT FROM AUTHOR]

Mechanical stimulation is prevalent within organisms, and appropriate regulation of such stimulation can significantly enhance cellular functions. Consequently, the in vitro construction and simulation of mechanical stimulation have emerged as a research hotspot in biomechanics. In recent years, a class of artificial muscles named electroactive polymers (EAPs), especially ionic EAPs, have shown promising applications in biomechanics. While several techniques utilizing ionic EAPs for cell mechanical stimulation have been reported, further research is needed to advance and enhance their practical applications. Here, we prepared a microactuator array based on ionic EAP artificial muscles for cell mechanical stimulation. As a preliminary effort, we created a 5 × 5 microactuator array on a supporting membrane by employing laser cutting. We evaluated the electro-actuation performance of the microactuators through experimental testing and numerical simulations, affirming the potential use of the microactuator array for cell mechanical stimulation. The devised approach could inspire innovative design concepts in the development of miniaturized intelligent electronic devices, not only in biomechanics and biomimetics but also in other related fields. [ABSTRACT FROM AUTHOR]

Vanadium dioxide (VO2) stands out for its versatility in numerous applications, thanks to its unique reversible insulator-to-metal phase transition. This transition can be initiated by various stimuli, leading to significant alterations in the material's characteristics, including its resistivity and optical properties. As the interest in the material is growing year by year, the purpose of this review is to explore the trends and current state of progress on some of the applications proposed for VO2 in the field of sensors and actuators using literature review methods. Some key applications identified are resistive sensors such as strain, temperature, light, gas concentration, and thermal fluid flow sensors for microfluidics and mechanical microactuators. Several critical challenges have been recognized in the field, including the expanded investigation of VO2-based applications across multiple domains, exploring various methods to enhance device performance such as modifying the phase transition temperature, advancing the fabrication techniques for VO2 structures, and developing innovative modelling approaches. Current research in the field shows a variety of different sensors, actuators, and material combinations, leading to different sensor and actuator performance input ranges and output sensitivities. [ABSTRACT FROM AUTHOR]

The drug delivery using microneedles has increased the comfort of patients with reduction of pain. This paper focuses on the effect of drug flow in bevel tip hollow microneedle. A transdermal drug delivery system is proposed with an electrochemical micropump and diaphragm microactuator. The analytical model of the microfluidic drug flow is formulated and the numerical model of the transdermal drug delivery system with microneedle is designed. The analysis of the effect of drug flow through the bevel tip hollow microneedle is performed. Various parameters such as pressure, velocity, geometry of the microneedle are considered in order to observe the efficiency of drug delivery. [ABSTRACT FROM AUTHOR]

The self-sensing technology of microactuators utilizes a smart material to concurrently actuate and sense in a closed-loop control system. This work aimed to develop a position feedback-control system of nickel electrothermal microactuators using a resistivity self-sensing technique. The system utilizes the change in heating/sensing elements’ resistance, due to the Joule heat, as the control parameter. Using this technique, the heating/sensing elements would concurrently sense and actuate in a closed loop control making the structures of microactuators simple. From a series of experiments, the proposed self-sensing feedback control system was successfully demonstrated. The tip’s displacement error was smaller than 3 µm out of the displacement span of 60 µm. In addition, the system was less sensitive to the abrupt temperature change in surroundings as it was able to displace the microactuator’s tip back to the desired position within 5 s, which was much faster than a feed-forward control system.

Mechanical stimulation is prevalent within organisms, and appropriate regulation of such stimulation can significantly enhance cellular functions. Consequently, the in vitro construction and simulation of mechanical stimulation have emerged as a research hotspot in biomechanics. In recent years, a class of artificial muscles named electroactive polymers (EAPs), especially ionic EAPs, have shown promising applications in biomechanics. While several techniques utilizing ionic EAPs for cell mechanical stimulation have been reported, further research is needed to advance and enhance their practical applications. Here, we prepared a microactuator array based on ionic EAP artificial muscles for cell mechanical stimulation. As a preliminary effort, we created a 5 × 5 microactuator array on a supporting membrane by employing laser cutting. We evaluated the electro-actuation performance of the microactuators through experimental testing and numerical simulations, affirming the potential use of the microactuator array for cell mechanical stimulation. The devised approach could inspire innovative design concepts in the development of miniaturized intelligent electronic devices, not only in biomechanics and biomimetics but also in other related fields.

Vanadium dioxide (VO2) stands out for its versatility in numerous applications, thanks to its unique reversible insulator-to-metal phase transition. This transition can be initiated by various stimuli, leading to significant alterations in the material’s characteristics, including its resistivity and optical properties. As the interest in the material is growing year by year, the purpose of this review is to explore the trends and current state of progress on some of the applications proposed for VO2 in the field of sensors and actuators using literature review methods. Some key applications identified are resistive sensors such as strain, temperature, light, gas concentration, and thermal fluid flow sensors for microfluidics and mechanical microactuators. Several critical challenges have been recognized in the field, including the expanded investigation of VO2-based applications across multiple domains, exploring various methods to enhance device performance such as modifying the phase transition temperature, advancing the fabrication techniques for VO2 structures, and developing innovative modelling approaches. Current research in the field shows a variety of different sensors, actuators, and material combinations, leading to different sensor and actuator performance input ranges and output sensitivities.

Biological systems convert chemical energy into mechanical work by using protein catalysts that assume kinetically controlled conformational states. Synthetic chemomechanical systems using chemical catalysis have been reported, but they are slow, require high temperatures to operate, or indirectly perform work by harnessing reaction products in liquids (e.g., heat or protons). Here, we introduce a bioinspired chemical strategy for gas-phase chemomechanical transduction that sequences the elementary steps of catalytic reactions on ultrathin (<10 nm) platinum sheets to generate surface stresses that directly drive microactuation (bending radii of 700 nm) at ambient conditions (T = 20 °C; Ptotal = 1 atm). When fueled by hydrogen gas and either oxygen or ozone gas, we show how kinetically controlled surface states of the catalyst can be exploited to achieve fast actuation (600 ms/cycle) at 20 °C. We also show that the approach can integrate photochemically controlled reactions and can be used to drive the reconfiguration of microhinges and complex origami- and kirigami-based microstructures. [ABSTRACT FROM AUTHOR]

Pneumatic actuators are of great interest for device miniaturization, microactuators, soft robots, biomedical engineering, and complex control systems. Recently, multi-material actuators have become of high interest to researchers due to their comprehensive range of suitable applications. Three-dimensional (3D) printing of multi-material pneumatic actuators would be the ideal way to fabricate customized actuators, but so far, this is mostly limited to deposition-based methodologies, such as fused deposition modeling (FDM) or Polyjetting. Vat-based stereolithography is one of the most relevant high-resolution 3D printing methods but is only rarely utilized in the multi-material 3D printing of materials. This study demonstrated multi-material stereolithography using combinations of materials with different Young's moduli, i.e., 0.5 MPa and 1.1 GPa, for manufacturing pneumatic actuators and microactuators with a resolution as small as 200 μm. These multi-material actuators have advantages over single-material actuators in terms of their deformation controllability and ease of assembly. [ABSTRACT FROM AUTHOR]

Microactuators that convert external stimuli such as heat, light, current, and magnetic field into mechanical motion are essential components in microelectro‐mechanical systems. To date, microactuators have been fabricated mainly using conventional microfabrication technologies and inorganic thin films, but although such technologies facilitate the mass production of microdevices, they are expensive and lack flexibility when either preparing only a few devices or facing special needs. Laser‐direct‐writing is an effective complement to microfabrication, but is seldom used in the construction of inorganic microactuators. In this work, a laser‐direct‐writing technique on the freestanding vanadium dioxide (VO2) film for fabricating microactuators with arbitrary shapes is developed. The precision of the laser direct writing attained 2 µm under ultralow pulse energy of 52 pJ. The pulse energy is two orders of magnitude lower than that needed for patterning VO2 film and other semiconductor materials on substrates. The overall performance of the resulting VO2 microactuators is comparable with that of those fabricated by conventional microfabrication technologies, but the fabricating efficiency and flexibility are increased. Such a fabrication strategy can also be used to fabricate other smart microdevices, such as strain sensors and photodetectors. [ABSTRACT FROM AUTHOR]

Microactuators are one of the main components of the microelectromechanical and microfluidic systems and play a key role in their development. Many such systems, e.g. micropumps and microvalves, utilize an electromagnetic microactuator with a displacement range of a few micrometers traversed within a few seconds. Most of the electromagnetic microactuators have low lifetime and fracture toughness or low recovery speed. Microactuators with metallic mass-spring structure can overcome the mentioned disadvantages or limitations. This paper presents the design and fabrication of a novel stainless steel electromagnetic microactuator fabricated using micro-wire electrical discharge machining. The microactuator in question consists of a mass-and-spring structure made of 304 stainless steel, a permanent magnet made of NdFeB, and a microcoil. The impacts of the number of turns, distance, and electric current on the magnetic field of the microcoil and the displacement of the microactuator membrane with time have been investigated to determine the microactuator characteristics. The results indicated a displacement of about ±10 (20) μ m within 7 s for an electric current of 1100 mA. This microactuator exhibits a faster response compared to the similar microactuators. Consequently, it can be used at higher operating frequencies and, thus, improves the fluid flow in micropumps. [ABSTRACT FROM AUTHOR]

The article offers an analytical model, finite-element analysis, and testing results of a microelectromechanical system (MEMS)-based hybrid thermal microactuator. A hybrid design of a thermal microactuator is designed and fabricated according to the standard microfabrication technology, silicon-on-insulator multiuser MEMS processes (SOIMUMPs) of MEMSCAP. Iterative coupled electromechanical and electrothermal finite-element analyses (FEAs) are performed showing a total displacement of $12.044 \mu \text{m}$ at an input power of 252.6 mW, which is quite comparable to the experimental result of $12.041 \mu \text{m}$ displacement at 264.7 mW. It is noted that a maximum temperature reading of 535 °C is achieved during electrothermal FEA which is in close correlation to the 495 °C of experimental thermal testing of the fabricated hybrid thermal microactuator. The analytical and simulated model is used to study the detailed profile behavior of dimensional displacements and temperature gradients of the designed hybrid thermal microactuator. Micromanipulation experiments successfully demonstrate the desired displacement at relatively low input power. The total size of the microactuator is reported to be $1.5\times0.47$ mm2. [ABSTRACT FROM AUTHOR]

Microactuators have been playing crucial roles in micromachine technologies because of their small sizes and light weights. The piezoelectric actuation is one of the most important driving methods to perform the motion output with miniature structures. The rotary piezoelectric microactuators are relatively mature, whereas the linear ones need to be further developed. Inspired by the hollowing art, a novel linear piezoelectric microactuator with miniature dimensions of 7.4 mm × 7.4 mm × 10 mm is proposed, which is designed to be an integrated hollow structure without a guide rail and can achieve bidirectional standing-wave drive. The bidirectional motions are achieved by the same first-order bending vibrations of two pairs of thin-walled beams, respectively, which are conducive to the consistency of the forward and backward motions indicate that the maximum velocity, resolution, and maximum thrust force achieved in the forward motion are 19.06 mm/s, 0.3 μm, and 17.45 mN, respectively, whereas those in the backward motion are 16.92 mm/s, 0.45 μm, and 15.28 mN, respectively. The design inspired by the hollowing art has the potential to be an effective and alternative solution for the development of linear piezoelectric microactuators. [ABSTRACT FROM AUTHOR]

Based on a V-shaped microactuator with a pair of beams, modifications were made to the length and width of a microactuator to observe the effects. A theoretical approach and numerical characterization of the modified microactuator were performed. Its performance was compared to a similar microactuator with equal beam widths, and a V-shaped microactuator. The proposed microactuator, fed at 2 V, compared to the V-shaped actuator, showed a 370.48% increase in force, but a 29.8% decrease in displacement. The equivalent von Mises stress level increased (until 74.2 MPa), but was below the silicon ultimate stress. When the modified microactuator was applied to the proposed microgripper, compared to the case using a V-shaped actuator, the displacement between the jaws increased from 0.85 µm to 4.85 µm, the force from 42.11 mN to 73.61 mN, and the natural frequency from 11.36 kHz to 37.99 kHz; although the temperature increased, on average, from 42 °C up to 73 °C, it is not a critical value for many microobjects. The maximum equivalent von Mises stress was equal to 68.65 MPa. Therefore, it has been demonstrated that the new modified microactuator with damping elements is useful for the proposed microgripper of novel geometry, while a reduced area is maintained. [ABSTRACT FROM AUTHOR]

In this work, we have proposed a new method to remotely control and operate the working mechanism of a suitable Ferromagnetic Shape Memory Alloy (FSMA) microactuator system using only a focused low powered laser beam. Model of a simple microgripper system fabricated from a FSMA material and operated by applying the newly discovered Photo Induced Micro Actuation (PIMA) property of FSMAs has been proposed in this report. The design of the fabricated FSMA microgripper was developed using a standard Computer Aided Engineering (CAE) software. The operating mechanism of the newly modelled microgripper assembly was thoroughly characterized numerically with Finite Element Analysis (FEA) method using the CAE software. A prototype of the microgripper system, as designed in the CAE software numerically, was fabricated and its working mechanism controlled by the PIMA effect was systematically studied. The main advantage of using this laser actuated microgripper system is the reduction in weight of the gripper assembly due to the absence of either electrical motors along with other electrical accessories or complex hydraulics systems as used in conventional gripper systems to control the working mechanism of the gripper end effectors. The gripping mechanism of the prototype microgripper system can be controlled only by the low powered laser beams. This is the first system attempted in the world where the PIMA effect was employed in any kind of microactuator application. [ABSTRACT FROM AUTHOR]

Pneumatic actuators are of great interest for device miniaturization, microactuators, soft robots, biomedical engineering, and complex control systems. Recently, multi-material actuators have become of high interest to researchers due to their comprehensive range of suitable applications. Three-dimensional (3D) printing of multi-material pneumatic actuators would be the ideal way to fabricate customized actuators, but so far, this is mostly limited to deposition-based methodologies, such as fused deposition modeling (FDM) or Polyjetting. Vat-based stereolithography is one of the most relevant high-resolution 3D printing methods but is only rarely utilized in the multi-material 3D printing of materials. This study demonstrated multi-material stereolithography using combinations of materials with different Young’s moduli, i.e., 0.5 MPa and 1.1 GPa, for manufacturing pneumatic actuators and microactuators with a resolution as small as 200 μm. These multi-material actuators have advantages over single-material actuators in terms of their deformation controllability and ease of assembly.

Existing tactile stimulation technologies powered by small actuators offer low-resolution stimuli compared to the enormous mechanoreceptor density of human skin. Arrays of soft pneumatic actuators initially show promise as small-resolution (1- to 3-mm diameter), highly conformable tactile display strategies yet ultimately fail because of their need for valves bulkier than the actuators themselves. In this paper, we demonstrate an array of individually addressable, soft fluidic actuators that operate without electromechanical valves. We achieve this by usingmicroscale combustion and localized thermal flame quenching. Precisely, liquid metal electrodes produce sparks to ignite fuel lean methane-oxygen mixtures in a 5-mm diameter, 2-mm tall silicone cylinder. The exothermic reaction quickly pressurizes the cylinder, displacing a silicone membrane up to 6 mm in under 1 ms. This device has an estimated free-inflation instantaneous stroke power of 3 W. The maximum reported operational frequency of these cylinders is 1.2 kHz with average displacements of ~100 μm. We demonstrate that, at these small scales, the wall-quenching flame behavior also allows operation of a 3 × 3 array of 3-mm diameter cylinders with 4-mm pitch. Though we primarily present our device as a tactile display technology, it is a platform microactuator technology with application beyond this one. [ABSTRACT FROM AUTHOR]

Based on a V-shaped microactuator with a pair of beams, modifications were made to the length and width of a microactuator to observe the effects. A theoretical approach and numerical characterization of the modified microactuator were performed. Its performance was compared to a similar microactuator with equal beam widths, and a V-shaped microactuator. The proposed microactuator, fed at 2 V, compared to the V-shaped actuator, showed a 370.48% increase in force, but a 29.8% decrease in displacement. The equivalent von Mises stress level increased (until 74.2 MPa), but was below the silicon ultimate stress. When the modified microactuator was applied to the proposed microgripper, compared to the case using a V-shaped actuator, the displacement between the jaws increased from 0.85 µm to 4.85 µm, the force from 42.11 mN to 73.61 mN, and the natural frequency from 11.36 kHz to 37.99 kHz; although the temperature increased, on average, from 42 °C up to 73 °C, it is not a critical value for many microobjects. The maximum equivalent von Mises stress was equal to 68.65 MPa. Therefore, it has been demonstrated that the new modified microactuator with damping elements is useful for the proposed microgripper of novel geometry, while a reduced area is maintained.

The ultrahigh surface area of two-dimensional materials can drive multimodal coupling between optical, electrical, and mechanical properties that leads to emergent dynamical responses not possible in three-dimensional systems. We observed that optical excitation of the WS 2 monolayer above the exciton energy creates symmetrically patterned mechanical protrusions which can be controlled by laser intensity and wavelength. This observed photostrictive behavior is attributed to lattice expansion due to the formation of polarons, which are charge carriers dressed by lattice vibrations. Scanning Kelvin probe force microscopy measurements and density functional theory calculations reveal unconventional charge transport properties such as the spatially and optical intensity-dependent conversion in the WS 2 monolayer from apparent n- to p-type and the subsequent formation of effective p-n junctions at the boundaries between regions with different defect densities. The strong opto-electrical-mechanical coupling in the WS 2 monolayer reveals previously unexplored properties, which can lead to new applications in optically driven ultrathin microactuators.

Light-responsive microactuators composed of vertically aligned carbon nanotube (CNT) forests mixed with poly(N-isopropylacrylamide) (PNIPAM) hydrogel composites are studied. The benefit of this composite is that CNTs act as a black absorber to efficiently capture radiative heating and trigger PNIPAM contraction. In addition, CNT forests can be patterned accurately using lithography to span structures ranging from a few micrometers to several millimeters in size, and these CNT-PNIPAM composites can achieve response times as fast as 15 ms. The kinetics of these microactuators are investigated through detailed analysis of high-speed videos. These are compared to a theoretical model for the deswelling dynamics, which combines thermal convection and polymer diffusion, and shows that polymer diffusion is the rate-limiting factor in this system. Applications of such CNT/hydrogel actuators as microswimmers are discussed, with light-actuating micro-jellyfish designs exemplified, and >1500 cycles demonstrated., (© 2023 The Authors. Small published by Wiley-VCH GmbH.)

In recent years, tissue engineering with mechanical stimulation has received considerable attention. In order to manipulate tissue samples, there is a need for electromechanical devices, such as constant-force actuators, with integrated deflection measurement. In this paper, we present an electrostatic constant-force actuator allowing the generation of a constant force and a simultaneous displacement measurement intended for tissue characterization. The system combines a comb drive structure and a constant-force spring system. A theoretical overview of both subsystems, as well as actual measurements of a demonstrator system, are provided. Based on the silicon-on-insulator technology, the fabrication process of a moveable system with an extending measurement tip is shown. Additionally, we compare measurement results with simulations. Our demonstrator reaches a constant-force of 79 ± 2 μN at an operating voltage of 25 V over a displacement range of approximately 40 μm, and the possibility of adjusting the constant-force by changing the voltage is demonstrated.

Submillimeter or micrometer scale electrically controlled soft actuators have immense potential in microrobotics, haptics, and biomedical applications. However, the fabrication of miniaturized and micropatterned open-air soft actuators has remained challenging. In this study, we demonstrate the microfabrication of trilayer electrochemical actuators (ECAs) through aerosol jet printing (AJP), a rapid prototyping method with a 10 μm lateral resolution. We make fully printed 1000 × 5000 × 12 μm 3 ultrathin ECAs, each of which comprises a Nafion electrolyte layer sandwiched between two poly(3,4-ethylenedioxythiophene) polystyrene sulfonate (PEDOT:PSS) electrode layers. The ECAs actuate due to the electric-field-driven migration of hydrated protons. Due to the thinness that gives rise to a low proton transport length and a low flexural rigidity, the printed ECAs can operate under low voltages (∼0.5 V) and have a relatively fast response (∼seconds). We print all the components of an actuator that consists of two individually controlled submillimeter segments and demonstrate its multimodal actuation. The convenience, versatility, rapidity, and low cost of our microfabrication strategy promise future developments in integrating arrays of intricately patterned individually controlled soft microactuators on compact stretchable electronic circuits.

Featured Application: This study constructs and analyzes the constitutive model of the giant magnetostrictive material actuator, which provides a theoretical basis for the development of a new intelligent structure of giant magnetostrictive material. Giant magnetostrictive actuators (GMA) driven by giant magnetostrictive material (GMM) has some advantages such as a large strain, high precision, large driving force, fast response, high reliability, and so on, and it has become the research hotspot in the field of microdrives. Research shows there is a nonlinear, intrinsic relationship between the output signal and the input signal of giant magnetostrictive actuators because of the strong coupling characteristics between the machine, electromagnetic field, and heat. It is very complicated to construct its nonlinear eigenmodel, and it is the basis of the practical process of giant magnetostrictive material to construct its nonlinear eigenmodel. Aiming at the design of giant magnetostrictive actuators, the magnetization model based on a free-energy hysteresis model has been deeply researched, constructed, and put forward by Smith, which combines Helmholtz–Gibbs free energy and statistical distribution theory, to simulate the hysteresis model at medium or high driving strengths. Its main input and output parameters include magnetic field strength, magnetization, and mechanical strain. Then, numerical realization and verification of the magnetization model are done by the Gauss–Legendre integral discretization method. The results show that the magnetization model and its numerical method are correct, and the research results provide a theoretical basis for the engineering application of giant magnetostrictive material and optimized structure of giant magnetostrictive material actuators, which have an important practical application value. [ABSTRACT FROM AUTHOR]

Lab-on-chip devices essentially require micropumps and valves which incorporate a microactuating mechanism to control fluid flow. In this work, a non-spiral type planar microcoil is reported for implementing an electromagnetic microactuator. The effect of variation in coil geometries on the microactuator performance is analyzed for the first time. The microcoil fabricated and characterized in this work considerably reduces the number of lithography layers, thus improving the ease of fabrication while reducing the series coil resistance. The microcoil structures are further analyzed for the microactuator performance using finite element method, and the effect of coil geometries on the electromagnetic force generated by the actuator is studied. Microfabrication and electrical characterization results of the non-spiral planar microcoils show the influence of the same on the actuator performance. A tapered square microcoil geometry is proposed to improve the outputs from the actuator. [ABSTRACT FROM AUTHOR]

Software defined radios (SDR) in the microwave X- and K-bands offer the promise of low cost, programmable operation with real-time frequency agility. However, the real world in which such radios operate requires them to be able to detect nanowatt signals in the vicinity of 100 kW transmitters. This imposes the need for selective RF filters on the front end of the receiver to block the large, out of band RF signals so that the finite dynamic range of the SDR is not overwhelmed and the desired nanowatt signals can be detected and digitally processed. This is currently typically done with a number of narrow band filters that are switched in and out under program control. What is needed is a small, fast, wide tuning range, high Q, and low loss filter that can continuously tune over large regions of the microwave spectrum. In this paper, we show how extreme throw MEMS actuators can be used to build such filters operating up to 15 GHz and beyond. The key enabling attribute of our MEMS actuators is that they have large, controllable, and out-of-plane actuation ranges of a millimeter or more. In a capacitance-post loaded cavity filter geometry, this gives sufficient precisely controllable motion to produce widely tunable devices in the 4–15 GHz regime. [2017-0280] [ABSTRACT FROM AUTHOR]

This paper reports on a bidirectional Knudsen pump (KP) with a 3D-printed thermal management platform; the pump is intended principally for microscale gas chromatography applications. Knudsen pumps utilize thermal transpiration, where non-viscous flow is created against a temperature gradient; no moving parts are necessary. Here, a specialized design leverages 3D direct metal laser sintering and provides thermal management that minimizes loss from a joule heater located on the outlet side of KP, while maintaining convective cooling on the inlet side. The 3D-KP design is integrative and compact, and is specifically intended to simplify assembly. The 3D-KP pumping area is ≈1.1 cm2; with the integrated heat sink, the structure has a footprint of 64.2 × 64.2 mm2. Using mixed cellulose ester (MCE) membranes with a 25 nm average pore diameter and 525 μm total membrane thickness as the pumping media, the 3D-KP achieves a maximum flow rate of 0.39 sccm and blocking pressure of 818.2 Pa at 2 W input power. The operating temperature is 72.2 °C at ambient room temperature. In addition to MCE membranes, anodic aluminum oxide (AAO) membranes are evaluated as the pumping media; these AAO membranes can accommodate higher operating temperatures than MCE membranes. The 3D-KP with AAO membranes with 0.2 μm average pore diameter and 531 μm total membrane thickness achieves a maximum flow rate of 0.75 sccm and blocking pressure of 496.1 Pa at 9.8 W at an operating temperature of 191.2 °C.

Laser annealing of polyimide enhances the characteristics such as actuation and substrate-to-film adhesion of the NiTi shape memory alloy (SMA) bimorph. This work investigated the laser annealing of Kapton polyimide with 355 nm Nd: YAG laser for varying fluence and % line overlap (% LO). The laser annealing has enhanced the crystallinity of the polyimide surface below the laser fluence of 1630 mJ/cm2. Furthermore, annealing at 500 mJ/cm2 fluence at 90% LO and 1630 mJ/cm2 at 50% LO and 70% LO yielded low contact angles of 58.1° ± 3.6°, 42.7° ± 1.5°, and 57.5° ± 2.1°, respectively. The deposited film adhesion has significantly improved for annealing at 1630 mJ/cm2 at 70% LO. The bimorph fabricated on the mentioned substrates has produced higher tip displacement than the pristine substrate in the electrical actuation study. The maximum increment in tip displacement of the NiTi SMA bimorph was 1.5 mm in samples with annealed substrate compared to the as-fabricated bimorph. Moreover, the laser-annealed bimorph has shown the capability of enhanced tip displacement even with a loading of 45 mg. [Display omitted] • Enhanced the surface capability of polyimide towards SMA bimorph for better film deposition and actuation characteristics. • Laser annealing reduces contact angle of polyimide from 82° to 42.7° for laser fluence of 1630 mJ/cm2 at 50% line overlap. • Laser fluence of 1630 mJ/cm2 at 70% line overlap has improved the deposited NiTi film adhesion. • Tip displacement of the bimorph with laser annealing increased by 1.5 mm without external load and 1 mm with external load. [ABSTRACT FROM AUTHOR]

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.

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 bar) 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 bar, but also retain a small effective form-factor of 5 mm × 5 mm × 1.8 mm. 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 μm at 150 V. The fabricated microvalve has a flow range of 0−90 μL min−1 at 1 bar inlet pressure. When fully closed, a leakage of 0.8% open-flow was observed with a power-consumption of 37.5 μW. A flow resolution of 0.2 μL min−1—De-ionized (DI) water was measured at 0.5 bar pressure.

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.

This paper reports the design, simulation and experimental study of a linear magnetic microactuator for portable electronic equipment and microsatellite high resolution remote sensing technology. The linear magnetic microactuator consists of a planar microcoil, a supporter and a microspring. Its bistable mechanism can be kept without current by external permanent magnetic force, and can be switched by the bidirectional electromagnetic force. The linearization and threshold of the bistable mechanism was optimized by topology structure design of the microspring. The linear microactuator was then fabricated based on non-silicon technology and the prototype was tested. The testing results indicated that the bistable mechanism was realized with a fast response of 0.96 ms, which verified the simulation and analysis. [ABSTRACT FROM AUTHOR]

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). [ABSTRACT FROM AUTHOR]

Vertical comb drives are critical for electrostatic optical switches and variable optical attenuators (VOAs), but fabricating vertical comb drives requires the formation of two levels of comb fingers and thus suffers from the difficulty of dealing with the comb-finger alignment. This paper presents a vertical comb drive design and its micro-fabrication method that can realize self-aligned two-level comb fingers. The self-aligned vertical comb fingers are enabled by a novel vertically-elevated flat-end (VEFE) bimorph structure. Both the stator and rotor fingers of the vertical comb drive are formed by the same photomask and the same silicon etching step, which automatically ensures accurate alignment of the stator and rotor fingers. The vertical separation between the stator and rotor is created by the VEFE structure. A 1mm-aperture MEMS mirror with the proposed VEFE comb drive has been fabricated using SOI wafers with buried cavities. The mirror rotates 0.94° at 8 Vdc. The resonant frequency is 1.428 kHz. The MEMS mirror has been assembled into a VOA module. Measurements show that the VOA achieved a dynamic range of 55 dB and an insertion loss of less than 0.4 dB and met the telecommunications standards on shock, vibration and long-term stability. [ABSTRACT FROM AUTHOR]

Giant magnetostrictive actuators (GMA) driven by giant magnetostrictive material (GMM) has some advantages such as a large strain, high precision, large driving force, fast response, high reliability, and so on, and it has become the research hotspot in the field of microdrives. Research shows there is a nonlinear, intrinsic relationship between the output signal and the input signal of giant magnetostrictive actuators because of the strong coupling characteristics between the machine, electromagnetic field, and heat. It is very complicated to construct its nonlinear eigenmodel, and it is the basis of the practical process of giant magnetostrictive material to construct its nonlinear eigenmodel. Aiming at the design of giant magnetostrictive actuators, the magnetization model based on a free-energy hysteresis model has been deeply researched, constructed, and put forward by Smith, which combines Helmholtz−Gibbs free energy and statistical distribution theory, to simulate the hysteresis model at medium or high driving strengths. Its main input and output parameters include magnetic field strength, magnetization, and mechanical strain. Then, numerical realization and verification of the magnetization model are done by the Gauss−Legendre integral discretization method. The results show that the magnetization model and its numerical method are correct, and the research results provide a theoretical basis for the engineering application of giant magnetostrictive material and optimized structure of giant magnetostrictive material actuators, which have an important practical application value.

A micro- to milli-sized linear traveling wave (TW) actuator fabricated with microelectromechanical systems (MEMS) technology is demonstrated. The device is a silicon cantilever actuated by piezoelectric aluminum nitride. Specifically designed top electrodes allow the generation of TWs at different frequencies, in air and liquid, by combining two neighboring resonant modes. This approach was supported by analytical calculations, and different TWs were measured on the same plate by laser Doppler vibrometry. Numerical simulations were also carried out and compared with the measurements in air, validating the wave features. A standing wave ratio as low as 1.45 was achieved in air, with a phase velocity of 652 m/s and a peak horizontal velocity on the device surface of 124 μm/s for a driving signal of 1 V at 921.9 kHz. The results show the potential of this kind of actuator for locomotion applications in contact with surfaces or under immersion in liquid.

This study proposes a non‐linear saturation‐aware controller for dual‐stage micro–nano actuators. Dual‐stage motion systems use two actuators in series in order to achieve an improved performance: a micro actuator responsible for a large range of actuation, and a nano actuator (NA) able to achieve a high bandwidth. The NA is commonly driven by flexure‐based piezoelectric actuators subject to a limited range which presents large oscillations in the presence of output saturation. In order to avoid these oscillations, a non‐linear smooth switching function that limits the actuation of the NA to only track references within its range is proposed. Experimental results demonstrate the effectiveness of the proposed approach, which is able to reduce oscillations and energy consumption without compromising settling time performance. [ABSTRACT FROM AUTHOR]

In this study, we explored the feasibility of employing Gd-doped ceria (GDC) thin films (1–2 μm) as functional, mechanically reliable material for microelectromechanical systems (MEMS). Self-supported structures, based on microscopic-scale GDC membranes, bridges, and cantilevers, were fabricated using Si-compatible processes and materials. With voltages of different amplitudes and frequencies and a variety of metal electrodes, we monitored structural stability and device response. The membrane-based structures displayed much higher stability under voltage and better mechanical robustness than those based on bridges or cantilevers. At low frequencies (a few Hz), the use of Ti contacts resulted in observable displacement of the membranes in the presence of moderately low voltage (≤10 V/1.6 μm), while Al, Cr, and Ni contacts did not provide such functionality. Although for all contact metals tested, formation of a blocking layer at room temperature is evident, for the case of Ti, the barrier height is much lower. In view of the fact that the crystallographic space group of weakly doped GDC is Fm -3 m, the electromechanical response of the microfabricated GDC membranes is most likely electrostrictive, but a strict proof is not yet available. At high frequencies (>100 kHz), the membranes produce lateral displacement as large as several microns due to Joule heating, i.e., a thermo-electromechanical response. [ABSTRACT FROM AUTHOR]

This paper presents the modelling, simulation, implementation and performance analysis of a novel electropermanent magnet based, bistable wireless microactuator for microvalves with milli Joule level energy consumption. The microactuator is powered wirelessly through inductive power transfer with energy buffered in a supercapacitor bank. Two millimeter sized rods of semi hard and hard magnetic materials are placed side by side with a current carrying coil around them. A 120 μs pulse of 15 V, 2.5 A is applied to the coil, which creates or eliminates the externally available magnetic field. The plunger is either attracted or repelled by this magnetic field to open or close the valve respectively. The theoretical analysis and modelling aligns well with the experimental results. The microactuator consume as little as 0.97–2.5 mJ of energy per actuation with no energy consumed between actuations. The actuation pulse width needs to be between 44 and 150 μs. The actuator is capable of delivering large deflections in the range of 0.3–2.5 mm, which is much greater than any of the state-of-the-art valves. The maximum holding force of the actuator is 220 mN and the attraction force varies between 9.8–98 mN. Energy consumption per actuation, actuation speed and deflection of the novel actuator are much better than any state-of-the-art microvalves, with the added advantages of wireless power and control. The momentary peak power requirement of 40 W is met by the supercapacitor energy buffer which stores 90 J per charge cycle, sourcing 37500 actuations. The energy efficiency and flexibility of this novel actuator can revolutionize the microactuator industry. [ABSTRACT FROM AUTHOR]