Part Of Actuator Research Articles

Environmentally responsive polymeric "intelligent" materials: the ideal components of non-mechanical valves that control flow in microfluidic systems

Miniaturization and commercialization of integrated microfluidic systems has had great success with the development of a wide variety of techniques in microfabrication, since they allowed their construction at a low cost and by following simple step-series procedures. However, one of the major challenges in the design of microfluidic systems is to achieve control of flow and delivery of different chemical reagents. This feature is especially important when using microfluidic systems in the development of cell culture systems, the construction of labs on a chip and the fabrication and design of chemical microreactors. Spatiotemporal control of the microenvironment in microfluidic devices has been only partially achieved by incorporating actuator parts (mechanical and non-mechanical) within these devices; nevertheless, recently there has been enormous progress due to advances in the materials sciences, and the development of novel polymeric "intelligent" materials. These materials have proved to be excellent candidates in the construction of non-mechanical actuators in the form of environmentally responsive valves. These valves can more efficiently control flows because these "intelligent" materials are capable of undergoing conformational changes and phase transitions in response to different local or external environmental stimuli; allowing them to turn the valves from "on" to "off". In addition, these valves have very simple designs, and are easy and cheap to incorporate into microfluidic systems. Therefore, although there are many reviews that focus on the development and design of non-mechanical actuators, the following review proceeds to describe the exciting characteristics, potential uses and synthesis methods of the building blocks of the most recent and innovative non-mechanical valves, environmentally responsive polymeric "intelligent" materials. In addition, the last section of this review will focus on the synthesis of composite materials that are capable of responding to more than one type of stimulus, since these materials are believed to be the future components that will boost the development of microfluidic systems with spatiotemporal controlled microenvironments.

水力学的骨格を利用した柔軟な機械システム

The purpose of this study is to develop a design method of a flexible mechanical system using a hydrostatic skeleton driving mechanism. The system consists of two types of flexible bags in order to separate the roles into a structural part and an actuator part. One is a constant pressure bag as a structural part, and the other is a pressure tunable bag as an actuator part. There are remarkable advantages of using this system as listed below: i) Because of the flexibility, the system can be applied safely to various kinds of workspaces where living beings and mechanical systems work together. ii) Because of using two types of bags, driving efficiency of the system is higher than that of other flexible systems using only one type of bag. The theoretical design method of the system is required to realize these advantages. In order to realize the design method, it is important to calculate the structural strength of the structural part and driving force generated by the actuator part. In this paper, strength evaluation of the structural part is performed by nonlinear FEA. From the comparison between the analytical result and measurement results, deflection of the structural part is obtained. On the other hand, the driving force that is generated by the actuator part is also analyzed. Based on the analytical results, an empirical equation about the driving force is induced. The validity of the empirical equation is confirmed by the comparison between measurement values and the values of the empirical equation. These results will contribute to an optimum design of the proposed flexible mechanical system.

B-4 圧電マイクロミラーアレーによる光通信デバイスの作製(口頭発表:マイクロナノメカトロニクス)

We studied a new fabrication process for a micro mirror array device with piezoelectric unimorph actuators and simulated its actuation. In this fabrication process, piezoelectric thin film (PZT ; Pb(Zr,Ti)O_3) is deposited on SOI substrate by sputtering after actuator parts are released by BHF wet etching. Therefore, patterning or etching piezoelectric layer is not necessary, which means that proposed fabrication process can apply to various piezoelectric devices. Furthermore, we confirmed the actuation of proposed micro mirrors by FEM simulation.

Translatory and Bending Micro Magnetostrictive Actuator using Iron–Gallium Alloys (Galfenol): A New Actuation Approach for Microrobots

There is strong demand for microactuators in medical and industrial fields. For example, minimally invasive surgery has been progressing, and a series of microactuators useful for positioning, grasping and cutting in a narrow space are required. For this purpose, we are investigating micro magnetostrictive actuators using iron–gallium alloy (Galfenol). Galfenol is an iron-based magnetostrictive material with magnetostriction greater than 200 p.p.m., a high relative permeability μ r greater than 100 and a Young's modulus of around 70 GPa. This material is machinable by conventional cutting techniques, and can operate under tensile, bending and impact loads without any degradation in performance. Therefore, a microactuator using Galfenol has advantages over conventional actuators such as electrical motors and piezoelectric actuators in terms of design simplicity, low drive voltage requirements and high robustness. In this paper, we describe two types of actuators consisting of a U-shape core of Galfenol — one providing 1 longitudinal d.o.f. and 2-d.o.f. bending deformation, and the other propelling by a friction drive. These actuators are simple and small, and easily integrated into actuation parts of microrobots.

Behavior Learning of Swarm Robot System using Bluetooth Network

With the development of techniques, robots are getting smaller, and the number of robots needed for application is greater and greater. How to coordinate large number of autonomous robots through local interactions has becoming an important research issue in robot community. Swarm Robot Systems (SRS) is a system that independent autonomous robots in the restricted environments infer their status from pre-assigned conditions and operate their jobs through the cooperation with each other. In the SRS, a robot contains sensor part to percept the situation around them, communication part to exchange information, and actuator part to do a work. Especially, in order to cooperate with other robots, communicating with other robots is one of the essential elements. Because Bluetooth has many advantages such as low power consumption, small size module package, and various standard protocols, it is rated as one of the efficient communicating technologies which can apply to small-sized robot system. In this paper, we will develop Bluetooth communicating system for autonomous robots. And we will discuss how to construct and what kind of procedure to develop the communicating system for group behavior of the SRS under intelligent space.

2A2-L03 磁気駆動Robot-on-a-chipに関する研究 : その1: 2自由度磁気駆動マイクロツールによるオンチップ微粒子操作

We proposed a two-degree-freedom magnetically driven microtool (2DOF-MMT) which can directly manipulate cells on a chip with high accuracy. The classified actuation method of MMT showed that using of the permanent magnet has an advantage over micro-electromagnetic coil in microscale in terms of the magnetic interference of MMT and actuation part. A fundamental experiment was carried out to confirm the displacement of the 2DOF-MMT actuated by a permanent magnet mounted below it. The displacement was in the range of 400-600 μm in x-direction and 250-400μm in y-direction, and the hybrid 2DOF-MMT which contain the Nickel plate show far larger displacement (30% in x-direction and 60% in y-direction). The 2DOF-MMT has potential to be used as micro-nano-robot on a chip which can be defined as Magnetically Driven Robot-on-a-Chip (MDRoC).

等温化した空気圧ゴム人工筋の体積からの収縮率推定

The applications of pneumatic artificial muscles (PARM) are increasing in the power assist and manipulator systems, because of its advantages such as high power-to-weight ratio and flexibility. Usually, we have to measure the contract ratio of PARM using a displacement sensor installed near the actuator which is not easy to make dust and water proof. In this paper, we propose an estimation method of the contract ratio from the volume change of the PARM which can make the actuator part sensor-less. The air charged and discharge to the PARM is measured by a quick response laminar flow meter. Then, the volume of the PARM is estimated from the flow rate and the pressure measured by a pressure sensor. In order to estimate the contract ratio accurately, thin copper wires are stuffed to the PARM to produce an almost isothermal condition during the charge and discharge. The effectiveness of the proposed method was confirmed experimentally.

Development of a Peristaltic Micropump for Bio-Medical Applications Based on Mini LIPCA

This paper presents the design, fabrication, and experimental characterization of a peristaltic micropump. The micropump is composed of two layers fabricated from Polydimethylsiloxane (PDMS) material. The first layer has a rectangular channel and two valve seals. Three rectangular mini lightweight piezo-composite actuators are integrated in the second layer, and used as actuation parts. Two layers are bonded, and covered by two Polymethyl Methacrylate (PMMA) plates, which help increase the stiffness of the micropump. A maximum flow rate of 900 μL·min −1 and a maximum backpressure of 1.8 kPa are recorded when water is used as pump liquid. We measured the power consumption of the micropump. The micropump is found to be a promising candidate for bio-medical application due to its bio-compatibility, portability, bidirectionality, and simple effective design.

Thermal effect on piezoelectric stick-slip actuator systems

The piezoelectric stick-slip (PZT-SS) actuator is known to achieve motion with a theoretically unlimited range yet high resolution (several nanometers). In this type of actuator, friction plays an active role in producing a meaningful stick-slip motion. However, friction is a source of heat which may cause significant temperature rise, affecting the dynamic performance of the actuator. Our study aimed to measure temperature rise in the stick-slip motion and to understand whether such a rise could significantly affect the displacement of the stick-slip motion. In this study, a temperature measurement system was developed using the off-the-shelf components, with which the temperature rise up to 0.436 degrees C was successfully measured on a proprietary PZT-SS actuator. The experiment further shows that the temperature rise affects the displacement of the actuator when operating voltage is at the low end (approximately 6 V). Therefore, one of the design recommendations for such an actuator system is that the operating voltage should be at the high end (approximately 30 V). The study also measured the temperature rise (approximately 0.263 degrees C after the system worked for 6300 s) at the friction interface due to the piezoelectric element which is a part of the whole PZT-SS actuator. This means that temperature rise is due to both the friction at two interacting surface and the operation of the piezoelectric element.

A mechanical model of a non-uniform ionomeric polymer metal composite actuator

This paper describes a mechanical model of an IPMC (ionomeric polymer metal composite)actuator in a cantilever beam configuration. The main contribution of our model is that itgives the most detailed description reported so far of the quasistatic mechanical behaviourof the actuator with non-uniform bending at large deflections. We also investigate a casewhere part of an IPMC actuator is replaced with a rigid elongation and demonstrate thatthis configuration would make the actuator behave more linearly. The model isexperimentally validated with MuscleSheet™ IPMCs, purchased from BioMimeticsInc.

RF MEMS Extended Tuning Range Varactor and Varactor Based True Time Delay Line Design

MEMS varactors are one of the important passive MEMS devices. Their applica- tions include use in VCOs, tunable impedance matching networks, tunable fllters, phase shifters, and true time delay lines. The shunt capacitive structure has been employed in most of the conventional MEMS varactor designs because of its simplicity. However, the capacitance ratio of this conventional shunt capacitive MEMS varactor is limited to 1.5 because of the MEMS Pull- In efiect, which happens when the de∞ection between the MEMS top and bottom metal plates increase beyond 1/3 of the airgap between the two metal plates. At that time, the top metal plate will quickly snap down. This efiect is the major limitation in MEMS varactor designs and can cause nonlinearity and mechanically instability. In order to eliminate this Pull-In efiect, the author employed the so-called MEMS extended tuning range structure. This structure utilizes a variable height top metal beam with separate actuation parts. The airgap between the center part of the top beam and the bottom plate has been designed to be less than 1/3 of the airgap between the top beam and the bottom actuation pads. When DC bias is applied to the actuation parts, the entire top beam will move down together. Consequently, before the Pull-In efiect happens at the actuation parts, the center part has already traveled through its entire tuning range, which means that the capacitive ratio of this kind of MEMS varactor can go to inflnity. A fabrication process employing a GaAs substrate has been designed based on surface micro- machining technology. The maximum capacitance ratio of the designed MEMS extended tuning range varactor is 5.39 with a Cmax value of 167fF. Based on this MEMS varactor design, a Ka-band MEMS varactor based distributed true time delay line has been designed. This dis- tributed true time delay line includes a high impedance CPW transmission line with 70› un- loaded impedance at 28GHz and eight MEMS extended tuning range varactors based on the varactor design periodically loaded on the CPW line. The testing results show that a 56 - phase delay variation has been achieved at 28GHz. The measured insertion loss at 28GHz is i1:07dB at the up-state and i2:36dB at the down-state. The measured return losses, S11 and S22, are both below i15dB at 28GHz and below i10dB over the entire tested frequency range of 5GHz to 40GHz.

Reliable Adaptive Control for Switched Fuzzy Systems

A model of a kind of uncertain switched fuzzy systems is presented first, in which each subsystem is an uncertain fuzzy system. Then the robust stabilization problem to the system is studied and a solution proposed. When the upper bounds of the disturbances are unknown, and the actuator is serious failure and the residual part of actuator can not make original system stable, a reliable robust adaptive controller is constructed to guarantee the closed-loop system is uniformly ultimately bounded via using switching technique and multiple Lyapunov function approach. The switching strategy achieving system uniformly ultimately bounded of the uncertain switched fuzzy system is given. An illustrative example is given that demonstrates the feasibility and the effectiveness of the proposed method.

Design and fabrication of in-plane resonant microcantilevers

An in-plane resonant bimetal microcantilever based on thermal actuation mechanism was developed utilizing the photolithography technique. The microcantilever structure consists of a platform, a long narrow anchor, and a U-shape actuation loop. Niobium and gold are used as materials for fabrication of the microcantilever. In the cantilever design the shortcoming of low actuation frequency was overcome by separating the thermal actuator part and the microcantilever part. According to the dynamic property tests, the in-plane resonant frequency of our microcantilevers is one order of magnitude higher than the out-of-plane one. With further optimizing the design, our microcantilevers may have applications as actuators and biosensors.

Output Feedback Sliding Mode Control for a Linear Focusing Actuator in Digital Video Cameras

The output feedback sliding mode control offers an effective positioning method by robustness to parameter variation and disturbance rejection. This paper presents the output feedback sliding mode control based on a position estimation algorithm written in the microprocessor for use in the focusing control system of a digital video camera to achieve fast focusing response and accurate positioning despite vibration and friction of the movable part of the linear focusing actuator. The focusing performance by utilizing the output feedback sliding mode control includes a 60-ms setting time and 7-m steady-state error, respectively, which are only half and one-third of those in proportional-integral-derivative control when the movable part of the linear focusing actuator moves at a 5-mm stroke.

Photocontrolled wettability changes in polymer microchannels doped with photochromic molecules

The authors demonstrate the possibility to control the fluid flow inside microfluidic networks by photoresponsive capillaries. The approach relies on the use of photochromic molecules undergoing reversible changes in their polarity when irradiated with light of specific wavelength, thus varying the wettability of cyclic olefin copolymer microchannels. The realized photoresponsive elements exhibit a decrease up to 20° between the water contact angles of the native and the irradiated surfaces, which could be exploited for enhancing the penetration flow rate of fluids inside microfluidic channels up to 25%. The photocontrollable microfluidic circuitry presents on-off valve behavior, allowing or blocking liquid filling processes on the base of optical control, thus allowing one to manipulate liquid flow within microfluidic networks without mechanical actuation parts.

Nanoenergetic Materials for MEMS: A Review

New energetic materials (EMs) are the key to great advances in microscale energy-demanding systems as actuation part, igniter, propulsion unit, and power. Nanoscale EMs (nEMs) particularly offer the promise of much higher energy densities, faster rate of energy release, greater stability, and more security (sensitivity to unwanted initiation). nEMs could therefore give response to microenergetics challenges. This paper provides a comprehensive review of current research activities in nEMs for microenergetics application. While thermodynamic calculations of flame temperature and reaction enthalpies are tools to choose desirable EMs, they are not sufficient for the choice of good material for microscale application where thermal losses are very penalizing. A strategy to select nEM is therefore proposed based on an analysis of the material diffusivity and heat of reaction. Finally, after a description of the different nEMs synthesis approaches, some guidelines for future investigations are provided.

Miniature bending manipulator for fetoscopic intrauterine laser therapy to treat twin-to-twin transfusion syndrome

Recent typical therapy for twin-to-twin transfusion syndrome (TTTS) is selective laser photocoagulation of anastomotic communicating vessels on the placenta using the fetoscopic approach. The difficulty of a conventional laser device approach for this procedure depends significantly on the placental location, so a new robotized device is required to bend the direction of laser irradiation flexibly within the narrow uterus. The authors designed a miniature bending mechanism impelled by a wire-guided linkage driving method that provides a stable procedure for bending laser irradiation from -90 degrees to 90 degrees . Using this bending mechanism, the authors developed a bending manipulator with a diameter of 3.5 mm and a hollow central channel with a diameter of 0.8 mm for passing a glass fiber for neodymium:yttrium-aluminum-garnet (Nd:YAG) laser photocoagulation. The bending mechanism is motorized by an electrical actuator and controlled by a grip-type interface with a small joystick. The robotized tip's part and the actuator's part are easily separable for cleaning and sterilization. In performance evaluations of the manipulator, the bending characteristics with a glass fiber were examined. The bending range was -52.6 degrees to 80 degrees, with a very small hysteresis error, and the bending repeatability error was 0.5 degrees +/- 0.2 degrees, which corresponds with the high accuracy of 0.2 +/- 0.1-mm positioning error at the glass fiber's tip. In the evaluation of Nd:YAG laser photocoagulation, the study confirmed that the manipulator performed effective laser photocoagulation of the placental phantom surface (underwater chicken liver). The large bending range, reaching 80 degrees, enabled a flexible approach from various directions with a high irradiation efficiency of no less than 96.6%. The authors' original miniature bending manipulator can change the laser irradiating direction with highly repeatable positioning accuracy for speedy, safe, and effective vessel occlusion in clinical practice.

Theoretical analysis and optimization of electromagnetic actuation in a valveless microimpedance pump

The construction of a novel valveless microimpedance pump is proposed and the utilized electromagnetic actuator is designed and optimized in this study. The actuating mechanism comprises an electroplated permanent magnet mounted on a flexible PDMS diaphragm and electroplated Cu coils located on a glass substrate. The electromagnetic force between the magnet and the Cu coils causes the diaphragm to deflect and then creates the accumulative effects of wave propagation and reflection at the junction of the compressible and rigid sections. The resulting pressure gradient in the fluid drives the flow from the inlet to the outlet of the micropump. The constituent parts of the electromagnetic actuator, namely the diaphragm, the microcoils, and the magnet are modeled and analyzed in order to optimize the actuator design. The design models are verified both theoretically and numerically and the relationships between the magnetic force, diaphragm displacement, and diaphragm strength are established. The magnitude of the magnetic force acting on the flexible diaphragm are calculated using Ansoft/Maxwell3D FEA software and the resulting diaphragm deflection simulated by ANSYS FEA software are found to agree with the theoretical predictions. Different diaphragm shapes are investigated and their relative strength and flexibility are compared. It is found that a circular PDMS diaphragm represents the most appropriate choice for the actuating mechanism in the micropump. The desired diaphragm deflection of 15μm is obtained using a compression force of 16μN, generated by a coil input current of 0.9A. The diaphragm deflection can be regulated by varying the current passed through the microcoil and hence the flow rate can be controlled. The valveless microimpedance pump proposed in this study is easily fabricated and can be readily integrated with existing biomedical chips due to its plane structure. The results of the present study provide a valuable contribution to the ongoing development of Lab-on-a Chip systems.

Modelling approaches for an ultrasonic percussion drill

This work deals with a novel piezoelectrically driven vibro-impact drilling tool which is designed to drill holes and take rock samples in NASA's future space missions. The drilling device consists of an ultrasonic transducer with a piezoelectric stack, a free flying mass and a drill stem. Excited by the high-frequency vibration of the transducer the free mass oscillates between the horn tip of the transducer and the drill stem. The shock waves in the drill stem caused by the impacts with the free mass affect hard and brittle materials so effectively that small holes can be performed with extremely low additional downforce and low power consumption. This paper provides measurements with a modified actuator which show an irregular motion of the free mass. For further optimization two model approaches are investigated: the finite element method and a discrete lumped parameter model. Each model is capable of predicting actuator's parts motion similar to measurements.

Mechanical Characteristics of FIB Deposited Carbon Nanowires Using an Electrostatic Actuated Nano Tensile Testing Device

This research is directed at the development of Electrostatic Actuated NAno Tensile testing devices (EANATs) for measuring mechanical properties of carbon nanowires, deposited by focused ion beam-assisted chemical vapor deposition (FIB-CVD) using phenanthrene gas. The EANATs were composed of the specimen part, actuator part and measurement part. 1000, 3000 and 5000 pairs of comb drive actuators were prepared within the actuator part for stretching the nanowires. The measurement part had a cantilever used as a lever motion amplification system for measuring tensile displacement of the nanowires. A theoretical resolution of 0.17 nm in tensile displacement was achieved using the amplification system and imaging analysis. The uniaxial tensile force was derived from the total spring constant of suspended beams built within the EANATs, with the theoretical resolutions ranging from 108 to 113 nN. This research was therefore successful in obtaining accurate load-displacement curves for carbon nanowires. The Young's modulus observed for the nanowires provided the scatter in absolute values ranging from 42.6 to 80.7 GPa. The fracture stress and strain of the nanowires exhibited larger values of 4.3 GPa and 0.08 strain, respectively. Discussion of the deformation behaviors and failure mechanisms of the nanowires is made from FE-SEM observations of the nanowires before and after tensile failure