Piezoelectrically actuated dome-shaped diaphragm micropump

This paper describes a piezoelectric micropump built on a dome-shaped diaphragm with one-way parylene valves. The micropump uses piezoelectric ZnO film (less than 10 /spl mu/m thick) to actuate a parylene dome diaphragm, which is fabricated with an innovative, IC-compatible process on a silicon substrate. Piezoelectric ZnO film is sputter-deposited on a parylene dome diaphragm with its C-axis oriented perpendicular to the dome surface. Two one-way check valves (made of parylene) are integrated with a piezoelectrically actuated dome diaphragm to form a multi-chip micropump. The fabricated micropump (10/spl times/10/spl times/1.6 mm/sup 3/) consumes extremely low power (i.e., 3 mW to pump 3.2 /spl mu/L/min) and shows negligible leak up to 700 Pa static differential pressure.     

Angular vertical comb-driven tunable capacitor with high-tuning capabilities

This paper reports on a novel tunable capacitor with electrostatic angular vertical comb-drive (AVC) actuators. The AVC tunable capacitor creates a large offset in comb fingers through a small rotation angle-an advantage not found in conventional lateral comb-drive devices. High capacitance and large continuous tuning ratio is achieved in a compact device area. The largest tuning varactor demonstrates capacitance values between 0.27-8.6 pF-a tuning ratio of more than 31:1, the highest ever reported. The maximum quality factor Q is 273 at 1 GHz near the minimum capacitance value.     

Fabrication and dynamic analysis of the electrostatically actuated MEMS variable capacitor

Future microwave networks require miniature high-performance tunable elements such as switches, inductors, and capacitors. In this paper, high performance variable capacitor was fabricated by simple microelectromechanical systems (MEMS) technology. The capacitance and quality (Q) factor at 1 GHz are 0.792 pF and 51.6. The pull-in voltage is 13.5 V and the tuning ratio of the capacitor is more than 1.31:1. A reduced-order model for the dynamic characteristics of the capacitor is established based on the equilibrium among the plate flexibility.     

Piezoelectrically scanned displays devices

A scanning system based on electro-acoustic bulk wave propagation in piezoelectric ceramics is described. Both ceramic and thin-film structures are applied to several display media, including liquid crystals, electrophoretics, gas discharge and electroluminescence. A single-member display structure is described using a PLZT piezoferroelectric ceramic substrate as a combined addressing and displaying material. Some experimental results are presented.     

Design of wide range MEMS tunable capacitor for RF applications

The RF applications like voltage controlled oscillators, tunable filters, resonators etc., requires tunable capacitors in their designs. This paper presents the design of wide range MEMS tunable capacitors for RF applications. This design consists of an air suspended bottom plate and a fixed top plate. The top fixed plate and the suspended bottom plate form the tunable capacitor. The capacitance range of this tunable capacitor is from 69.172 to 138.344?nF. This range is wider compared with the conventional MEMS tunable capacitors of tuning ranges in pico Farads. The fabrication process is similar to that of the existing standard integrated circuit fabrication processes, which makes this design suitable for integrated RF applications.     

On the implementation of adaptive sliding mode robust controller in the stabilization of electrically actuated micro-tunable capacitor

Microsystem Technologies - Parallel-plates based micro-tunable capacitors are known to have low travel ranges, which deteriorate as going even lower in terms of their initials gap sizes. Such...     

Dissipatively actuated manipulation

This paper addresses the design of control systems whose actuation can only dissipate energy. Such systems provide intrinsic safety, and can be used in scenarios where energy is supplied by external entities and point-stabilization is possible with only energy dissipation. Three control synthesis methods are proposed that range from model-based to a learning approach and their validity is demonstrated on a passively controlled manipulator performing a positioning task. These three methods are the Zero Control Velocity Field, Monte-Carlo Tree Search and Reinforcement Learning. The simulation results are corroborated by experiments on a physical two link manipulator.     

Magnetically actuated micromechanical tweezers

Two planar actuators with magnetic thin films are used for magnetic tweezers. The planar actuators consisting of a pair of a 75 × 0.8 × 0.3 μm³ silicon oxide beam and a 72 × 13 × 0.3 μm³ silicon oxide plate deposited with a 65 × 4 × 0.1 μm³ Ni magnetic thin film are successfully fabricated and successfully gripped to a single NPC-tw01 cell consisting of Fe₃O₄ magnetic nanoparticles under a vertical magnetic field. The planar actuator bends under an external magnetic field because of the high shape magnetic anisotropy of the Ni magnetic thin film and a highly sensitive microcantilever. NPC-tw01 cells, which are adherent cells, are cultivated in a culture solution. The two planar actuators are placed in water to move and grip a living cell.     

Spherically actuated platform manipulator

This article presents the inverse and forward pose and rate kinematics solutions for a novel 6‐DOF platform manipulator, actuated by two base‐mounted spherical actuators. The moving platform is connected to the fixed base by two identical spherical‐prismatic‐universal serial chain legs. The S‐joint is active, and the remaining two joints in each chain are passive. An analytical solution is presented for the inverse pose problems, a semi‐analytical solution is presented for the rate problems, and the numerical Newton–Raphson technique is employed to solve the forward pose problem. Unfortunately, the passive joint variables cannot be ignored in the kinematics solutions as they can for the Gough–Stewart platform. Examples are presented and hardware has been built, using two Rosheim Omni‐Wrists on loan from NASA as the spherical actuators. © 2001 John Wiley & Sons, Inc.     

Magnetically actuated, addressable microstructures

Surface-micromachined, batch-fabricated structures that combine plated-nickel films with polysilicon mechanical flexures to produce individually addressable, magnetically activated devices have been fabricated and tested. Individual microactuator control has been achieved in two ways: (1) by actuating devices using the magnetic field generated by coils integrated around each device and (2) by using electrostatic forces to clamp selected devices to an insulated ground plane while unclamped devices are freely moved through large out-of-plane excursions by an off-chip magnetic field. The present application for these structures is as micromirrors for microphotonic systems where they can be used either for selection from an array of mirrors or else individually for switching among fiber paths     

Thin-film shape-memory alloy actuated micropumps

Micropumps capable of precise handling of low-fluid volumes have the potential to revolutionize applications in fields such as drug delivery, fuel injection, and micrototal chemical analysis systems (μTAS). Traditional microactuators used in micropumps suffer from low strokes and, as a result, are unsuitable for achieving large fluid displacement. They also suffer low-actuation work densities, which translate to low forces. We investigate the use of the shape-memory effect (SMA) in sputter-deposited thin-film shape-memory alloy (SMA) titanium nickel (TiNi) as an actuator for microelectromechanical systems (MEMS)-based microfluidic devices, as it is capable of both high force and high strains. The resistivity of the SMA thin film is suitable for Joule heating, which allows direct electrical control of the actuator. Two micropump designs were fabricated-one with a novel complementary actuator and the other with a polyimide-biased actuator-which provided thermal isolation between the heated microactuator and the fluid being pumped. A maximum water flow rate of 50 μl/min was achieved     

Mechanisms for actuated assistive hip orthoses

Mobility is often a central problem for people having muscle weaknesses. The need for new devices to assist walking and walk related activities is therefore growing. Lower limb actuated orthoses have already proven their positive impact with paraplegic patients and are potentially promising for assisting people with weak muscles. However, the transfer from the existing systems of mobilization towards assistance implies several technical challenges as the seamless integration and the reduction of power consumption. In this paper two assistive orthoses which use different types of actuation mechanisms are presented and discussed. The first one is based on a ball screw and an excavator-like mechanism while the second one is based on a double differential actuation. Their technical capabilities are compared and contextualized for diverse activities. Objective characteristics such as the range of motion of the devices, the transparency, the maximal torque that they can provide or the RMS torque during cyclic trajectories are compared to point out which device is better adapted for specific situations.     

Fully integrated magnetically actuated micromachined relays

A fully integrated magnetically actuated micromachined relay has been successfully fabricated and tested. This particular device uses a single-layer coil to actuate a movable upper magnetically responsive platform. The minimum current for actuation was 180 mA, resulting in an actuation power of 33 mW. Devices have been tested which can make and break 1.2 A of current through the relay contacts when the relay is electromagnetically switched. Operational lifetimes in excess of 850000 operations have been observed. Contact resistances as low as 22.4 mΩ have been observed under electromagnetic actuation. Magnetic and structural finite-element (FE) simulations have been performed using ANSYS to calculate both the actuation and contact forces     

Development of ICPF Actuated Underwater Microrobots

It is our target to develop underwater microrobots for medical and industrial applications. This kind of underwater microrobots should have the characteristics of flexibility,good response and safety. Its structure should be simple and it can be driven by low voltage and produces no pollution or noise. The low actuating voltage and quick bending responses of Ionic Conducting Polymer Film (ICPF) are considered very useful and attractive for constructing various types of actuators and sensors. In this paper, we will first study the characteristics of the ICPF actuator used in underwater microrobot to realize swimming and walking. Then, we propose a new prototype model of underwater swimming microrobot utilizing only one piece of ICPF as the servo actuator. Through theoretic analysis, the motion mechanism of the microrobot is illustrated. It can swim forward and vertically. The relationships between moving speed and signal voltage amplitude and signal frequency is obtained after experimental study. Lastly, we present a novel underwater crab-like walking microrobot named crabliker-1.It has eight legs, and each leg is made up of two pieces of ICPF. Three sample processes of the octopod gait are proposed with a new analyzing method. The experimental results indicate that the crab-like underwater microrobot can perform transverse and rotation movement when the legs of the crab collaborate.     

Enhancing nanoparticle deposition using actuated synthetic cilia

We use computational modeling to probe the utility of actuated synthetic cilia lining walls of a microfluidic channel for enhancing the deposition of nanoparticles dispersed in a viscous fluid filling the channel. We demonstrate that elastic cilia actuated by a sinusoidal force applied to their free ends generate circulatory secondary flows facilitating nanoparticle transport. We identify optimal operational conditions in which the effect of cilia beating on particle deposition is maximized. Our simulations also reveal that cilia transition to a three-dimensional beating pattern when the actuation force exceeds a critical value. This transition is associated with buckling instability experienced by elastic cilia. Our findings guide the optimal design of ciliated microfluidic systems for uses such as deposition of particulates onto sensory surfaces and microfluidic mixing.     

Complex nonlinear oscillations in electrostatically actuated microstructures

In this paper, new nonlinear dynamic properties of electrostatically actuated microstructures [referred to as electrostatic microelectromechanical systems (MEMS)] observed under superharmonic excitations are presented using numerical simulations. Application of a large dc bias (close to the pull-in voltage of the device) is found to bring the device to a nonlinear state. This nonlinear state (referred to as "dc-symmetry breaking") can be clearly observed from the characteristic change in the phase-plot of the device. Once a steady nonlinear state is reached, application of an ac signal at the Mth superharmonic frequency with an amplitude around "ac-symmetry breaking" gives rise to M oscillations per period or M-cycles in the MEM device. "ac-symmetry breaking" can also be observed by a characteristic change in the phase-plot of the device. On further increasing the ac voltage, a period doubling sequence takes place resulting in the formation of 2/sup n/M-cycles in the system at the Mth superharmonic frequency. An interesting chaotic transition (banded chaos) is observed during the period doubling bifurcations. The nonlinear nature of the electrostatic force acting on the MEM device is found to be responsible for the reported observations. The significance of the mechanical and the fluidic nonlinearities is also studied.     

Autonomous magnetically actuated continuous flow microimmunofluorocytometry assay

This article presents a microfluidic device which integrates autonomous serial immunofluorocytometry binding reactions of cytometric beads with fluorescence detection and quantification in a continuous flow environment. The microdevice assay is intended to alleviate the extensive benchwork and large sample volumes used when conducting traditional immunoassays, without requiring complex external controls. The technology is based on the miniaturization and automation of the serial processing steps of an antigen sandwich immunoassay, with integrated fluorescence detection using paramagnetic microbeads. The continuous flow design may enable temporal tracking of time-varying protein concentrations in a continuously infused sample for clinical applications, specifically for monitoring inflammation marker proteins in blood produced during cardiac surgeries involving cardiopulmonary bypass (CPB) procedures. The device operation was first validated via a single incubation device which measured the concentration of a fluorescently labeled biotin molecule using streptavidin-coated paramagnetic cytometric beads. Subsequently, a dual incubation device was tested with samples of the anaphylatoxin complement protein C3a, and was shown to be capable of differentiating between samples at typical systemic concentrations of the protein (1–5 μg/ml), with very low sample usage (<6 μl/h). It is believed that this continuous flow, automated microimmunosensor technology will be a platform for high sample rate immunoassays capable of tracking and more thoroughly characterizing the systemic inflammation process, and may aid in the development of better treatment options for systemic inflammation during and after CPB.     

Design of an electro-thermally actuated cell microgripper

The study of cells mechanical properties is of great interest both in medicine and biology to recognize and prevent some diseases causing alterations in cellular behaviour and resistance. Biological micro electro-mechanical systems allow the application of extremely small and precise forces increasing, as a consequence, the number of results possible per experiment and the number of experiments that can be performed simultaneously. The presented work deals with the analysis of an electro-thermally actuated microgripper for single-cell manipulation. Specifications and targets impose several limitations and difficulties in micro manipulators design and these obstacles are even more important when the target of microgripping are biological particles (e.g. living cells). The main parameters that have to be taken into account while designing a cell micromanipulator are, aside from its actuation principle, its kinematics, its fingertips shape, its releasing strategy and its material biocompatibility. More specifically in thermal actuation also thermal stability, insulation and high temperature in the device have to be considered to ensure the cell’s integrity during its micromanipulation.     

Integrated centering control of inertially actuated systems

Inertially actuated systems are often hindered by the requirement that the actuator or controller be explicitly designed so that the actuator's proof mass never exceeds the available stroke length. When the actuator's proof mass reaches the end of its stroke a destabilizing input is created, which reduces performance. An integrated centering controller design that balances control effort with proof mass centering is presented. This approach enables the creation of controllers with reduced potential for stroke saturation. The controller developed is verified numerically for a buckling stabilization problem and experimentally for a vibration control example.