Multi Material Micro Manufacture Network of Excellence - actuators

Fabrication of piezoelectric thick-film bimorph micro-actuators from bulk ceramics using batch-scale methods

Tue, 29 Jul 2008 12:52:44 +0000

R.P.Jourdain and S.A.Wilson
Materials Department, School of Applied Sciences, Cranfield University, Cranfield, Bedfordshire, MK43 0AL, United Kingdom

Abstract

Piezoelectric ceramic films in the 20-60 micron thickness range are rarely employed today in commercial micro-mechanical devices, even though their expected force capability suggests that they are well suited to many micro-fluidic and micro-pneumatic applications. Some examples would be micro-scale fuel cells and micro-combustors. Head sliders, radio-frequency (RF) micro-switches and powered micro-optics are further potential application areas. These are only a few and the barriers in bringing them into reality are those of processing compatibility rather than commercial desirability. Such issues are being addressed in the EU Framework 6 Project ‘Q2M’, which focuses on batch-scale fabrication issues for high quality new micromechanical devices that are cost-effective and which have extended capabilities.
This paper discusses a potential batch-scale production route for piezoelectric thick-film bimorph microactuators that combines ultra-precision grinding of ceramics and femto-second laser machining, along with standard micro-fabrication techniques such as wafer bonding. This new method has the key advantage that many different shapes and thicknesses of actuator can be made with only minor process changes, meaning that actuators can be designed to suit their intended application. It contrasts with current practice whereby micro-actuators are often designed around a limited range of standard components, with consequent reduction in their achievable performance. The examples used are a 6mm diameter plane-spiral bimorph actuator for integration into a polymeric micro-valve and 2-5mm long bimorph cantilevers intended for use in
a new type of silicon ‘house’ micro-valve, with pneumatic applications.

Towards Batch Integration of SMA into Microsystems: An Actuator Prototype

Tue, 29 Jul 2008 12:41:18 +0000

D. Clausi, J. Peirs, D. Reynaerts
Katholieke Universiteit Leuven, Department of Mechanical Engineering, Division PMA

Abstract

Shape Memory Alloys have a considerable potential for integration into microsystems, where scaling down of their size allows favorable exploitation of the intrinsic adaptive capabilities, providing an actuation mechanism for applications (e.g. micropneumatics) requiring large force control and large actuator stroke. However, the implementation of these materials into actual structures is rather complex and mostly confined to depositing thin NiTi films onto certain target substrates, resulting in devices having a relatively high cost-per-piece. This paper is aimed at investigating a novel approach for batch integration of SMA to microactuators, which might provide a cost-effective alternative to thin film technology while enhancing functional properties and design flexibility. Indicative requirements for the actuator design have been drawn from typical microvalve applications. In order to evaluate the actuator performance, brass microcantilevers have been produced, with prestrained SMA thin wires bonded on top of them, eccentrically with respect to the cantilever’s neutral plane. The activation of SMA element is obtained by direct heating through electrical current. The bending actuation of the cantilever leads to large strokes, expected to match the requirements of a wide range of applications.

Wafer-scale manufacturing of robust trimorph bulk SMA microactuators

Tue, 29 Jul 2008 12:01:00 +0000

N. Sandström (a), S. Braun (a), T. Grund (b), G. Stemme (a), M. Kohl (b), W. van der Wijngaart (a)
a Microsystem Technology Lab, KTH - Royal Institute of Technology, Stockholm, SWEDEN
b Institut für Mikrostrukturtechnik, Forschungszentrum Karlsruhe GmbH, Karlsruhe, GERMANY

Abstract

This paper demonstrates the concept of wafer-level fabrication and integration of robust bulk SMA microactuators based on adhesive bonding of cold-rolled SMA sheets to silicon wafers. Contact printing of an adhesive polymer ensures a selective bonding when transferring full SMA sheets to silicon structures on a patterned wafer. The induced stress of a thin dielectric film deposited on top of the SMA sheet ensures a stable and built-in reset mechanism of the actuators. The trimorph microactuators can be actuated by indirect resistive heating through a thin metal film. We report on the successful wafer-scale fabrication of actuator cantilevers and their characteristics. First test cantilevers show a cold-state deflection of 300 μm which, however, is limited by the silicon substrate. Upon heating, the cantilever shows a stroke of approx. 80 μm.

Design and Optimization of Flat Solenoid MEMS Actuator by Selection of Proper Material Properties

Mon, 12 Nov 2007 16:23:32 +0000

G. Todorov, K. Kamberov, and L. Dimitrov
CAD/CAM/CAE Laboratory, Technical University of Sofia, Sofia 1000, Bulgaria

Abstract

MEMS actuators are widely used in modern industry. Their main advantage is the concentration of desired mechanical characteristics in a limited space. This paper presents a design and optimization of a flat solid MEMS actuator. The optimization is based of the selection of material properties needed for the achievement of the actuator mechanical characteristics required for good performance. The main goal is to reach necessary output mechanical force with minimal side force effects. The output mechanical force is evaluated by modeling and simulation of the magnetic field and its parameters by the use of FE Analyses. In order to make proper simulations, a finite element model of the complete actuator structure is made up suggested).

Another problem that has been solved in the paper is checking of actuator’s geometry and its dimensions in order to evaluate the effective use of the material. As a result of the study, the optimal output function of the mechanical force versus the stage position has been determined. This has been done on the basis of updated material specifications. The optimal design of a flat solenoid MEMS actuator is proposed.

Thin Film Polymer Actuators for Micro-Fluid Applications

Mon, 12 Nov 2007 16:23:32 +0000

A. Boersma, R. de Zwart, R. Boot, P.J. Bolt
TNO Science and Industry, Eindhoven, The Netherlands

Abstract

Thin film actuators have been manufactured for application in small devices, such as valves and (micro)pump. These actuators are based on new materials especially suited to be used as electro-active dielectric elastomers. The properties of these elastomers are tuned to the specific requirements. It was found that the electric voltage required for operating could be lowered by a factor of three to five. The thin film actuators were processed into small valves and pumps for the manipulation of gasses and liquids. It was shown that the actuators could be operated when immersed in a liquid (e.g. water) and can be used as valves in microfluidic sensor array devices. The next step in the development is fine-tuning of the valve setting in order to minimize leakage and optimize performance and durability.

Simulation of Micropart Motion under 2D Force Fields Implemented on a Cilia Microactuator Array

Mon, 12 Nov 2007 16:23:32 +0000

P. Lazarou, N. A. Aspragathos
Robotics Group, Department of Mechanical Engineering and Aeronautics, University of Patras, Patras T.K. 26500, Greece

Abstract

Micromanipulation is a hot topic in the manufacturing of MEMS products. Alternatives to established manipulation techniques that have been proposed in the recent years include manipulation with force fields and microcilia actuator arrays. In this paper, a simulator for the positioning and alignment of microparts on a microcilia array under two dimensional force fields is presented. A description of its design and motion dynamics is given and the simulation results are presented and discussed.

Method for Overcoming the Unwanted Displacements of an Electro-Thermally Actuated Microgripper

Mon, 12 Nov 2007 16:23:32 +0000

R. Voicu, D. Esinenco, R. Müller, L. Eftime, C. Tibeica
National Institute for Research and Development in Microtechnologies – IMT Bucharest, 126A, Erou Iancu Nicolae Street, Bucharest, Romania

Abstract

Thermal microactuators are based on the principle of material deformation due to heat generated by Joule effect. As a class of microactuators, the microgrippers are promising tools for manipulation of micro and nano - scaled objects. The designs of two models of SU-8 microgrippers electro-thermally actuated are described. A simple design for an electro-thermaly actuated polymeric microgripper is compared with an improved design using a pair of heaters on both sides of the microgripper. We demonstrated that it is possible to reduce the unwanted out of plane displacement, the second model capable of being more stable to the out of plane deflection, generated by the stress, when a voltage is applied. Electro-thermo-mechanical simulations based on finite element method were performed for each of the model in order to make a comparison between the results. Preliminary results on the fabrication of the last model, using a surface micromachining technique and an SU-8 polymer as functional material are presented.

Novel Piezoresistive e-NOSE Sensor Array Cell

Mon, 12 Nov 2007 16:23:32 +0000

V.Stavrov(a), P.Vitanov(b), E.Tomerov(a), E.Goranova(b), G.Stavreva(a)
a: Nano ToolShop Ltd., Microelectronica Industrial Zone, 2140 Botevgrad, Bulgaria
b: Central Laboratory of Solar Energy and New Energy Sources, Bulgarian Academy of Sciences, 72”Tzarigradsko chaussee”, blvd, 1784 Sofia, Bulgaria

Abstract

Future of analytical and manufacturing methods based on micro-mechanical cantilevers, depends critically on the ability to implement parallel operation and fast signal processing [1]. There are two mean reasons: high throughput requirement and complexity (multidimensionality) of analyzed value. In order to get parallel function, any single device should be simultaneously: recognizable, autonomously actuated and independently accessible for readout. Devices, fulfilling these requirements, are suffering from a substantial increase in complexity of both layout and manufacturing technology. In present paper, we demonstrate a novel design of a MEMS (Micro-Electro-Mechanical Systems) cell designed for e-NOSE applications, using results of previous works [2,3], which solves above mentioned problems.

The cell consists of four integrated cantilevers, each having a separate piezoresistor. Additionally, the cantilevers are designed to be different in length and thus having different resonance frequencies. Thus, individual cantilevers are frequency recognizable/addressable. Samples of self-actuated piezoresistive cantilever sensor have been fabricated on n-type, silicon, applying combined surface and bulk micromachining techniques. The cantilever dimensions were chosen to provide approx. 1.8 kHz resonance frequency gap between neighbor individual sensors. The new micro-machined cell is suitable for chemical and biological recognition as a micro-balance.

Preliminary Experiments for the Fabrication of Thermally Actuated Bimorph Cantilever arrays on non-silicon wafers with vertical interconnects

Mon, 12 Nov 2007 16:23:32 +0000

S. G. Serra(a), Z. Rozynek(b), A. Almansa(b), V. Djakov(a), A. Schneider(a), S. E. Huq(a), I. Montealegre(b), P. Castillo(b), S. Bou(b)
a: Science and Technology Facilities Council, Rutherford Appleton Laboratory (RAL), Technology – Central Microstructure Facility, Harwell Science and Innovation Campus, Didcot, Oxfordshire, OX11 0QX, UK
b: Profactor Research and Solutions GmbH, 2444 Seibersdorf, Austria

Abstract

This paper describes the first steps for the fabrication of low-cost cantilever arrays, developed at RAL, on nonsilicon polymer substrates with vertical interconnects, produced at Profactor. The deflection and actuation of these cantilevers is based on the bimorph thermal actuation principle. The fabrication of the cantilever arrays requires many process steps which are presented in this article. The first one is the planarization between the via-holes interconnects with a uniform layer. This was achieved by spin coating of a thick (~58μm) SU-8 layer. Next, two thin metal layers of Cr (500Ǻ) and Au (1000Ǻ) were thermally deposited and patterned, using UV lithography with a mask alignment process and wet etching. The following step was the coating of a 1μm structural Au layer, in which the deposited layer had a very poor adhesion. Alternative procedures were explored to overcome this problem in the future. Modifications of the photo masks design and the substrates will be carried out to make the RAL microcantilevers technology more compatible with Profactor substrates.

Bimaterial Actuators and Sensor with Built-in Compensation of the Ambient Temperature Interference

Mon, 12 Nov 2007 16:23:32 +0000

J. Matović(a), Z. Jakšić(b)
a: ISAS, Technical University, 1040, Vienna, Austria
b: IHTM, University of Belgrade, 11000, Belgrade, Serbia

Abstract

We present a novel simple and efficient method for the full removal of the influence of ambient temperature variations to the operation of bimaterial-based MEMS actuators and sensors. The removal of the undesired interference is achieved through the very structure of the bimaterial cantilever, by reversing the order of bimaterial constituent materials at a certain length. Thus an extremely simple geometry is obtained for full self-compensation of the structures. We performed the full simulation of our devices by the finite element method. The structures require standard surface micromachining and utilize only Si-technology compatible materials like polyimides or SU-8. A simple rule for the determination of the zero-deflection condition is presented. The described compensation method enables a significantly reduced bimaterial device area and a much higher packaging density in element arrays, as well as an improved signal-to-noise ratio. The method is especially convenient for photodetector arrays for direct conversion of infrared radiation spatial distribution into a visible image.

USTUTT

Tue, 30 Jan 2007 13:05:53 +0000

Facilities/Hardware:

Sensors and actuators based on metallized polymers, precision micro injection moulding, environmental testing
website: www.uni-stuttgart.de/izfm

RAS contact:
kueck

Thu, 01 Jan 1970 00:00:00 +0000

n/a

FEMTO-ST/DPT. LPMO

Mon, 14 Aug 2006 12:56:52 +0000

Facilities/Hardware:

FEMTO-ST has fully equipped clean room equipment (laser mask writer; photolithography; RIE and DRIE); hot embossing; ultrasonic machining.

For more information about the facilities available, visit the FEMTO-ST website at:

RAS contact:
Chantal

KTH - Microsystem Technology & Cleanroom fabrication facility

Thu, 19 May 2005 15:20:45 +0000

Facilities/Hardware:

our research and advisory potential: http://www.s3.kth.se/mst/research/index.shtml.
For our cleanroom facilities: http://www.electrumlaboratoriet.se/.

The Microsystem Technology lab (MST) is a part of the department of Signals, Sensors and Systems (S3). Our research is mainly centered around Microelectromechanical Systems (MEMS) and its applications, with a focus on silicon-based applied sensor and actuator technology. Our research staff has developed a significant number of devices with promising performance. The group fabricates its silicon structures and devices at the KTH microelectronics laboratory, comprising 1200m2 of cleanroom area with all the facilities of small-scale microelectronics and for research on and development of special purpose structures and components in silicon. The group works on applications in the medical field (MedMEMS), the biotechnology field (BioMEMS), optical components (OptoMEMS) and radio frequency signal components (RFMEMS).

RAS contact:
wouter

Bayerisches Laserzentrum

Wed, 18 May 2005 09:08:57 +0000

Facilities/Hardware:

Various laser systems for ablation, soldering, welding, marking, adjustment, sintering, stereolithography, LOM.

RAS contact:
Stephan Roth