4M Knowledge base - papers

T.Rogers & I.Malmros
Applied Microengineering Limited, Unit 8 Library Avenue, Didcot, Oxon.,OX11 0SG, UK

Abstract

A new multi-purpose MEMS fabrication tool is described. The tool enables in-situ aligned embossing and nanoimprinting, in addition to surface activation and aligned wafer bonding. De-embossing is also included in-situ via the use of vacuum chucks and chamber pressurisation. The multi-purpose tool enables the fabrication of bonded, embossed, multi-layer, micro-fluidic devices, for example PDMS structures on silicon, including the alignment of the embossed structure to any pre-existing patterning on the silicon. Examples are presented of various structures that have been made using the tool along with a description of the principles of operation.

J. Dalin (a), J. Wilde (a), A. Synodinos (b), P. Lazarou (b)and N. Aspragathos (b)

(a) University of Freiburg – IMTEK, Department of Microsystems Engineering, Georges-Köhler Allee 103, 79110, Freiburg, Germany, contact: Johan.Dalin@imtek.uni-freiburg.de
(b) Robotics Group, Department of Mechanical Engineering and Aeronautics, University of Patras, Greece, contact: Lazarou@mech.upatras.gr

Abstract

Self-assembly is relatively unused in industrial micro-fabrication, although it offers opportunities to simplify processes and to lower manufacturing costs. A variety of self-assembly procedures have been introduced that take advantage of various forces, e.g. capillary, gravitational, electro-static. In this paper a concept for the alignment of micro-parts on a substrate using fluidic-self-assembly with electro-static attraction is presented. Further, FEM-simulations for the electro-static alignment force are performed and its dependence on several geometric parameters, e.g. the width of the binding sites and the distance between micro-part and substrate at the binding sites, is investigated. Based on results an analytic model is extracted. Furthermore, simulations are also performed to estimate capillary alignment forces, acting on micro-parts that are self-aligned. Finally, the magnitude of electro-static and capillary forces is compared. This novel assembly concept, where the alignment of the component at the binding site is achieved due to electro-static energy minimisation and, optionally, in combination with capillary alignment, could be beneficial in the manufacturing of heterogeneously integrated MEMS, such as optical and RF micro-systems.

P. Lazarou (a), N.A. Aspragathos (a), E. Jung (b)

(a) Robotics Group, Department of Mechanical Engineering and Aeronautics, University of Patras, Patras T.K. 26500, Greece
(b) Chip Interconnection Technologies, Fraunhofer IZM Berlin, Germany

Abstract

Micromanipulation is a very important issue in several fields of technology (microelectronics, optoelectronics & MEMS device packaging). Current implementations do not provide both sub-micron accuracy and movement of parts over centimeter-scale to a ~100μm final alignment precision. A micropart-inside-a-liquid-droplet manipulation concept that manages to bridge the gap from meso via the micro to the sub-micron scale in a fully contained process has been previously introduced by integrating the phenomena of electrowetting, dielectrophoresis and fluidic self-assembly. In this paper, an investigation of the electric fields that drive the manipulation of the droplet and micropart during the stages of electrowettng and dielectrophoresis is presented. Information for critical factors such as electrostatic force, Maxwell stress and surface charge density distribution is provided. Their effect on the manipulation process is verified, in accordance to theory.

Karl F. Böhringer
Department of Electrical Engineering, University of Washington, Seattle, WA 98195-2500, USA

Abstract

Self-assembly is the autonomous and spontaneous organization of components into patterns or structures. Self-assembly is ubiquitous in nature, e.g. in the growth of crystals and organisms, but also at macroscopic scales – it is nature’s prevalent paradigm for manufacturing. Self-assembly also provides the basis for important new industrial manufacturing techniques, especially for components at the milli, micro, and nano scales: their small sizes and large numbers scale unfavorably for common serial techniques but favorably for a new, massively parallel approach. We believe that self-assembling systems will be able to create complex, heterogeneous, non-periodic, three-dimensional
devices in massively parallel production processes. Hence, our research investigates the scientific and engineering foundations of self-assembly processes for integrated micro/nanoelectromechanical systems (MEMS/NEMS).

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.