4M Knowledge base - papers

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

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


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.

Submitted on November 12, 2007 - 16:23.

Biphasic reactions in microreactors

B. Ahmed-Omera (b), D. Barrow (b), T. Wirth (a)

(a) Cardiff School of Chemistry, Cardiff University, Cardiff, CF10 3AT, UK
(b) Laboratory for Applied Microsystems, Cardiff School of Engineering, Cardiff University, Cardiff, CF24 3TF, UK


The contact between immiscible liquids in a microfluidic system creating segmented flow offers great potential in the study of biphasic reactions in organic chemistry with significant advantages with respect to conventional flask techniques. As organic solvents play a key role in many chemical processes within the pharmaceutical and chemical industry, there are many applications of biphasic reactions in different areas of chemistry. For a simple biphasic reactions, we show that the application of various reaction conditions in microreactors using segmented flow can dramatically increase the reaction rate, especially when microwave irradiation, sonication or phase transfer catalysis
are combined with segmentation.

Submitted on July 29, 2008 - 10:28.

Capability study of the Fcubic direct shell process for casting micro-components

J-F. Charmeux (a), R. Minev (a), S. Dimov (a), E. Minev (a), S. Su (a), U. Harrysson (b)

a Manufacturing Engineering Center, Cardiff University, Cardiff, CF24 3AA, UK
b Fcubic, Kallarlyckevagen 6, 42935 Kullavik, Sweden


The paper investigates the capability of a new technology, ‘Fcubic’, for a faster and less expensive production of investment casting shells directly from CAD data for the manufacture of micro-components. The technology utilises high resolution 3D printing heads for building shells using zirconia ceramics.

The capabilities of the ‘Fcubic’ process are compared to those of classical two-stage lost wax processes to produce metal micro-components. The tests are carried out on a machine incorporating units for centrifugal and pressure/vacuum casting specially developed to facilitate the replication of components with small features. In particular, this comparative study involved the manufacture of test parts in aluminium/zinc alloys and stainless steel with micro-features in the range of 250 to 700 μm and aspect ratios up to 2.4. The dimensional accuracy and the surface quality of the produced parts were measured. In addition, the production cost of the two different manufacturing routes was assessed to determine the economic viability of the ‘Fcubic’ direct shell technology for casting components incorporating micro-features.

Submitted on May 20, 2008 - 10:28.

Carbon nanotubes grown directly on printed electrode of electrochemical sensor

J. Prasek (a), J. Hubalek (a), M. Adamek (a), O. Jasek (b)

(a) Department of Microelectronics, Brno University of Technology, Brno 60200, Czech Republic
(b) Department of Physical Electronics, Masaryk University, Brno 60200, Czech Republic


This paper is devoted to the area of electrochemical sensors. In this work several screen-printed thick-film electrodes are prepared. These electrodes are commonly used as the working electrodes of electrochemical sensors. The surface of the electrode has been modified with nanopatterned nanostructures. The nanostructures have been formed as vertically aligned carbon nanotubes that were grown directly on the screen-printed working electrode using plasma enhanced chemical vapour deposition method. The aim was to improve electrochemical properties of the electrode by creating homogeneous and high density carbon nanotubes directly on the thick-film layer. The created structures have been investigated by scanning electron microscopy. The electrochemical properties have been investigated by electrochemical detection of cadmium ions in aqueous solutions. The concentration of cadmium ions in units of μmol/L can be determined with the modified electrode.

Submitted on July 30, 2008 - 12:46.

Characterization of Parylene-C Film as an Encapsulation Material for Neural Interface Devices

Jui-Mei Hsu(a), Sascha Kammer(b), Erik Jung(c), Loren Rieth(d), A. Richard Normann(e), Florian Solzbacher(a)(d)(e)
a: Department of Material Science and Engineering, University of Utah, Salt Lake City, UT, USA
b: Fraunhofer IBMT, St. Ingbert, Germany
c: Fraunhofer IZM, Berlin, Germany
d: Department of Electrical Engineering, University of Utah, Salt Lake City, UT, USA
e: Department of Bioengineering, University of Utah, Salt Lake City, UT, USA


Neural interfaces, devices that interact with nervous system, have been developed to help patients with neural disorders to restore lost neural function. The neural interface device requires a conformal and biocompatible encapsulation layer to protect the device during chronic implantation, and to electrically isolate individual electrodes. Parylene-C thin films deposited by a chemical vapour deposition system were studied as an encapsulation layer for neural interface devices. Leakage current tests were used to investigate the encapsulation performance of Parylene-C films, and the results showed hermetic protection as well as long-term (>100 days) stability of the films. The adhesion between Parylene-C and the silicon substrate after several thermal treatments was studied by ASTM tape adhesion tests. Results from these tests suggested that thermal stress may degrade the adhesion force. Parylene samples were subjected to accelerated lifetime testing (85 % relative humidity (RH) and 85 °C) for 20 days, and the film did not show appearance changes as observed by optical microscopy. However, X-ray diffractograms show that the film crystallinity increased during this test.

Submitted on November 12, 2007 - 16:23.


Medical | polymers

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