Novel materials: characterisation and processing
3D micro and nanostructuring of an epoxy based resist by electron beam lithography
G. Rius, J. Bausells, C. Martín, A. Llobera and F. Pérez-Murano
Institut de Microelectrònica de Barcelona, IMB-CNM-CSIC, Barcelona, SPAIN
Abstract
We present the results of producing three dimensional micro- and nanostructures on an epoxy based resist. Epoxy based resists are very interesting in microsystems technology for their good mechanical properties, that allow to produce high aspect ratio microstructures. We have optimized the definition of free standing structures by either using electron beam lithography alone or combining electron beam lithography and UV optical lithography. To tune the energy and dose of the electron beam exposure properly, Monte Carlo simulations are used.
An analysis of the effects of nanolayered nitride coatings on the lifetimes and wear of tungsten carbide micromilling tools
D. Zdebski (a), D.M. Allen (a), D.J.Stephenson (a), J. Hedge (a), C. Ducros (b) and F. Sanchette (b)
(a) Precision Engineering Centre, Cranfield University, Bedford MK43 0AL, UK
(b) CEA Grenoble, Labatoire des Technologies des Surfaces, 17 rue des Martyrs 38054 Grenoble CEDEX, France
Abstract
Micromilling is becoming increasingly important for a wide range of manufacturing tasks in the general field of microengineering, such as milling small channels in micromoulds designed for the fabrication of microfluidic devices by microinjection moulding of polymers. However, micromilling tools, often less than 1mm in diameter, are rather delicate, fracturing when forces become excessive and, consequently, micromilling can become an expensive process. In an attempt to increase tool lifetimes and reduce costs, micromilling forces have been measured with a microdynamometer and the effects of chromium nitride/titanium nitride and titanium aluminium nitride/titanium nitride coatings have been evaluated as an aid to decreasing tool wear and extending the lifetime of tungsten carbide micromilling tools. The surface finish of the milled workpiece has also been measured to monitor how tool wear affects the resultant milled surface.
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
Abstract
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.
Dielectric properties of hydroxyapatite based ceramics
J.P. Gittings (1), C.R.Bowen (1), I.G.Turner (1), A.C.E.Dent, F.R.Baxter (1), (2) and J.B. Chaudhuri (2)
(1) Department of Mechanical Engineering, University of Bath,BATH, BA2 7AY.
(2) Department of Chemical Engineering, University of Bath,BATH, BA2 7AY.
Abstract
This paper studies the ac conductivity and permittivity of hydroxyapatite based ceramics (HA) at temperatures from room temperature to 1000ºC. HA ceramics were prepared either as dense ceramics or in porous form with interconnected porosity and were sintered in either air or water vapour. Samples were thermally cycled to examine the influence of surface adsorbed water on conductivity and permittivity. Surface bound water was thought to contribute to conductivity for both dense and porous materials at temperature below 200ºC. At temperatures below 700ºC the permittivity and ac conductivity of HA was also influenced by the degree of dehydration and thermal history. At higher temperatures (700-1000ºC), bulk ionic conduction was dominant and activation energies are in the range of ~2eV, indicating that hydroxyl ions are responsible for conductivity.
DRIE of non-conventional materials: first results
Samuel Queste, Gwenn Ulliac, Jean-Claude Jeannot and Chantal Khan Malek
Institute FEMTO-ST/Dpt. MN2S, CNRS UMR 6174, 32 Av. de l’Observatoire, 25044 Besançon, FRANCE
Abstract
High speed directional etching of non conventional materials is still insufficiently developed for producing high aspect ratio microstructures. Compared to deep silicon etching, the plasma etching of these materials has suffered from limitations in achievable depth, aspect ratio, verticality and smoothness of surfaces. Inductively coupled plasma (ICP) reactive ion etching (RIE) of quartz crystal, lithium niobate and glass was conducted using fluorine and fluorocarbon based plasma-chemical etching processes. Optimization of etched depth, verticality of the walls, etch rate, etch selectivity towards the etch mask, and surface smoothness was investigated and compared to results of the literature. Deep etching with nearly vertical walls was successfully demonstrated for all three materials.
Explosive welding of Ni- based amorphous foils for micro-tooling applications
R.M. Minev (a), S.S. Dimov (b), S.R. Koev (c), G.Lalev (b), N.H. Festchiev (a)
(a) Department of Materials and Manufacturing Engineering, Rousse University, 8 Studentska, 7017 Rousse, Bulgaria
(b) Manufacturing Engineering Center, Cardiff University, Cardiff, CF24 3AA, UK
(c) BOM Ltd, Basarbovo, 7071 Rousse, Bulgaria
Abstract
In spite of the commercial advantages the available engineering materials for IC and MEMS processes are not able to meet the manufacturing demands for 3D high-aspect-ratio nano/micro structures and high precision. There is a group of energy assisted processes, such as laser ablation, e-beam and ion beam machining that could provide the needed high specific processing energy to create 3D microstructures. However, the required surface integrity of the manufactured nano/micro structures cannot be achieved without developing appropriate materials with adequate processing response. Thus, to broaden the range of micro-engineering products and multiply their capabilities the introduction of “novel” compatible amorphous or composite materials is required.
The study presents the capability of the explosive welding technology to create a bimetallic sandwich with amorphous Ni-based alloys foils (40 μm thick) without affecting the structure of the materials. Direct patterning by Focused Ion Beam (FIB) was used to produce masters from these materials for injection moulding and hot embossing tools. It was demonstrated that high feature resolution and surface quality of the manufactured nano/micro structures can be easily achieved by employing this technological chain.
FT-IR study of nanosurface phenomena
I. Markova – Deneva
University of Chemical Technology and Metallurgy –Sofia, 8 St. Kl. Ohridski blvd., 1756 Sofia, e-mail:vania@uctm.edu
Abstract
IR study of metal nanoparticles in amorphous or crystalline state obtained via water solution of metal salts by borohydride reduction with NaBH4, as well as of nanowires prepared using mesopore ceramic supports has been carried out. FT-IR spectra in mid-infrared region of visible spectrum (4000-400 cm-1) of these nanoscaled materials have been undertaken. IR spectroscopy possibilities have allowed to investigate the nanosurface phenomena and to prove the creation of different chemical bonds such as B-O, B-H, Si-O, O-H in surface atom groups. FT-IR spectra have provided information about the technological and hydrodynamic conditions such as a kind of the initial salt, a type of the reactor used (T, Y, A methods), different ceramic supports used (SiO2, SiMCM and ALMCM), different variants of the support introducing surface wetting), as well as about the nanosclaled materials composition, their structure state and nucleation.
Investigation of the mechanical behaviour of thin metal sheets using the hydraulic bulge test
A. Diehl, D. Staud, U. Engel
Chair of Manufacturing Technology, University of Erlangen-Nuremberg Egerlandstr. 11, D-91058 Erlangen / Germany
Abstract
Ongoing miniaturisation leads to increasing complexity of micro parts linked with continuously decreasing development time. Hence, the demand for reliable material data and means to collect these data in a most efficient way is rising. Since the mechanical properties and thus material forming behaviour are dependent on the stress and strain conditions, the test methods have to be as close as possible to real conditions. Further, due to the so called size effects, data gathered from conventional length scale experiments cannot be used for the description of material used for parts with feature sizes in the micrometer range. In the present paper, the hydraulic bulge test as a means for the mechanical characterisation of thin metal sheets with thicknesses in the range of 25 μm to 500 μm is discussed and compared to data obtained by conventional tensile testing. Challenges due to the small sheet thickness are emphasized and the effect of strain rate on the flow curve is shown. The influence of geometric dimensions on the evaluation of the experiments is investigated by downscaling of the hydraulic bulge test. The material flow curves, as well as the forming limits are discussed in dependence of the sheet thickness.
Machining of polystyrene by UV laser radiation for patch clamping device fabrication
S. Wilson (a),(b), W.Pfleging (c), A. Welle (d), P.Kirby (b), M.Przylbyski (e)
(a) Institute for Microstructure Technology, Forschungszentrum Karlsruhe, 76344 Eggenstein-L, DE
(b) School of Applied Sciences., Cranfield University, Cranfield, Beds. MK43 0AL, UK
(c) Institute for Materials Research 1, Forschungszentrum Karlsruhe, 76344 Eggenstein-L, DE
(d) Institute for Biological Interfaces, Forschungszentrum Karlsruhe, 76344 Eggenstein-L, DE
(e) ATL Lasertechnik GmbH, Burger Str. 48, 42929 Wermelskirchen, Germany
Abstract
Laser patterning is of interest for MST applications; direct ablation of polymer material for generating 2D and 3D shapes such as microfluidic channels, curved shapes or micro-holes and alternatively photo-induced change of chemical or physical surface properties. Correct laser choice and process parameters enables new approaches for the fabrication of lab-on-chip devices with integrated functionalities. Laser-assisted ablation and modification of polystyrene (PS) is introduced with respect to the fabrication of polymer devices for high throughput planar patch clamping - a method of measuring the electrical activity of a cell currently a focus for high throughput systems (HTS). There are currently no marketed systems using novel materials that have surface modifications for either individual cell placement, or for dealing with cell networks, a physiologically important consideration for tissue engineering and understanding cell to cell interactions.
Within 4M, a design jointly proposed by FZK and Cranfield University for the fabrication of a polymer patch clamping system, laser micro-drilling of PS and subsequent surface functionalisation for cell adhesion has been investigated as a function of laser and process parameters. High power ArF laser with a pulse of 20 ns as well as high repetition ArF excimer laser sources with pulse lengths of 4-6 ns were used in order to study the influence of laser pulse length on laser drilling and laser induced surface modification. Micro-drilling of PS with diameters down to 1.5 μm have been demonstrated. Furthermore, localized formation of chemical structures suitable for improved single cell and cell network adhesion has been achieved on PS surfaces.
Micro Electrical Discharge Machining of Si3N4-based Ceramic Composites
K. Liu, J. Peirs, E. Ferraris, B. Lauwers, D. Reynaerts
Afd. PMA, Department of Mechanical Engineering, Katholieke Universiteit Leuven, Leuven, BE-3001, Belgium
Abstract
The Electrical Discharge Machining (EDM) behaviour and machining properties of advanced engineering Si3N4-based ceramic composites Si3N4-TiN are investigated and discussed in this paper. Two types of EDM machining configurations, micro-EDM milling and die-sinking EDM, are employed in the investigation. Relaxation type of pulse is used, and the performances of EDM process in the form of material removal rate, tool wear and surface quality are studied. These tests result in a performance comparison and a discussion on the ceramic composites material removal mechanism. The feature of material removal mechanism is characterised as chemical decomposition of Si3N4 and TiN at elevated temperature rather than melting/evaporation. The generation of nitrogen gas bubbles leads to a porous and foamy top surface structure. Due to the ideal mechanical and physical property of Si3N4-TiN ceramic composites, an application example - a turbine impeller -
as a crucial component in a micro power generation system is manufactured with obtained knowledge in both
machining configurations.
Micro-extrusion of an ultrafine grained copper can
S. Geißdörfer (a), A. Rosochowski (b), L. Olejnik (c), U. Engel (a)
(a) Chair of Manufacturing Technology, University of Erlangen-Nuremberg, Egerlandstrasse 11, 91058 Erlangen, Germany
(b) Department of Design, Manufacture and Engineering Management, University of Strathclyde, 75 Montrose Street, Glasgow, United Kingdom, G1 1XJ
(c) Institute of Materials Processing, Warsaw University of Technology, 85 Narbutta Street, 02-524 Warsaw, Poland
Abstract
Because of the well known virtues of low cost and high productivity, metal forming technology is well suited for mass production of metal micro-components. However, scaling down traditional metal forming processes proves to be problematic because, among other factors, the relatively coarse grain (CG) structure of micro-billets leads to nonuniform material flow and lack of repeatability during microforming. The aim of the presented study is to investigate a possibility of using an ultrafine grained (UFG) copper for micro-extrusion. The UFG version of Cu is produced by severe plastic deformation at room temperature using 4 and 8 passes of equal channel angular pressing (ECAP). The microstructure and compression properties of the UFG copper are investigated. For visualisation purposes, the microforming process of backward extrusion is carried out at room temperature using half cylindrical billets and transparent tools. The extrusion results, for billets subjected to 4 and 8 passes of ECAP, are compared in terms of the extrusion force, grain flow, shape representation and surface quality and show clearly that applying ultrafine grained material to microforming processes reduces scaling effects.
Micromachined silicon electrodes for electrochemical micromachining
C. Blattert (a), C. Müller (b), H. Reinecke (a),(b)
(a) Hahn-Schickard-Gesellschaft e. V. Institute for Micromachining and Information Technology (HSG-IMIT),Villingen-Schwenningen, Germany
(b) Laboratory for Process Technology, Department of Microsystems Engineering (IMTEK), University of Freiburg, Germany
Abstract
Piracy and counterfeiting as well as retraceability demands of products such as plastic parts or tablets require new and innovative methods for unique product identification. An opportunity is the placement of microstructured codes in moulding tools. These tools are often made from materials that do not allow for highly precise micromachining by traditional technologies. Electrochemical machining (ECM) is a method for structuring construction materials such as steel or titanium. The current paper presents a new technology for the fabrication of microstructured tool electrodes for electrochemical machining by using highly doped silicon as electrode material. A simple and low priced fabrication of microstructured silicon electrodes with locally isolated areas is demonstrated by using wellestablished silicon processing technologies. Prototypes based on this new tool electrode technology are fabricated. Therewith electrochemical machining of microstructures in stainless steel is successfully demonstrated. Machining gaps down to 10 μm and average surface roughness of 60 nm are achieved. Typical rates of removal between 60 - 240 μm/min are reached. The local isolation of electrode areas advances the machining accuracy.
Micromachining of amorphous and crystalline Ni78B14Si8 alloys using micro-second and pico-second lasers
I. Quintana (1), T. Dobrev (3), A. Aranzabe (2), G. Lalev (3), S. Dimov (3)
(1) CIC marGUNE. Pol. Ibaitarte 5, 20870; Elgoibar; Guipúzcoa, Spain
(2) Manufacturing Processes Department, Fundación Tekniker, Av. Otaola 20, 2060, Eibar, Guipúzcoa, Spain
(3) Manufacturing Engineering Centre, Cardiff University, Cardiff, CF24 3AA
Abstract
The machining response of amorphous and polycrystalline Ni-based alloys (Ni78B14Si8) to micro-second and pico-second laser processing was investigated. The shape and topography of craters created with single pulses as a function of laser energy together with holes drilled in both materials were studied. The carried out FIB analysis of craters in amorphous and polycrystalline samples revealed that processing both with micro-second and pico-second lasers does not lead to materials crystallization and the short-range atomic ordering of metallic glasses can be retained. When processing the amorphous sample the material laser interactions resulted in a significant ejection of molten material from the bulk that was then followed by its partial re-deposition around the craters. Additionally, there were no signs of crack formation that indicate a higher surface integrity after laser machining. A conclusion is made that laser processing both with short and long pulses is a promising technique for micromachining metallic glasses because does not lead to material crystallisation.