4M Knowledge base - papers

Severin Dahms, Frederik Bundgaard and Oliver Geschke
MIC - Department of Micro and Nanotechnology, Technical University of Denmark (DTU), Building 345 East, 2800 Kgs. Lyngby, Denmark

Abstract

Waveguides are an excellent means of integrating sensor components in single use microfluidic polymer systems. However, most processes for producing on-chip waveguides require several process steps, some of which are not suited for mass production. We report a simple procedure in which two different grades of the cyclic olefin copolymer (COC) Topas® are used as substrate and core layer. In a spin coating process a Topas® grade with high refractive index is spin coated onto the injection moulded substrate with lower refractive index, thereby generating a core layer. A simple hot embossing process enables simultaneous structuring of waveguides and microfluidic channels in the core layer. In a final step the microfluidic structures can be closed with a lid, either by thermal bonding or by laser transmission welding.

The refractive index and glass transition temperature Tg can be altered by changing the ratio between the two copolymers of Topas®. The low optical transmission loss of the material, along with its chemical resistance and low water absorption, makes Topas® a good choice for making integrated optics in microfluidic systems.

S. G. Serra(a), A. Schneider(a), K. Malecki(b), S. E. Huq(a), W. Brenner(b)
a: Science and Technology Facilities Council, Rutherford Appleton Laboratory,Technology – Central Microstructure Facility, Harwell Science and Innovation Campus, Didcot, OX11 0QX, UK
b: Institute of Sensor and Actuator Systems Vienna University of Technology, Floragasse Str./E366 MST, Vienna 1040, Austria

Abstract

This paper describes a simple process of adhesive bonding between a glass lid and a SU-8 microfluidic device. The bonding is made by applying pressure, between 1.24 MPa – 3.72 MPa, and heat, above the SU-8 glass transition temperature (Tg). The advantages of this process are low cost, simplicity and no need of extra adhesive material, which could block microchannels and inlets. The SU-8 microchannels are fabricated on a glass substrate by UV photolithography. The resist thickness is 30 μm and the smallest channels are 5 μm in width. The bonding process was performed using a simple uniaxial press, a torque wrench and a convection oven as an alternative to the complex and expensive bonding machines with a vacuum chamber and alignment tools. To identify a suitable bonding temperature, a Tg of 175°C for the patterned SU-8 was obtained by Dynamic Mechanical Analysis (DMA). The bonding strength was 1.15MPa, measured by a pull-out test, and a bonding area of 90% was achieved, which was observed by visual inspection. It was also investigated the effect of an O2 plasma cleaning process on the bonding quality.

D. S. Trifonov(a), Y.E. Toshev(b)
a: Institute of Information Technology, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria
b: Institute of Mechanics and Biomechanics, Bulgarian Academy of Sciences, 1113 Sofia, Bulgaria

Abstract

3D CAD models of different variants of the sprue system design of an experimental optical disc mould are developed. The main purpose of the present work is to be predicted the correct geometry shape and parameters of the sprue system before these elements to be produced. The 3D CAD models are built as a combination of the polymer substrate and the sprue system, considered as one object. This approach allows achieving a precise design of the sprue system, before to import the 3D CAD model in the computer simulation program. Different variants of the sprue system design are defined and three parameters are chosen as variables: the gate length and depth and the sprue draft. By means of iterative steps in the frame of the mould filling simulation software, correct variants of the gate geometry and parameters and the processing conditions are achieved. The best results are obtained using the new proposed sprue system with symmetrical melt distribution area.

M. Sahli(a)(b)(c), C. Millot(a), C. Roques-Carmes(a), C. Khan Malek(b), J.C. Gelin(c) and T. Barriere(c)
a: Surface Microanalysis Laboratory (LMS), ENSMM, 25030 Besançon cedex, France
b: FEMTO-ST Institute/Dpt. LPMO, CNRS UMR 6174, , 25044 Besançon cedex, France
c: FEMTO-ST Institute, CNRS UMR 6174, ENSMM, 25030 Besançon cedex, France

Abstract

This paper focuses on the comparison between two manufacturing techniques to realize micro-structural replications on a polymer substrate. The micro-technologies that are considered consist in replication through micro-injection moulding on one hand, and in replication through hot embossing in the other hand. The same mould with microstructured cavities produced by high-speed milling or indentation was used for both replication methods. The replication process parameters are analyzed in both cases, and the resulting polymeric shapes and surface states are characterized in using 3D scanning mechanical microscopy. It is shown that both replication processes give accurate results if the processing cycle as well as pressure and temperature are well adapted.

S. Wilson(a)(b), A. Welle(c), E.Gottwald(c), A. Molleman(d), P.B.Kirby(b), W.Pfleging(e), J.J.Ramsden(b), M. Heckele(a)
a: Institute for Microstructure Technology, Forschungszentrum Karlsruhe, 76344 Eggenstein-Leo., Germany
b: School of Applied Sciences., Cranfield University, Cranfield, Beds. MK43 0AL, UK
c: Institute for Biological Interfaces, Forschungszentrum Karlsruhe, 76344 Eggenstein-Leo., Germany
d: School of Life Sciences, University of Hertfordshire, Hatfield, Herts.AL10 9AB, UK
e: Institute for Materials Research 1, Forschungszentrum Karlsruhe, 76344 Eggenstein-Leo., Germany
A. Herrero(a), J. Esmoris(a), S. Azcarate(a), S. Geissdoerfer(b), U. Engel(b)
a: Department of Micro & Nano Technologies, Tekniker, Avda. Otaola 20, 20600 Eibar, Spain
b: Universität Erlangen-Nürnberg, Egerlandstrasse 11, 91058 Erlangen, Germany

Abstract

The mass production of micro and meso scale products made of polymers or metals is intimately related to the production of high quality microtooling in stable materials capable to provide an accurate and repetitive performance throughout the whole demanded production. As it is widely known, the WEDM process provides high accuracy but is conceptually limited to the production of ruled features. The SEDM process can be a complement to this aspect but the electrodes must be manufactured by other technologies like WEDM, micromilling, turning, etc. Given the importance of several parameters like dimensional accuracy, tooling material for the different replication processes or tooling production technology, the present paper introduces some tests performed by the 4M Metals Workgroup. The analysis of some components manufactured by members of the group is presented discussing the influence of the EDM process on the machined tooling components and the consequent influence on the replication process.

Patch clamping is a highly sensitive technique used to measure the electrical activity of a cell. It is presently a low throughput cumbersome method which requires highly trained and skilled operators to obtain results of value. Patch Clamping is used in applications which include drug screening where there is demand for high throughput systems (HTS). While there are a few commercially available HTS patch clamping systems on the market using traditional patch clamping materials, there are no systems on the market using novel materials, or for dealing with cell networks – a physiologically important consideration for the developing fields of tissue engineering and understanding cell to cell interactions. This paper presents a summary of traditional patch clamping, mentions some commercially available high throughput patch clamping systems based on traditional materials then, using 4M technologies, introduces some novel materials and potential design approaches and processes for producing a polymer based automated patch clamping system.