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.

T. Brenner, C. Müller, H. Reinecke, R. Zengerle, and J. Ducrée
IMTEK – University of Freiburg, Georges-Koehler-Allee 106, D-79110 Freiburg, Germany

Abstract

We established an integrated prototyping chain for rapid fabrication of microfluidic chips in polymers comprising fabrication of masters made from elastomers, replication into polymers by soft embossing, surface modification and thermal sealing. Our techniques enable rapid and precise fabrication of fully functionalized microfluidic chips featuring typical minimum lateral dimensions of 50 μm and aspect ratios smaller than one.

R. Jurischka (a), Ch. Blattert (a), I. Tahhan (a), A. Schoth (a), H. Reinecke (a),
a Laboratory for Process Technology, Institute of Microsystem Technology, University of Freiburg, 79110 Freiburg, Germany

Abstract

Present main applications of microfluidic devices are within the life sciences or chemical analysis. Polymers are ideally suited for these applications due to their material properties and their applicability for high volume production. In this study, we developed a rapid manufacturing technology for disposable microfluidic devices using UV-LIGA and injection molding. Exchangeable inserts for the molding tool were fabricated by a modified UV-LIGA technology. The UV-LIGA process is based on a SU-8 lithography with a metal substrate, which allows for a reduction of the nickel electroplating time. These inserts enable a cost effective structuring of polymers. Different prototypes of chips for microfluidic applications with channel dimensions down to 10 μm and aspect ratios of 8 have been fabricated. The electroplated nickel structure has a hardness of 800 Vickers and an excellent top surface roughness of Ra < 20 nm. Taper angles of 3-8 degrees result in low demolding forces. The main advantage of our rapid processing technology is the availability of the geometry, the specific target material and manufacturing technology right from the start of the development to a cost effective high volume production of microfluidic devices.

M. Sahli (a,c), C. Roques-Carmes (a), R. Duffait (b) and C. Khan Malek (c)
a Laboratoire de Microanalyse des Surfaces (LMS), ENSMM, 26 Rue de l’Epitaphe,
b Centre de Transfert des Micro et Nanotechnologies (CTMN), 39 Avenue de l’Observatoire,
c Laboratoire FEMTO-ST, CNRS UMR 6174, Département LPMO, 32 Avenue de l’Observatoire, 25000 Besançon, France.

Abstract

A study of the rheological properties of two types of amorphous polymeric materials (PMMA and COC) was conducted in order to optimize the operating conditions for the hot embossing of the polymers. The glass transition temperature (Tg), the melt flow index (IF), and the viscosity as a function of shear stress were determined. These intrinsic properties were related to the aptitude of the polymers to reproduce the geometrical shape and surface states of a microstructured mould. The flow imposed to the polymeric material in shear or elongational mode was correlated to this rheological approach.