Hot/UV embossing

M. Heckele (a), M. Worgull (a), T. Mappes (b), G. Tosello (c), T. Metz (d), J. Gavillet (e), P. Koltay (d), H. N. Hansen (c)

(a) Forschungszentrum Karlsruhe (FZK), Institute for Microstructure Technology (IMT), D-76344 Eggenstein-Leopoldshafen, Germany
(b) University of Karlsruhe (TH), Institute for Microstructure Technology (IMT), D-76344 Eggenstein-Leopoldshafen, Germany
(c) Technical University of Denmark (DTU), Department of Mechanical Engineering, DK-2800 Kgs. Lyngby, Denmark
(d) Laboratory for MEMS Applications, Department of Microsystems Engineering (IMTEK), University of Freiburg, George-Koehler-Allee 103,79110 Freiburg, Germany
(e) French Atomic Energy Commission (CEA), Laboratory of Innovation for New Energy Technologies and Nanomaterials (LITEN), 38054 Grenoble, France

Abstract

Sub-micro structured surfaces allow modifying the behaviour of polymer films or components. Especially in micro fluidics a lotus-like characteristic is requested for many applications. Structure details with a high aspect ratio are necessary to decouple the bottom and the top of the functional layer. Unlike to stochastic methods patterning with a LIGA-mould insert it is possible to structure surfaces very uniformly or even with controlled variations (e.g. with gradients). In this paper the process chain to realize polymer sub-micro structures with minimum lateral feature size of 400 nm and up to 4 μm height is presented.

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.

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.

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.

Chantal Khan Maleka, Gaël Thuilliera, Roland Duffaitb , Laurent Guyoutc
a Laboratoire FEMTO-ST, CNRS UMR 6174, Département LPMO, 32 Avenue de l’Observatoire, 25044 Besançon Cedex, France.
b Centre de Transfert des Micro et Nanotechnologies (CTMN), 39 Avenue de l’Observatoire, BP 1445-25007 Besançon Cedex 3, France.
c Department of Applied Mechanical Engineering, University of Franche Comté, 16 Route de Gray, 25030 Besançon Cedex, France.

Abstract

Our approach uses a two-step replication process for hot embossing and a rigid polymeric intermediate mould. This process overcomes some geometrical limitations in microstructured mould fabrication, enables positive-tone imprinting, prolongs the lifetime of the master, and lowers the overall cost of the replication process.