4M Knowledge base - papers

A. Frick (a), C. Stern (a), U. Berger (b)
a Polymer Sciences and Processing, Aalen University of Applied Sciences AAUAS, Aalen 73430, Germany
b Department of Mechatronics, Aalen University of Applied Sciences AAUAS, Aalen 73430, Germany

Abstract

A larger number of polymeric prototypes with special material properties are often demanded for research and development. Thereby, it is most essential that the prototypes are made from the target material and the related processing technique. A sophisticated and fast possibility to obtain a mold for replicating parts (prototypes) by injection molding is making inserts for hybrid molds, using a rapid prototyping (RP) technique. RP technique (e.g. stereolithography) allows shaping complex mold cavity geometries as well as curved cooling conducts, what is not possible by conventional manufacturing.

The manufacturing of high quality micro parts by injection molding requires a plasticizing unit with small screw channel volume to reduce the residence time of the polymeric melt. Nowadays, the minimal commercially available screw diameter is 14 mm. A newly developed plasticizing unit with a screw diameter of 12mm, which was done at AAUAS in collaboration with ARBURG, permits a gentle processing of polymers, spending only half of the residence time. This is an advantage when micro prototypes are manufactured in a single-cavity mold.

The present work points out, how the combination of the benefits of stereolithography and micro injection molding can be successfully used for producing micro prototypes. By means of some examples, it is shown that the performance of small plastic products (part mass in the milligram range) can be optimized by choosing the right material and processing technique. Thus the spectrum of application of micro parts can be extended.

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.