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There are increasing demands for polymer based microfluidic devices as polymer devices
can be mass produced using the injection molding process for disposable analytical applications.
However, fabrication of precision injection molds with micro features down to tens of micro meters
is a challenging task. The most efficient manufacturing method for this type of high precision micro
mold is the tool-based micro machining. In this paper, studies have been conducted to develop
metal injection mould manufacturing technologies for polymer microfluidic device fabrication. An
injection mould with a micro feature of 29μm wall thickness, 20μm height and 9.8mm length has
been successfully achieved on brass with very precise dimensional accuracy and surface quality for
molding process of polymer microfluidic devices. Polymer microfluidic chips with micro channels
of 30μm width have been successfully produced using the machined metal injection mould.
Microfluidic devices have attracted considerable interests in recent years from various industries
such as biomedical, electronics, biology, life science and chemistry [1]. In order to manufacture
devices with micro features, several micro process technologies have been studied and developed
such as laser machining, micro EDM, and silicon etching methods. However, the most efficient
manufacturing method for micro feature fabrication is the tool-based micro machining [2]. There
are many issues in tool-based machining that can affect the micro structure shape and dimensional
accuracy of machined work pieces, such as burr formation, cutting tool geometry, chip formation,
tool-path strategy, material properties, etc [2-4]. In this paper, studies have been conducted to
develop micro metal injection mould manufacturing technologies for polymer microfluidic device
fabrication. Metal injection moulds with micro features down to tens of micro meters have been
machined out using a single crystalline diamond endmill on an ultra-precision 5-axis machining
center. The single crystal diamond endmill is able to minimize the machining burr formation and
micro feature distortion because a tens nanometer sharpness of diamond tools would significantly
reduce the cutting forces. An injection mould with a micro feature of 29μm wall thickness, 20μm
height and 9.8mm length has been successfully achieved on brass with very precise dimensional
accuracy and surface quality.
The experimental study was conducted on an ultra-precision 5-axis machining center with 1nm
resolution using a micro milling setup to machine out a micro mould insert for molding of micro
channels on polymer microfluidic devices. The micro machining setup is shown in Fig. 1, where a
high speed spindle was fixed on the B-axis of the ultra-precision machining center. The material
selected for the mold insert is brass. The sample size of the mold insert is 75x25x40mm. The insert
was mounted on an Ø100mm aluminum disk with a thickness of 15mm using an L-shape clamp.
The aluminum disk together with brass sample was held by a vacuum chuck on the main spindle of
the machine, as shown in Fig. 1. Air and oil mist was used as coolant. An Ø0.5mm straight cutting
edge single crystalline diamond endmill was used for the tests, as shown in Fig. 2. The micro
Key Engineering Materials Vols. 447-448 (2010) pp 456-460
© (2010) Trans Tech Publications, Switzerland
doi:10.4028/www.scientific.net/KEM.447-448.456
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of the
publisher: Trans Tech Publications Ltd, Switzerland, www.ttp.net. (ID: 192.122.131.20-07/06/10,11:17:00)