Prototyping of microfluidic systems with integrated ... - DTU Nanotech

Chapter 4
Fabrication methods
4.1 Introduction
During this project a number of different fabrication methods for microfluidic
structures have been employed. Some of the methods are
well-known from macroscopic fabrication, and have simply been scaled
down to the micrometer range. Others have come from the world of
silicon processing, and have been developed specifically for micro and
nano scale fabrication. For all the methods, however, one factor is very
important, namely the accuracy.
Micro milling has been investigated by a lot of research groups, and
has been characterised on machines weighing several tons and taking
up a small room, and yet micro milling of structures with feature sizes
down to tens of micrometer is possible because of the overall accuracy
of the entire system. This precision is only possible, if all parts of the
milling machine are produced with very small tolerances. Also, with
bulky equipment, thermal expansion must be taken into consideration,
since a small relative thermal expansion or contraction can result in
large deviations when comparing with the size of the tools used and the
structures that are produced.
When spin coating substances onto substrates, the area is macroscopic,
typically some 100 cm 2 . The layer thickness, on the contrary, can
go down to tens of nanometer, with nanometer accuracy. For metals,
sputtering devices even allow deposition of ˚Angström-thin layers.
In this chapter, a general introduction will be given to the fabrication
and machining methods used in the project. Also, the experiences
achieved through the work will be presented and commented. The
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