Abstract:
Microfluidic (also known as lab-on-a-chip) devices offer the capability
ofmanipulating very low volumes of fluids (of the order of micro litres) for
severalapplications including medical diagnostics. This property makes
microfluidicdevices very attractive when the fluid, such as blood, has a limited
supply becausethe patients cannot easily and frequently provide a large sample.
This is typically thecase for aged, diseased patients that do require frequent
sampling during acute careor of older people that have the option of being
treated and cared for at home [1].Prototype lab-on-a-chip devices for medical
diagnostics comprise a number ofelements which separately perform different
functions within the system. Activitywithin the research community is focusing
on the better integration of devicefunctionalities with the long term goal of
creating fully integrated, portable,affordable clinical devices. However,
engineering these solutions for the largevolume production of lab-on-a-chip
devices requires design rules which are not yetentirely available.This paper
describes the results obtained from a set of experiments run to drawgeneric
design rules for the manufacture of a cells/plasma micro separator [2].
Thecells/plasma micro separator was selected for investigation because it is a
strategicelement required in the preparation of blood samples for many different
analyticaldevices. The experiments focused on the study of the behaviour of
whole bloodpassing through micro constrictions which are required for enhancing
the separationeffect [3].The test microfluidic device was an aluminium specimen
designed andmanufactured to incorporate micro constrictions of different width
and length. The metallic aluminium test device was designed for manufacturing by
micromilling anddiamond cutting processes in view of applying these techniques
to the manufactureof micro-moulds for the high-volume production of plastic
microfluidic devices viamicro-injection moulding.The widths of the constrictions
were 23, 53 and 93µm and the lengths were 300 and700µm. The blood flow pattern
and the level of haemolysis generated in the wholeblood were determined for flow
rates between 0.2 and 1 ml/min. Initial resultssuggested that the above
conditions generate a stable flow and do not cause bloodhaemolysis following
passage through the narrow constrictions. This result impliesthat constrictions
as narrow as 23 µm and as long as 700µm can be safely used inblood microfluidic
devices under appropriate flow conditions without the risk ofdamaging the blood
compone