Jahresbericht 2005 - IPHT Jena

70
application of LabOnChip based microfluidic
devices for integrated sample preparation and
placement in micro optical systems. The newly
developed technology for the preparation of allglass
microfluidic devices with coplanar faces are
in compliance with the requirements of microoptical
systems.
A. Microfluidics of liquid-liquid
segmented sample streams
Liquid-liquid segmented flow based on highly
integrated LabOnChip devices offers a powerful
and versatile approach for high-throughput processing
of linearly organized sample streams.
Currently, these fluidic networks are built up from
individual chip modules which are interconnected
by HPLC-capillaries. Since all operations have to
be in plug mode, micro droplets need to be large
enough, to seal a given channel completely. For
widely used HPLC capillaries with an inner diameter
of 0.5 mm this critical volume is about
64 nl. With respect to this, modular systems are
limited in compartment size and thus in throughput
and sample density. Processing of segmented
sample streams uses interface-generated
forces for the maniplation of the micro droplets at
functional nodes with optimized geometry and
wetting conditions. Miniaturization of the channel
system and the droplet volume increases the curvature
of the interfaces and thus the pressure
drop generated at the interface. In conclusion,
not only throughput and sample density, but also
reliability of the processes benefit from miniaturization
and integration. Considering this, our work
in development of LabOnChip devices is focused
on the development of integrated LabOnChip
devices for segmented flow based application.
Toolkit for computational fluidic simulation
and interactive parametrization
of segmented-flow based fluidic networks
(N. Gleichmann, M. Kielpinski, D. Malsch,
T. Henkel)
The main objectives of this work are the application
of principles of electronic design automation
(EDA) to the model based design and parameterization
of segmented-flow based micro fluidic
networks. This approach will significantly increase
the efficiency in development of highly
integrated LabOnChip devices for custom fluidic
and micro chemical protocols. By that way,
research and development of micro chemical and
screening applications will benefit of the promising
micro droplet-based approach of segmented
flow. Our toolkit is based on a computational network
of fluidic nodes, which are interconnected
by virtual fluid ports for the transfer of segment
streams. The particular behaviour of a functional
node may be given by user definable rules, which
MIKROSYSTEME / MICROSYSTEMS
are derived from experimental data and Computational
Fluid Dynamics (CFD) simulations of the
functional element. The geometry is dynamically
generated from photolithographic mask data and
process parameters. Segmented sample streams
are implemented as lists. For interactive inspection
of the interface geometries inside a functional
node a software interface to the surface evolver
is implemented.
Fig. 3.12: Geometry of a drop passing a Tshaped
junction with nozzle.
The surface evolver starts with a dynamically
generated mesh of the node itself and the correct
position of the micro droplets inside the element.
Wetting conditions and local contact angles
are non-constraints and dynamically calculated
from the interface energies. Channel geometry is
generated from the photo lithographical mask
data and the parameters of the etch process. The
parameterization is realized by interactively
changing the mask geometry of the fluidic nodes
and analysing the results of the fluidic simulation.
A complete run for a dynamic simulation takes a
view minutes only. The network can operate with
pressure and volume flow constraints. Currently it
is implemented for non compressible liquid/liquid
two-phase flows and the micro system technology
of isotropic wet etching. The Toolkit consists of
a C++ class library of components for fluidic network
simulation, for user interaction and network
visualization and for interfacing the surface
evolver. In a first test case it was successfully
applied for modelling a double injector module.
Conceptual work on self-controled fluidic
networks for segmented-flow based applications
(M. Kielpinski, D. Malsch, G. Mayer, J. Albert,
T. Henkel)
Functional elements for sample generation, dosing
of liquid into droplets and retrieval of individual
samples from the sample stack, generation of
stacked sequences and controlled fusion of adjacent
segments within it’s segment stream have
been reported and successfully applied for highthroughput
applications. These processes are
mainly effected and controlled by the dynamics of
interface evolution at functional nodes and spe-