Jahresbericht 2005 - IPHT Jena

cial flow dynamics inside the micro droplets.
Additional functionality is requested and proposed.
This includes controlled 1:N fusion of multiple
droplet sequences and controlled 1:N segment
splitting. Unfortunately, these operations
require synchronization of the flow of multiple
droplet sequences and seem to require integration
of actors and sensors for closed loop flow
control into the micro fluidic device. Application of
these approaches to fluidic networks would
require a huge amount of integrated sensors and
actors, each of them interfering with the others
and thus, the software for control of these networks
would be very complicated.
Analyzing a segmented flow based system we
can recognize, that all prerequisites for application
of self control to these special micro fluidic
systems are available. There are mobile interfaces,
which can be used to seal junctions of the
main channels temporarily. Obstructions can be
used to increase or widenings to decrease the
pressure, generated by the curved droplet inter-
Fig. 3.13: CFD-Simulation (right column) and
experimental data (left column) of self-synchronized
1:1 droplet fusion at a Y-junction with integrated
bypass. Two sequences of micro droplets
are transported each with constant flow rate to
the Y-junction. The droplet, which first arrives at
the stricture stops (Part B) and the carrier flow is
guided through the bypass until a droplet from the
opposite sequence arrives (Part C). Now droplet
fusion occures (Part D) and the coalesced volume
is ejected from the element.
MIKROSYSTEME / MICROSYSTEMS
Fig. 3.14: y-Shaped junction for self syncronized
droplet fusion of two generated sample streams
(above) and microfluidic device, consisting of the
element and a total of four injectors for sample
stream generation and postprocessing by dosing
operations (below).
face. By that way, segmented flow provides the
basics for the implementation of self-controlled
functional elements and their integration into
micro fluidic networks.
Actual development has been focused on a first
implementation of these concepts for the selfsynchronized
1:1 fusion of two segment sequences.
The functional node consists of a Y-shaped
junction, where each inlet is equipped with an
obstruction. The two inlet ports are connected by
a bypass. If one segment reaches the obstruction
it stops and the carrier flow is guided along the
bypass to the second inlet of the Y-junction. It
remains at the obstruction until a second droplet
from the opposite channel reaches the junction.
After this, fusion occurs followed by ejection of
the formed droplet.
Microfluidic devices for investigation of the fusion
process have been developed and fabricated.
LabOnChip based system for identification
of cancer cells
(J. Felbel, M. Urban, M. Kielpinski, G. Mayer,
T. Henkel)
Main aim of the collaboration between health professionals,
molecular biologists and micro system
experts is the development of a LabOnChip based
analysis system permitting the partly automated
execution of micro flow-through-RT-PCR for the
detection and counting of cancer cells in samples
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