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micro-fluidics
Microfluidic systems are often used because of the rapidity and low costs. They can be embedded in online monitoring systems very easily, with a minimum on consumed substances. Such systems are made of glass, silicon, ceramic or polymers.
The chip can be designed in a serial structure out of: Inlets, micro mixer, detection windows, delays and an outlet. It is possible to optimize the settings for one application.
The volume of the micro mixer is in the range from few nl to some µl. The function of this part is to mix two or more substances. Because of the small dimension, only a laminar flow is possible by a pressure drop of maximum 5 bar. So for the mixing process diffusion has to be used. Because of this injection, rotation, twist or the inertia of the fluids are applied as mixing principles (Figure 1).
Figure 1: CFD Simulations of different micro mixers which combine some mixing principles
For the characterization of the fluid behavior in the research group ANSYS CFX a modern CFD (computational fluid dynamics) Software is appropriated. This allows a construction of micro fluidic systems without the need of prototypes.
For the chemical Industry it is necessary to know the parameter of a chemical reaction, to have an optimum of conversion. Out of this, with the Cetoni GmbH we developed a system to measuring reaction kinetics (Figure 2).
Figure 2: Photo (left) and a schematic drawing (right) of the measuring setup
In the system a mini-spectrometer and a micro fluidic chip (16mm x 12,5mm) are combined. The connection between the chip, pumps and mini-spectrometer or APD is ensured by a chip holder. The reaction kinetic is measured during the variety of the flow rates of the substances. So the delay time can be easily varied. In the next steps, a temperature control and new software will be developed.
PUMA
The pump concepts currently available are either not able to produce a continuous flow by volumetrical and pulsation-free
delivery or they are too expensive and difficult to process, for example the alternating application of syringe pumps.
The project PUMA (Pulsation-free pUmp for Microfluidic Analysis) is working on the development of pulsation-free micro pumps. Four different implementations of an innovative pump
concept are being developed. The basic concept of the delivery is based on the linear peristaltic pump. In version 1, 3 and 4, a specific
flow chart controls 5 actuators. These create a linear entrance and exit flow through internal compensation processes
. Version 2 is designed to stop the common problem of pulsation at peristaltic pumps through damping elements.
The single pumps will have a flow rate range between several µl/min and 100ml/min. The actuator of the pump chambers will be adapted to the flow rate.
Piezostacks will control the pump versions with the smallest flow rates. A replaceable pumpchip allows for the pump to adapt quickly
in case of medium changes. The pump versions with higher flow rates are controlled by a camshafts
actuator. This affects the pump chip (for flow rates up until 1ml/min) or the economical tube cassette (for flow rates up until 100ml/min).
The processing is done by our project partners HSG-IMIT for version 2 and the workgroup instrumental analysis of the university of applied sciences
in Jena for versions 1, 3 and 4. The industrial project partners are ModellTechnik Rapid Prototyping GmbH, with extensive experience in plastics
processing and production of prototypes, and cetoni GmbH as an established company in the area of microsystem technology and microfluidics.
For the implementation of the task the displacement behavior of the individual pump chambers will first be examined. In order to linearize the
behavior, a compensation graph will be created, as a base for the construction of the cam resp. piezo-electric control. By using the control
plan for 5 pump chambers the occurring pulsation will be compensated internally. The planned pump versions will allow adaptation in various
areas, like microreaction technology, medical technology, biotechnology and microbiology.
Aside from the project PUMA we have a wide range of pump technology. Piezoelectric membrane pumps, roller pumps, syringe pumps and
piston-driven diaphragm pumps are constantly being integrated into various experimental setups. The analysis of the pump characteristics,
ike pulsation, flow rate profile and delivery spectrum are an additional part our research and help find the right pump for the desired application.
Figure 3: left: multi-chamber pump with camshaft actor and changeable pumping chip
right: pump type with piezo-stack actor as possible part of an analysis setup
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