How does it work?
Microfluidic channel carriers can become expensive and complicated. On the other hand, microfluidic chips are sensitive and just for single use. E.g. diagnostic stuff for routine use typically features hot embossed microplastics, a procedure which initially requires expensive casting machines and layout specific casting tools.
For R/D purposes the MicCell combines an affordable casting process using PDMS and a convenient mechanical setup for quick replacement of the used PDMS channel plate. The mechanical frame of the MicCell fits on standard microscope stages.
Core of the MicCell is an optical transparent PDMS (Polydimethylsiloxane) chip with a user specific microfluidic channel layout. It is accomplished by “channel spacers” for fluidic interconnections and calottes/ polycarbonate frames for mechanical adaptation to standard microscope systems.
The disposable PDMS chip can be done by the customer using the included casting set. It is easily replacable, therefore microfluidic experiments can be done at affordable costs.
Standard sizes for the PDMS channel plate are:
- 22 x 22 mm
- 22 x 50 mm
- 25 x 75 mm
The PDMS channel plate goes in between the Polycarbonate carrier and the calotte and gets sealed by a standard glass lid. Glass lids wih electrode structures on the inner side are available on request.
On top of all, the MicCell channel plate carrier can be completed with other microfluidic parts, tubes, filters, bottles, syringe systems and an operation software. Move on to Options for more information.
The flyer on the right side provides an overview of the MicCell system. The catalogue reveals technical specs and all accessories along with ordering information.
How to make the PDMS Channel Plate
The casting set mainly comprises the casting station, Polycarbonate carriers, liquid PDMS and syringes. In addition, you will need a “Master Chip” introducing your particular channel layout.
The master chip is made from Teflon coated silicon and made at GeSiM on request. Basically we accept any layout provided by a CAD drawing; a set of typical channel layouts is on the shelf. Please ask.
The Hydrogel Valve – Properties and Function
To add liquid, to start and stop reactions, a dead volume free microvalve (GeSiM patent) can be placed into the flow system.
The valve is made from a silicon chip but comes with different housings for convenient handling. Most popular version is called “HG-7″, based on a PEEK-housing with 1/16” fitting.
The valve chip incorporates a small but well defined amount of a hydrogel immobilized in a liquid transparent chamber. The surrounding heater controls the temperature of the chamber in a limited range around the swelling temperature of the hydrogel.
For operation of the valve nothing but 250 mW power is required. The Fluid Processor provides full control of the device.
The sample liquid gets in contact with the enclosed hydrogel. Therefore the valve is mainly made for aqueous solutions but tolerates <15 % methanol, acetone.
Measurement of Tiny Flows
The GeSiM flow sensors has been designed for flow rates in the range of 0…100 Microliters per minute. It is a thermocalorimetric sensor measuring the heat transfer in a very tiny chamber. The fluid sample is negligibly heated whereas the surroundig temperature distribution is monitored.
As larger the heat transport through the chamber as more precisely the measurement result will be. In other terms, as more time is allowed for a single measurement as better the accuracy.
The sensor can be used along with the MicCell Fluid Processor (See next article) but is available for standalone operation too. The sensor is cascadable, it allows to measure several independent fluid flows simultaneously. Up to four stacked sensors can be managed by a single controller. The controller connects to a PC through serial interface, a dedicated software displays the measurement result.
Please download the flyer (right) for more information.
Controlling of Complex Setups
The GeSiM Fluidprocessor is a racked unit combining several types of valves and syringe pumps. It is usually built to a particular application.
In addition, a Windows based software (“MicCell-Software”) is available for controlling
- Hydrogel Valves
- Piezoelectric Dispensers
- Flow Sensors
The MicCell System gained much attention from researchers world wide. Here we present a list of applications already done. Please contact us for further details.
- Micro-reaction technology, e.g., hybridization or stoppedflow chamber, using fluorescence detection
- Immobilization of biomolecules (e.g., protein or DNA) in the microchannels before assembly, e.g., by microarraying
- Generation of concentration gradients perpendicular to the microchannel cross section by a “gradient mixer”
- Semi-automatic drug screening using adherent cells or tissue slices
- Viability tests and other cell-based physiological assays
- Measurement of the interaction of cells with immobilized proteins, DNA, RNA, oligo- or polysaccharides, lipids, and other ligands
- Cell handling and sorting using optical tweezers
- Identification of cancer or stem cells using an “optical stretcher” (patent University of Leipzig)
- Electroporation in the flow
- Testing of the uniformity of microbeads and other particles, potentially with sorting
- Manipulation of elongated macromolecules (e.g., DNA or motor proteins) in hydrodynamic flow fields for the bottom-up construction of nanostructures, force measurements, etc.
- Micro-capillary electrophoresis under the microscope
- Integration of, e.g., column or filtration material for micro-purifying with or without microscope control
- Liquid processing independent of a microscope (e.g., assays using electrochemical detection)
Chemical synthesis on the nanoscale
- Observation of opaque objects in the MicCell using the pivotable sample carrier
Primary Cell Adhesion and Biofilm Formation on Anti-(bio)fouling Surfaces
In order to exploit the potential of biofilms or minimize the risk of their formation it is important to study and characterize them. To meet these aims the biomonitoring group of the Institute of Food Technology and Bioprocess Engineering at TU Dresden has established a modular flow cell system with a parallel plate flow chamber. It is based on GeSiM’s MicCell and offers possibilities to study biofilms on opaque surfaces in continuous flows under a fluorescence microscope.
The centrepiece of the flow chamber is a microfluidic chip, consisting of a glass slide, a fluidic layer and the substrate. The fluidic layer is made from a polymer 3D printed on the glass slide and both its thickness and shape can be modified.
Recently an innovative sample holder was designed. It is made of stainless steel with holes to ensure liquid flow across the sample surface. The advantage of this setup is that samples with various geometries can be examined with no need for drilling before analyses. Hence the flow cell can be easily and rapidly adapted to meet different requirements.
Furthermore, due to the laminar flow inside the microfluidic channel, conditions can be tightly controlled, and we can regulate variables such as oxygen and nutrient levels simply by varying the medium supply.
We use the flow chamber to study the adhesion behaviour of microorganisms and the first stages of biofilm formation on various materials. The acquired data are used to characterize the local and time-related biofilm formation and to derive parameters like growth rate, biofilm height and biomass volume.
Technische Universität Dresden
Faculty of Mechanical Science and Engineering
Institute for Food Technology and Bioprocess Engineering
Chair of Bioprocess Engineering, Prof. Th. Bley
Biomonitoring Group, Assoc. Prof. E. Boschke, Dipl.-Ing. S. Mulansky