Which components do you need to set up the MicCell™ system?
- An inverted fluorescence microscope that is not included in the shipment
- A mechanical support for the PDMS channel layer that is placed above the microscope objective
- A MicCell Channel Plate that contains the microchannel and that is located under the MicCell lid. The microchannel is capped by a coverslip. You can obtain either a ready-made channel plate from GeSiM (including lid) or you mold it in our casting station.
- An adapter ("working plate") that connects the support (with the flow cell/channel plate) with the microscope
- A module ("fluid processor") containing all active components of the external fluidic system (syringe pumps, distribution valves), plus reservoirs and tubes ®
- A Windows control software for both the interactive and the programmable control of all active elements
- Optional: hydrogel microvalves for automated sample injection
Some customers do not use a computer-controlled external fluidic system, but manual syringes or their own syringe pumps. In this case, however, you will not have access to the flexibility and ease of use of the GeSiM fluidics and must develop your own peripheral system.
What type of microscope is recommended?
We usually design our systems for the Axiovert 200M from Zeiss, but we can build adapters for virtually every microscope (Leica, Olympus, and others), with both inverted and standard optics.
Is it possible to use the MicCell™ platform without an inverted microscope?
Yes, but then you miss all the advantages of the current high-performance microscopy, such as automatic image analysis, and so you must resort to other detection methods, e.g., a stereo microscope with CCD camera or electrochemical detection using microelectrodes (for the recording of electrically active cells, for instance). Design changes can be provided to a certain degree; please inquire.
Which type of external pumps and valves are used in the MicCell™ and what are their properties?
Plug-in modules of syringe pumps and distribution valves from Tecan Systems (Cavro) are built into a special housing with a single RS 232 interface for all modules. The minimal addressable volume of the pump is 10 nanoliters and the pumps can address up to 24000 steps in a maximum period of 20 min. GeSiM can deliver a two-pump module for continuous fluid delivery. The available 4/1 or 6/1-port distribution valves (one channel in/four or six out, or vice versa) allow the automatic switching of liquids. Pump(s) + valves + hydrogel valve controller make up the so-called "fluid processor."
Which materials get in contact with the sample?
Glass, PTFE (Teflon), PEEK, and PDMS. If PDMS monomers are a problem (e.g., for the activity of proteins), the PDMS layer must be soaked in buffer for a prolonged period.
When does the use of PDMS make sense or no sense?
PDMS is an ideal material, as it is chemically inert and soft enough to seal any channel efficiently. It is, however, permeable for small molecules such as alcohol or oxygen. So if oxygen must be kept away from your sample (e.g., to avoid oxidative photodamage), a glass flow cell with polymer walls should be used instead.
The PDMS channel plate is the heart of the MicCell™. Can GeSiM fabricate it in large quantities?
Yes, the production of hundreds of units per month is possible, if the user does not want to cast it himself/herself.
How can the MicCell™ be adapted to a new application? How long does it take?
In most cases, only the channel configuration will change, but not the support (i.e., the holder), not the external fluidics, and not the interface to the external tube system. So we usually only need to manufacture a new silicon master to mold the PDMS channel plate, which takes about six weeks. If we must redesign the coverslip or the support plate, add microelectrodes, or rewrite the control software (all of which can be done), such changes may require ten weeks.
Can GeSiM deliver special coverslips, e.g., ones with metal electrodes?
Yes, 150 μm to 1 mm thick, rectangular coverslips of almost any size can be shipped. GeSiM can pre-structure the coverslip surface, if needed. We can manufacture customized microelectrodes of almost any material, but recommend to use platinum, gold, or the transparent ITO (indium tin oxide). To insulate all parts except the electrode pads, plasma deposition of silicon oxide (SiO2) or silicon nitride (Si3N4) is possible. The minimum size of a single electrode is 5 μm. GeSiM has found a way to contact the coverslip reversibly and can also fabricate systems in which both the top and the bottom of the microchannel contain microelectrodes. In this case, however, the channel layer cannot be made of PDMS, but consists of a glass plate with polymer channel walls.
Is the MicCellTM restricted to coverslips of standard size (22x22 mm)?
No, we offer a solution for a size of 22x50 mm whose default setup contains 10 fluid connections, among others.
Is it possible to introduce tiny volumes (microliters) of sample with almost no dead volume into the channel system?
Yes, the GeSiM hydrogel microinjector was designed to do exactly this. Here a standard fitting with a built-in hydrogel valve is directly attached to the MicCell. Hydrogels can also be integrated into the microsystem, if needed.
Can a hydrogel valve open slowly or can the switching behavior be influenced by a slow temperature ramp?
No, there is a single defined phase transition temperature. When it is reached, the microvalve switches instantaneously, without intermediate state.
What other accessories can be built into the MicCellTM?
- Integrated flow and pressure sensors
- Temperature control: heating and cooling by integrated or external devices, with sensing,
- Microelectrodes of all kind (multielectrode arrays, dielectrophoretic control, impedance sensor)
Can one observe intransparent objects in the MicCellTM under an inverted microscope?
Yes, we have designed a MicCell with integrated sample carrier, which is a movable holder that allows to move a 2.5x2.5 mm chip into the fluidic channel. As sample and sample carrier are opaque, the object must be illuminated from the objective side along the optical path. The specimen can be turned at full 360° around the optical axis of the microscope.
Is the system expensive?
It is at least much cheaper than an inverted microscope. The naked flow cell consisting of MicCell support, working plate (adapter), and flow channel will be around 1000 €. If you let us make the PDMS channel plate, it costs less than 100 € (including a recycled PMMA lid) and can be reused several times. Apart from this, you need only new coverslips, i.e. the total cost of ownership will be low. A complete external fluid processor for an automatic liquid handling, including control software, can be obtained from ca. 7500 €, a hydrogel valve costs around 600 €.