The Precision Pressure Control System P2CS is designed for precise and artefact-free fluid flow in μ-channels and capillaries. The goal is to provide an unparalleled precise control over flow rates and pressures to increase the quality of your measurements.
It achieves fastest and best possible flow control in microfluidics limited only by physical laws. Gentle and ultra constant flow rates (low pressure) do preserve fragile polymers of biological structures in the channels, fast flow rates (high pressure) are used to rapidly exchange fluids and remove dust and air bubbles.
Continuous transition from negative to positive pressures allow e. g. oscillatory flow.
The P2CS is the most compact and lightweight system on the market. It is easy to handle, thus permitting you to put your focus on your research.
ADVANTAGES OF THE SYSTEM
Ø Compact and rugged design. Simple to use.
Ø No contact with fluids, no contamination, no cleaning is required. All liquids reside externally on-chip
Ø Pressure range covers negative and positive pressures from ±1 mbar up to 2 bars. A high pressure and low pressure sensor provide high precision and robustness
Ø Resolution down to 1 μbar which corresponds to a water column of 10 μm
Ø Open control interface protocol allows control with LabVIEW, Matlab, VisualBasic and many others (RS232, TCP/IP, USB2, Bluetooth), source code is provided
Ø Optimum of precision and speed
SOME APPLICATIONS
Ø Dynamic perfusion during experiment (e.g. in electrophysiology)
Ø Stimulation of immune responses or signalling pathways or shear flow
Ø Pressure driven actuation of membranes and molecules
Ø Shear flow assays (cardiomyocytes)
Ø Polymer and nanotube orientation
What are the advantages compared to other systems?
The P2CS is the most advanced pressure controller for microsystems and it is not much more expensive (most extended version) or even cheaper.
Check it on your own: Our system is equipped with positive and negative pressures in each channel as standard and we could significantly improve the control response by our new control method.
The pressure range of the extended version covers 6 orders of magnitude which is unique on the market. This allows totally new experiments. Maybe the power of the additional assets becomes not clear right now and you may prefer to save money.
Once working with the system, the convenience to have the option to apply a high pressure flush in all channels for cleaning or purging without chip removal or interruption of the experiment will be mostly satisfactory.
You have the option to upgrade the system, of course.
Why is your system not much more expensive than the competitors system?
As we build and program all parts in house or with our long-term partners we do not depend on the price policy of external suppliers of modules.
Our systems are very flexible and can be reassembled to new systems and modified to your requirements without rebuilding everything and without waiting a long time for the sub contractors.
This allows us to give you more and faster for a competitive price.
Why are response, rise and falling times so important?
fast reaction of the system results in a more stable and constant flow as small perturbations are compensated more swiftly.
For example FACS, if you want to sweep cells through the channel, stop them in the focus of the observing microscope, take measurements and remove them and inject the next cell.
You strongly accelerate the screening with high and low pressures.
How can I characterize the transients of a dynamic system properly?
Why is it arbitrary/not correct to characterize the system with the settling time?
If you wish to change the flow speed you want to know how long this may take before the new value becomes „stable“. What does „stable“ mean?
Maybe, once the measured value equals the desired value for the first or second time? This can easily be realized by tuning the system to be too „nervous“, i.e. with tendency to overshoot.
What is settling time?
Click here to find a good explanation on this very instructive wikipedia page
This may be good for the sales manager but overshoots may perturb your experiment significantly.
Furthermore, the settling time depends strongly on the tuning of the control loop and it is therefore quite arbitrary.
The engineer may tune the settling time to any value when disregarding the overshoot dynamics.
The ideal case would be that the observed quantity rises swiftly but smoothly until it reaches the new value and settles there. We could realize that with the P2CS. Therefore we claim that the dynamics of the P2CS relies uniquely on quantities as the compressibility of materials and air and the dead volumes of the valves and manifolds. Otherwise the system is optimal limited only by physical laws (causality).
Now the problem is how to characterize the transition time in a well defined manner: theoretically speaking the settling time is infinite in this case and of no use.
The solution is to characterize the system with the rise and fall time (see the next FAQ).
How do we use rise/fall times to characterize the transient dynamics of the P2CS?
First: What is rise and fall time?
Click here to find a good explanation on this very instructive wikipedia page
The P2CS lacks any overshoot and the flow increases/decreases until it reaches the desired value. Therefore we cannot define an error band.
The rise/fall time, however, gives the delay between 10% and 90% of the pressure and flow speed difference. These values are fixed by convention.
In physics 1/e is often used to characterize the time scale for the exponential approach to the final value.
This time period can be obtained from the 10%-90% time perriod, or shortly 10%-value by t1/e = t10% / ln(10) (The numerical value of ln(10) ~2.3).
What does overshooting mean?
In conventional designs being on the market you observe a damped oscillation before the object stabilizes its position in the microscopy image.
This is a consequence of the classical control method called „PID“ (For more information about PID check this very instructive wikipedia page) and non-linear response function of the system.
If you choose the PID-parameters too tight, overshoots appear. This is similar to a harmonic oscillator with a too small damping constant.
If choosing the parameters so that the overshoot disappears, the system’s settling time becomes much more slowly – no choice to get around this limitation – its the law of physics!
Therefore we developed a new control method, which removes such artifacts and improves strongly the response time, for rising as well as falling edges.
As physicist I can say that this method presents the best possible allowed by hard physical laws (there is a hard limit because of a kind of uncertainty principle very similar to quantum mechanics).
You will be surprised of the result because it gives a feeling as if you pushed the cells with your own fingers directly.
Why do I need two pressure levels?
You need it
· if you want to have a very fine control an stop objects (e.g. cells or molecules) and at the next moment remove them fast and get the next object, or,
· if you want to study the effect of shear flow over a flow range of 6 orders of magnitude
· if you are working with small channels of very different lengths or sizes
· if you mix large and very small channels (meso- and microfluidics)
· if you need to remove debris of dead cells or dust from your channel and you do not want to remove the chip from the set-up