What is Microfluidics?
Manipulating and controlling fluids
Microfluidics is the science and technology of manipulating and controlling fluids, usually in the range of micro liters (10-6) to pico liters (10-12), in networks of channels with lowest dimensions from ten to hundred micrometers. This emerging discipline takes its origin in the early 1990s and has known a dramatic growth since then, partly due to the increasing popularity of microscale analytical chemistry techniques and the development of microelectronic technologies.
A very attractive technology
Microfluidics is a very attractive technology for both academic researchers and industrials since it considerably:
- Decreases sample and reagent consumptions
- Shortens time of experiments and doing so
- Reduces the overall costs of applications
Thanks to the low volume required, microfluidics represents a promising alternative to conventional laboratory techniques as it allows achieving complete laboratory protocols on a single chip of few square centimeters.
A specific design
Microfluidic chips are the devices used in microfluidics in which a micro-channels network has been modelled or patterned. Thanks to a various number of inlet and outlet ports, these microfluidic instruments allow your fluids to pass through different channels of different diameter, usually ranging from 5 to 500 µm1. The micro-channels network must be specifically designed for your application and the analyses you want to carry out.
Microfluidic devices such as chips have many advantages as they can decrease your sample and reagent consumption and increase automation, thus minimizing your analysis time. Such devices allow applications in many areas such as medicine, biology, chemistry and physics. Three types of materials are commonly used to create microfluidic chips: silicon, glass, and polymers. Each material has its specific chemical and physical characteristics. The choice of the material depends on the needs and conditions of your applications (type of solvant, samples, etc.), the design of the chip you want to obtain and your budget.
Microfluidic chip in silicon
Advantages of silicon are its superior thermal conductivity, surface stability and solvent compatibility. However no applications in optical detection can be done due to its optical opacity.
Microfluidic chip in glass
Glass shares with silicon the same advantages mentioned above. Its well-defined surface chemistries, superior optical transparency and excellent high-pressure resistance make it a material of choice for many applications. Glass is also biocompatible, chemically inert, and hydrophilic and allows efficient coatings. The main hurdle with this material remains its rather high cost, even though prices have been significantly reduced.
Microfluidic chip in polymers
Polymers offer an attractive alternative to glass and silicon as they are cheaper, robust and require faster fabrication processes. Many polymers can be used to build chips : Polystyrene (PS), Polycarbonate (PC), Polyvinyl chloride (PVC), Cyclic Olefin Copolymer (COC), Polymethyl methacrylate (PMMA) and Polydimethylsiloxane (PDMS).
Our microfluidic chip is designed in PDMS by Microfactory.
Microfactory is a spin-off from ESPCI, more specifically from the MMN Lab (Microfluidics, Microelectromechanical systems - MEMS and Nanostructures laboratory)
Our first goal in this game is to interact with the real world throw a computer game. The game is based on the movement of a bubble in a microfluidic system, then we add a virtual part to the microscope video and integrate our virtual game.
The bubble detection
First of all, we add to detect the bubble in the system, so we use the Hough circle detection algorithm to find it and return it position. We decided to use a microfluidic chip of 1,2x1,6 cm of size with 0,3 mm sized channels. The detection have to find the bubble of 0,3 mm diameter in a channel used as a circuit. To detect the bubble, the contrast between the bubble and the environment have to be sufficient to locate the bubble in the microscope image. So, we decided to use a transparent and blue environment to respect this contrast.
The game part
Once we have detected the bubble in the image, we have to integrate it into a game, the location of the bubble gives us a position in the image and a size, and the virtual part can be added to interact with the bubble. All the virtual part is construct like a game engine, we have the Game User Interface engine (GUI engine), the Graphical engine, the Physical engine, etc. The bubble has also its own virtual part to interact with the virtual world. As we said, the player has to move the bubble into the chip from a beginning point to the end of the circuit, and this circuit have a lot of virtual objects like lasers, checkpoints, etc. The player have to interact with the bubble to dodge the lasers, and if he touch one off them, the game detect a collision between the bubble detected with our Hough circle detection and the virtual laser. That’s how we interact between the real world and our virtual world.
3D printing the Bio-Console
In order to transport and move properly and safely our Bio-Console we decided to 3D print a Bio-Console container box. This box is designed by sketchup exclusively for the Bio-Console in ABS. Using this technology, we managed to print this box in twice 12h of printing: 12h for each part of the box. Indeed, the 3D printer could'nt print the box in one time, because the container dimension was to big for the printer. As a result, we had to design the box in two parts.
Going further about microfluidics
Microfluidic properties and notions
As the dimensions of the microfluidic devices are reduced, some physics characteristics are different compared to conventional laboratory-scale assay.
For these reasons, dedicated microfluidic instruments have been developed to precisely control fluids (liquids or gas) inside microchannels. Some of these systems can be used directly inside the chip (electrodes, valves, etc) while some others are used as external actuators or accessories such as flow controllers (pressure pumps, syringe pumps, peristaltic pump, etc) or external valves.
Electrical analogy and Ohm's law
Microfluidic flows are characterized by the prevalence of the viscosity effects compared to inertia. From a physics point of view, this behavior is pointed out by a low Reynolds number. It leads to a drastic simplification of the complex Navier-Stokes equations describing fluid mechanics. Thus, a very simple equation linking:
- Mean flow-rate
- Microfluidic resistance can be deduced based on the electrical analogy (Ohm’s law)
Microfluidic Flow Control System (MFCS TM-EZ)
The MFCS-EZ is a unique pressure-based flow controller for micro-fluidics and nano-fluidics applications.
- Easy to install and use
- Easy to automate
- Fast and stable
- Field proven technology
- The best service at critical times
Current microfluidic control systems such as syringe, peristaltic or piston pumps are poorly adapted to the manipulation of fluid volumes in the nanoliter range, leading to long equilibration times, irreproducibility and pulsing.
To solve this problem, FLUIGENT has developed the patented FASTABTM technology: a pressure driven technology including an advanced feedback control algorithm with no mechanical part involved. These specificities enable a pulseless flow as well as a greater responsiveness.
Based on the FASTABTM technology, our MFCSTM (Microfluidic Flow Control Systems) series are compatible with any microfluidic application.