Microfluidics Chips How It is Made

Microfluidic chips are the devices used in microfluidics in which a micro-channels network has been molded 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 (cell culture, organ-on-a-chip, DNA analysis etc.)

Microfluidic devices such as chips have many advantages as they can decrease your sample and reagent consumption and increase automation, thus minimizing your analysis time2. Such devices allow applications in many areas such as medicine, biology, chemistry and physics3. 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.

For some experiments, a combination of these three materials will be needed to create the desired microfluidic chip:

MICROFLUIDIC CHIPS 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 opacity2, 4.

MICROFLUIDIC CHIPS IN GLASS Glass shares with silicon the same advantages mentioned above. Its well-defined surface chemistries, superior optical transparency and excellent high-pressure resistance2,4 make it a material of choice for many applications. Glass is also biocompatible, chemically inert, hydrophilic and allows efficient coatings. The main hurdle with this material remains its rather high cost, even though prices have been significantly reduced.

MICROFLUIDIC CHIPS IN POLYMERS Polymers offer an attractive alternative to glass and silicon as they are cheaper, robust and require faster fabrication processes4. 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).

PDMS is the material of choice for fast prototyping microfluidic devices. PDMS chips are commonly used in laboratories, especially in the academic community due to their low cost and ease of fabrication. Here are listed main advantages of such chips: Oxygen and gas permeability Optical transparency, robustness Non toxicity Biocompatibility

One of the main drawbacks of PDMS chips is its hydrophobicity. Consequently, introducing aqueous solutions into the microchannels is difficult and hydrophobic analytes can adsorb onto the PDMS surface, thus interfering with analysis. There are now PDMS surface modification methods such as gas phase processing methods and wet chemical methods (or combination of both) to avoid issues due to hydrophobicity2. Another main issue of PDMS chips is that they are non-suitable for high pressure operation as it can alter channels geometry4.