A Brief Thing to Know About Microfluidic Chips

A microfluidic chip is a set of micro-channels etched or molded into a material (glass, silicon or polymer such as PDMS, for PolyDimethylSiloxane). The micro-channels forming the microfluidic chip are connected together in order to achieve the desired features (mix, pump, sort, control bio-chemical environment).

This network of micro-channels trapped into the microfluidic chip is connected to the outside by inputs and outputs pierced through the chip, as an interface between the macro- and micro-world.

It is through these holes that the liquids (or gas) are injected and removed from the microfluidic chip (through tubing, syringe adapters or even simple holes in the chip) with external active systems (pressure controller, push-syringe or peristatic pump) or passive ways (e.g. hydrostatic pressure). If searchers can now choose between a full set of materials to build his microfluidic chips, one must consider that, initially, the fabrication process of a microfluidic chip was based on photolithographic methods, derived from the well-developped semiconductor industry.

The use of diverse materials for microfluidics chips such as polymers (e.g. PDMS), ceramics (e.g. glass), semi-conductors (e.g. silicon) and metal is currently possible because of the development of specific processes: deposition and electrodeposition, etching, bonding, injection molding, embossing and soft lithography (especially with PDMS).

Accessing these materials makes possible to design microfluidic chips with new features like specific optical characteristics, biological or chemical compatibility, faster prototyping or lower production costs, possibility of electrosensing, etc… The final choice depends on the aimed application.

Nowadays, a lot of searchers use PDMS and soft-lithography due to their easiness and fast process. They allow searchers to rapidly build prototypes and test their applications/setups, instead of wasting time in laborious fabrication protocols. Contrary to common beliefs, soft-lithography does not require hundreds of square meters of clean room space. Indeed, a little bench space under a lab fume hood is sufficient to place essential rapid PDMS prototyping instruments to quickly assess microfluidic concepts and obtain publishable results.