Thermoplastics for Microfluidic Chips
Polymers for Microfluidic Applications offer a broad range of attractive properties and have thus been considered for Lab-on-a-Chip systems since the late 90’s.
Common thermoplastics such as polyethylene (PE), polystyrene (PS), polyethylene terephtalate (PET), polypropylene (PP), polycarbonate (PC) or cyclic olefin (co)polymers (COC/COP) are widely available as monolayer foils.
Polymers consist of single macromolecules that are iteratively linked to each other forming constituting long chains. These chains are arranged in linear or branched fashion in the polymer matrix.
Knowledge on the temperature behaviour is important for polymer processing. Heating a polymer matrix induces energy that leads to breakage of secondary valences between adjacent polymer chains. Above certain temperature, these chains are free to slide along each other resulting in higher chain mobility and thus elasticity. The temperature required to soften the material is called glass transition temperature Tg.
Thermoplastics are a highly attractive substrate material for microfluidics systems, with important benefits in the development of low cost disposable devices for a host of bioanalytical applications.
Thermoplastics are a class of synthetic polymers which exhibit softening behavior above a characteristic glass transition temperature (Tg) resulting from a long-range motion of the polymer backbone, while returning to their original chemical state upon cooling. Thermoplastic polymers differ from elastomer or thermoset plastics by their ability to be softened or fully melted and reshaped upon heating, while remaining chemically and dimensionally stable over a wide range of operational temperatures and pressures.
More recently cyclic olefins (COC and COP) have emerged as highly attractive microfluidic materials, with high optical clarity into the deep-UV range (~250 nm), low water absorption, and exceptionally good resistance to solvents including organics such as acetonitrile commonly used in liquid chromatography.