Thermoplastic polymers are commonly used for manufacturing microfluidic biochips. However, proteins tend to adsorb to these materials, causing biofouling. Moreover, all common thermoplastics require hydrophilic surface modification to facilitate passive (capillary) flow of biological liquids through the chip. These problems can be overcome by applying a hydrophilic, antifouling coating to the channel surface.
An additional challenge is the compatibility of the coating process with the bonding of the top and bottom parts of the microfluidic chip. If the coating is applied before bonding, the bonding process may damage the coating, or the presence of the coating may affect the bond strength. And if bonding is done first, the coating must be applied in a closed microchannel, which is highly disadvantageous in terms of (scalable) manufacturability.