Aryl‐Diazonium Salts Offer a Rapid and Cost‐Efficient Method to Functionalize Plastic Microfluidic Devices for Increased Immunoaffinity Capture

Microfluidic devices have been used for decades to isolate cells, viruses, and proteins using on‐chip immunoaffinity capture using biotinylated antibodies, proteins, or aptamers. To accomplish this, the inner surface is modified to present binding moieties for the desired analyte. While this approach is successful in research settings, it is challenging to scale many surface modification strategies. Traditional polydimethylsiloxane (PDMS) devices can be effectively functionalized using silane‐based methods; however, it requires high labor hours, equipment, and hazardous chemicals. Manufacture of microfluidic devices using plastics, including cyclic olefin copolymer (COC), allows chips to be mass produced, but most functionalization methods used with PDMS are not compatible with plastic. Herein, this work demonstrates how to deposit biotin onto the surface of a plastic microfluidic chips using aryl‐diazonium. This method chemically bonds biotin to the surface, allowing for the addition of streptavidin nanoparticles to the surface. Nanoparticles increase the surface area of the chip and allow for proper capture moiety orientation. This process is faster, can be performed outside of a fume hood, is very cost‐effective using readily available laboratory equipment, and demonstrates higher rates of capture. Additionally, this method allows for more rapid and scalable production of devices, including for diagnostic testing.