Fabrication of smart COC chips: Advantages of N-vinylpyrrolidone (NVP) monomer over other hydrophilic monomers

This paper presents a comparative study on surface modification of cyclic olefin copolymer (COC) through UV-photografting with acrylic acid (AAc), acrylamide (AAm), 2-hydroxyethyl methacrylate (HEMA) and N-vinylpyrrolidone (NVP) monomers with the aim to identify the most suitable process for the development of smart capillary electrophoresis LOC devices with excellent biocompatible channel surfaces. It was noticed that all the surface treatments enable to generate extremely high thermal bond strength at temperatures well below the glass transition temperature (Tg) of the COC polymer, ensured that the dimensions of the microchannels in the chip remains unaltered after thermal sealing. However, the NVP grafted substrates exhibits the highest bonding strength which is about 203% higher than that of the untreated sample. The contact angle measurement indicates that the NVP grafted surfaces have the highest surface wettability than that of AAc, AAm and HEMA modified surfaces. UV–vis spectroscopy measurement reveals that of the four modified surfaces the NVP grafted COC shows the highest optical clarity. The in vitro platelet adhesion and protein adsorption experiment indicates that the NVP grafted substrates are extremely biocompatible. These results clearly demonstrate that the UV-photografting using NVP is indeed a promising surface modification technique for constructing COC capillary electrophoretic chips for protein and peptide separation.