It has been shown that although silanization is an effective way to bond COC to PDMS, it is not generally applicable for COC-COC bonding . CVD polymerization of 4aminomethyl[2.2]paracyclophane and 4-formyl [2,2] paracyclophane approach introduced by Chen et al. could also be a potential way for chemical bonding of thermoplastic polymers 111 . The CVD treatment involved sublimation of the precursors in vacuum and condensation of the precursors on the substrates at 15 ℃. The induced poly(4-aminomethyl-p-xylylene)-co-(pxylylene) (polymer 1) and poly(4-formyl-p-xylylene-co-p-xylylene) (polymer 2) coatings on the two layers of the microfluidic device could covalently bind to each other through the reaction between the amine groups of polymer 1 and aldehyde groups of polymer 2. To accomplish the covalent bonding, the substrates were placed in touch at 140 ℃ for 3 h. Use of initiated chemical vapor deposition (iCVD) is another way for chemical bonding of polymers . iCVD is a solvent-free process where a monomer together with an initiator are simultaneously introduced to the substrate at gas phase. A heating filament is used in the chamber to thermally radicalize the initiator at 150-300 ℃ 112 . The radicals react with the adsorbed monomer on the cool substrate and initiate polymerization. As iCVD is solvent-free and the polymer is maintained at (15-40 ℃), the process does not generate delamination, swelling, shrinkage, or wrinkling on the membrane or sensitive polymers 112 . Im et al. employed this technique for chemical bonding of different polymers such as PDMS, PS petri dishes, PET, PC, and poly(tetrafluoro ethylene) (PTFE) 100 . In the proposed protocol, allylamine plasma treatment was done to create polyallylamine (PAAm) on one layer. Poly(glycidyl methacrylate) (PGMA) formed another layer via iCVD using tertbutyl peroxide as the initiator and glycidyl methacrylate as the monomer. Oxygen plasma treatment prior to the coatings promoted adhesion for polymers with low surface energies such as PTFE. After the coatings, the substrates were brought into contact under 0.1 bar pressure at 70 ℃. The layers could covalently bind owing to the ring opening reaction between the epoxy and amine terminates. iCVD method is also used in a work done by Xu et al. . Here, tert-Butyl peroxide was used as the initiator and 4-Aminostyrene (4-AS) as well as glycidyl methacrylate (GMA) as the monomers to create poly(glycidyl methacrylate) (PGMA) and poly(4-aminostyrene) (PAS) coatings, respectively. The process was applied on different substrates including PDMS, PC, PET, polyethylene (PE), polyacrylate (PA), and COC. Before iCVD, the substrates were oxygen plasma treated for better adhesion. PGMA and PAS films were polymerized on the flat and channelled layers, respectively. The layers could covalently bind without any need for high pressure or temperature. Moreover, the remaining functional groups inside the sealed channel could further be incorporated in covalent immobilization of biomolecules. They demonstrated this via the attachment of conjugated quantum dots via DCC chemistry (Figure ).