Fig. 2. Reversible physical bonding of the PDMS microfluidic chip and APTES-silanized glass substrate.

a The mechanism of the bonding occurs through silicon alkoxides (Si–O⁻) and protonated nitrogens (–N${\mathrm{H}}_3^{+}$) at room temperature and under atmospheric pressure. This creates firm PDMS-to-glass attachment via NH–O hydrogen bonds. b After microfluidic device assembly, linker chemistry steps involving the reaction of amine (–NH₂) groups with a modular crosslinker BMPS were used to covalently immobilize antibodies on the device glass surface. c The fluorescence micrograph of the green area within the microfluidic channel indicates that anti-EpCAM antibodies have been successfully immobilized with high density and the desired orientation (activity). The accessibility of the antigen-binding sites of anti-EpCAM antibodies was evaluated by labeling them with NHS-fluorescein