In situ surface reaction induced adhesion force change for mobility control, droplet sorting and bio-detection

Abstract

Water droplet mobility can be reversibly controlled based on surface grafted stimuli-responsive polymer brushes by in situ liquid–solid interface chemical reactions. By regulating the pH of a droplet in situ, the real-time dynamic tuning of the chain conformation between the swollen state (hydrophilic) and collapsed state (hydrophobic) can be realized, and the hydrophobic PFOTS background results in the in situ droplets mobility control. Droplet sorting can also be realized by smart stimuli-responsive surfaces due to the different pHs of the droplets. Based on a similar mechanism, protein detection between antibodies and antigens can be realized by immobilizing biotin ligands on a hydrophobic PFTEOS background using probing liquids with or without streptavidin. These methods possess potential applications in microfluidics, micro-reactors and bio-detection.