Flocculated carbon nanotube composites for solvent resistant soft templated microfeatures

The swelling of a commercial thiol-ene adhesive and surfactant dispersed single wall carbon nanotubes (swCNTs) nanocomposites is investigated in a variety of organic solvents. These nanocomposites can be used to form well-defined microstructures via soft lithography. swCNTs are flocculated in suspension using a novel surfactant based on poly(fluorooxetane-block-polyethylene oxide-block-fluorooxetane); this procedure yields a loose floc, where the hydrophobic end blocks effectively create inter-tube bridges to provide a swCNT network structure in the thiol-ene prior to curing. Microfeatures (0.5 μm posts) fabricated in the thiol-ene and its composite using soft templating demonstrate similar fidelity in the pattern transfer. A significant decrease in the swelling by organic solvents occurs upon the incorporation of swCNTs (18.3%-1.6% for toluene at 1 wt%). Both mechanical reinforcement by the swCNT network and reduced swelling results in stable microfeatures after exposure to toluene for 24 h, while the neat cured thiol-ene microstructure is significantly deformed. These nanocomposites appear promising alternatives to glass for enabling organic syntheses in microfluidic devices due to their structural integrity when exposed to solvents.