Robust, Flexible Superhydrophobic Films from a Simple Solvent-Free Process under Ambient Conditions

A. Davis, I.S. Bayer, E. Loth
Italian Institute of Technology, IT

Keywords: robust superhydrophobicity, nanostructured surface, flame treatment, water jets

Summary:

Robustness of superhydrophobic films has attracted considerable attention recently due to increasing interest from various industries towards applications. Robustness usually refers to good substrate adhesion; scratch resistance, thermal and solvent resistance as well as underwater saturation resistance or resistance against impacting water sprays and streams. Here, we report fabrication and characterization of flexible free-standing superhydrophobic materials using a simple, solvent free process under ambient conditions which display remarkable resistance to impacting water jet streams. In the fabrication process, initially, sub-micrometer hydrophobic polymer particles were deposited on micro-rough surfaces by friction induced rubbing process. The deposited particle layer was subsequently treated with a small diffusion flame which melted the polymer and simultaneously deposited alpha-carbon nanoparticles. Deposited carbon nanoparticles were found to have strong adhesion to the polymer layer preserving their nano-structured morphology. Resistance to impacting jets was measured by placing the films under water streams with varying back pressures for different time intervals. Conditions under which loss of superhydrophobicity were observed were studied in detail by contact angle measurements and electron microscopy. The process is simple, inexpensive and can be applied to various substrates as long as proper surface micro-roughness exists and the surfaces can hold electrostatic charges.