Magnetically Induced Drop Movement on Nanorough Micropatterned Nanocomposites

摘要

Here is presented a study of smart solid superhydrophobic magnetic surfaces, which show tunable wetting behavior by varying the geometrical arrangement of the surface roughness, and by applying an external magnetic field. In particular, hybrid organic/inorganic rough surfaces were developed by exploiting photo-lithographically tailored patterns of SU-8 polymer nanocomposites containing a small amount of colloidal nanoparticles of iron oxide, either mixed directly in the polymer matrix or casted on the surface by a spraying technique. The role of the nanoparticles has two aspects. The first one is to induce surface nanoscale roughness which can be enhanced upon their vertical alignment inside the matrix, and the second one is that after the UV photopatterning the resulting pillars are able to move upon the application of an external magnetic field. The resulting nanocomposite patterns exhibit higher hydrophobicity compared to the same pillars formed only with the SU-8. Moreover the actuation of these structures by the external magnetic field is able to drive the movement of water drops deposited on them towards specific directions. For the further modification of these smart surfaces it is applied on the final surface a coating of superhydrophobic polytetrafluoroethylene (PTFE) particles with the spraying technique, enhancing thus the already existing roughness. This results in the increase of the superhydrophobicity of the nanomposite system, giving thus the possibility for easier drop movement.