Electrospray deposition (ESD) can produce monodisperse generations of droplets down to hundreds of nanometers in diameter by applying high voltage to liquids flowing through capillaries. This deposition method has been combined with insulated stencil masks for fabricating micro patterns by spraying nanoparticles, polymers, or biomaterials. To optimize the fabrication process for micro coatings, a self-limiting electrospray deposition (SLED) method has recently been developed. Here we combine SLED with a pre-existing polymer film to study the fundamental behavior of this process in a bilayer geometry. SLED has been observed when insulating materials are sprayed onto conductive substrates. A thickness-limited film will occur when charge accumulates and repels the arrival of additional charged droplets. In this study, polystyrene (PS) and Parylene C thin films of varying thicknesses are utilized as insulated spraying substrates. Polyvinypyrrolidone (PVP), a thermoplastic polymer is sprayed below its glass transition temperature (T<sub>g</sub>) to investigate the SLED behavior on the pre-deposited insulating films. Moreover, to examine the effects of in-plane confinement on the spray, a microhole array patterned onto the PS thin film by focused laser spike (FLaSk) dewetting was sprayed with PVP in the SLED mode. The results show that the coating thickness of SLED can be adjusted by the thickness of pre-deposited thin films, and that the selection of polymer coating, in particular the electrical conductivity of the coating, can change the magnitude of this effect. The use of near-field stencil created by dewetting is shown to increase the thickness of the spray due to charge lensing, coupling the thickness of the SLED coating to the shape of the mask. Both methods allow for the greyscale templating of the hierarchical microcoatings deposited by SLED.

Self-limiting electrospray deposition on polymer masks

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.