Targeted functional methylcellulose-nanocomposite materials via self-limiting electrospray deposition

Electrospray deposition (ESD) uses strong electric fields to produce monodisperse droplets from solutions that are driven towards grounded targets. Self-limiting electrospray deposition (SLED) is a regime of ESD that achieves targeted coatings by spraying insulating polymers below their glass transition temperatures, with sprayed material trapping charge and repelling incoming spray. Methylcellulose (MC) has been demonstrated as SLED compatible and uniquely forms nanowire morphologies when sprayed. Here, it is hypothesized that these nanowires can be used to prevent electrical percolation in sprays of conductive particles and allow for highly controlled deposition. However, it was also observed that nanoparticle size and shape impact nanowire morphology, which complicates this interaction. For this study, we use 2D Ti3C2 MXene of two different sizes as well as spherical ITO in MC composite sprays. To quantify material spread, photolithography patterned chips, with gratings of varying widths and spacings were designed and sprayed with varying particle concentration, and the resulting feature sizes were measured by optical microscopy. Scanning electron microscopy shows these deposited materials are able to maintain unique low-density morphologies. Informed by these studies, MXene containing spray was used to functionalize interdigitated electrodes with features and spacings as low as 50 microns and a substantial increase in capacitance was measured.