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Abstract We establish a sample‐ and data‐processing pipeline that allows for high‐throughput optical microscope measurement of porous films, provided they are sufficiently optically scattering. Here, self‐limiting electrospray deposition (SLED) is used to manufacture scattering films of different morphologies. This technique compensates for the scattering of the films through background subtraction of the reflection image with the transmission image. This process is implemented through a combination of an ImageJ and MATLAB data pipeline; the Canny edge‐detector is used as the image‐processing algorithm to identify the boundaries of the film. This process is verified against manually measured images; a comparative study between cross‐sectional scanning electron microscopy (where scattering effects are diminished) and optical microscopy also verifies that our optical microscopy technique can be used to consistently, non‐destructively measure film thickness regardless of film morphology. In addition, this technique can be used in combination with dense film measurements to measure film porosity. 

Multilayer polymer films are extensively used in multiphase separation. Electrospray deposition (ESD) is an important technique for fabricating such films with tunable morphology. Viscoelastic properties of polystyrene (PS) nanoshell coatings produced by ESD on gold and spin‐coated PS surfaces are evaluated using Quartz Crystal Microbalance with Dissipation (QCM‐D). The thickness of PS films on gold increases with flow rate from ∼200 nm at 0.5 to ∼400 nm at 1.5 mL h^−1, accompanied by an order‐of‐magnitude increase in dissipation due to larger particle sizes from shorter droplet flight times. This effect is absent on spin–coated PS films, suggesting the onset of the self‐limiting effect of charges. Although the shear moduli for ESD films calculated from Voigt models is only 0.08%–0.20% of the bulk PS modulus, the stiffness ratio of spray‐coated PS to a single shell is (5.00–13.3) × 10^3  m^−1, due to shell–shell and shell–substrate interactions. These are novel results related to the interparticle friction obtained using QCM‐D for the first time. This work demonstrates  that mechanical properties of particulate viscoelastic films with potential applications in high surface area sensors, such as size‐selective membranes for protein or electrolyte adsorption, can be evaluated by QCM‐D with nanograms of material. 

Electrospray deposition (ESD) is employed to produce separator membranes for coin-cell lithium-ion batteries (LIBs) using off-the-shelf polyimide (PI). The PI coatings are deposited directly onto planar LiNi0.6Mn0.2Co0.2O2 (NMC) electrodes via self-limiting electrospray deposition (SLED). Scanning electron microscopy (SEM), optical microscopy, and spectroscopic microreflectometry are implemented in combination to evaluate the porosity, thickness, and morphology of sprayed PI films. Furthermore, ultraviolet-visual wavelength spectroscopy (UV vis) is utilized to qualitatively assess variation in film porosity within a temperature range of 20-400oC, to determine the stable temperature range of the separator. UV vis results underscore the ability of the SLED PI separator to maintain its porous microstructure up to ~350oC. Electrochemical performance of the PI separators is analyzed via charge/discharge cycle rate tests. Discharge capacities of the SLED PI separators are within 83-99.8% of commercial Celgard 2325 PP/PE/PP separators. This study points to the unique possibility of SLED as a separator manufacturing technique for geometrically complex energy storage systems. Further research is needed to optimize the polymer-solvent system to enhance control of porosity, pore size, and coating thickness. This can lead to significant improvement in rate and cycle life performance in more advanced energy storage devices. 

Electrospray deposition (ESD) uses strong electric fields applied to solutions and dispersions exiting a capillary to produce charged monodisperse droplets driven toward grounded targets. Self‐limiting electrospray deposition (SLED) is a phenomenon in which highly directed, uniform, and even 3D coatings can be achieved by trapping charge in the deposited film, redirecting the field lines to uncoated regions of the target. However, when inorganic particles are added to SLED sprays, the buildup of charge required to repel incoming material is disrupted as particle loading increases. Due to its fibril gelling behavior, methylcellulose (MC) SLED can form nanowire morphologies. These wires, when used as a binder, can separate particles and prevent percolation. In this work, a variety of conductive and insulating particles are explored using patterned and un‐patterned substrates. This exploration allows us to maximally load particles for high‐concentration and highly controlled self‐limiting functional sprays. This is demonstrated using Ti3C2Tx MXene to functionalize an interdigitated electrode for use as a supercapacitor.