Control and characterization of thin film formation by electrospray deposition techniques*

Electrospray deposition (ESD) offers a precise and continuous manner by which to deliver sub-micron sized droplets of soft matter in dilute solution to a substrate. Preparation of thin films by ESD have offered advantages of making sequentially deposited, continually equilibrated or even compositionally varying systems on a single substrate for high-throughput characterization. However, understanding and control of the thin film formation are important to limit the Marangoni effects of the droplets on the surface to ensure uniform deposition and coverage. We describe a simple feedback control for visual analysis of various electrospray modes and their corresponding film formation. We also model the surface coverage of the films as a function of deposition time of varying molecular weight homopolymer and block copolymer systems. Furthermore, by changing the geometry of the ESD setup, the area of deposition can be tuned to fit the needs of transmission or reflection X-ray scattering experiments.