We report highly reproducible gravimetric and optical measurements of microdroplets enabled by fluidic pressure feedback control and state-of-the-art measurement systems that lend new insights into the process of drop-on-demand (DOD) printing. Baseline fluidic pressure within the DOD dispenser was controlled to within 0.02 hPa, enabling long-term stability in dispensed droplet mass with observed variations between 0.6 % and 1.6 % (RSD) for isobutanol. With mass, the high precision of velocity measurement enabled consistent determination of droplet kinetic energy, which governed baseline behavior. Mass and velocity were influenced in a non-linear manner by the frequency of droplet ejection, the fluidic pressure applied, and the number of droplets dispensed. Non-linear mass effects were attributable to acoustic resonances, energy partitioning, and pressure wavelets created during first-drop formation, although mechanistic clarity is far from complete.
Pub Type: Journals
droplet, drop-on-demand, first-drop, fluidic pressure, gravitmetry, inkjet, microbalance, piez