Ultra-High Speed Particle Image Velocimetry on Drop-on-Demand Jetting
An experimental setup to study the dynamics of droplet jetting from a commercially available print-head is described. A MicroFab print-head with an 80 µm diameter transparent nozzle was set to print droplets at a speed of 5 m/s at a frequency of 7 kHz. A Particle Image Velocimetry (PIV) scheme consisting of an optical microscope coupled to an ultra-high speed camera is utilized to capture the motion of particles suspended in a model transparent ink. This experimental arrangement images the flow at the centre of a glass cylindrical nozzle and above the fluid meniscus at a speed of half a million frames per second. Velocity fields are obtained from an approximately 200 µm thickness layer of fluid at the inside of the nozzle. Experimental results are compared with Lagrangian finite-element numerical simulations under identical fluid and jetting conditions with good agreement. The advantages, challenges and current limitations of this approach are discussed.