Optimization of a Pneumatic Valve Control Microdrop-on-demand System

To increase the jetting frequency of our previously home-built pneumatic microdrop-on-demand system, the influences of chamber volume and solenoid valve control on the maximum stable jetting frequency were studied. The key components of the system included a chamber, a tiny orifice of micron dimension, a gas path with a high speed solenoid valve and a venting tube, and a photographic system used for evaluating the uniformity and consistency of the micron size droplet. A pressure pulse was created within the chamber via opening the solenoid valve for a brief period of time. The liquid was pushed out through the nozzle, generating a droplet. The gas was then released through the venting tube, recovering the system back to equilibrium. Results show that reducing the volume of the chamber and reducing the opening time can significantly improve the highest stable jetting frequency of the system. The speed of the droplet shows a trend of increasing as the jetting frequency becomes higher. For shorter "on" period of the valve, the diameter of the droplet shrinks, and it can effectively improve the control of the system for precision samples.