Valveless pressure regulation with a submerged micro‐hole

Abstract

This study aims at controlling air pressure fluctuation in a chamber from which liquid is being drained continuously by using a submerged micro‐hole. In practical applications, this test chamber is used to simulate the commercial ink cartridge of a thermal bubble inkjet printhead. The chamber air pressure drops owing to liquid being drained from the chamber, and it rises again as bubbles are generated and detached from a submerged micro‐hole connecting liquid and the atmosphere. The chamber air pressure fluctuation can be controlled in a designated range that depends on factors such as physical properties of liquid used in the chamber, micro‐hole diameter, and liquid drain rate. In this study, both distilled water and 10% wt. isopropanol solution are tested with micro‐hole diameter ranging from 60 to 1200 μm. To simulate practical ink injection rates, the liquid drain rate ranges from 0.006 to 0.10 ml/s. For conditions tested in this study, our measured results show that the chamber air pressure variation and detached bubble volume depend mainly on micro‐hole diameter and physical properties of liquid, and only slightly on liquid drain rate. Two correlations are proposed to obtain both the detached bubble volume and chamber air pressure fluctuation from physical properties of liquid and micro‐hole diameter.