A prototype of ultrasonic micro-degassing device for portable dialysis system

Abstract

The design, fabrication and evaluation of a micro-degasser are described. The intended use of the device is in portable dialysis systems. Degassing processes were based on ultrasound induced cavitation. The pattern of the degassing chamber was formed in a glass wafer and that of the gas-venting channels were formed in a silicon wafer. The entire flow path network was encapsulated by the anodic bonding of the Si to the glass wafer. A diaphragm (6mm×6mm×0.1mm) was etched on the Si side for oscillation. The ultrasonic vibration originated from a bulk piezoelectric PZT ceramic (5mm×4mm×0.15mm) which was excited by a 49 kHz square wave at 100 V (peak-to-peak). The gas-venting channels (2 μm wide and 2.7 μm deep) were hydrophobically passivated using a functional silicone. Cavitation occurred in a degassing chamber (6mm×6mm×0.02mm) when the Si oscillating diaphragm was driven by the PZT. Water was used to demonstrate the degassing process. The entire process was recorded using a microscope equipped with a video camera. The gas bubbles were vented effectively and no gas bubble flowing out of the degassing chamber with water was observed. Thirty-eight percent of the dissolved oxygen was removed.