High-pressure microfluidic systems (HPMS): flow and cavitation measurements in supported silicon microsystems

Conventionally fabricated silicon microfluidic systems with glass coverage were stabilized by a specially developed frame to withstand high-pressure drops of up to 500 bar. Velocity measurements were carried out with an optical non-intrusive measurement technique (μPIV) to characterize the flow in the microfluidic systems. High-pressure applications in microsystems differ compared to more conventional microfluidic applications especially in the higher Reynolds numbers up to 11,500, higher shear forces and the presence of hydrodynamic cavitation. In order to characterize the cavitation phenomena, a photo-optical cavitation measurement technique on the basis of a μPIV setup was applied to visualize the cavitation pattern. The flow of a T- and an orifice geometry were investigated. It was found out that hydrodynamic cavitation, which is a source of abrasion, influences the flow to a great extent and, in orifice geometries, also the volume flow. By applying a backpressure cavitation could be decreased and, at a sufficiently high backpressure, eliminated. Besides the photo-optical cavitation measurements, volume flow measurements could be used to determine the critical backpressure at which cavitation is restricted to the vena contracta in orifice microchannels. With the presented techniques, beginning with the micro fabrication process over the external stabilization up to the high-speed flow characterization, a concept of a high-pressure microfluidic system is introduced, which is suitable for a wide range of applications in research and process development in high-pressure microsystems.