Electrohydrodynamic pumping and flow measurement

A micromachined electrohydrodynamic (EHD) injection pump with improved characteristics and a novel method for flow measurement with the same structure are presented. Based on the structure of the EHD injection pump, an improved design with grid distances in the range between 10 μm and 60 μm was achieved, yielding a reduction in the required driving voltage. Grid areas of 2.5×2.5 mm² and 1×1 mm² were accomplished. The outer dimensions of the smallest pumps are 3×3×1.0 mm³. One of the grids is etched back from the frontside and mounted upside down on the lower grid in order to reduce the grid distance. The two grids are bounded together by anodic bonding. The pump is mounted in a ceramic housing with two fluid ports. Based on this structure, a novel method for the measurement of fluid flow and velocity was developed. This technique is well suited for small flow rates below 100 mL/min down to some μL/min. Volumetric flow rates down to 8 μL/min were measured with a 2.5×2.5 mm² grid area