Dear Xiaochuan, We have been using CFD-ACE+ package of Computational Fluid Dynamics Research Corporation (CFDRC) for design and optimization of microfluidic devices. It is the best package I can recommend you in microfluidics area. The geometry and mesh generation tool (CFD-GEOM) is very easy and flexible in use as well as data visualization package (CFD-VIEW). The solver part (CFD-ACE) itself is very powerful allowing you to simulate all sorts of problems in microfluidics from channel flow through droplet ejection tofluid-structure interaction and stress problems in solids (CFD-FEMSTRESS). Everything (geometry and grid generation, solving, data visualisation) is seamless and very easy to use. Their software has been successfully used to simulate all sorts of microfluidic devices such as micropumps, inkjet printheads, fluidic amplifiers, mixers and others. To my best knowledge they are leading company in microfluidics-modeling softwaremarket and are mentioned in all major mems-simulation related sites on the internet. Their web page address is: www.cfdrc.com Best regards, Andrzej