Hydrodynamic focusing micropump module with PDMS/nickel-particle composite diaphragms for microfluidic systems

In this research, a rapid prototype hydrodynamic focusing module with three multi-fluidic speed-modulating (MFSM) micropumps in micro-fluidic flow has been designed, fabricated, and characterized. The module comprises of three MFSM micropumps having the dimension of 33 × 25 × 5 mm to achieve hydrodynamic focusing and the stream modulation. Each micropump consists of top, middle and bottom including actuation/modulation source, PDMS/nickel-particle composite (PNPC) diaphragm and Tesla-type valve/chamber, respectively. Three MFSM micropumps share one pneumatic actuation source and two individual permanent magnet modulation sources which are located above the right and left diaphragms. Each permanent magnet is manually controlled by a screw. The PNPC diaphragm deflection is obtained by the external pneumatic force, and the permanent magnet limits the displacement resulting from the interaction between the magnetic field and the nickel particles of the PNPC diaphragm. Hydrodynamic focusing is realized by the flow rate control of two side micropumps with magnetic diaphragm displacement modulation. Analyses of the magnetic modulation field, the flow rate of the MFSM micropump, and the hydrodynamic focused stream modulation are presented. The individual micropump can pump DI water with a flow rate of about 107 μl/min, and the hydrodynamic focusing channel can achieve a flow rate of about 321 μl/min, under the frequency of 2 Hz. This research examines the modulation feasibility of hydrodynamic focused center stream by controlling the neighboring stream flow rate and this technique can be utilized for possible applications in lab-on-a-chip, micro total analysis system and point of care testing system.