DESIGN AND ANALYSIS OF A POLYSILICON SURFACE MICROMACHINED VISCOUS DRAG SPIRAL PUMP

Abstract eng:
The paper introduces a new viscous micropump targeting the surface micromachining technology. The pump works by rotating a disk with a spiral protrusion at a close proximity over a stationary plate. Fluid contained in the spiral channel created by this geometry is subject to a net tangential viscous stress, and a positive pressure gradient is established in the flow direction. The paper describes the implementation of this concept in five levels of polysilicon using the standard surface micromachining technology SUMMiT, illustrating the power transmission mechanism and the mask layouts used in producing the rotating spiral channel. For the purpose of flow field analysis, an approximation is employed that neglects the curvature of the spiral channel and replaces it by an equivalent straight channel. The conditions under which this approximation is justifiable are discussed and a mapping relating the spiral channel model to the straight channel representations is developed. The straight channel representation is further simplified using symmetry into the 2D flow in the mid-axial plane. Analytical solution of this model at the lubrication limit relates the flow rate, torque and power consumption in the spiral pump to the pressure head and rotation rate through simple formulas.

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