Bubble-Driven Inertial Micropump

TL;DR

This paper investigates the physics and performance of a bubble-driven inertial micropump with no moving parts, combining numerical simulations, a phenomenological model, and experimental validation to understand flow regimes and optimize design.

Contribution

It introduces a comprehensive numerical and physical model of the micropump, identifying flow regimes and demonstrating experimental semi-continuous pumping.

Findings

Net flow maximizes at the axial to non-axial regime crossover.

Flow behavior varies with channel geometry and fluid properties.

Experimental results agree with simulations regarding viscosity effects.

Abstract

The fundamental action of the bubble-driven inertial micropump is investigated. The pump has no moving parts and consists of a thermal resistor placed asymmetrically within a straight channel connecting two reservoirs. Using numerical simulations, the net flow is studied as a function of channel geometry, resistor location, vapor bubble strength, fluid viscosity, and surface tension. Two major regimes of behavior are identified: axial and non-axial. In the axial regime, the drive bubble either remains inside the channel or continues to grow axially when it reaches the reservoir. In the non-axial regime the bubble grows out of the channel and in all three dimensions while inside the reservoir. The net flow in the axial regime is parabolic with respect to the hydraulic diameter of the channel cross-section but in the non-axial regime it is not. From numerical modeling, it is determined that the net flow is maximal when the axial regime crosses over to the non-axial regime. To elucidate the basic physical principles of the pump, a phenomenological one-dimensional model is developed and solved. A linear array of micropumps has been built using silicon-SU8 fabrication technology, and semi-continuous pumping across a 2 mm-wide channel has been demonstrated experimentally. Measured variation of the net flow with fluid viscosity is in excellent agreement with simulation results.