Nonlinear modeling and control of a mechanically coupled variable resistance and squeeze pump for pressure regulation in microfluidics

The position of the laminar flow interface between parallel streams in a microfluidic network can be controlled by regulating the inlet pressure of the microfluidic device. To supply fluid from a reservoir of an arbitrary size, we developed a novel regulating mechanism separated from the fluid reservoir which employs a coupled variable resistance and squeeze pump in the fluid network. In this paper we present a nonlinear model of the dynamics of this mechanism. Analysis of the linearized dynamics shows why this mechanism has high bandwidth. We use the linearized model to design a linear controller and demonstrate its effectiveness for the full nonlinear dynamics in simulation.