Syringe Pressure Pump Design Experimental Setup.

<p>A) An illustration of our syringe pump design. The liquid containing syringe is held in place by the 3D printed syringe pump parts, shown in black. These parts connect to a stepper motor (i.), depicted with grey and black stripes. When this stepper motor is actuated, the syringe pushes liquid through Tygon tubing, which passes through a piezoresistive pressure sensor (ii.) before entering a microfluidic channel. The electrical signal from the sensor is passed to an instrumentation amplifier (iii.), shown with the dark blue rectangle, before being transmitted and received by analog pins on an Arduino microcontroller (iv.). In response to these signals, the Arduino actuates the syringe pump via a stepper motor driver (v.), closing the feedback loop. B) Block diagram representation of the PID control structure detailing a mathematical abstraction for the feedback loop illustrated in Fig 1A. R(t) represents the commanded pressure, while e(t) represents the error in pressure between command and actual pressure, p(t). S(t) represents the step signal from the stepper driver. M(t) represents the stepper motor position, while L(t) represents the linear position of the syringe plunger that actuates flow through the syringe into the microfluidic system. q(t) is the flow rate through the system. C) Two different microfluidic chip geometries were used for this experiment, a linear channel shown on the left hand side of (C) and a Y-junction chip shown to its right. Both of these geometries may be modeled using hydraulic resistance abstractions for laminar flow regimes encountered within typical microfluidic testing conditions.