Driving complex flow waveforms with a linear voice coil actuator

Abstract

Oscillatory and pulsatile fluid flows for use in microfluidic applications were generated using a deformable chamber driven by a low cost linear voice coil actuator. Compliance in the fluidic system originating in the deformable chamber and the fluidic tubing produced a strong frequency dependence in the relationship between the system's input and the output flow rate. The effects of this frequency dependence were overcome by precise system calibration, enabling on-demand generation of sinusoidal oscillations in the fluid flow rate with a controlled amplitude in the range from 0.1 to over 1 ml/min across a frequency range from 0.1 Hz to 10 Hz. The calibration data further enabled the optimization of a multistage exponential smoothing model of the system that allowed the generation of arbitrary complex waveforms. This was demonstrated by combining flow modulation with a constant background flow generated by a syringe pump to mimic the pulsatile flow found in the human vascular system.

FIG. 1.

(a) Schematic of the deformable chamber and voice coil actuator. (b) Schematic of the deformable chamber geometry. (c) Schematic of the lightsheet imaging system and the flow visualization cell used for particle image velocimetry of flows driven by the voice coil actuator. (d) Typical image from the microsphere suspension in the flow viewing cell.

FIG. 2.

(a) A real time comparison of VCA driving voltage, the position of the actuator’s piston, and the associated fluid flow waveform for an input sinusoidal waveform with a frequency of 2 Hz. (b) Phase and amplitude plots for driving voltage and piston position. (c) Phase and amplitude plots for the piston velocity and fluid flow waveform.

FIG. 3.

(a) Sinusoidal fluid flow waveforms with programmed amplitude of 0.4 ml/min at three frequencies. Lines are sinusoidal fits to the data. (b) Comparison between the end-to-end Bode plot for the fluidic system (dots) with the optimized 3-stage exponential smoothing model (solid lines).

FIG. 4.

Generation of pulsatile fluid flows resembling those found in the human vascular system. The waveforms were reproduced at frequencies of 0.1, 0.5, 1, 5, and 10 Hz based on the three step filter model for the microfluidic system. The optimized input waveforms are shown in the left column, while the right column shows the target waveform (dashed lines) and measured output flow rates (dots).