Viscosity Measurement in Microfluidic Chips via Fast Fourier Transform (FFT)

This study introduces a novel method to measure the viscosity of fluids using a microfluidic viscometer designed to assess the bending behavior of micropillar arrays. These arrays are fabricated from flexible polydimethylsiloxane (PDMS) which bend in response to fluid flow. The microfluidic chips are fabricated using a soft lithography process. Two cameras, one looking from the top and the other from the side, are used to capture the images of the micropillars over a synchronized time interval to calculate their bending angles. The circle detection and region tracking algorithm are used to analyze the top view images, while Fast Fourier Transform (FFT) is used to analyze the side view images. The computation time of the three methods are compared. FFT-based approach reduced the calculation time by up to 20 folds for the same frames while showing a significant similarity with a mean overlap of $\gt 99 \%$.