Real time completely bio-compatible flow control technique for microchannel based physiological studies
thesisposted on 01.03.2017 by Galhena, Dilendra
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A real-time and biocompatible flow control technique for microchannel based physiological experiments has been developed. Current micro flow control techniques are limited in their ability to develop physiological waveforms and maintain high flow accuracy. The new technique provides accurate real time flow control of steady and user specified complex waveforms. This low impact flow control technique offers high adaptability for a wide range of frequencies and flow rates. The system is highly scalable as the operating parameters rely on the scale of specific components. A prototype system was constructed incorporating a constant air pressure source to supply the base flow rate, a compact, disposable flow probe to measure the flow rate and a real time feedback control system to drive a fluid control valve. The fluid control valve allows for finer control over the base flow by pinching the silicone tube carrying the flow. Performance tests were completed for this prototype, showing a steady flow error of 1.2%. The optimum pulsatile range was for oscillations between 1 – 3 Hz. For sinusoidal waveforms within this range the total harmonic distortion was under 2% and the root mean square error was under 8 %. Micro PIV and thrombus growth experiments were completed to demonstrate the capacity of this flow control systems ability to be used in microchannel based physiological experiments. Micro PIV results indicate that viscous forces affect the flow profile within a high aspect ratio microchannel with fluid viscosity of 4 x 10-3 N.s/m2 and a Womersley number between 0.117 and 0.2925. Thrombus growth experiments comparing the pulsatile flow with steady flow at the microchannel wall showed that pulsatile flow promoted higher thrombi growth. It was hypothesised that pulsatile velocities varying between 33.1 and 67.5 mm/s in a platelet rich region would significantly promote the development of thrombi.