Controlling the injection of picoliter volumes in droplet microfluidics
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Inclou dades d'ús des de 2022
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hdl:2117/333747
Tipus de documentProjecte Final de Màster Oficial
Data2020-07-09
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Abstract
An electrode based pico-injector chip is a microfluidic device aimed at injecting a precise
amount of volume into every picoliter droplet of a continuous emulsion flow. This is
possible because of the application of an electric field disturbance near the injection
junction. In this study, two pico-injector designs have been proposed, modelled,
simulated and analysed.
First of all, the manufacturing process of pico-injector chips, including the electrode
positioning and implementation, have been studied in order to produce the two said
designs. In addition, an estimation of the voltage signal parameters required to disrupt the
electric field has been done.
Secondly, the behaviour of the chip has been studied through fluidic modelling. Fluidic
systems can be easily modelled by a linear equation system using an electrical analogy,
where the flow passing through a channel is directly proportional to the pressure drop
divided by the fluidic resistance.
However, the dispersed phase (droplets) introduces nonlinear effects into this system,
making both the pressure drop and the fluidic resistance vary depending on the number
and volume of all droplets inside the channel at a given time. In other words, the flow
rates do not only depend on the inlet pressure inputs, but also on the current droplet
distribution of the channel.
Adding this modification yields a nonlinear two dimensional system, whose solution
provides all the system variables to control (flow rates, droplet generation frequency and
volume, injected volume) given the three input pressures (water, oil and injection
pressures). This system has been used to:
Find the equilibrium points that will eventually be reached given a specific
pressure input configuration.
Generate a discrete computational model implemented by the software Matlab,
which simulates transient states between two equilibrium points produced by
pressure input step changes.
In addition, these equilibrium points have been studied by means of the analysis of a
simplified and linearized continuous model, which proves the stability of all equilibria
4
since small disturbances producing alterations in the state of the system will be dimmed
and the system will come back to the equilibrium point.
Finally, five different simulations involving different input pressure variations have been
performed, including a water pressure step response, an oil pressure step response, an
injection pressure step response and a combined pressure step response. With the results
provided by the simulations, a final dynamic analysis of time constants and overshoots in
variables such as flow rates and injected volume has been conducted.
TitulacióMÀSTER UNIVERSITARI EN ENGINYERIA INDUSTRIAL (Pla 2014)
Col·leccions
Fitxers | Descripció | Mida | Format | Visualitza |
---|---|---|---|---|
controlling-the ... -droplet-microfluidics.pdf | 2,040Mb | Accés restringit | ||
appendix.zip | 403,3Kb | application/zip | Accés restringit |