Smooth Flow Control for On-Chip Pneumatic Micropumps

Abstract

Advancements in cellular biology, microfabrication methods, and the field of microfluidics allow biologists to closely replicate in vitro environments on organ-on-a-chip devices. In order to reproduce physiological conditions and processes as accurately as possible, it is necessary to generate the same flow profiles found in vitro. This thesis presents the development, implementation, testing, and iterative improvement of both hardware and software that composes a flow control system that produces smooth flow for on-chip pneumatic micropumps. By establishing a flow control system that can achieve smooth flow, fluidic conditions of microphysiological systems can be controlled to accurately mimic biological conditions. Biological experiments can require flow profiles anywhere on the spectrum of smooth flow to highly pulsatile flow. A smooth flow profile can be modified with pumping delays to make the flow profile as pulsatile as desired.

The main outcome of the work presented in this thesis is three flow control system approaches for smooth flow that can achieve smooth flow profiles at flow rates up to 1 𝜇L/s. Two different iterative learning control (ILC) algorithms relying on either direct or indirect sensing methods were developed to allow for feedback driven flow control systems. A packaged open-loop flow control platform was also developed and is less-complex than its ILC driven counterparts and can be used without modifying the chips since sensing is not necessary. These systems all perform consistently and maintain accurate flow rates while producing smooth flow profiles. Use of these flow control systems in future biological experiments will provide insight into the effect of having smooth on-chip flow.