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Title: Harnessing Rayleigh-Plateau Instability in Polymer Melts
Authors: Cai, Lingzhi
Advisors: Brun, Pierre-Thomas P.-T.
Contributors: Chemical and Biological Engineering Department
Keywords: 3-dimensional printing
architected soft material
Subjects: Chemical engineering
Fluid mechanics
Issue Date: 2022
Publisher: Princeton, NJ : Princeton University
Abstract: In this dissertation, I study the breakup of liquid threads and generation of liquid droplets within an immiscible fluid using an embedded 3-dimensional (3D) printing system. Firstly, we develop a robust fluid-mediated route for the rapid fabrication of soft elastomers architected with liquid inclusions. Our approach consists of depositing water drops at the surface of an immiscible liquid elastomer bath. As the elastomer cures, the drops are encapsulated in the polymer and impart shape and function to the newly formed elastic matrix. Using the framework of fluid mechanics, we show how this type of composite material can be tailored. In the second part, I study the droplet forming instability of a thin jet extruded from a nozzle moving horizontally below the surface of an iso-viscous immiscible fluid bath. While this interfacial instability is a classic problem in fluid mechanics, it has never been studied in the context of the deposition of a thread into a reservoir, an open-sky version of microfluidics. As the nozzle translates through the reservoir, drops may form at the nozzle (dripping) or further downstream (jetting). We first focus on rectilinear printing paths and derive a scaling law to rationalize the transition between dripping and jetting. We then leverage the flexibility of our system and study the dynamics of breakup when printing sinusoidal paths. We unravel a methodology to control both the size of the drops formed by the instability and the distance that separates them. Finally, we show that the breakup of closely spaced liquid threads sequentially printed in an immiscible bath locks into crystal-like lattices of droplets. We rationalize the hydrodynamics at the origin of this previously unknown phenomenon. We leverage this knowledge to tune the lattice pattern via the control of injection flow rate and nozzle translation speed. We further demonstrate that the drop crystals have the ability to self-correct and a simple mechanism is proposed to describe the convergence towards a uniform pattern of drops. Our printing techniques can serve as a new pathway for the fabrication of droplet patterns, which could be adapted to the existing droplet-based technologies and open up previously unexplored opportunities in additive manufacturing.
Alternate format: The Mudd Manuscript Library retains one bound copy of each dissertation. Search for these copies in the library's main catalog:
Type of Material: Academic dissertations (Ph.D.)
Language: en
Appears in Collections:Chemical and Biological Engineering

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