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Abstract Advanced synthetic materials are needed to produce nano‐ and mesoscale structures that function autonomously, catalyze reactions, and convert chemical energy into motion. This paper describes supracolloidal fiber‐like structures that are composed of self‐adhering, or “sticky,” oil‐in‐water emulsion droplets. Polymer zwitterion surfactants serve as the key interfacial components of these materials, enabling multiple functions simultaneously, including acting as droplet‐stabilizing surfactants, interdroplet adhesives, and building blocks of the fibers. This fiber motion, a surprising additional feature of these supracolloidal structures, is observed at the air–water interface and hinged on the chemistry of the polymer surfactant. The origin of this motion is hypothesized to involve transport of polymer from the oil–water interface to the air–water interface, which generates a Marangoni (interfacial) stress. Harnessing this fiber motion with functional polymer surfactants, and selection of the oil phase, produced worm‐like objects capable of rotation, oscillation, and/or response to external fields. Overall, these supracolloidal fibers fill a design gap between self‐propelled nano/microscale particles and macroscale motors, and have the potential to serve as new components of soft, responsive materials structures.
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Modulating outcomes of oil drops bursting at a water–air interface
Recent studies have shown that capillary waves generated by the bursting of an oil drop at the water–air interface produces a daughter droplet inside the bath, while a part of it floats above it. Successive bursting events produce next generations of daughter droplets, gradually diminishing in size until the entire volume of oil rests atop the water–air interface. In this work, we demonstrate two different ways to modulate this process by modifying the constitution of the drop. First, we introduce hydrophilic clay particles inside the parent oil drop and show that it arrests the cascade of daughter droplet generation preventing it from floating over the water–air interface. Second, we show that bursting behavior can be modified by a compound water–oil–air interface made of a film of oil with finite thickness and design a regime map, which displays each of these outcomes. We underpin both of these demonstrations by theoretical arguments providing criteria to predict outcomes resulting therein. Finally, all our scenarios have a direct relation to control of oil–water separation and stability of emulsified solutions in a wide variety of applications, which include drug delivery, enhanced oil recovery, oil spills, and food processing, where a dispersed oil phase tries to separate from a continuous phase.
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- Award ID(s):
- 2028571
- PAR ID:
- 10580720
- Publisher / Repository:
- American Institute of Physics
- Date Published:
- Journal Name:
- Applied Physics Letters
- Volume:
- 125
- Issue:
- 14
- ISSN:
- 0003-6951
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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- Free Publicly Accessible Full Text
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Accepted Manuscript1.0
- Journal Article:
- https://doi.org/10.1063/5.0216820
