Stabile, Thermoresponsive Colloidal Clusters: An Unusual Morphology of Polymer Dispersions

AbstractSelf-propelling microparticles are often proposed as synthetic models for biological microswimmers, yet they lack the internally regulated adaptation of their biological counterparts. Conversely, adaptation can be encoded in larger-scale soft-robotic devices but remains elusive to transfer to the colloidal scale. Here, we create responsive microswimmers, powered by electro-hydrodynamic flows, which can adapt their motility via internal reconfiguration. Using sequential capillary assembly, we fabricate deterministic colloidal clusters comprising soft thermo-responsive microgels and light-absorbing particles. Light absorption induces preferential local heating and triggers the volume phase transition of the microgels, leading to an adaptation of the clusters’ motility, which is orthogonal to their propulsion scheme. We rationalize this response via the coupling between self-propulsion and variations of particle shape and dielectric properties upon heating. Harnessing such coupling allows for strategies to achieve local dynamical control with simple illumination patterns, revealing exciting opportunities for developing tactic active materials.

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A Surprisingly Gentle Approach to Cavity Containing Spherocylindrical Microparticles from Ordinary Polymer Dispersions in Flow

Materials Horizons ◽

10.1039/d1mh01108a ◽

2021 ◽

Author(s):

Amit K. Tripathi ◽

John G. Tsavalas

Keyword(s):

Internal Cavity ◽

Polymeric Microparticles ◽

Polymer Dispersions

Herein, we demonstrate a facile approach to fully transform spherical polymeric microparticles to elongated spherocylinders containing an internal cavity under ambient and mild stirring conditions. Critical to the process is...

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Holographic measurements of anisotropic three-dimensional diffusion of colloidal clusters

Physical Review E ◽

10.1103/physreve.88.020302 ◽

2013 ◽

Vol 88 (2) ◽

Cited By ~ 27

Author(s):

Jerome Fung ◽

Vinothan N. Manoharan

Keyword(s):

Three Dimensional ◽

Colloidal Clusters ◽

Dimensional Diffusion

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Stability of Chemically Degraded Friction Reducers and Their Relationship to Regain Conductivity

10.2118/206308-ms ◽

2021 ◽

Author(s):

Philip Ayazi ◽

Gabriel Monreal ◽

Hassan Bleibel ◽

Frank Zamora ◽

Larry Watters

Keyword(s):

Zeta Potential ◽

Selection Process ◽

Quantitative Relationship ◽

Reaction Rates ◽

Friction Reduction ◽

Chemical Degradation ◽

Industry Standard ◽

Different Temperatures ◽

Tracking Behavior ◽

Polymer Dispersions

Abstract Previously, it was shown that zeta potential could be used as a metric to determine friction reducer (FR) performance. Specifically, the extent of and how quickly the FR reaches peak friction reduction in source water. A correlation postulated from the previous work is zeta potentials relationship to an FR's stability during mechanical or chemical degradation. In other words, can zeta potential be used as a metric to determine the extent of polymer breaking and can this relationship be translated to regained conductivity? This paper describes a laboratory study of zeta potential measurements to track breaker reaction rates, stability of broken polymer dispersions, and the relationship between chemical degradation of FRs and regained conductivity. The approach of this investigation involves measuring zeta potential of frac fluids formulated using anionic and cationic FRs with varying types and concentrations of breakers at different temperatures and times. These metrics are then correlated with regain conductivity. A quantitative relationship exists between zeta potential, fluid rheology, and regain conductivity. Zeta potential evaluation of degraded FR's in frac fluids correlate to performance in regain conductivity testing. These measurements can expedite the selection of chemical breakers with respect to performance. Zeta potential measurements of degraded FR are indicative of broken FR dispersion stability which has impact on regain conductivity. Tracking behavior of cationic FR's using zeta potential reveals the materials can become anionic with time and temperature and become susceptible to agglomeration with iron. Zeta potential measurements can be used during a chemical breaker selection process as a viable supplement to industry standard tests for assessing the comparative effectiveness of chemical breakers in frac fluids.

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