Chemical design of self-propelled Janus droplets

Meredith, Caleb H.; Castonguay, Alexander; Chiu, Yu-Jen; Brooks, Allan M.; Moerman, Pepijn G.; Torab, Peter; Wong, Pak Kin; Sen, Ayusman; Velegol, Darrell; Zarzar, Lauren D.

doi:10.1016/j.matt.2021.12.014

Cited by 50 publications

(37 citation statements)

References 43 publications

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“…[25][26][27][28] Rotating clusters with torques resulting from off-centre propulsion can also be engineered using binary mixtures or Janus swimmers. [29][30][31] However, as we demonstrate in this study, similar individual and collective dynamics may also emerge from systems without any pre-engineered symmetries.…”

Section: Introductionsupporting

confidence: 52%

Spontaneously rotating clusters of active droplets

et al. 2022

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Section: Introductionsupporting

confidence: 52%

Spontaneously rotating clusters of active droplets

et al. 2022

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“…The results reported here provide an inroad modeling framework for hydrodynamics of active colloids 2,13,57,58 . The present study also helps us understand the rheology of JP oligomers that may be realized in the experiments.…”

Section: Discussionmentioning

confidence: 94%

“…Janus particles are colloids combining two dissimilar chemical or physical functionalities at their opposite sides 1 . Self-propelling Janus particles, for example, with a permanent biphasic asymmetry, have emerged as a rich chemical platform for the exploration of active matter 2 . In the absence of mobility and any imposed flow, Janus particles (JPs) self-assemble into oligomers of various geometries and sizes depending on the interactions between JPs and the viscous solvent [3][4][5] , with tunable functions for biomedical engineering applications 1,[6][7][8][9][10] .…”

Section: Introductionmentioning

confidence: 99%

Effects of Tunable Hydrophobicity on the Collective Hydrodynamics of Janus Particles under Flows

Fu¹,

Ryham²,

Quaife³

et al. 2022

Preprint

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Active colloidal systems with non-equilibrium self-organization is a long-standing, challenging area in biology. To understand how hydrodynamic flow may be used to actively control self-assembly of Janus particles (JPs), we use a model recently developed for the many-body hydrodynamics of amphiphilic JPs suspended in a viscous background flow (JFM, 941, 2022). We investigate how various morphologies arise from tuning the hydrophobic distribution of the JP-solvent interface. We find JPs assembled into uni-lamella, multi-lamella and striated structures. To introduce dynamics, we include a linear shear flow and a steady Taylor-Green mixing flow, and measure the collective dynamics of JP particles in terms of their (a) free energy from the hydrophobic interactions between the JPs, (b) order parameter for the ordering of JPs in terms of alignment of their directors, and (c) strain parameter that captures the deformation in the assembly.We characterize the effective material properties of the JP structures and find that the uni-lamellar structures increases orientation order under shear flow, the multilamellar structure behaves as a shear thinning fluid, and the striated structure possesses a yield stress. These numerical results provide insights into dynamic control of non-equilibrium active biological systems with similar self-organization.

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“…We also tested surfactant concentrations between 1 wt % and 5 wt %, which are all orders of magnitude above the CMC of each surfactant (CMC=0.006 wt %, 0.0085 wt %, 0.009 wt %, and 0.0157 wt % for NP‐9, NP‐12, NP‐15, and NP‐30, respectively, as reported by the supplier). We note that NP‐9 has a very similar chemical structure to Triton X‐100, which is another nonionic surfactant previously used to generate active behavior in solubilizing droplets [8a, 10, 12] . For each combination of oil, surfactant type, and surfactant concentration, we produced droplets by vortex mixing and then introduced a single droplet (diameter 100–150 μm) to a cuvette containing surfactant solution and tracer particles.…”

Section: Resultsmentioning

confidence: 99%

Chemically Tuning Attractive and Repulsive Interactions between Solubilizing Oil Droplets

et al. 2022

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Micellar solubilization is a transport process occurring in surfactant-stabilized emulsions that can lead to Marangoni flow and droplet motility. Active droplets exhibit self-propulsion and pairwise repulsion due to solubilization processes and/or solubilization products raising the droplet's interfacial tension. Here, we report emulsions with the opposite behavior, wherein solubilization decreases the interfacial tension and causes droplets to attract. We characterize the influence of oil chemical structure, nonionic surfactant structure, and surfactant concentration on the interfacial tensions and Marangoni flows of solubilizing oil-in-water drops. Three regimes corresponding to droplet "attraction", "repulsion" or "inactivity" are identified. We believe these studies contribute to a fundamental understanding of solubilization processes in emulsions and provide guidance as to how chemical parameters can influence the dynamics and chemotactic interactions between active droplets.

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Chemical design of self-propelled Janus droplets

Cited by 50 publications

References 43 publications

Spontaneously rotating clusters of active droplets

Spontaneously rotating clusters of active droplets

Effects of Tunable Hydrophobicity on the Collective Hydrodynamics of Janus Particles under Flows

Chemically Tuning Attractive and Repulsive Interactions between Solubilizing Oil Droplets

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