Diffusiophoresis: a novel transport mechanism - fundamentals, applications, and future opportunities

Ganguly, Arkava; Alessio, Benjamin M.; Gupta, Ankur

doi:10.3389/fsens.2023.1322906

Cited by 6 publications

(2 citation statements)

References 90 publications

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“…In these cases, chemically active colloids react, decompose, or hydrolyze to release neutral or ionic species into the surrounding medium. The resulting chemical gradient causes colloids to interact with each other or with nearby tracers via diffusiophoresis and/or diffusioosmosis, − which refer to the transport of colloidal particles and interfacial flows in said chemical gradient, respectively. These phoretic and/or osmotic interactions could lead to rich mesoscopic structures such as clusters, exclusion zones, and phase separation.…”

Section: Introductionmentioning

confidence: 99%

A Conceptual Framework to Understand the Self-Assembly of Chemically Active Colloids

Cao,

Yan,

Cui

et al. 2024

Langmuir

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Colloids that generate chemicals, or "chemically active colloids", can interact with their neighbors and generate patterns via forces arising from such chemical gradients. Examples of such assemblies of chemically active colloids are abundant in the literature, but a unified theoretical framework is needed to rationalize the scattered results. Combining experiments, theory, Brownian dynamics, and finite element simulations, we present here a conceptual framework for understanding how immotile, yet chemically active, colloids assemble. This framework is based on the principle of ionic diffusiophoresis and diffusioosmosis and predicts that a chemically active colloid interacts with its neighbors through short-and long-range interactions that can be either repulsive or attractive, depending on the relative diffusivity of the released cations and anions, and the relative zeta potential of a colloidal particle and the planar surface on which it resides. As a result, 4 types of pairwise interactions arise, leading to 4 different types of colloidal assemblies with distinct patterns. Using short-range attraction and long-range attraction (SALR) systems as an example, we show quantitative agreement between the framework and experiments. The framework is then applied to rationalize a wide range of patterns assembled from chemically active colloids in the literature exhibiting other types of pairwise interactions. In addition, the framework can predict what the assembly looks like with minimal experimental information and help infer ionic diffusivity and zeta potential values in systems where these values are inaccessible. Our results represent a solid step toward building a complete theory for understanding and controlling chemically active colloids, from the molecular level to their mesoscopic superstructures and ultimately to the macroscopic properties of the assembled materials.

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Section: Introductionmentioning

confidence: 99%

A Conceptual Framework to Understand the Self-Assembly of Chemically Active Colloids

Cao,

Yan,

Cui

et al. 2024

Langmuir

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“…In the field-driven mode of swimming, phoretic mechanisms, e.g., diffusiophoresis (the focus of this work) [40][41][42][43][44][45][46][47][48][49][50][51][52], thermophoresis [53][54][55], electrophoresis [56][57][58][59][60][61][62][63][64], and electrodiffusiophoresis [65,66], are used to achieve directed motion at the microscale. Diffusiophoresis, the movement of particles in chemical gradients [67][68][69][70][71][72][73][74][75][76][77][78][79][80], has been a particularly rich area of research due to similarities with cell chemotaxis [81,82]. Active diffusiophoretic particles use reactive patches on the particle surface, enabling the particle to generate local concentration gradients and achieve locomotion [40,51,83].…”

Section: Introductionmentioning

confidence: 99%

Motion of an active bent rod with an articulating hinge: exploring mechanical and chemical modes of swimming

Raj,

Ganguly,

Becker

et al. 2023

Front. Phys.

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Swimming at the microscale typically involves two modes of motion: mechanical propulsion and propulsion due to field interactions. During mechanical propulsion, particles swim by reconfiguring their geometry. When propelled by field interactions, body forces such as phoretic interactions drive mobility. In this work, we employ slender-body theory to explore how a bent rod actuator propels due to a mechanical mode of swimming via hinge articulations and due to a chemical mode of swimming via diffusiophoretic interactions with a solute field. Although previous theoretical studies have examined mechanical and chemical modes of swimming in isolation, the simultaneous investigation of both modes has remained unexplored. For the mechanical mode of swimming, our calculations, both numerical and analytical, recover Purcell’s scallop theorem and show that the bent rod actuator experiences zero net displacement during reciprocal motion. Additionally, we calculate the trajectories traced by a bent rod actuator under a non-reciprocal hinge articulation, revealing that these trajectories are influenced by the amplitude of the hinge articulation, geometric asymmetry, and the angular velocity distribution between the two arms of the bent rod actuator. We provide intuitive explanations for these effects using free-body diagrams. Furthermore, we explore the motion induced by simultaneous hinge articulations and self-diffusiophoresis. We observe that hinge articulations can modify the effective phoretic forces and torques acting on the bent rod actuator, either supporting or impeding propulsion. Additionally, during self-diffusiophoretic propulsion, reciprocal hinge articulations no longer result in zero net displacement. In summary, our findings chart a new direction for designing micron-sized objects that harness both mechanical and chemical modes of propulsion synchronously, offering a mechanism to enact control over trajectories.

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Unified mobility expressions for externally driven and self-phoretic propulsion of particles

Ganguly,

Roychowdhury,

Gupta

2024

J. Fluid Mech.

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The mobility of externally driven phoretic propulsion of particles is evaluated by simultaneously solving the solute conservation equation, interaction potential equation and the modified Stokes equation. While accurate, this approach is cumbersome, especially when the interaction potential decays slowly compared with the particle size. In contrast to external phoresis, the motion of self-phoretic particles is typically estimated by relating the translation and rotation velocities with the local slip velocity. While this approach is convenient and thus widely used, it is only valid when the interaction decay length is significantly smaller than the particle size. Here, by taking inspiration from Brady (J. Fluid Mech., vol. 922, 2021, A10), which combines the benefits of two approaches, we reproduce their unified mobility expressions with arbitrary interaction potentials and show that these expressions can conveniently recover the well-known mobility relationships of external electrophoresis and diffusiophoresis for arbitrary double-layer thickness. Additionally, we show that for a spherical microswimmer, the derived expressions relax to the slip velocity calculations in the limit of the thin interaction length scales. We also employ the derived mobility expressions to calculate the velocities of an autophoretic Janus particle. We find that there is significant dampening in the translation velocity even when the interaction length is an order of magnitude larger than the particle size. Finally, we study the motion of a catalytically self-propelled particle, while it also propels due to external concentration gradients, and demonstrate how the two propulsion modes compete with each other.

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Diffusiophoresis: a novel transport mechanism - fundamentals, applications, and future opportunities

Cited by 6 publications

References 90 publications

A Conceptual Framework to Understand the Self-Assembly of Chemically Active Colloids

A Conceptual Framework to Understand the Self-Assembly of Chemically Active Colloids

Motion of an active bent rod with an articulating hinge: exploring mechanical and chemical modes of swimming

Unified mobility expressions for externally driven and self-phoretic propulsion of particles

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