The efficiency of self-phoretic propulsion mechanisms with surface reaction heterogeneity

Kreissl, Patrick; Holm, Christian; Graaf, Joost de

doi:10.1063/1.4951699

Cited by 27 publications

(28 citation statements)

References 58 publications

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“…To understand the dissociation of a purely neutral flux, we must look in detail at the parameter α in Eq. (48). The form of α can be explained by the fact that in the absence of a net electrical current, e.g., for S • swimmers, the ionic currents are constrained by j j j + = j j j − .…”

Section: Dissociation Of the Neutral Flux (Model S • )mentioning

confidence: 99%

Ionic screening and dissociation are crucial for understanding chemical self-propulsion in polar solvents

et al. 2017

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Polar solvents like water support the bulk dissociation of themselves and their solutes into ions, and the re-association of these ions into neutral molecules in a dynamic equilibrium, e.g., HO ⇌ H + HO. Using continuum theory, we study the influence of these association-dissociation reactions on the self-propulsion of colloids driven by surface chemical reactions (chemical swimmers). We find that association-dissociation reactions should have a strong influence on swimmers' behaviour, and therefore should be included in future modelling. In particular, such bulk reactions should permit charged swimmers to propel electrophoretically even if all species involved in the surface reactions are neutral. The bulk reactions also significantly modify the predicted speed of chemical swimmers propelled by ionic currents, by up to an order of magnitude. For swimmers whose surface reactions produce both anions and cations (ionic self-diffusiophoresis), the bulk reactions produce an additional reactive screening length, analogous to the Debye length in electrostatics. This in turn leads to an inverse relationship between swimmer radius and swimming speed, which could provide an alternative explanation for recent experimental observations on Pt-polystyrene Janus swimmers [S. Ebbens et al., Phys. Rev. E: Stat., Nonlinear, Soft Matter Phys., 2012, 85, 020401]. We also use our continuum theory to investigate the effect of the Debye screening length itself, going beyond the infinitely-thin-screening-length approximation used by previous analytical theories. We identify significant departures from this limiting behaviour for micron-sized swimmers under typical experimental conditions and find that the approximation fails entirely for nanoscale swimmers.

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Section: Dissociation Of the Neutral Flux (Model S • )mentioning

confidence: 99%

Ionic screening and dissociation are crucial for understanding chemical self-propulsion in polar solvents

et al. 2017

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“…Nevertheless, molecular dynamics 96 and theoretical studies 97 suggest that other mechanisms, e.g. self-diffusiophoresis, can be simultaneously in action in this system.…”

Section: Janus Nanomotorsmentioning

confidence: 97%

Artificial molecular and nanostructures for advanced nanomachinery

et al. 2018

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“…Achieving this requires a carefully crafted mesh as depicted in Figure . Highly anisotropic triangular elements lead to ill‐conditioned equation systems after discretization through the FEM, which is why we discretize the double layers using quad elements, as we found this approach useful for other finite‐element calculations as well . This allows us to discretize the large gradients in the normal direction of the charged surfaces optimally, while at the same time taking advantage of the slow variation of the fields parallel to these surfaces.…”

Section: Finite‐element Modelmentioning

confidence: 99%

Nanoparticle Translocation through Conical Nanopores: A Finite Element Study of Electrokinetic Transport

Rempfer

Ehrhardt

Holm

et al. 2016

Macro Theory & Simulations

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Recent years have seen a surge of interest in nanopores because such structures show a strong potential for characterizing macromolecules, e.g., DNA. Here, the authors theoretically investigate the translocation of a spherical nanoparticle through a conical nanocapillary, by numerically solving the coupled system of electrokinetic continuum equations. Based on their findings, the authors formulate simple guidelines for obtaining the maximum current signal during the translocation event, which should be transferable to other nanopore geometries. In addition, the dependence of the signal strength on particle properties, such as surface charge and size, is evaluated. Finally, the authors identify conditions under which the translocation is prevented by the formation of a strong electroosmotic barrier and show that the particle may even become trapped at the pore orifice, without imposing an external hydrostatic pressure difference.

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The efficiency of self-phoretic propulsion mechanisms with surface reaction heterogeneity

Cited by 27 publications

References 58 publications

Ionic screening and dissociation are crucial for understanding chemical self-propulsion in polar solvents

Ionic screening and dissociation are crucial for understanding chemical self-propulsion in polar solvents

Artificial molecular and nanostructures for advanced nanomachinery

Nanoparticle Translocation through Conical Nanopores: A Finite Element Study of Electrokinetic Transport

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