Motion of an active particle in a linear concentration gradient

Abstract

Janus particles self-propel by generating local tangential concentration gradients along their surface. These gradients are present in a layer whose thickness is small compared to the particle size. Chemical asymmetry along the surface is a pre requisite to generate tangential chemical gradients, which gives rise to diffusioosmotic flows in a thin region around the particle.This results in an effective slip on the particle surface. This slip results in the observed "swimming" motion of a freely suspended particle even in the absence of externally imposed concentration gradients. Motivated by the chemotactic behavior of their biological counterparts (such as sperm cells, neutrophils, macrophages, bacteria etc.), which sense and respond to external chemical gradients, the current work aims at developing a theoretical framework to study the motion of a Janus particle in an externally imposed linear concentration gradient. The external gradient along with the self-generated concentration gradient determines the swimming velocity and orientation of the particle. The dominance of each of these effects is characterized by a nondimensional activity number 𝐴. The surface of Janus particle is modelled as having a different activity and mobility coefficient on the two halves. Using the Lorentz Reciprocal theorem, an analytical expression for the rotational and translational velocity is obtained. The analytical framework helps us divide the parameter space of surface activity and mobility into four regions where the particle exhibits different trajectories.

Polymeric Micro/Nanocarriers and Motors for Cargo Transport and Phototriggered Delivery

“…A body in a medium without motion has potential or static energy [253], representing a system in equilibrium [254]. Gradients of temperature [255] and concentration [256], along with transfer of momentum [257], electrons [258], protons [259], photons [260], and sound waves [261], alter the body's systemic equilibrium, transforming the potential energy into a dynamic state with kinetic energy [253]. Micro/nanomotors (MNs) are devices that suffer internal and external fluctuations in fluids by interacting with their environment and external fields, converting their static energy into kinetic energy and, thus, generating mechanical movement [262] that often seeks to accelerate the kinetics of the involved process, improving its efficiency (Figure 1(Bf)) [263].…”

Recycling and rheology of poly(lactic acid) (PLA) to make foams using supercritical fluid

“…155 In addition, the solidification of matrix also affects the expansion of the matrix. 156 If a composite with ceramic particles was used as in this study, the gas-solid interaction, 157 movement of the particles, 158 relation between transport phenomena and thermodynamics, 159 and the assembly of the particles due to the generation of strong acoustic noise 160 during foaming will be the additional variables to the process. Thus, it is not possible to separate an effect of one variable from other variables in relation to foam properties, but we can still analyze the certain effects of variables.…”

Thermotactic navigation of an artificial microswimmer near a plane wall

“…2013; Popescu et al. 2018; Vinze, Choudhary & Pushpavanam 2021), light (Lozano et al. 2016), electrostatic potential (Boymelgreen & Miloh 2012; Bayati & Najafi 2019), temperature (Bickel, Zecua & Würger 2014; Auschra et al.…”

“…2014; Vinze et al. 2021). Among the studies on similar fuel-free phoretic mechanisms, the recent work of Auschra et al.…”

“…2021; Vinze et al. 2021), but these studies were limited to the free-space dynamics of micromotors only, and the effects of a confining substrate were not considered. On the other hand, the near-wall dynamics of synthetic microswimmers is understood under the sole influence of self-phoresis (Uspal et al.…”