Depletion forces exerted by self-propelled particles on circular and elliptical passive objects are studied using numerical simulations. We show that a bath of active particles can induce repulsive and attractive forces which are sensitive to the shape and orientation of the passive objects (either horizontal or vertical ellipses). The resultant force on the passive objects due to the active particles is studied as a function of the shape and orientation of the passive objects, magnitude of the angular noise, distance between the passive objects. By increasing the distance between obstacles the magnitude of the repulsive depletion force increases, as long as such a distance is less than one active particle diameter. For longer distances, the magnitude of the force always decrease with increasing distance. We also found that attractive forces may arise for vertical ellipses at high enough area fraction.

Diffusive properties of colloidal crystals in a quasi-one-dimensional channel are studied using numerical simulations. In order to study the influence of the attractive interaction between particles, it was introduced as an artificial dimensionless parameter β in the attractive term of the interaction potential. Changing the value of β, we can tune the effect of attraction between particles. We show that charged particles can change their mobility and the diffusion exponent of a one-chain like system. Variation on exponent diffusion can be induced by tuning the attractive part of interaction potential, making possible the existence of diffusive regimes between single-file diffusion (SFD) and normal diffusion, without changing confinement strength. System stoichiometry was changed, imposing particles in different arrangements in small clusters, which varies the diffusive behaviour. If stoichiometry is different from 1:1, it is possible to have particles with equal charges but with different mobilities. Another important observation is that mean-square displacement (MSD) for different charges is different for different values.

Resumo Neste trabalho ajustes são realizados em algumas equações do artigo “Sobre a Dinâmica de Partículas Carregadas em Campos Elétrico e Magnético Estáticos”, publicado nesta revista em 2017 [1]. Nossos cálculos mostram que (i) no caso particular 1, a trajetória circular da partícula carregada acontece em um quadrante diferente; (ii) no caso particular 2, a trajetória da partícula deve ser deslocada para o semieixo negativo de y e (iii) no caso particular 3 mostramos a necessidade da troca dos eixos estudados bem como o sinal de uma das equações, o que modifica a trajetória da partícula carregada. Com estes três ajustes mencionados, agora as equações da trajetória passam a obedecer a regra da mão direita.