Starting from a microscopic model for a spherically symmetric active Janus particle, we study the interactions between two such active motors. The ambient fluid mediates a long range hydrodynamic interaction between two motors. This interaction has both direct and indirect hydrodynamic contributions. The direct contribution is due to the propagation of fluid flow that originated from a moving motor and affects the motion of the other motor. The indirect contribution emerges from the re-distribution of the ionic concentrations in the presence of both motors. Electric force exerted on the fluid from this ionic solution enhances the flow pattern and subsequently changes the motion of both motors. By formulating a perturbation method for very far separated motors, we derive analytic results for the transnational and rotational dynamics of the motors. We show that the overall interaction at the leading order, modifies the translational and rotational speeds of

Dynamics of chemically active particles moving by self-phoresis near chemically inert walls is studied theoretically by employing various choices for the activity function.

We theoretically consider the dynamics of a self-propelled active Janus motor moving in an external electric field. The external field can manipulate the route of a Janus particle and enforce it to move towards the desired targets. To investigate the trajectory of this active motor, we use a perturbative scheme. At the leading orders of surface activity of the Janus particle and also the external field, the orientational dynamics of the Janus particles behave like a mathematical pendulum with an angular the velocity that is sensitive to both the electric field and surface activity of the motor.

While compressing a colloidal state by optical means alone has been previously achieved through a specific time-dependence of the trap stiffness, realizing quickly the reverse transformation stumbles upon the necessity of a transiently expulsive trap. To circumvent this difficulty, we propose to drive the colloids by a combination of optical trapping and diffusiophoretic forces, both time-dependent. Forcing via diffusiophoresis is enforced by controlling the salt concentration at the boundary of the domain where the colloids are confined. The method takes advantage of the separation of time scales between salt and colloidal dynamics, and realizes a fast decompression in an optical trap that remains confining at all times. We thereby obtain a so-called shortcut to adiabaticity protocol where colloidal dynamics, enslaved to salt dynamics, can nevertheless be controlled as desired.