Colloidal transport through optical tweezer arrays

Abstract

Viscously damped particles driven past an evenly spaced array of potential energy wells or barriers may become kinetically locked in to the array, or else may escape from the array. The transition between locked-in and free-running states has been predicted to depend sensitively on the ratio between the particles' size and the separation between wells. This prediction is confirmed by measurements on monodisperse colloidal spheres driven through arrays of holographic optical traps.

Multidirectional sorting modes in deterministic lateral displacement devices

“…Of interest in the present context is that many numerical simulations of trajectories through various two-dimensional periodic potentials have been done to study these and other phenomena, including sorting of particles [9,10,11,12].…”

“…The novel sorting mode and its relation to kinetically locked-in transport DLD devices have thus far been made with a fixed flow direction and almost exclusively with M = 1. However, in theoretical work studying transport through periodic potential landscapes, the direction of the applied force is varied for a fixed array geometry and the transport direction is calculated [9,10,11,12]. To calculate the correspondence between varying the array parameters M and N used here and changing the flow direction in a fixed array as in [9,10,11,12] is cumbersome, but for a range of flow directions near t B− = 3e x − 1 10 e y , the angles to the flow direction θ B− and θ C vary as the flow directions change, but the relative angle between them, θ C − θ B− , remains a constant defined by the array.…”

Dumbbell diffusion in a spatially periodic potential

“…Introduction.-Investigations on the diffusion of different colloidal particles in a homogeneous solvent have a long history [1,2], while studies on the diffusion of small spheres, dimers and polymers in different potentials attract considerable interest only for a short time [3,4,5,6,7,8,9]. Laser-tweezer arrays are a new powerful tool for generating the desired spatially periodic, correlated or unstructured potentials in order to study the effects of inhomogeneous potential landscapes on the motion of colloidal particles [3,4,5,10]. Furthermore recent studies of dumbbells and polymers in random potentials are exciting issues in statistical physics [11,12].…”

Large-angular separation of particles induced by cascaded deflection angles in optical sorting

“…The multiinterference and phase contrast approach to generate the required interconnected optical lattice in references has experimentally been demonstrated. 7,12 Recently it has also been proven that discrete optical spots array is capable of realizing a deflection angle of 45° but it requires laser power higher than 1 W. 13 In order to realize large deflection angles but with moderate laser power, we propose a composite optical lattice pattern with two cascaded deflection axes to realize optical separation with a larger deflection angle. The composite spots pattern is enabled by a composite microlens array (MLA) fabricated in melted positive photoresist, which is employed efficiently to project the optical pattern into the microchamber on a sample stage.…”