Migration Behavior of Low-Density Particles in Lab-on-a-Disc Devices: Effect of Walls

Abstract

The effect of the lateral walls of a Lab-On-a-Disc device on the dynamics of a model system of particles with a density lower than that of the solvent (modelling parasites eggs) is analyzed theoretically and experimentally. In the absence of lateral walls, a particle always moves in the direction of the centrifugal force, while its trajectory is deflected in the tangential direction by the inertial Coriolis and Euler forces. Lateral walls, depending on the angle forming with the radial direction, can guide the particle either in the same or in the opposite direction to the centrifugal force, thus resulting in unusual particle trajectories including zig-zag or backwards particle motion. The effect is pronounced in the case of short operation times when the acceleration of the angular rotation, and thus the Euler force, is considerable. The predicted unusual motion is demonstrated by numerically solving the equation of motion in the presence of lateral walls and verified in the experiment with particles of density lower than that of the solvent. Our analysis is useful for design and operational considerations of Lab-On-a-Disc devices aiming for or involving (bio)particle handling.

Enhancing the Yield of a Lab-on-a-Disk-Based Single-Image Parasite Quantification Device

“…Since the density of parasite eggs is lower than that of the solvent, they move towards the center of rotation during centrifugation. It is worth noting that the revealed behavior occurs mainly near the center of rotation where the centrifugal force is small, and the interplay of the tangential Euler and Coriolis forces and the interaction with the walls could cause the backward motion [27]. Therefore, the undesirable effects occur near the entrance to the FOV, as confirmed by the experimental observations.…”

“…The effect of the lateral walls of a LOD device on the dynamics of a model system of particles with a density lower than that of the solvent (modelling parasite eggs) has been analyzed theoretically and experimentally [27]. It has been shown that the trajectory of a particle moving under the action of the centrifugal force is deflected in the tangential direction by the inertial Coriolis and Euler forces, and in this situation, the particle easily reaches the lateral walls of the narrow channel.…”

“…Being confined in a narrow channel, a particle (egg) can therefore easily reach the lateral walls of the channel. The walls, depending on the angle they form with the radial direction, can guide the particle either in the same or in the opposite direction to the centrifugal force, thus resulting in unusual particle trajectories including zig-zag or backwards particle motion [27] (see Figure 1b). This effect is pronounced in the case of short operation times and for repeated ramping up and down cycles when the acceleration of the angular rotation, and, thus, the Euler force, is considerable.…”

“…A particle trajectory is affected by the Coriolis force, −2𝑚𝜔 ⃗ × 𝑣 ⃗, and the Euler force, − 𝑚 ⃗ × 𝑟 ⃗. These forces, which are tangential to either the velocity vector of the moving particle (the Coriolis force) or the radial direction (the Euler force), lead to a deviation in the direction of motion of particles (eggs) from the direction of the centrifugal force, −𝑚𝜔 ⃗ × 𝜔 ⃗ × 𝑟 ⃗ (i.e., the radial direction) [27]. Being confined in a narrow channel, a particle (egg) can therefore easily reach the lateral walls of the channel.…”

In Situ Mechanochemical Treatment of the Fe–Si–PGMs Alloy for Enhanced Platinum Group Metal Recovery: Overcoming Thermodynamic and Kinetic Barriers

“…The movement of a planetary ball milling device is illustrated in Figure a, which results from the combination of two opposing centrifugal fields generated by rotation and revolution . We assume that the grinding ball is a particle with mass m and that its motion in the planetary ball milling process obeys Newton’s second law of motion F⃗ = m a⃗ = ∑ i F⃗ i F⃗ = prefix− m ω⃗ 1 × ( ω⃗ 1 × L⃗ ) − m ω⃗ 2 × ( ω⃗ 2 × R⃗ 2 ) − 2 m ω⃗ 1 × ( ω⃗ 2 × R⃗ 2 ) − m normald ω⃗ 1 normald t × L⃗ + ∑ i F⃗ i Here, a⃗ represents the acceleration (eq ), ω⃗ 1 and ω⃗ 2 represent the angular velocities of the revolution and rotation, respectively. L⃗ and R⃗ 2 represent the radii of the revolution and rotation, respectively.…”