Kinetics of Colloidal Particle Deposition From Electrokinetic Microfluidic Flows

ASME 2009 7th International Conference on Nanochannels, Microchannels and Minichannels ◽

10.1115/icnmm2009-82183 ◽

2009 ◽

Author(s):

Harikrishnan N. Unni ◽

Chun Yang

Keyword(s):

Brownian Dynamics ◽

Parallel Plate ◽

Particle Deposition ◽

Colloidal Particles ◽

Transport Model ◽

Polystyrene Latex ◽

Dynamics Simulation ◽

Brownian Dynamics Simulation ◽

Theoretical Predictions ◽

Kinetics Of

This paper presents a theoretical and experimental investigation on the irreversible deposition of colloidal particles from electrokinetic microfluidic flow in parallel plate channels. The electrokinetic particle transport model presented in this study is based on the stochastic Langevin equation, incorporating the electrical, hydrodynamic, DLVO colloidal interactions and random Brownian motion of colloidal particles. The particle trajectories are computed via the Brownian dynamics simulation technique and the particle deposition is quantified in terms of the surface coverage. Direct videomicroscopic observation using the parallel-plate flow cell technique, is employed to determine the deposition kinetics of polystyrene latex particles in NaCl electrolytes. The theoretical predictions are compared with experimental results, and a reasonable agreement is found.

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Scale-free, programmable design of morphable chain loops of kilobots and colloidal motors

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1922635117 ◽

2020 ◽

Vol 117 (16) ◽

pp. 8700-8710

Author(s):

Mayank Agrawal ◽

Sharon C. Glotzer

Keyword(s):

Brownian Dynamics ◽

Colloidal Particles ◽

Autonomous Robots ◽

Design Strategy ◽

Dynamics Simulation ◽

Design Parameters ◽

Brownian Dynamics Simulation ◽

Scale Invariant ◽

Scale Free ◽

Mechanical Constraints

Micron-scale robots require systems that can morph into arbitrary target configurations controlled by external agents such as heat, light, electricity, and chemical environment. Achieving this behavior using conventional approaches is challenging because the available materials at these scales are not programmable like their macroscopic counterparts. To overcome this challenge, we propose a design strategy to make a robotic machine that is both programmable and compatible with colloidal-scale physics. Our strategy uses motors in the form of active colloidal particles that constantly propel forward. We sequence these motors end-to-end in a closed chain forming a two-dimensional loop that folds under its mechanical constraints. We encode the target loop shape and its motion by regulating six design parameters, each scale-invariant and achievable at the colloidal scale. We demonstrate the plausibility of our design strategy using centimeter-scale robots called kilobots. We use Brownian dynamics simulation to explore the large design space beyond that possible with kilobots, and present an analytical theory to aid the design process. Multiple loops can also be fused together to achieve several complex shapes and robotic behaviors, demonstrated by folding a letter shape “M,” a dynamic gripper, and a dynamic pacman. The material-agnostic, scale-free, and programmable nature of our design enables building a variety of reconfigurable and autonomous robots at both colloidal scales and macroscales.

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