Colloidal caterpillars for cargo transportation

Abstract

Tunable transport of tiny objects in fluid systems is demanding in diverse fields of science such as drug delivery, active matter far from equilibrium, and lab-on-a-chip applications. Here, we report the directed motion of colloidal particles and self-assembled colloidal chains in a nematic liquid crystal matrix using electrohydrodynamic convection (EHC) rolls. The asymmetric distortion of the molecular orientation around the particles results -for single particles -in a hopping motion from one EHC roll to the next and -for colloidal chains -in a caterpillar-like motion in the direction perpendicular to the roll axes. We demonstrate the use of the colloidal chains as micro traction engines for the transport of various types of micro cargo.

Nonlinear Electrophoresis of Colloids Controlled by Anisotropic Conductivity and Permittivity of Liquid-Crystalline Electrolyte

“…We direct the structural dipole is antiparallel to the direction of dipole, 0 v < [9]. Theoretically, the amplitude of electrophoretic velocity is predicted to be [9] ( ) [8,9,11,[13][14][15] and in the guiding effect of the director field [8,11,[16][17][18][19], there are no experimental data on how v depends on ε% and σ% , the two crucial properties of the nematic electrolyte. As predicted by Eq.…”

Microscopic characterisation of self-assembled colloidal particles in electrohydrodynamic convection of a low-birefringence nematic liquid crystal

“…The contrast of the stripe pattern is weak because of the small ∆n. The value is smaller than that of MBBA ∼ 15 µm in the earlier report [22] where the same commercial cells are used. It is also found that the temperature does not change the width so much.…”

“…The similar nature is observed for MBBA. [22] However the structure still cannot be maintained in Williams domains. On the other hand, we found that chains with moderate length consisting of ∼ 30 particles or fewer can exhibit a caterpillar-like motion in Williams domains.…”

“…Such collective dynamics is a topic of general interest from experimental and theoretical perspectives. [24,25] On the other hand, the NLC material used in earlier reports [22,23] is limited to MBBA ((4-methoxybenzylidene)-4-butylaniline). It is interesting to explore other systems to obtain further information.…”

“…Recently it is found that the chain of elastic dipoles shows a directed caterpillar-like motion in EHC. [22,23] This system provides a unique nature that enables a motion of self-assembled particles whose deformation occurs out of the focal plane of the microscope. Such collective dynamics is a topic of general interest from experimental and theoretical perspectives.…”