Curvature-mediated programming of liquid crystal microflows

Abstract

We use experiments and numerical simulations to demonstrate that the curvature of microfluidic devices allows for flow programming in liquid crystals.

Electrically-driven modulation of flow patterns in liquid crystal microfludics

“…Boundary and initial conditions We use no-slip boundary conditions for the velocity on all walls in each configuration. Perfect ordering of the LC is assumed on the boundary and homeotropic anchoring with infinite strength is imposed in the rectangular channel; this is consistent with our previous research 24 , 25 , 44 , 45 and other researchers who have investigated the rheology of liquid crystals (Denniston and Yeomans 32 , 34 , Rey and coworkers 46 – 48 , and Sengupta and coworkers 22 , 23 ).…”

“…Numerical solutions were obtained using the OpenFOAM solver rheoFoamLC 43 . The solver has been previously used to model liquid crystal flows in other complex geometries 44 , and is capable of capturing defects 25 , 45 . Combination of the extended definition of the free energy (Eq.…”

“…In more complex domains, the competition between viscous and elastic effects, combined with geometric curvature, can be used to obtain a localised metering valve-like behaviour 25 . In extreme curvature cases (sharp right-angle bends), shear banding arises from the co-existence of subdomains where the director aligns either with the flow direction, or with the velocity gradient direction.…”

Defect-influenced particle advection in highly confined liquid crystal flows

“…22,23 Confinement effects, often in combination with the behaviour in external electric fields, were also investigated in liquid crystalline emulsions 24 as well as in droplets and shells. 25 The study of flowing liquid crystals covered primarily pure and confined phases 23,26–29 as they appear frequently in microfluidic setups.…”

Lock-key microfluidics: simulating nematic colloid advection along wavy-walled channels

“…[4][5][6][7] One means of sculpting particle trajectories is by suspending them in complex carrier fluids, as in topological microfluidics, 8 in which particles are guided by liquid crystalline carrier fluids. 9 Liquid crystalline materials are alluring for microfluidic transport because they are highly responsive to flows, [10][11][12] suspended inclusions 13,14 and confining surfaces. [15][16][17] When colloidal particles are dispersed in liquid crystalline fluids, the anisotropic nature of liquid crystals gives rise to emergent properties [18][19][20][21] and imposed anchoring at colloidal surfaces results in topological defects in the vicinity of the colloids to ensure topological charge neutrality.…”