Tuning Fluidic Resistance via Liquid Crystal Microfluidics

Sengupta, Anupam

doi:10.3390/ijms141122826

Cited by 21 publications

(26 citation statements)

References 27 publications

(34 reference statements)

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“…Zhou and Forest 20 performed calculations for two-dimensional flow in the low-flow-rate, strong-anchoring limit for the cases of homeotropic, planar and tilted anchoring. Sengupta et al 21,22 performed experiments and lattice Boltzmann simulations of flow in rectangular channels over a wider range of flow rates. Feng and Leal 23 and Quintans Carou et al 24 investigated, by analytical and numerical techniques, nematic flow between plates of narrowing or widening separation, while Manneville and Dubois-Violette 25 and Tarasov et al 26 investigated the onset of instabilities in channel flow.…”

Section: Introductionmentioning

confidence: 99%

The effect of anchoring on the nematic flow in channels

2015

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Understanding the flow of liquid crystals in microfluidic environments plays an important role in many fields, including device design and microbiology. We perform hybrid lattice-Boltzmann simulations of a nematic liquid crystal flowing under an applied pressure gradient in two-dimensional channels with various anchoring boundary conditions at the substrate walls. We investigate the relation between flow rate and pressure gradient and the corresponding profile of the nematic director, and find significant departures from the linear Poiseuille relation. We also identify a morphological transition in the director profile and explain this in terms of an instability in the dynamical equations. We examine the qualitative and quantitative effects of changing the type and strength of the anchoring. Understanding such effects may provide a useful means of quantifying the anchoring of a substrate by measuring its flow properties.

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Section: Introductionmentioning

confidence: 99%

The effect of anchoring on the nematic flow in channels

2015

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“…This work is motivated by recent reports on the unique thermofluidic properties of 5CB in its native form [25][26][27][28] and our own findings related to the macroscopic phase behaviour of 5CB and MeOH. 30 When studied in the bulk, this mixture exhibits an UCST of 24.4°C, a temperature range that can conveniently be accessed.…”

Section: Resultsmentioning

confidence: 99%

“…In recent years, 4-cyano-4′-pentylbiphenyl (5CB) in its native form has attracted significant interest in liquid crystal microfluidics due to unique thermofluidic properties, including a temperature-tunable flow profile and fluidic resistance, as well as temperature-induced molecular reorientation and controlled nucleation and growth of stable reconfigurable domains. [25][26][27][28] Herein, we investigate the fluidic behaviour in a 50/50 v/v blend of 5CB with methanol (MeOH), in particular the influence of temperature. We carefully mix and phase separate the liquid blend and relate the observed flow patterns to the role of temperature-modulated interfacial tension and viscosity.…”

Section: Introductionmentioning

confidence: 99%

Microfluidics of binary liquid mixtures with temperature-dependent miscibility

Fornerod

Amstad

Guldin

2020

Mol. Syst. Des. Eng.

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Liquid-liquid microfluidic systems rely on the intricate control over the fluid properties of either miscible or immiscible mixtures. Herein, we report on the use of partially miscible binary liquid mixtures that lend their microfluidic properties from a highly temperature-sensitive mixing and phase separation behaviour. For a blend composed of the thermotropic liquid crystal 4-cyano-4′-pentylbiphenyl (5CB) and methanol, mixing at temperatures above the upper critical solution temperature (UCST; 24.4°C) leads to a uniform single phase while partial mixing can be achieved at temperatures below the UCST. Thermally-driven phase separation inside the microfluidic channels results in the spontaneous formation of very regular phase arrangements, namely in droplets, plug, slug and annular flow. We map different flow regimes and relate findings to the role of interfacial tension and viscosity and their temperature dependence. Importantly, different flow regimes can be achieved at constant channel architecture and flow rate by varying the temperature of the blend. A consistent behaviour is observed for a binary liquid mixture with lower critical solution temperature, namely 2,6-lutidine and water. This temperature-responsive approach to microfluidics is an interesting candidate for multi-stage processes, selective extraction and sensing applications.358 | Mol. Syst. Des. Eng., 2020, 5, 358-365 This journal isMicrofluidic processes generally rely on the handling of either miscible or immiscible liquid mixtures. In this work, we introduce a novel temperaturebased microfluidic concept that is driven by and engineered through the underlying molecular characteristics rather than active or passive components on the microchannel architecture. We demonstrate how the temperature-dependent properties of regular solutions, namely miscibility, interfacial tension and viscosity, enable the detailed control over mixing and the formation of highly regular flow patterns. Such systems allow seamless switching between mixed and phase separated states in distinct flow regimes, thus offering novel routes for complex multi-stage processes, selective extraction and sensing applications.

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“…One can harness the flow-director coupling to pattern different pathways, both passive and active, to modulate the fluidic resistance within microfluidic devices. [37] Appropriate surface anchoring conditionswhich imprint distinct fluidic resistances within microchannels under similar hydrodynamic parameters -act as passive cues. The fluidic resistance was actively modulated using temperature as an external field.…”

Section: Applicationsmentioning

confidence: 99%

“…This registered the initial conditions for the subsequent flow experiments. By varying the pressure difference between the inlet and outlet of the microchannel, we studied the dynamic variation of the nematic viscosity for different anchoring conditions (see [37] for experimental details). Rheologically, a channel with homeotropic surface anchoring offered higher hydrodynamic resistance than one possessing uniform planar anchoring.…”

Section: Flow Of Nlcs Within Microchannelsmentioning

confidence: 99%

Topological microfluidics: present and prospects

Sengupta

2015

Liquid Crystals Today

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Liquid crystals (LCs) are mesogenic phases of matter which combine liquid fluidity with crystalline solid properties. Precise knowledge of the molecular orientations -close to the boundaries and within the material bulk -is necessary for understanding their flow behaviour, especially in microfluidic settings. While the boundary conditions are set, passively, by surface-induced molecular orientations, the bulk orientation in flow is determined, actively, by the anisotropic coupling between the flow and the molecular orientation. Together, the surface and the bulk orientations offer a range of topological constraints within microfluidic channels, which affect the evolution and sustenance of flow-induced phenomena in LC-based systems. The concept of topological microfluidics can be extended to different classes of anisotropic fluids, allowing us to explore and to employ such fluids as complex functional materials for microfluidics, thereby significantly broadening the reach of conventional microfluidics.

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Tuning Fluidic Resistance via Liquid Crystal Microfluidics

Cited by 21 publications

References 27 publications

The effect of anchoring on the nematic flow in channels

The effect of anchoring on the nematic flow in channels

Microfluidics of binary liquid mixtures with temperature-dependent miscibility

Topological microfluidics: present and prospects

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