Abstract
The nematic fluid pumping mechanism responsible for the heat driven flow in microfluidic nematic channels and capillaries is described in a number of applications. This heat driven flow can be generated either by a laser beam focused inside the nematic microvolume and at the nematic channel boundary, or by inhomogeneous heating of the nematic channel or capillary boundaries. As an example, the scenario of the vortex flow excitation in microsized nematic volume, under the influence of a temperature gradient caused by the heat flux through the bounding surface of the channel, is described. In order to clarify the role of heat flux in the formation of the vortex flow in microsized nematic volume, a number of hydrodynamic regimes based on a nonlinear extension of the Ericksen–Leslie theory, supplemented by thermomechanical correction of the shear stress and Rayleigh dissipation function, as well as taking into account the entropy balance equation, are analyzed. It is shown that the features of the vortex flow are affected not only by the power of the laser radiation, but also by the duration of the energy injection into the microsized nematic channel.
Highlights
Impact of liquid crystal (LC) materials on modern technology is very impressive [1].The recent technological revolution has been brought by these LC materials in the field of displays
Nematic drops of appropriate size confined in the capillary are microdevices, whose molecular orientations can be manipulated by a temperature gradient ∇T, generated, for instance, by a laser beam focused both in the microfluidic volume or on the boundary of the LC channel
We are primary concerned here with the description of the physical mechanism responsible for the flow in the LC channel confined between solid surfaces, which is excited by the temperature gradient ∇T, and the magnitude of that flow is proportional to ∆T, whereas the direction of v influences both the direction of the heat flux q and the character of the preferred anchoring of the average molecular direction nto the restricted surfaces
Summary
Impact of liquid crystal (LC) materials on modern technology is very impressive [1]. The recent technological revolution has been brought by these LC materials in the field of displays. They have various advantages in comparison with other types of microsensors and microactuators; simple structure, high shape adaptability, easy downsizing, and low driving voltages This is due to the fact that liquid crystals are extremely sensitive to external stimuli and can be used for the construction of stimuli-responsive devices, such as sensors or actuators. This review is devoted to the latest results describing the possibilities of computational methods implemented in the framework of the nonlinear extension of the Ericksen–Leslie theory, with accounting the entropy balance equation [18] Another purpose of our review is to show some routes in describing the laser-excited motion of nematics enclosed in a microsized channel with a free surface.
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