Electrically driven nematic flow in microfluidic devices containing a temperature gradient

Area of Science:

• Physics
• Materials Science
• Fluid Dynamics

Background:

• Homogeneously aligned liquid crystals (HALC) are used in microfluidic channels.
• Interactions between electric fields, director field gradients, and temperature gradients are key.
• Understanding these interactions is crucial for developing novel fluid manipulation techniques.

Purpose of the Study:

• To develop a fluid pumping principle based on coupled fields in HALC microfluidic channels.
• To investigate the excitation of horizontal flow (v) due to electric field (E) and temperature gradient (∇T).
• To analyze the influence of heat flux (q) and electric field strength on fluid flow.

Main Methods:

• Utilized a nonlinear extension of the Ericksen-Leslie theory.
• Incorporated the entropy balance equation into calculations.
• Modeled the fluid pumping principle within a HALC microfluidic channel.

Main Results:

• Excitation of horizontal flow (v) was demonstrated through the coupling of ∇T, ∇n, and E.
• Flow direction and magnitude are dependent on heat flux (q) and electric field strength (E).
• Maximum flow velocity observed at E/E_th = 2.0; flow stops at E >> E_th, enabling kink-like wave reorientation.

Conclusions:

• A novel fluid pumping principle has been successfully developed.
• The study reveals a mechanism for converting electric fields into fluid flow and director reorientation.
• Findings suggest potential for new applications in microfluidics and liquid crystal devices.