Photoinduced thermomechanical effect in homogeneous nematics

Dissipative versus reversible contributions to macroscopic dynamics: the role of time-reversal symmetry and entropy production

“…Already in Akopyan and Zeldovich (1984) thermomechanical effects in deformed nematics have been suggested. Without invoking time reversal, they erroneously assumed that those effects are dissipative and can be derived from a dissipation function, cf.…”

“…45. This means the two approaches, Brand and Pleiner (1987) and Akopyan and Zeldovich (1984) are not equal, but the difference becomes manifest only, if both, the direct thermomechanical effect in the heat current and the inverse effect in the stress tensor are considered. The claim of Hakobyan et al (2004) that the two descriptions are equal, is wrong, since they overlooked that our definition of the stress tensor differs from theirs by a sign (in our case σ D ij = −∂R/∂A ij while they use σ R ij = ∂R thm /∂A ij ).…”

“…In the "Dynamic thermo-mechanical effects in textured nematic liquid crystals" section, it is shown, using timereversal behavior, that the dynamic thermo-mechanical and electro-mechanical effects in textured nematic liquid crystals are reversible. On the contrary, Akopyan and Zeldovich (1984) have erroneously assumed these thermomechanical couplings to be dissipative. The failure of their description becomes apparent when both, the direct and the inverse effects are measured simultaneously.…”

Lehmann rotation of cholesteric droplets driven by Marangoni convection

“…We immediately eliminated the explanation based on the existence of Leslie, Akopyan and Zel'dovich thermomechanical torques [8][9][10] . These torques exist [11][12][13][14][15] but are too small to explain the observed phenomena [14][15][16] .…”

Thermally excited vortical flow in a microsized nematic cell

“…In the field of LC phases, a great deal is known about their deformations under the influence of electric and magnetic fields, 2 whereas, on the other hand, comparatively little is known about the effect of a temperature gradient on their structure properties. [3][4][5][6] Recently, a new method to control LC flow dynamics using a bidirectionally aligned liquid crystal (BALC) film has been proposed. 7 It was shown for the case of bistable twisted nematic (BTN) devices, that dynamic flow is essential to the switching mechanism.…”