Fig. 2
From: Robust thermoelastic microactuator based on an organic molecular crystal
Two directions of shape deformation during the phase transition. a, b Optical microscope images show that the temperature dependent shape deformation from the α- to β-phase can proceed in two independent directions. The position of the phase boundary is indicated with black arrows. c, d Overlapped microscope images of the same crystal before and after the phase transition, showing that the crystal orientations relate to the direction of the phase boundaries. The arrows indicate the corresponding shear directions. Scale bar is 20 μm. e Schematic presentations of the corresponding crystallographic planes and the shear directions (black arrows). The blue planes indicate the possible directions of the phase boundaries, which are parallel to the (101) or (10-1) plane. f Schematic presentations of the origin of the shear force and its relation to the shrinking/contraction (a-axis) and contraction/shrinking (c-axis) in the (010) plane during heating (short red arrows)/cooling (short blue arrows). The black and the gray grids represent the lattices of the α-phase and the β-phase, respectively. The long red and blue arrows show the shear forces that result in the migration of the phase boundary during heating and cooling, respectively
