Crystal microstructure
The crystal morphology of MKF crystallized with and without the
application of HIU was observed using a polarized light microscope
(Olympus BX51, Olympus Corp., Tokyo, Japan), with images captured using
a digital video camera (Canon-DS126431, Canon Inc., Japan). After the
HIU was applied to the sample for 5 s at 25 °C, 3 μL of the sample was
placed on a glass slide and covered by a cover slip. The temperature of
the glass slide and the cover slip was maintained at 25 °C by storing
them in a temperature-controlled cabinet prior use. The temperature of
the sample was set constant at 25 °C for 60 min using a temperature
controller (computer-controlled hot stage; Linkam LK-600PM, with cooling
unit; Linkam L-600A, Linkam Scientific Instruments, Ltd., UK). Crystal
image was captured at 1 min and at every 10 min of the isothermal time.