Bremer et al described a material (UUQU-4-N, Fig. ) which undergoes a direct Isotropic to NF transition. Although the NF phase is monotropic, the melting point of this material is sufficiently low as to permit room temperature studies on the NF phase; below 20 °C the dielectric permittivity of the material is in excess of 20000. Recently, Huang et al have reported two highly fluorinated rod-like mesogens which exhibit the NF phase (Figure ). As with all NF materials known to date, these materials feature polar groups (in this case, 1,3-dioxane, 2,5-difluorophenyl, nitrile) oriented in such a way to give a large longitudinal molecular electric dipole moment. Although the high melting points of these materials render them somewhat impractical, the development of a new class of NF materials is nonetheless extremely welcome. Appending a pendant acrylate unit to the structure of RM734 enabled Dai et al to perform in situ photopolymerisation, yielding the polymeric material SP1, which exhibits both N and NF mesophases (Figure ). Positioning the pendant acrylate unit on other rings or in the terminal position of the monomer gave only a conventional nematic phase. More recently, Nishikawa et al employed a photoisomerisable azobenzene additive (using DIO as a nematic host) to demonstrate a ferroelectric nematic material in which irradiation controls the dielectric permittivities (Figure ). Nishikawa et al find a photoresponsive dielectric permittivity of 200 < ε < 18,000, and demonstrate a photovariable capacitor which enables modulation of sound frequencies (in the range of 0.1-8.5 kHz).