Topology is a universal concept that is encountered in daily life and is known to determine many static and dynamical properties of matter. Taming and controlling the topology of materials therefore constitutes a contemporary interdisciplinary challenge. Building on the controllable spatial properties of soft matter appears as a relevant strategy to address the challenge, in particular, because it may lead to paradigmatic model systems that allow checking theories experimentally. Here we report experimentally on a wealth of complex free-standing metastable topological architectures at the micron scale, in frustrated chiral nematic droplets. These results support recent works predicting the formation of free-standing knotted and linked disclination structures in confined chiral nematic fluids. We also demonstrate that various kinds of external fields (thermal, electrical and optical) can be used to achieve topological remote control. All this may foster the development of new devices based on topologically structured soft media.

Diarylethene derivatives, which have an optically active l- or d-menthyl group at the 2-position of benzo[b]thiophene ring, were synthesized. Irradiation with 450 nm light in solution led to the formation of diastereomer pairs of the closed-ring forms. The product ratio of the diastereomers was dependent on solvent polarity and temperature. In slightly polar (or polarizable) solvents, such as THF and toluene, an asymmetric photocyclization was observed. At −40 °C in toluene, a diastereomer excess as large as 86.6% was observed. The mechanism of the asymmetric photocyclization is discussed.

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Light technology is based on generating, detecting and controlling the wavelength, polarization and direction of light. Emerging applications range from electronics and telecommunication to health, defence and security. In particular, data transmission and communication technologies are currently asking for increasingly complex and fast devices, and therefore there is a growing interest in materials that can be used to transmit light and also to control the distribution of light in space and time. Here, we design chiral nematic microspheres whose shape enables them to reflect light of different wavelengths and handedness in all directions. Assembled in organized hexagonal superstructures, these microspheres of well-defined sizes communicate optically with high selectivity for the colour and chirality of light. Importantly, when the microspheres are doped with photo-responsive molecular switches, their chiroptical communication can be tuned, both gradually in wavelength and reversibly in polarization. Since the kinetics of the “on” and “off” switching can be adjusted by molecular engineering of the dopants and because the photonic cross-communication is selective with respect to the chirality of the incoming light, these photo-responsive microspheres show potential for chiroptical all-optical distributors and switches, in which wavelength, chirality and direction of the reflected light can be controlled independently and reversibly.

The physico-chemical processes supporting life’s purposeful movement remain essentially unknown. Self-propelling chiral droplets offer a minimalistic model of swimming cells and, in surfactant-rich water, droplets of chiral nematic liquid crystals follow the threads of a screw. We demonstrate that the geometry of their trajectory is determined by both the number of turns in, and the handedness of, their spiral organization. Using molecular motors as photo-invertible chiral dopants allows converting between right-handed and left-handed trajectories dynamically, and droplets subjected to such an inversion reorient in a direction that is also encoded by the number of spiral turns. This motile behavior stems from dynamic transmission of chirality, from the artificial molecular motors to the liquid crystal in confinement and eventually to the helical trajectory, in analogy with the chirality-operated motion and reorientation of swimming cells and unicellular organisms.

The causes of recurrence after microvascular decompression for trigeminal neuralgia and the results of re-operations were studied in 6 cases. Eighty-two patients with trigeminal neuralgia were operated on through microvascular decompression using the technique of interposing Teflon felt between the offending artery and the pons and/or nerve. Recurrence occurred in 14 cases (17.1%) and re-operations were carried out in 6 severe cases at which time the sling retraction technique was used. At the second operation, the adhesion of the interposed Teflon felt was found at the trigeminal nerve in all cases and the adhesions were the main cause of recurrence. The Teflon felt was dissected from the nerve, and the sling of the Teflon felt adhering to the offending arteries was fixed to the tentorium in order to transpose the arteries and avoid re-adhesion. All cases resulted in an excellent relief from pain and experienced no pain for at least 2 years. The intra-operative findings of our cases indicated that the microvascular decompression using the interposing technique may result in adhesion of the prosthesis to the nerve and thus eventually lead to recurrence. Our surgical experience also suggests that such recurrent cases should be re-operated on using the sling retraction technique instead of the interposing technique, even for the first microvascular decompression procedure.

[reaction: see text] Photochromic diarylethene derivatives having benzofuran heteroaryl groups, bis(2-methyl-1-benzofuran-3-yl)perfluorocyclopentene and bis(2-butyl-1-benzofuran-3-yl)perfluorocyclopentene, were synthesized, and their photochromic performance was examined in hexane solution as well as in the single-crystalline phase. The compounds exhibited photochromic reactivity even in the single-crystalline phase.

Photochromic diarylethene dimer derivatives with large two-photon absorption (TPA) cross-sections have been designed and synthesized. The derivatives have a D-pi-D structure in which indole rings are used as donor units (D) and 1,4-bis(ethynyl)benzene or 1,4-bis(ethenyl)benzene as a pi-conjugated chain unit (pi). Compound 5 a, which has oxazole rings as one of the aryl groups, showed a TPA cross-section of 23 GM at 820 nm and exhibited efficient two-photon photochromic reactivity.