Satoshi Aya

South China University of Technology | SCUT · South China Advanced Institute for Soft Matter Science and Technology（AISMST）

Ferroelectric nematic liquid crystals are polar fluids characterized by microscopic orientational ordering and macroscopic spontaneous polarizations. Within these fluids, walls that separate domains of different polarizations are ubiquitous. We demonstrate that the {\pi} walls in films of polar fluids consist of twin half-integer surface disclinati...

Ferroelectric nematic (NF) liquid crystals are an intriguing polar system for exploring topological defects, and their properties are subject to significant influence by ionic doping. A prior theory based on a modified XY model predicts that string defects with half-integer vortex-antivortex pairs can be excited, while such stable string defects ha...

Polar nematic liquid crystals are new classes of condensed-matter states, where the inversion symmetry common to the traditional apolar nematics is broken. Establishing theoretical descriptions for the novel phase states...

In the traditional chiral nematic liquid crystal, the apolar cholesterics, the dielectric effect is the main driving force for responding to an electric field. The emerging polar chiral nematics, dubbed...

The recent discovery of ferroelectric nematics provides new opportunities for exploring polar topology in liquid matter. Here, we report numerous potential polarization topological states (e.g., polar vortex-like and line disclination mediated structures) in confined ferroelectric nematics with similar free-energy levels. In the experiment, they ap...

Magnetic and electric dipoles have similar symmetry and are therefore expected to exhibit many common structures. However, despite frequent reports of various spin textures composed of magnetic dipoles, investigations on long-range ordered electric dipoles have been scarce, until recently. Here we discover spontaneous toroidal polar topology in an...

An emergent liquid ferroelectric material is dispersed into polydimethylsiloxane as microdroplets, realizing a stretchable and ferroelectric high-κ elastomer.

A great deal of effort has been recently devoted to the study of dielectric relaxation processes in ferroelectric nematic liquid crystals, yet their interpretation remains unclear. In this work, we present the results of broadband dielectric spectroscopy experiments of a prototypical ferroelectric nematogen in the frequency range 10 Hz–110 MHz at d...

Magnetic and electric dipoles share the symmetry similarity, being expected to exhibit many common structures. However, despite various spin textures composed of magnetic dipoles being reported frequently, investigations on long-range ordered electric dipoles have been scarcely made until recently. Here, we discover spontaneous toroidal polar topol...

A great deal of effort has been recently devoted to the study of dielectric relaxation processes in ferroelectric nematic liquid crystals, yet their interpretation remains unclear. In this work, we present the results of broadband dielectric spectroscopy experiments of a prototypical ferroelectric nematogen in the frequency range 10 Hz-110 MHz at d...

By analogy with spin waves in ferromagnetic systems, the polarization (or dipole) wave is the electric counterpart that remains elusive. Here, we discover that the helielectricity, i.e., a polarization field with helicoidal helices that corresponds to a quasi-layered chiral nematic environment, causes a spontaneous formation of large-scale polariza...

In nonlinear optical systems, the optical superposition principle breaks down. The system's response (including electric polarization, current density, etc) is not proportional to the stimulus it receives. Over the past half century, nonlinear optics has grown from an individual frequency doubling experiment into a broad academic field. The nonline...

The recently discovered ferroelectric nematic liquids incorporate to the functional combination of fluidity, processability and anisotropic optical properties of nematic liquids, an astonishing range of physical properties derived from the phase polarity. Among them, the remarkably large values of second order optical susceptibility encourage to ex...

It is an ongoing endeavor in chemistry and materials science to regulate coacervate droplets on a physiologically relevant spatiotemporal scale to ultimately match or even surpass living cells' precision, complexity, and functionality. Herein, we develop a magnetic strategy orthogonal to the thermal, pH, light, or chemical counterparts that are com...

Circular dichroism is a technologically important phenomenon contrasting the absorption and resultant emission properties between left- and right-handed circularly polarized light. While the chiral handedness of systems mainly determines the mechanism of the circular dichroism in linear optics, the counterpart in the nonlinear optical regime is non...

The recently discovered ferroelectric nematic liquids incorporate to the functional combination of fluidity, processability and anisotropic optical properties of nematic liquids, an astonishing range of physical properties derived from the phase polarity. Among them, the remarkably large values of second order optical susceptibility encourage to ex...

Sessile droplets of a ferroelectric nematic liquid crystalline material were exposed to surface electric fields produced by pyroelectric and photogalvanic (photovoltaic) effects in X-cut iron-doped lithium niobate crystals. The resulting dynamic processes were monitored by polarisation optical (video)microscopy (POM). During heating/cooling cycles,...

Circular dichroism is a technologically important phenomenon contrasting the absorption and resultant emission properties between left- and right-handed circularly polarized light. While the chiral handedness of systems mainly determines the...

The second-order nonlinear optical effect is the foundation of realizing optical wavelength regulation and conversion technology. In recent decades, it was shown that improved organic nonlinear optical materials could deliver...

Topological textures have fascinated people in different areas of physics and technologies. However, the observations are limited in magnetic and solid-state ferroelectric systems. Ferroelectric nematic is the first liquid-state ferroelectric that would carry many possibilities of spatially-distributed polarization fields. Contrary to traditional m...

For over decades, nematic liquid crystals have been recognized as highly fluidic materials that respond to electric field on the millisecond scale. In contrast to traditional nematics with fast responsivity, we herein report nontrivial ultraslow electric-driven dynamics in bent-shaped nematic materials. Varying the alkyl chain spacers of bent-shape...

Topological spin and polar textures have fascinated people in different areas of physics and technologies. However, the observations are limited in magnetic and solid-state ferroelectric systems. Ferroelectric nematic is the first liquid-state ferroelectric that would carry many possibilities of spatially distributed polarization fields. Contrary t...

Determination of material and optical properties in structured films and fluids, e.g., refractive index and material thickness, usually requires special optical geometries and instruments. This prevents one from studying optical properties especially in soft matter systems with nonuniform hierarchical and orientational structures. Here we develop a...

The emerging matter category of liquid-matter ferroelectrics, i.e., ferroelectric nematics, demonstrates an unprecedented combination of fluidity and spontaneous polarization. However, unlike traditional ferroelectrics, the field-switched polarization at zero-field cannot be conserved, so the memory effect remains challenging. Here we report anothe...

Sessile droplets of a ferroelectric nematic liquid crystalline material were exposed to surface electric fields produced by pyroelectric and photogalvanic (photovoltaic) effects in X-cut iron-doped lithium niobate crystals. The resulting dynamic processes were monitored by polarization optical (video)microscopy (POM). During heating/cooling cycles,...

Ferroelectric nematic phase is a novel state of matter, i.e. the sixth nematic liquid crystalline state, that represents high degrees of fluidity and polarity simultaneously. Thanks to the unique dielectric response and strong optical nonlinearity originated from the spontaneous polarisation, this new category of materials has begun to receive trem...

Second-order optical nonlinearity is the essential concept for realizing modern technologies of optical wavelength conversion. The emerging helical polarization fluid, dubbed helielectric nematic, now makes it possible to design and easily fabricate various polarization structures and control their optical responses. The matter family is demonstrat...

Ferroelectricity is a property with spontaneous polarization, which is of paramount importance in modern electrooptic applications. Yet, its observations are mostly limited to solids or chiral smectic C liquid crystals with nearly no fluidity. The fluidic ferroelectrics, called ferroelectric nematics, have recently become available by incorporating...

The emerging ferroelectric nematic liquid crystals have been attracting broader interests in new liquid crystal physics and their unique material properties. One big challenge for the ferroelectric nematic research is to enrich the material choice, which is now limited to RM734 and DIO families as representatives, in sharp contrast to the enormousl...

Combinations of different geometries and surface anchoring conditions give rise to the diversity of topological structures in nematic colloid systems. Tuning these parameters in a single system offers possibilities for observing the evolution of the topological transformation and for manipulating colloids through topological forces. Here we investi...

Toron is one of the fundamental chiral topological textures appearing in many spintronic and soft matter systems. Here we report on the observation of torons in cholesteric liquid crystals with positive dielectric anisotropy (Δε>0). In addition, the materials show smectic-A phase beneath the cholesteric phase, enabling us to see the pretransitional...

Ferroelectric nematic is an emerging liquid crystalline state, cohabiting fluidity and ferroelectricity. The incidence of such a unique state necessitates special requirements on molecular geometry and physicochemical parameters. However, how...

Just like in living organisms, if precise coherent operation of tiny movable components is possible, one may generate a macroscopic mechanical motion. Here we report that ~1010 pieces of colloidally dispersed nanosheets in aqueous media can be made to operate coherently to generate a propagating macroscopic wave under a non-equilibrium state. The n...

Significance The recent discovery of the emerging ferroelectric nematics opens an avenue not only for exploring exotic polar matter states in condensed matter physics but also for providing opportunities toward brand new liquid crystal technologies. Here, we revealed the existence of a helielectric nematic state by introducing the chirality into th...

Shape-transformable molecular additives with photoresponsivity, such as azobenzene or spiropyran, in matter are known to decrease the local order parameter and lead to drastic state variations under light irradiation. For example, a liquid crystalline state can be transformed to an isotropic liquid state by photo-exciting a tiny amount of azobenzen...

About a century ago, Born proposed a possible matter of state, ferroelectric fluid, might exist if the dipole moment is strong enough. The experimental realisation of such states needs magnifying molecular polar nature to macroscopic scales in liquids. Here, we report on the discovery of a novel chiral liquid matter state, dubbed chiral ferronemati...

Superhigh-ε materials that exhibit exceptionally high dielectric permittivity are recognized as potential candidates for a wide range of next-generation photonic and electronic devices. In general, achieving a high-ε state requires low material symmetry, as most known high-ε materials are symmetry-broken crystals. There are few reports on fluidic h...

The understanding of correlations between molecular-details and macroscopic material behaviors is a fundamental question of molecular chemistry/physics and offers practical interests in material design with fine-property-tunability. Herein, we demonstrate extreme...

This study focused on the use of nonconventional bent-core π-electronic systems, 2,2'-bipyrroles substituted with modified benzoyl units, as building units of stimuli-responsive assemblies. Electric-field-responsive mesophase behaviors were observed in homochiral synclinic ferroelectric smectic C structures comprising the syn conformations. Electri...

Super-high-\k{appa} materials that exhibit exceptionally high dielectric permittivity are recognized as potential candidates for a wide range of next-generation photonic and electronic devices. Generally, the high dielectricity for achieving a high-\k{appa} state requires a low symmetry of materials so that most of the discovered high-\k{appa} mate...

Azodendrimer is a class of branched polymer, whose structure can be modulated by light irradiation. Recently, a new type of liquid crystalline dendrimers that serve as a command surface has been reported. They received tremendous attention due to the fundamental interests of the variation of their properties (e.g., alignment, topology) in response...

The generation of spatially localized, soliton-like hydrodynamic disturbances in microscale fluidic systems is an intriguing challenge. Herein, we introduce nonequilibrium solitons in nematic liquid crystals stimulated by an electric field. These dynamic solitons are robust as long as the electric field is maintained. Interestingly, their kinetic b...

Large‐scale patterning of topological defects is vital and challenging from both fundamental and technological points of view in anisotropic fluids. However, this is usually difficult because of their unfavorably high‐energy states. Here, a simple but general pathway for topology engineering is presented: processing topological defects and shape la...

Twist-bend nematic (NTB) phase is one of the new types of nematics found recently, which possesses local nematic order with a heliconical orientational modulation at nanoscale. Herein, we report for the first time a comprehensive study on the both the properties in both the N and NTB phases over a wide temperature range, based on a thioether-linked...

Solitary waves, dubbed "solitons", are special types of waves that propagate for an infinite distance under ideal conditions. These waves are ubiquitously found in nature such as typhoon or neuron signals. Yet, their artificial generation and the control of their propagation remain outstanding challenges in materials science owing to an insufficien...

The construction of hierarchical nanostructures with precise morphological and dimensional control has been one of the ultimate goals of contemporary materials science and chemistry, and the emulation of tailor-made nanoscale superstructures realized in the nature, using artificial building blocks, poses outstanding challenges. Herein we report a o...

In article number 1802032 Satoshi Aya, Fumito Araoka, Antal Jákli, and coworkers demonstrate that a liquid crystal dimer can work as a switchable photorheological material between a solid (shown in orange) and liquid crystal (blue) states by shining a ultraviolet (UV) light (purple). The photorheological switching is based on a geometrical variatio...

Mechanically responsive organic materials can change their viscoelastic properties in response to external stimuli. However, materials that exhibit highly contrasting viscoelastic properties coupled with fast and reversible switching between the states involved have remained elusive. Here, it is shown that a nonsymmetric photoresponsive liquid crys...

We investigate the structure and the magnetooptical response of isotropic and anisotropic fibrillous organoferrogels with mobile magnetic nanoparticles (MNPs). We demonstrate that the presence of the gel network restricts the magnetooptical response of the ferrogel. Even though the ferrogel exhibits no magnetic hysteresis, an optical hysteresis has...

Azobenzene-based molecular systems are used as photoreswitchable smart materials with applications in many areas, including designing surface orientational patterning of anisotropic molecules. It is important and challenging to probe the real-time photoresponsive behaviors of these systems, particularly the photodynamic processes from the mesoscopi...

We present an unusual temperature dependence of polar anchoring torque in a nematic liquid crystal contacting with a perfluoropolymer surface. Whereas the anchoring torque is conventionally expected to increase with decreasing temperature, we show that the polar anchoring torque in the present system decreases with decreasing temperature. This caus...

In liquid crystal (LC) physical chemistry, molecules near the surface play a great role in controlling bulk orientation. Thus far, mainly to achieve desired molecular orientation states in LC displays, the "static" surface property of LCs, so-called surface anchoring, has been intensively studied. As a rule of thumb, once the initial orientation of...

The physical properties of bulk liquid crystals might be altered significantly when local orderings/structures are present and act as “external fields”. To date, there exist scarce reports on such anomalies in bulk liquid crystals due to the lack of both (i) the understanding of how nano- scopic local assembly might amplify its characteristics to t...

Surface-specific liquid crystal (LC) nanostructures provide a unique platform for studying surface wetting phenomena and also towards technological applications. The most important studies of LC properties are related to bulk alignment, surface anchoring and so on. In this study, we study a LC system with a nematic liquid crystal on a perfluoropoly...

We determine elastic constants K11, K22, and K33 in two diphenylacetylene-core-based liquid crystals with azo and ester linkages. As we have already reported (Adv. Mater. (2014) 26, 1918), K33 is extremely large (sub-nN) compared with K11 (pN) in the azo compound, since cybotactic smectic (Sm) clusters exist in whole the nematic (N) phase range. As...

A periodic stripe pattern is found in the nematic phase close to the smectic phase of photoresponsive achiral liquid-crystalline compounds. The origin of the stripe patterns can be ascribed to an extremely large bent elastic constant K33. In addition, we succeeded in controlling the pattern by the following two methods: 1) the stripe disappears by...

Elastic constants in liquid crystals are known to be in the range of pico- and several-tens piconewton (pN). We report herein that a bend elastic constant, K_{33}, remarkably varies depending on a slight modification of the chemical structure in an analogous series of calamitic liquid crystals. In contrast to the record-high bend elastic constants...

Thermal diffusivity of a liquid crystal, 4'-butyl-4-heptyl-bicyclohexyl-4-carbonitrile, was measured using a temperature wave method. The liquid crystal was sandwiched by two glass substrates, which were treated with three different surface agents for providing distinct molecular orientations. Here, we demonstrate that: 1) a large thermal diffusivi...

We report that an asymmetric bent dimer, consisting of a rod mesogen and a cholesterol mesogen linked by a flexible spacer with 9 carbon atoms, was found to form blue phases with a record-wide temperature range. Moreover, highly stable, fast electro-optic switching is possible. In addition to the stable Kerr effect, the electrostriction effect was...

A surprisingly high-bending elastic constant K33 is obtained in a newly synthesized compound shown here. Mixtures containing a few percent of this compound confirm the influence of the unusual K33 values, and show an improved electro-optic response. The origin of the huge K33 is discussed based on the formation of smectic cluster structure formed i...

During a phase transition in a bulk material, heat is exchanged with matter to balance the changes in the internal energy and the entropy of the system. Here we report on the thermal detection of a surface-mediated anchoring transition, a spontaneous and discontinuous orientation change between planar (P) and homeotropic (H) alignments within a sin...

We studied the relationship between the stability of the blue phase (BP) and the helical twisting power (HTP) of chiral molecules doped in a non-chiral bent-core liquid crystal. Contrary to common wisdom, HTP values were found not to directly affect BP stabilisation, i.e. a wide temperature range of BPs was obtained in mixtures containing chiral do...

A light-driven bistable device was fabricated using nematic liquid crystal (NLC) cells with bare glass and perfluoro-polymer (CYTOP) surfaces. The CYTOP surface induces a discontinuous anchoring transition, when a particular NLC (CCN-47) is introduced into the cells. By doping CCN-47 with a small amount of photoisomerizable azo-dendrimer molecules,...

In a newly designed four-ring asymmetrical bent-core compound, we observed smectic-C-type diffuse layer reflection over the entire nematic temperature range. At the nematic–smectic C phase transi-tion, a sharp layer reflection emerges in addition to the diffuse reflection with different layer tilt angles. The discovery of spontaneous polarity 1 and...

Anchoring transition (ATr), resulting in the orientational change of liquid crystal (LC) molecules at surfaces with temperature variation, is shown to be essentially affected by the application of an electric field (E field). By combining defocusing polarizing microscopy with retardation measurement, a detailed investigation of the molecular orient...

We carried out an improved characterization of phase transitions among chiral smectic-C subphases observed for various antiferroelectric liquid crystals by precise heat capacity measurements. It was found that the phase transitions are intrinsically first order exhibiting a remarkable heat anomaly which involves little pretransitional thermal fluct...

A sequence of seven nematic phases has been observed in chiral mesogenic dimers, having odd number of carbon atoms in the spacer, thus a bent shape. The highest temperature phase is a chiral nematic (cholesteric) phase on heating or blue phases on cooling. The lowest temperature nematic phase expels the chiral twist and exhibits spontaneous bent–sp...

Anchoring transition in cholesteric liquid crystals (CLCs) was studied in this article. The orientational change is not simple in CLCs; instead of the orientational change of the helical axis, a variety of molecular orientations in cells such as planar, Grandjean, fingerprint, and homeotropic orientations were observed depending on chiral dopant, i...

We report an anchoring transition of a liquid crystal under the influence of an electric field (E field) in the vicinity of a first-order anchoring transition (ATr) temperature showing bistable homeotropic (H) and planar (P) states. By means of polarizing microscopy combined with retardation and switching and dielectric measurements, three importan...

The molecular mean-field theory for the nematic-isotropic (N-Iso) phase transition in the vicinity of the surface is derived. We have shown that the nematic order parameter in liquid crystal near the surface is generally different from that in the bulk. It is never equal to zero if the anisotropic interaction with the surface is present. At the sam...

We reexamined the isotropic-nematic (Iso-N) phase transitions of 4-n-heptyl cyanobiphenyl (7CB) embedded in aerosils of silica nanoparticle dispersions using highly sensitive differential scanning calorimetry (HS-DSC), polarizing optical microscopy (POM), and retardation measurements. We found a simple and very profound relationship between the cal...

We fabricated, in a polymer matrix, liquid crystal (LC) nanosized droplets with a correlation length xi of about 140 nm, which appear as an optically isotropic film. Differential scanning calorimetry (DSC) and light scattering measurements gave unambiguous evidences of an existence of nematic LC (NLC) order and fluctuation over a wide temperature r...

Using specified conditions, we succeeded in observing the isotropic-nematic (Iso-N) liquid crystal phase transition at surfaces followed by that in bulk for the first time. An additional heat anomaly peak was found at a higher temperature side of a main phase transition peak using highly sensitive differential scanning calorimetry (HS-DSC). The pea...

An amorphous blue phase III with low and wide thermal range (20 °C) including room temperature is induced by doping a bent-core nematic with a strong chiral material. We confirm that the electrooptical response is due to the Kerr effect, with the Kerr constant being up to two orders of magnitude larger than conventional Kerr materials such as nitro...

In this paper, we demonstrate two types of optically isotropic liquid crystalline states; (1) nano-segregated droplets of a nematic liquid crystal, dispersed in a photo-crosslinked polymer matrix, and (2) BPIII with a very short pitch of the UV region using bent-core nematogens with chiral-dopant. In both cases, we realize a complete dark state (OF...