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Liquid crystals (LCs) have garnered significant attention for their unique optical and electrical properties, making them promising candidates in various technological applications such as smart displays, sensors, telecommunications, biomedicals or wearable electronics. In this study, we explore the potential of several highly emissive benzothioxanthene imide (BTI) derivatives as LC materials with a focus on their robustness and temperature-stable emission behavior. By tailoring the molecular structure of BTIs, we have accomplished exceptional emissive properties while maintaining the inherent advantages of LCs, such as their self-organizing ability and responsive nature. We describe the formation of enantiotropic liquid crystals whose mesomorphic properties dependent on the nature, length, and position of the side chain. Moreover, we have investigated the thermal stability of their emission spectra over a wide range of temperature, highlighting their potential use in demanding conditions where precise optical performances are critical. Our findings underscore the importance of molecular design in achieving highly emissive LC materials with enhanced robustness and temperature stability, opening new avenues for the use of BTI derivatives., Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub, APC financiada por la UCM

Topological defects play a central role in the physics of many materials, including magnets, superconductors, and liquid crystals. In active fluids, defects become autonomous particles that spontaneously propel from internal active stresses and drive chaotic flows stirring the fluid. The intimate connection between defect textures and active flow suggests that properties of active materials can be engineered by controlling defects, but design principles for their spatiotemporal control remain elusive. Here, we propose a symmetry-based additive strategy for using elementary activity patterns, as active topological tweezers, to create, move, and braid such defects. By combining theory and simulations, we demonstrate how, at the collective level, spatial activity gradients act like electric fields which, when strong enough, induce an inverted topological polarization of defects, akin to a negative susceptibility dielectric. We harness this feature in a dynamic setting to collectively pattern and transport interacting active defects. Our work establishes an additive framework to sculpt flows and manipulate active defects in both space and time, paving the way to design programmable active and living materials for transport, memory, and logic.

Most paints contain pigments that absorb light and fade over time. A robust alternative can be found in nature, where structural coloration arises from the interference of light with submicron features. Plant-derived, cellulose nanocrystals (CNCs) mimic these features by self-assembling into a cholesteric liquid crystal that exhibits structural coloration when dried. While much research has been done on CNCs in aqueous solutions, less is known about transferring CNCs to apolar solvents that are widely employed in paints. This study uses a common surfactant in agricultural and industrial products to suspend CNCs in toluene. Surprisingly, a stable liquid crystal phase is formed within hours, even with concentrations of up to 50 wt%. Evaporating the apolar CNC suspensions results in photonic films with peak wavelengths ranging from 660 to 920 nm. The resulting flexible films have variable mechanical properties with surfactant content, allowing for an optical response with applied force. The films also act as humidity sensors, with increasing relative humidity swelling the films, yielding a redshift in the reflected wavelength. With the addition of a single surfactant, CNCs can be made compatible with existing production methods of industrial coatings, while improving the strength and responsiveness of structurally colored films to external stimuli.

Photoalignment by azo dye nanolayers can provide high alignment quality for large-area liquid crystal devices. Application of this technology to active optical elements for signal processing and communications is a hot topic of photonics research. In this article, we review recent demonstrations and performance of liquid crystal photonic devices, discuss the advantages of the proposed technology, and identify challenges and future prospects in the research field of photoaligned multi-domain liquid crystal structures. We believe that the developments discussed here can provide directions for future research and potential opportunities for applications of liquid crystal devices based on multi-domain photoalignment. © 2024 by the authors.

Structured light refers to the light field tailored by various degrees of freedom including intensity, phase, and polarization states in both spatial and temporal domains, which may greatly vitalize the technologies in both optics, such as the next-generation optical communication as well as subwavelength imaging and the materials science in both fabrication and characterization. The structured characteristics of the structure light need materials also with structured optical properties that can generate or manipulate structured light in a straightforward way, which can be well satisfied by liquid crystals, a soft mater that can self-assemble into tunable ordered structures through external stimuli. This review summarizes the research progress of the liquid crystal-based devices used in structured light generations and modulations, including the well-established techniques in the market, like the spatial light modulator, q-plate and the liquid crystal integrated optical metasurfaces. Especially, light-matter interactions are discussed from the topological view of both the structured light and the liquid crystal structures. Such a perfect matching in topology makes the liquid crystal a promising star together with structured light in future optic and photonic technologies. © 2024 Wiley-VCH GmbH.

Conventional ocean wave observation instruments are powered by batteries, limiting the continuous observation time. Besides, the waste of batteries brings environmental contaminations. Triboelectric nanogenerators (TENGs) can reveal ocean wave information through their electrical output, taking the triboelectric charge as the information carrier. However, charge amplification is necessary, consuming additional energy. Herein, taking the photons rather than electrons as the information carrier, we developed a fully self-powered natural light-enabled sensing system for ocean wave monitoring by coupling two rotary-freestanding sliding TENGs (RFS-TENGs) and a polymer network liquid crystal (PNLC)-triggered optical system. The natural light is modulated by the PNLC driven by ocean wave-induced friction. With the assistance of a one-way bearing, the rise and fall of the wave will trigger different RFS-TENGs to power the PNLC in different voltage drops, leading to different transmitted natural light intensities. The wave height information can be obtained through the number of pulse signals with the same trough light intensity, while the wave period can be obtained through the duration between the same two sets of pulse signals. The effectiveness of the developed sensing paradigm in practical applications was verified by flume-based experiments, with the highest accuracies of 90.7% in wave height and 99.8% in wave period. © 2024 American Chemical Society

4D microstructured actuators are micro-objects made of stimuli-responsive materials capable of induced shape deformations, with applications ranging from microrobotics to smart micropatterned haptic surfaces. The novel technology dual-wavelength volumetric micro-lithography (DWVML) realizes rapid printing of high-resolution 3D microstructures and so has the potential to pave the way to feasible manufacturing of 4D microdevices. In this work, DWVML is applied for the first time to printing stimuli-responsive materials, namely liquid crystal networks (LCNs). An LCN photoresist is developed and characterized, and large arrays of up to 5625 LCN micropillars with programmable shape changes are produced by means of DWVML in the time span of seconds, over areas as large as ~5.4 mm2. The production rate of 0.3 mm3 h-1 is achieved, exceeding speeds previously reported for additive manufacturing of LCNs by two orders of magnitude. Finally, a membrane with tunable micrometer sized pores is fabricated to illustrate the potential DWVML holds for real-world applications.

A novel family of square-planar Pd(II) complexes based on isoquinoline-functionalised pyrazolate ligands [Pd(pzR(n,n)iq)2] (R(n,n) = C6H3(OCnH2n+1)2, n = 4, 6, 8, 10, 12, 14, 16, 18) has been synthesised and characterised. The new complexes show mesomorphic properties and exhibit columnar mesophases that are highly-stable in exceptionally wide temperature ranges of up to 345 °C. The formation of nanochannels in the fluid liquid crystal phases generates continuous pathways for one-dimensional proton conduction on the basis of C–H⋯N proton transfer. The complex with an intermediate chain length (n = 12) shows the highest proton conductivity of 1.34 × 10−4 S m−1 at 269 °C in the hexagonal columnar mesophase, and an activation energy of 0.84 eV. The influence of both the terminal alkyl chain length and the mesophase columnar organisation on the proton conduction mechanism is demonstrated. The series of Pd(II) complexes investigated in this work constitutes one of the first examples of proton-conducting metallomesogens with potential applications in PEM fuel cells., Ministerio de Economía y Competitividad, Programa de Financiación de Universidad Complutense de Madrid-Santander Universidades (Spain), Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

The use of liquid crystals for the fabrication of displays incorporated in technological devices (TVs, calculators, screens of eBook’s, tablets, watches) demonstrates the relevance that these materials have had in our way of living. However, society evolves, and improved devices are looked for as we create a more efficient and safe technology. In this context, metallomesogens can behave as multifunctional materials because they can combine the fluidic state of the mesophases with properties such as photo and electroluminescence, which offers new exciting possibilities in the field of optoelectronics, energy, environment, and even biomedicine. Herein, it has been established the role of the molecular geometry induced by the metal center in metallomesogens to achieve the self-assembly required in the liquid-crystalline mesophase. Likewise, the effect of the coordination environment in metallomesogens has been further analyzed because of its importance to induce mesomorphism. The structural analysis has been combined with an in-depth discussion of the properties of these materials, including their current and potential future applications. This review will provide a solid background to stimulate the development of novel and attractive metallomesogens that allow designing improved optoelectronic and microelectronic components. Additionally, nanoscience and nanotechnology could be used as a tool to approach the design of nanosystems based on luminescent metallomesogens for use in bioimaging or drug delivery., Associate Laboratory for Green Chemistry—LAQV, FCT/MCTES (Portugal), Projects UIDB/50006/2020, PROTEOMASS Scientific Society (Portugal), Proteomass 2020 funds, Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

New dicatenar isoquinoline-functionalized pyrazoles, [HpzR(n,n)iq] (R(n,n)=C6H3(OCnH2n+1)2; n=4, 6, 8, 10, 12, 14, 16, 18), have been strategically designed and synthesized to induce mesomorphic and luminescence properties into the corresponding bis(isoquinolinylpyrazolate)platinum(II) complexes [Pt(pzR(n,n)iq)2]. Thermal studies reveal that all platinum(II) compounds exhibit columnar mesophases over an exceptionally wide temperature range, above 300 °C in most cases. The photophysical behavior was also investigated in solution and in the solid state. As a consequence of the formation of Pt⋅⋅⋅Pt interactions, the weak greenish emission of the platinum derivatives turns bright orange in the mesophase. Additionally, the complexes are sensitive to a great variety of external inputs, such as temperature, mechanical grinding, pressure, solvents, and vapors. On this basis, they are used as dopant agents of a polyvinylpyrrolidone or poly(methyl methacrylate) polymer matrix to achieve stimuli-responsive thin films., Ministerio de Economía y Competitividad (Spain), project CTQ2011-25172, Universidad Complutense de Madrid (Spain), project GR3/14-910300, Programa de Financiación de Universidad Complutense de Madrid-Santander Universidades (Spain), Unidade de Ciências Biomoleculares Aplicadas-UCIBIO (Portugal), FCT/MEC (UID/Multi/04378/2013), cofinanciated by ERDF under the PT2020 Partnership Agreement, Scientific Society PROTEOMASS (Portugal), Depto. de Química Inorgánica, Fac. de Ciencias Químicas, TRUE, pub

Since the early observations of plane polarized light rotation by tartaric acid by Jean-Baptiste Biot (1) and Louis Pasteur’s later discovery of tartrate enantiomers in 1848, (2) the significance of chirality persists throughout natural sciences, technology, engineering, and architecture. We now understand that the building blocks of life, such as nucleic acids, sugars, amino acids, and therefore oligosaccharides and proteins are almost exclusively homochiral. (3) That is, they lack mirror reflection symmetry and tend to exist in nature with only one handedness, right- (d-isomers) or left-handed (l-isomers). Not 40 years after Pasteur’s work on tartrate crystals, Friedrich Reinitzer and Otto Lehmann discovered what would later be termed cholesteric (chiral nematic) liquid crystals. (4,5) In the 21st century, liquid crystal displays (LCDs) remain the technology of choice for a wide variety of commercial devices, such as mobile phones, televisions, monitors, instrument panels and signage, although the development of the first operational LCD took nearly 80 years since Reinitzer’s and Lehmann’s first observations. This historical context provides some perspective on where we stand in a new age of liquid crystal research, in which some have turned their attention to colloids by virtue of their promise in photonics and metamaterials. In this regard, we have only just begun., The author wishes to also acknowledge the financial support of the Spanish Ministry of Science and Innovation for the project HAMMER (PID2021-125595NB-I00) and the Serra Húnter Fellowship from the Generalitat de Catalunya., Peer Reviewed, Postprint (published version)

Liquid crystal (LC) is a unique state of matter that exhibits properties of both liquids and solids. One main property is that the nematic phase allows the possibility to orientate and align molecules in any direction by application of external perturbations such as electric, magnetic field, heat or pressure. This thesis will study the implementation of LC waveguide samples and its characterization at normal incidence light in a transmission optical setup in two different ways: in-plane (azimuthal rotation) and out-of-plane (polar rotation). This will provide a holistic approach for electro-optical characterization on the change in azimuthal and polar angles of the nematic LC waveguide with reference to the applied voltage.

Using experiments and numerical simulations, we demonstrate that the curvature of microscale conduits allow programming of liquid crystal (LC) flows. Focusing on a nematic LC flowing through U- and L-shaped channels of rectangular cross-section, our results reveal that curved flow paths can trigger gradients of flow-induced director field in the transverse direction. The emergent director field feeds back into the flow field, ultimately leading to LC flows controlled by the channel curvature. This curvature-mediated flow control, identified by polarizing optical microscopy and supported by the nematofluidic solutions, offers novel concepts in LC-based microfluidic valves and throttles, wherein the throughput distribution is determined by the Ericksen number and the variations in the local curvature. Finally, this work highlights the role of deformation history on flow-induced director alignments, when the viscous and elastic effects comparable in strength.

Zhang Y., Yoshida H., Wang Q.H., et al. Electro-optics of blue phase liquid crystal in field-perpendicular direction. Applied Physics Letters 122, 161107 (2023); https://doi.org/10.1063/5.0142383., The electro-optic effect is the working principle of blue phase (BP) liquid crystals, and it describes the relationship between the field-induced birefringence of BPs and the field strength. Due to the electrostriction of BP crystals under the electric field, an orthorhombic or tetragonal crystal is usually obtained when the field is applied along one of the twofold axes of a BP crystal, leading to the optical biaxiality under electric field. Such field-induced optical biaxiality of BPs has been predicted and observed, but its dependence on the field strength has not been investigated. In this research, we analyze the electro-optics in the field-perpendicular direction by measuring the birefringence in highly ordered BP I(110) crystals perpendicular to the electric field. Results reveal that BP I crystals in the field-perpendicular direction show an electro-optic coefficient of the order of 10−10 m/V2 that may result from the large lattice deformation of BP crystals perpendicular to the electric field. Our research provides important experimental evidence for the tensorial properties of BP Kerr effect and may have important implications on the engineering of BP electro-optical devices in practical applications.

This dissertation is concerned with the numerical analysis and computation of variationalmodels related to liquid crystals (LCs) and liquid crystal polymer networks (LCNs) as well as modeling of LCNs. We first present a finite element method and projection free gradient flow to minimize theFrank-Oseen energy of nematic liquid crystals. The Frank-Oseen model is a continuum model that represents the liquid crystal with a vector field that must satisfy a nonconvex unit-length constraint pointwise. We prove convergence of minimizers of the discrete problem to minimizers of the continuous problem using the framework of Gamma-convergence. The convergence analysis has no restrictions on the elastic constants or regularity of the solution beyond that required for existence of minimizers. Due to the low regularity requirement, the method can capture point defects. We also propose a projection free gradient flow algorithm to compute critical points of the discrete energy. The gradient flow is conditionally stable under a mild restriction on the numerical parameters. We finally present computations illustrating the influence of the elastic constants on point defects as well as the influence of external magnetic fields. The second part of this dissertation is concerned with modeling, numerical analysis, andcomputation of thin LCNs. We first begin from a classical 3D energy of LCN and use Kirchhoff- Love asymptotics to derive a reduced 2D membrane model. We then prove many properties of the membrane model including a pointwise metric condition that zero energy states must satisfy and construct a formal method to approximate configurations of LCN from higher degree defects that approximately match this pointwise condition. To conclude, we develop a finite element method to minimize the stretching energy. A key component of the discrete energy is to introduce a regularization that is inspired by a bending energy for LCN, which is also derived in this dissertation. We prove converg

Zhang Y., Yoshida H., Wang Q.H., et al. Electro-optics of blue phase liquid crystal in field-perpendicular direction. Applied Physics Letters 122, 161107 (2023); https://doi.org/10.1063/5.0142383., The electro-optic effect is the working principle of blue phase (BP) liquid crystals, and it describes the relationship between the field-induced birefringence of BPs and the field strength. Due to the electrostriction of BP crystals under the electric field, an orthorhombic or tetragonal crystal is usually obtained when the field is applied along one of the twofold axes of a BP crystal, leading to the optical biaxiality under electric field. Such field-induced optical biaxiality of BPs has been predicted and observed, but its dependence on the field strength has not been investigated. In this research, we analyze the electro-optics in the field-perpendicular direction by measuring the birefringence in highly ordered BP I(110) crystals perpendicular to the electric field. Results reveal that BP I crystals in the field-perpendicular direction show an electro-optic coefficient of the order of 10−10 m/V2 that may result from the large lattice deformation of BP crystals perpendicular to the electric field. Our research provides important experimental evidence for the tensorial properties of BP Kerr effect and may have important implications on the engineering of BP electro-optical devices in practical applications.

The study of liquid crystal (LC) director distribution is an important area of research in materials science and technology. Parallel-aligned liquid crystal (PA-LC) devices have been extensively studied due to their applications in liquid crystal displays, optical devices, and sensors. Estimating the LC director distribution is a critical step in designing and optimising PA-LC devices. This work shows the results derived from apply- ing novel optimisation techniques to estimate the liquid crystal (LC) director distribution in parallel-aligned liquid crystal (PA-LC) devices. Moreover, the genetic algorithm (GA) has been applied and compared with the minimisation of the Frank-Oseen free energy through the Euler-Lagrange equations. The GA is a stochastic optimisation technique that can effectively explore the search space and find the global optimum. Overall, this study’s results demonstrate the GA’s effectiveness in estimating the LC director distribution in PA-LC devices. This approach can improve the performance and design of liquid crystal displays, optical devices, and sensors. Furthermore, it can be extended to other fields where the optimisation of complex systems is required. Further research is needed to optimise the GA parameters and to explore its potential in other applications.

We report an experimental work on the liquid crystal dimer 1’’,7’-bis(4-cyanobiphenyl-4’-yl) heptane (CB7CB) confined to Anopore membranes. We have studied the behaviour of the dielectric relaxation modes in the isotropic (I), nematic (N) and twist-bend nematic (NTB) phases by broadband dielectric spectroscopy and compared to the results of the bulk sample. We have found that the strength of the components of the static dielectric permittivity for bulk and confined samples diminishes when cooling but, once in the NTB phase, those of the confined CB7CB tend to decrease in a slower rate compared to the ones of bulk CB7CB. This work is meant to play a humble tribute to the first report on a cyanobiphenyl-based LC in its 50th anniversary., N.S acknowledges the support of the Slovenian Research and Innovation Agency (grant number P1-0192). MRF acknowledges the financial support by Eusko Jaurlaritza-- Basque Government (Project IT1458-22)., Postprint (author's final draft)

Liquid crystalline polymers are attractive materials for untethered miniature soft robots. When they contain azo dyes, they acquire light-responsive actuation properties. However, the manipulation of such photoresponsive polymers at the micrometer scale remains largely unexplored. Here, uni- and bidirectional rotation and speed control of polymerized azo-containing chiral liquid crystalline photonic microparticles powered by light is reported. The rotation of these polymer particles is first studied in an optical trap experimentally and theoretically. The micro-sized polymer particles respond to the handedness of a circularly polarized trapping laser due to their chirality and exhibit uni- and bidirectional rotation depending on their alignment within the optical tweezers. The attained optical torque causes the particles to spin with a rotation rate of several hertz. The angular speed can be controlled by small structural changes, induced by ultraviolet (UV) light absorption. After switching off the UV illumination, the particle recovers its rotation speed. The results provide evidence of uni- and bidirectional motion and speed control in light-responsive polymer particles and offer a new way to devise light-controlled rotary microengines at the micrometer scale.

Liquid crystalline polymers are attractive materials for untethered miniature soft robots. When they contain azo dyes, they acquire light-responsive actuation properties. However, the manipulation of such photoresponsive polymers at the micrometer scale remains largely unexplored. Here, uni- and bidirectional rotation and speed control of polymerized azo-containing chiral liquid crystalline photonic microparticles powered by light is reported. The rotation of these polymer particles is first studied in an optical trap experimentally and theoretically. The micro-sized polymer particles respond to the handedness of a circularly polarized trapping laser due to their chirality and exhibit uni- and bidirectional rotation depending on their alignment within the optical tweezers. The attained optical torque causes the particles to spin with a rotation rate of several hertz. The angular speed can be controlled by small structural changes, induced by ultraviolet (UV) light absorption. After switching off the UV illumination, the particle recovers its rotation speed. The results provide evidence of uni- and bidirectional motion and speed control in light-responsive polymer particles and offer a new way to devise light-controlled rotary microengines at the micrometer scale. © 2023 Wiley-VCH GmbH.

By using well-designed anchoring patterns in a liquid crystal (LC) device, novel electro-optic components with enhanced functionality can be designed. We present two types of nematic LC diffraction gratings with varying periodicity, manufactured with patterned photoalignment at the confining substrates. By varying the surface anchoring periodicity, the incident light can be redirected into many different diffraction orders, giving rise to a scattering appearance of the grating. In Type I gratings the anchoring patterns at the top and bottom substrates are aligned in the same direction, whereas in the Type II grating the anchoring patterns at the top and bottom substrates have a relative rotation of 90°. The structural and optical properties of the gratings can be tuned by applying an external voltage. The director configuration in the bulk is revealed with the use of polarizing optical microscopy images and numerical simulations. Experimental results of the diffraction spectra and intensities of different diffraction orders are supported by finite difference time domain (FDTD) simulations. The results specifically aim at tunable LC diffraction gratings which are highly dispersive and have weak zeroth order diffraction. In general, this work is a contribution to the field of LC flat optical components with electric tunability. © 2023 Elsevier B.V.

Liquid crystals (LCs) possess unique physicochemical properties, translatable into a wide range of applications. To date, lipidic lyotropic LCs (LLCs) have been extensively explored in drug delivery and imaging owing to the capability to encapsulate and release payloads with different characteristics. The current landscape of lipidic LLCs in biomedical applications is provided in this review. Initially, the main properties, types, methods of fabrication and applications of LCs are showcased. Then, a comprehensive discussion of the main biomedical applications of lipidic LLCs accordingly to the application (drug and biomacromolecule delivery, tissue engineering and molecular imaging) and route of administration is examined. Further discussion of the main limitations and perspectives of lipidic LLCs in biomedical applications are also provided

The arrangement of nanoscale building blocks into patterns with microscale periodicity is challenging to achieve via self-assembly processes. Here, we report on the phase-transition-driven collective assembly of gold nanoparticles in a thermotropic liquid crystal. A temperature-induced transition from the isotropic to the nematic phase under anchoring-driven planar alignment leads to the assembly of individual nanometer-sized particles into arrays of micrometer-sized agglomerates, whose size and characteristic spacing can be tuned by varying the cooling rate. Phase field simulations coupling the conserved and nonconserved order parameters exhibit a similar evolution of the morphology as the experimental observations. This fully reversible process offers control over structural order on the microscopic level and is an interesting model system for the programmable and reconfigurable patterning of nanocomposites with access to micrometer-sized periodicities.

With the advancement of information display technologies, research on liquid crystals is undergoing a tremendous shift to photonic devices. For example, devices and configurations based on liquid crystal materials are being developed for various applications, such as spectroscopy, imaging, and fiber optics. One of the problems behind the development of photonic devices lies in the preparation of patterned surfaces that can provide high resolution. Among all liquid crystal alignment techniques, photoalignment represents a promising non-contact method for the fabrication of patterned surfaces. In this review, we discuss the original research findings on electro-optic effects, which were mainly achieved at the Department of Electronic and Computer Engineering of the Hong Kong University of Science and Technology and the collaborating research laboratories.

Soft and mechanically responsive actuators hold the promise to revolutionize the design and manufacturing of devices in the areas of microfluidics, soft robotics and biomedical engineering. In many of these applications, the actuators need to operate in a wet environment that can strongly affect their performance. In this paper, we report on the photomechanical response in a biological buffer of azobenzene-containing liquid crystal elastomer (LCE)-based actuators, prepared by four-dimensional (4D) printing. Although the photothermal contribution to the photoresponse is largely cancelled by the heat withdrawing capacity of the employed buffer, a significant photoinduced reversible contraction, in the range of 7% of its initial length, has been achieved under load, taking just a few seconds to reach half of the maximum contraction. Effective photomechanical work performance under physiological conditions has, therefore, been demonstrated in the 4D-printed actuators. Advantageously, the photomechanical response is not sensitive to salts present in the buffer differently to hydrogels with responses highly dependent on the fluid composition. Our work highlights the capabilities of photomechanical actuators, created using 4D printing, when operating under physiological conditions, thus showing their potential for application in the microfluidics and biomedical fields.

The current wireless networks can face congestion issues due to the increasing number of digital devices. One way to overcome this is to establish communica-tion at a different range of frequencies, specifically in visible light. Most studies in Visible Light Communication (VLC) systems use active light sources like LEDs for transmission, but due to its high power consumption, studies have explored the domain of passive VLC that employs Liquid Crystal (LC)s. These systems utilize the existing lighting infrastructure, without needing dedicated LED transmitters. LCs modulate ambient light by controlling its polarization, thus encoding information. At the receiving end, a camera consisting of optical sensors captures and decodes these signals. However, single-pixel LC-to-Camera systems struggle to transmit data at high capacity. On the other hand, recent developments reveal that LCs can convert incoming light to polarized color sig- nals under certain conditions. This thesis work exploits these properties to design a method that employs colors as data symbols in order to tackle the throughput issue. Therefore, we propose a multi-symbol, multi-channel LC-to-Camera system. We develop a modulation-demodulation mechanism that helps to establish a robust link. Experiments demonstrate an 8-symbol scheme results in a three-time throughput increase at per-pixel level with distances up to 160 cm at minimal error. We explore the scalability with a 2x2 pixel system that operates at rates four times that of a single pixel., Electrical Engineering | Embedded Systems

Recent years have seen major advances in the additive manufacturing of stimuli-responsive materials, also known as “4D printing,” among which liquid crystal elastomers (LCEs) play an important role. However, during fabrication photo-crosslinking of the LCEs is required, but this step is time-consuming and efficient polymerization is challenging, especially in the case of light-responsive materials. In this work, the first light-fueled supramolecular LCEs suitable for the direct ink writing (DIW) of soft actuators are synthesized in which a photopolymerization step is not needed. With the responsive supramolecular material, 3D-printed objects are fabricated by exploiting the thermoreversible interplay of the hydrogen-bonding physical cross-links. After printing, the supramolecular LCE shows reversible shape changes in response to light and is capable of bending and lifting a load. Through the combined photothermal and photochemical contributions of the incorporated azobenzene, the actuators can be triggered both in air and water. The freedom provided by DIW allows for the printing of complex responsive objects, as demonstrated by fabricating re-entrant honeycomb and spiral director structures. This approach of printing light-responsive supramolecular soft actuators opens avenues toward the application of “smart” and sustainable materials for additive manufacturing without the requirement of photo-crosslinking.

The recently discovered ferroelectric nematic liquid crystals have been reported to exhibit very large dielectric permittivity values. Here, we report a systematic investigation of the dielectric behavior of a prototypical ferroelectric nematogen by varying the thickness of the parallel capacitor measuring cell. While in the non-polar high temperature nematic phase results show only slight differences due to slight variations of the alignment, the measured permittivity values in the ferroelectric nematic phase show a linear dependence on the cell thickness. It is also shown that the characteristic relaxation frequency decreases inversely proportionally to the thickness. The results are discussed in terms of three different available models based on different underlying mechanisms, accounting for cancellation of the probe electric fields by polarization reorientation or by ionic charges, or based on a recently proposed continuous phenomenological model.

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).

Materiały z wystawy „Ciekłe kryształy / Liquid Crystals” prezentowanej w Wypożyczalni Studenckiej na parterze Gmachu Głównego PW od listopada 2023 r. Projekt realizowany z okazji Święta Politechniki Warszawskiej (15 listopada).