Inverse design method - topology optimization - is used to design broadband soft matter optical filters with different transmission spectra. The broadband filters are optimized for different wavelength ranges and can function either as standalone photonic devices or as components integrated into waveguides. The structure of the optical filters is modeled as layers of continuously varying refractive index characteristic of soft matter and as birefringent soft matter materials - specifically liquid crystals - where the orientation of the optical axis varies along the optical filter length. The results demonstrate that the proposed setup based on liquid crystals is a viable method for realizing optical broadband filters with highly different transmission spectra.

Molecular chirality is a source of broken mirror symmetry, but using it to control mesoscale structures with a tunable length scale remains challenging. Here, we demonstrate that adding a chiral dopant to nematic liquid crystal droplets bounded by a deformable two-surfactant interface controls their morphogenesis: the ratio of droplet diameter to cholesteric pitch determines whether droplets divide asymmetrically or symmetrically upon cooling, and whether they transform into single- or double-strand helical fibers. The fiber periodicity and thickness both scale linearly with the cholesteric pitch, which varies by less than 2

We report a nondissipative optomechanical approach to separate the spin and orbital components of transverse energy flows of light beams. Focusing on uniformly polarized paraxial fields, the method relies on detecting the radiation-pressure-induced reorientation of the optical axis in anisotropic media—specifically, liquid crystals. Within a perturbative analytical approach, we demonstrate the selective encoding of the transverse spin and orbital components of the Poynting vector into orthogonal orientational elastic modes, whose relative weights are mediated by the Gouy phase. The spatial distributions of spin and orbital momentum can therefore be retrieved without resorting to point-by-point measurements using absorbing or scattering probe particles. Analytical results are supported by a fully self-consistent numerical solution coupling Maxwell’s equations and Landau-de Gennes nematodynamics in three dimensions. This exact framework captures higher-order and nonparaxial effects beyond the analytical perturbative regime and allows us to validate the predicted Gouy-phase-mediated optomechanical response. These results establish a practical route toward optomechanical imaging of the internal momentum structure of light, fostering momentum-resolved optical metrology and light-matter interaction studies with structured beams.

The viscosity of monoclonal antibody solutions is critical in their biopharmaceutical application, as it directly influences the ease of subcutaneous injection. Although many descriptors have been developed to enable the in silico prediction of viscosity, they are typically based on electrostatic properties while neglecting hydrophobicity, or rely on AI-based approaches with limited generalizability, both rendering the models inadequate. Moreover, the scarcity of high-quality experimental datasets further limits the use of machine learning algorithms, necessitating interpretable analysis of protein-protein interactions. In this work, we combine computational modeling with experimental viscosity measurements for a set of monoclonal antibodies. We introduce an algorithm for surface patch analysis capable of quantifying the characteristics of hydrophobic patches. By calculating physically meaningful interaction energies, we can discern between the propensity for high and low viscosity due to the hydrophobic effect. Furthermore, by analyzing antibodies with problematic hydrophobic patches, we introduce a theory explaining their solubilization. This method is adaptable to any protein format and can be generalized for early in silico screening of viscosity in protein-based biopharmaceutical solutions.

The growing demand for holography and its wide-ranging applications necessitate advancements to make this technology more accessible and adaptable to modern technological requirements. Nematic liquid crystals (NLCs) enable holographic projection by exploiting the geometric phase of light through carefully designed phase patterns. However, NLC-based holography faces challenges, particularly in terms of projection quality and the presence of zero-order leakage-a bright spot that overlaps the reconstructed image. The efficiency of the reconstructed image is strictly related to the thickness of the NLC layer, which is challenging to control with high precision. In this work, we use chiral liquid crystal (CLC) to fabricate reflective holograms. To address the issue of leakage waves overlapping the reconstructed image, we propose an interference-based fabrication approach. This approach combines the phase pattern of the hologram with a diffraction grating by interfering a plane wave with a tailored wavefront precisely matching the hologram's phase pattern. As a result, the image is reconstructed away from the zero-order reflection, and the leakage overlapping with the reconstructed image is reduced significantly.

The all-optical control of light has been explored in hard matter,but to control light by light in soft matter is a major experimental and conceptual challenge that remains largely unexplored.We propose and verify experimentally and numerically that nanosecond light pulses can be controlled by light pulses using resonant stimulated-emission depletion(STED)in a liquid-crystal optical cavity that acts as a nanosecond optical switch.This light-by-light control is realized in a micrometer-diameter droplet of fluorescent-dye-doped nematic liquid crystal that is submersed in an aqueous solution.A set of laser-printed optical waveguides touches the surface of the droplet and provides flow of light in and out of the droplet.We demonstrate that nanosecond light pulses launched through the waveguides initiate the lasing of whispering gallery modes in the droplet.However,the lasing can be suppressed very efficiently on a nanosecond scale by another,red-shifted light pulse before the lasing takes place.The proposed concept of light control in soft matter using STED in an optical cavity requires fewer production steps because of self-assembly.It could be massively replicated using soft imprint lithography,uses less production energy due to low production temperatures,requires less toxic materials,and could be made entirely biocompatible and flexible.

We demonstrate that the Whispering Gallery Mode (WGM) lasing spectroscopy is a versatile high resolution tool to study the structure of interfaces of liquid crystalline (LC) droplets immersed in an immiscible fluid, such as water. The eigenfrequencies of WGMs in spherical microcavities are very sensitive to the refractive index profile in the nanometer thin interfacial region. This makes it possible to detect interfacial phenomena and temperature change in LC droplets with interferometric accuracy. We use 10-30 µm diameter droplets of a nematic liquid crystal labeled with a fluorescent dye and floating in water as an optical microcavity that sustains the WGMs. At the isotropic-nematic transition we observe wetting of the droplet's interface by a nanometer-thin layer of paranematic LC. Just below this transition, we observe red-shift and strong fluctuations of WGM spectra just before spherical droplet elongates into a fiber. The experiments are modeled with Finite-Difference Time-domain (FDTD) analysis of WGMs in nematic droplet and we find very good qualitative agreement.

We use polarized optical microscopy and confocal fluorescence microscopy to explore electric-field induced swimming of direct laser written polymer microrods in a nematic liquid crystal in the regime of very low frequencies. The rods are of variable aspect ratio and swim in a liquid crystal layer with a thickness comparable to that of the longest rods. We observe significant spatial reorientation of the microrods under an applied electric field, which is characterized by their up and down movement along the applied electric field, oscillation in their tilting with respect to the field, sidewise wobbling of their center of mass and propulsion along the direction perpendicular to the electric field. The velocity of propulsion shows a power law behaviour on the electric field magnitude, vx ∝ Eα, where α is between 3 and 5 for different aspect ratio rods and can be partially explained by the shear thinning of the viscosity at higher velocity. The time analysis of 3D trajectories of swimming microrods shows a linear coupling of the microrod's center of mass to the applied electric field, and quadratic (i.e. dielectric) coupling of the microrod's tilt to the field, which appears to be the main driving mechanism for microrod propulsion.

Liquid Crystal Waveguiding A layer of nematic liquid crystal forms a complex three-dimensional structure on top of a substrate with patterned alignment, to minimize the total free energy. Roughly in the middle of the layer, there is a region where the director is perpendicular to the substrates, forming a multimode waveguide for TE polarized light. The figure illustrates how a green laser beam follows the curved waveguide formed by the patterned liquid crystal. More details can be found in article 2402174 by Kristiaan Neyts and co-workers.

In isotropic fluids like water, micrometer-scale swimmers have evolved swim strokes to translate despite their tiny size. As described by Purcell in his Scallop Theorem, reciprocal motions, like those performed by a scallop, cannot drive swimming when inertial effects are absent, as is typical at micrometer length scales. Thus, microswimmers have evolved complex structures that can perform non-reciprocal swim strokes or body displacements to generate motion. Microswimmer dynamics in structured fluids differ fundamentally from those in isotropic fluids because of their inherent asymmetry. The orientation of elongated constituents and the topological defects that spontaneously form near microswimmers provide broken symmetries, even atequilibrium. This is sufficient for the dynamic disturbance of even the simplest isotropic swimmers to generate propulsion. We combine experiments on magnetically rotated colloids in nematic liquid crystals with analytic non-equilibrium solutions to formulate propulsion strategies for microswimmers in nematic fluids and determine how swimming velocity depends on the rotation rate, materials parameters, and forcing regimes. For example, we find that micro-scale spherical colloids swim effectively under continuous rotation and under reciprocal forcing.Thus, swim strokes that are ineffective in isotropic fluids are highly effective in nematic liquid crystals. In light of these observations, the Scallop Theorem is extended for structured fluids.

We demonstrate the generation of diverse material flow regimes in nematic liquid cells as driven by time-variable active surface anchoring, including no-net flow, oscillatory flow, steady flow, and pulsating flow. Specifically, we numerically simulate a passive nematic fluid inside a cell bounded with two flat solid boundaries at which the time-dependent anchoring is applied with the dynamically variable surface anchoring easy axis. We show that different flow regimes emerge as the result of different anchoring driving directions (i.e. co-rotating or counter-rotating) and relative phase of anchoring driving. The flow magnitude is tunable by cell thickness and anchoring driving frequency. More generally, this work aims towards possible applications of responsive time-variable surfaces, including photonics or synthetic active matter.

Cholesteric liquid crystals (CLCs) are birefringent materials with a helical molecular orientation that enables the selective reflection of circularly polarized light, making them valuable for various optical applications. While extensively studied in planar geometries, their optical properties in cylindrical and droplet-shaped confinements remain less understood. This article numerically investigates photonic eigenmodes in 2D cylindrical CLC resonators with concentric layered and spiral configurations. We demonstrate that the interplay of cylindrical confinement and cholesteric helicity gives rise to distinct optical modes: (i) Bragg-like modes, (ii) central defect modes, and (iii) whispering gallery modes at the boundary or within the bulk. These findings connect the well-known behavior of 1D CLC layers with more complex 2D cylindrical and 3D spherical systems and provide insight into the polarization-dependent mode structure in anisotropic media. The results have implications for designing advanced CLC-based photonic elements such as soft-matter-based lasers and spherical reflectors.

The softness of liquid crystals, their anisotropic material properties, their strong response to external fields and their ability to align on patterned surfaces makes them unsurpassable for a number of photonic applications, such as flat-panel displays, light modulators, tunable filters, entangled photon light sources, lasers and many others. However, the microscale integration of liquid crystals into microphotonic devices that not only perform like silicon photonic chips but also use less energy, operate exclusively on light, are biocompatible and can self-assemble has not been explored. Here we demonstrate a soft-matter photonic chip that integrates tunable liquid-crystal microlasers and laser microprinted polymer waveguides. We demonstrate the control of the liquid crystal's microlaser emission by nanosecond optical pulses and introduce the concept of resonant stimulated-emission depletion to switch the light by light. This opens a way to design an entirely new class of photonic integrated devices that can be made both biodegradable and biocompatible with a rich variety of applications in medicine, wearable photonics and logic circuits. We anticipate that soft-matter photonic circuits will not only outperform solid-state photonics in terms of a huge reduction in the number of production steps, the use of non-toxic chemicals and a better energy efficiency, but also could open an avenue to the paradigm of soft-matter photonics.

Protein aggregation is one of the key challenges in the biopharmaceutical industry as its control is crucial in achieving long-term stability and efficacy of biopharmaceuticals. Attempts have been made to develop regression models for predicting the aggregation of monoclonal antibodies in solution using machine learning methods. These efforts have yielded varying levels of success, with current state-of-the-art AI approaches achieving good prediction accuracies ([Formula: see text]). Here, we demonstrate the prediction of aggregation rate in monoclonal antibodies with beyond state-of-the-art reliability using a coupled AI-MD-Molecular surface curvature modelling platform. The scientific novelty of this approach lies in using local geometrical surface curvature of proteins as the core element for protein stability analysis. By combining local surface curvature and hydrophobicity, as derived from time-dependent MD simulations, we are able to construct aggregation predictive features that, when coupled with linear regression machine learning techniques, give a high prediction accuracy ([Formula: see text]) on a dataset of 20 molecules. More generally, this approach shows significant potential for quantitative in silico screening and prediction of protein aggregation, which is of great scientific and industrial relevance, particularly in biopharmaceutics.

Blue phase liquid crystals (BPLCs) are chiral self-assembled three-dimensional (3D) periodic structures which have attracted a lot of attention due to their electro-optical properties, relevant for tunable soft photonic crystals and fast-response displays. However, to realize this application potential, controlling the BPLC alignment at the surfaces is crucial, and one way to obtain the desired alignment is by photoalignment patterning. In this article, monodomain BPLC samples with controlled orientation are achieved by imposing different alignment patterns that have a periodicity that is compatible with the size of the BPLC unit cell, using two-step photoalignment with polarized ultraviolet (UV) light. Experiments are complemented by numerical simulations to design striped surface alignment patterns, which induce specific director orientations on the boundary layer of the confined BPLC. By designing the patterns and matching the periodicity to a specific BP material, we can control the orientation of the blue phase unit cell lattice in the sample, including the azimuthal angle. The orientation is measured by the Kossel patterns and matches the optimal configuration predicted by stability analysis using Landau-de Gennes free energy modeling. The detailed structure and reduced symmetry of the BP near the surface are investigated, and the corresponding (meta)stable structures are demonstrated. Overall, we demonstrate that two-step photoalignment patterning is a reliable, relatively simple, and reconfigurable method to achieve a high-quality monodomain BP with controlled and tunable crystalline orientation.

Photonic crystals manipulate light in unique and beneficial ways, acting as waveguides, laser cavities, and facilitating topological light propagation. However, the reconfiguration of photonic crystals has been limited, hindering their versatility. We have recently introduced the concept of pixelated 2D photonic crystals, where a pixelated matrix of the material enables variability in the dielectric profile. By changing the orientation state of liquid crystal molecules within individual pixels an effective refractive index for a specific input polarisation is altered. In this work we numerically show how different distributions of "on" and "off" state pixels and therefore different effective refractive index configurations in the periodically repeated unit cell effect the band structure of the material and its optical properties. Considering the size of pixels and unit cells, such photonic crystals would enable dynamic control of THz waves.

We demonstrate that Direct Laser Writing (DLW) can be used to print low loss planar polymer waveguides on glass, thus promising a novel soft matter platform for polymer all-optic micro-photonics. We printed straight waveguides with various cross sections and lengths up to 900 mu m on a 500 nm thin layer of low refractive index CYTOP on glass. We also printed two rectangular micro-prisms at each end of the waveguide, which provides coupling of light in and out of the waveguides. The printed structures were imaged and characterized by SEM and we measured the attenuation of light, propagating along the waveguides. While the high refractive index photosensitive resin IP-n162 shows moderate attenuation of similar to 14 dB/cm at 580 nm, the IP-S photosensitive resin shows lower attenuation of similar to 5-9 dB/cm in a rather broad window around 580 nm.

Various active materials exhibit strong spatio-temporal variability of their orientational order known as active turbulence, characterised by irregular and chaotic motion of topological defects, including colloidal suspensions, biofilaments, and bacterial colonies.In particular in three dimensions, it has not yet been explored how active turbulence responds to changes in material parameters and chirality.Here, we present a numerical study of three-dimensional (3D) active nematic turbulence, examining the influence of main material constants: (i) the flow-alignment viscosity, (ii) the magnitude and anisotropy of elastic deformation modes (elastic constants), and (iii) the chirality. Specifically, this main parameter space covers contractile or extensile, flow-aligning or flow tumbling, chiral or achiral elastically anisotropic active nematic fluids. The results are presented using time- and space-averaged fields of defect density and mean square velocity. The results also discuss defect density and mean square velocity as possible effective order parameters in chiral active nematics, distinguishing two chiral nematic states-active nematic blue phase and chiral active turbulence. This research contributes to the understanding of active turbulence, providing a numerical main phase space parameter sweep to help guide future experimental design and use of active materials. Active turbulence is a dynamic state of active nematics that is in three dimensions realized as a network of reconfiguring and proliferating disclination lines. This work explores the scaling properties of active turbulence with material constants and the chirality-driven transition from a chiral active turbulence to an active blue phase.

Mechanical properties of biological tissues fundamentally underlie various biological processes and noncontact, local, and microscopic methods can provide fundamental insights. Here, we present an approach for quantifying the local mechanical properties of biological materials at the microscale, based on measuring the spectral shifts of the optical resonances in droplet microcavities. Specifically, the developed method allows for measurements of deformations in dye-doped oil droplets embedded in soft materials or biological tissues with an error of only 1 nm, which in turn enables measurements of anisotropic stress inside tissues as small as a few pN/μm2. Furthermore, by applying an external strain, Young's modulus can be measured in the range from 1 Pa to 35 kPa, which covers most human soft tissues. Using multiple droplet microcavities, our approach could enable mapping of stiffness and forces in inhomogeneous soft tissues and could also be applied to in vivo and single-cell experiments. The developed method can potentially lead to insights into the mechanics of biological tissues.