Submersed micropatterned structures control active nematic flow, topology, and concentration.

Coupling between flows and material properties imbues rheological matter with its wide-ranging applicability, hence the excitement for harnessing the rheology of active fluids for which internal structure and continuous energy injection lead to spontaneous flows and complex, out-of-equilibrium dynamics. We propose and demonstrate a convenient, highly tunable method for controlling flow, topology, and composition within active films. Our approach establishes rheological coupling via the indirect presence of fully submersed micropatterned structures within a thin, underlying oil layer. Simulations reveal that micropatterned structures produce effective virtual boundaries within the superjacent active nematic film due to differences in viscous dissipation as a function of depth. This accessible method of applying position-dependent, effective dissipation to the active films presents a nonintrusive pathway for engineering active microfluidic systems.

Effect of airflow rate and drainage on the properties of 2D smectic liquid crystal foams.

As a two-phase system, foams are widely applied in the industry and exist ubiquitously in our daily lives. For this reason, studying them and investigating the parameters that affect their properties is crucial for the development of new and improved foam-based products. In this paper, we create 2D foam using an ordered fluid, the smectic liquid crystal (LC), and discuss the experimental parameters that affect their fabrication, including temperature and confining conditions. Then, we examine the influence of the injected airflow rate and drainage on their structure, size, liquid fraction, and stability. Finally, we compare their behavior to that of low-viscosity liquid foams and discuss the difference between them. Our findings indicate that surface tension is the dominant parameter in LC foam systems. Despite the strong elasticity of LCs, surface tension plays a crucial role in determining the properties of elastic foams. These results provide valuable insights that can be applied to different industrial applications. For instance, they may find relevance in the fields of cosmetics, thermal insulation, oil recovery, and sensing, where the fabrication of foams with high-viscosity fluids is required.

Plasmon enhancement of third-order nonlinear optical absorption of gold nanoparticles dispersed in planar oriented nematic liquid crystals.

We report structural and nonlinear optical properties of 20 nm gold (Au) nanoparticles (NPs) that are dispersed in planar degenerate (non-oriented) and planar oriented nematic liquid crystals (LCs) (4'-Pentyl-4-biphenylcarbonitrile-5CB). Taking advantage of elastic forces in the planar oriented nematic LC, we aligned AuNPs parallel to the 5CB director axis. In the case of planar degenerate, 5CB is not aligned and has no preferred orientation, forcing the AuNPs to disperse randomly. Results show that the linear optical absorption coefficient for the planar oriented 5CB/AuNPs mixture is larger than the corresponding planar degenerate sample. The nonlinear absorption coefficients are greatly enhanced in planar oriented samples at relatively high concentrations which can be attributed to plasmon coupling between the aligned AuNPs. This study demonstrates the utility of LCs for developing the assembly of NPs with enhanced optical properties which may offer important insight and technological advancement for novel applications, including photonic nanomaterials and optoelectronic devices.

Hierarchical assembly of smectic liquid crystal defects at undulated interfaces.

The assembly of topological defects in liquid crystals has drawn significant interest in the last decade due to their ability to trap colloidal objects and direct their arrangements. They have also brought about a high impact in modern technologies, in particular in optics, e.g., microlens arrays, soft lithography templates, and optically selective masks. Here we study the formation of defects in smectic A liquid crystal with hybrid texture at undulated surfaces. We investigate the role of surface topography on the organization of focal conic domains (FCDs) in smectic films. We demonstrate new methods for assembling FCDs and disclinations into hierarchical structures. When the liquid crystal is heated to the nematic phase, we observe stable defect lines forming at specific locations. These defects are created to satisfy anchoring conditions and the geometry of confinement imposed by the boundaries. Once the liquid crystal is cooled to the smectic A phase, the disclinations maintain their positions, but periodic structures of reversible FCDs facing opposite directions arise between them. We report the correlation between the size of these FCDs and their eccentricities with the morphology of the interface. This work paves the way for creating new procedures to control the assembly of functional nanomaterials into tunable assemblies that may find relevance in the field of energy technology including in optoelectronic and photonic applications.

Elastocapillary Driven Assembly of Particles at Free-Standing Smectic-A Films.

Colloidal particles at complex fluid interfaces and within films assemble to form ordered structures with high degrees of symmetry via interactions that include capillarity, elasticity, and other fields like electrostatic charge. Here we study microparticle interactions within free-standing smectic-A films, in which the elasticity arising from the director field distortion and capillary interactions arising from interface deformation compete to direct the assembly of motile particles. New colloidal assemblies and patterns, ranging from 1D chains to 2D aggregates, sensitive to the initial wetting conditions of particles at the smectic film, are reported. This work paves the way to exploiting LC interfaces as a means to direct spontaneously formed, reconfigurable, and optically active materials.

Dynamics of ordered colloidal particle monolayers at nematic liquid crystal interfaces.

We prepare two-dimensional crystalline packings of colloidal particles on surfaces of the nematic liquid crystal (NLC) 5CB, and we investigate the diffusion and vibrational phonon modes of these particles using video microscopy. Short-time particle diffusion at the air-NLC interface is well described by a Stokes-Einstein model with viscosity similar to that of 5CB. Crystal phonon modes, measured by particle displacement covariance techniques, are demonstrated to depend on the elastic constants of 5CB through interparticle forces produced by LC defects that extend from the interface into the underlying bulk material. The displacement correlations permit characterization of transverse and longitudinal sound velocities of the crystal packings, as well as the particle interactions produced by the LC defects. All behaviors are studied in the nematic phase as a function of increasing temperature up to the nematic-isotropic transition.

An unusual cause of inguinal swelling: Primary synovial osteochondromatosis.

Inguinal swelling should raise suspicion for hip joint osteochondromatosis. Early recognition, accurate diagnosis, and prompt surgical intervention are essential for optimizing patient outcomes.

Primary extrahepatic hydatid cyst of the thigh, an unusual presentation of sciatica: A case report of a diagnostic challenge.

INTRODUCTION: Sciatica, a condition characterized by pain along the sciatic nerve distribution, is commonly associated with nerve compression or irritation. However, its etiology can vary, including rare non-spinal causes such as hydatid cysts. We present a case of hydatid cyst in the thigh causing sciatica-like symptoms, highlighting the diagnostic challenges and management approach. CASE PRESENTATION: A 40-year-old patient with a history of pulmonary tuberculosis presented with persistent lumbosciatic pain despite conservative treatment. Physical examination revealed left sciatica without spinal abnormalities. MRI revealed a hydatid cyst in the thigh, causing nerve irritation. Surgical resection of the cyst was performed, achieving symptom resolution. DISCUSSION: Hydatid cysts in skeletal muscles are rare, with atypical presentations complicating diagnosis. Localization in the thigh, particularly the biceps femoris muscle, is uncommon. Diagnostic modalities include imaging and serological tests, while treatment involves surgical excision and postoperative albendazole therapy. CONCLUSION: Recognition of rare presentations like thigh hydatid cysts causing sciatica-like symptoms is crucial for timely diagnosis and management. This case emphasizes the importance of considering unusual etiologies in refractory sciatica cases and underscores the complexity of medical diagnosis. Increased awareness among healthcare providers can lead to improved patient outcomes and prevent diagnostic delays.

Capillary force on a micrometric sphere trapped at a fluid interface exhibiting arbitrary curvature gradients.

We report theoretical predictions and measurements of the capillary force acting on a spherical colloid smaller than the capillary length that is placed on a curved fluid interface of arbitrary shape. By coupling direct imaging and interferometry, we are able to measure the in situ colloid contact angle and to correlate its position with respect to the interface curvature. Extremely tiny capillary forces down to femtonewtons can be measured with this method. Measurements agree well with a theory relating the capillary force to the gradient of Gaussian curvature and to the mean curvature of the interface prior to colloidal deposition. Numerical calculations corroborate these results.

Polarization Z-Scan Studies Revealing Plasmon Coupling Enhancement Due to Dimer Formation of Gold Nanoparticles in Nematic Liquid Crystals.

We investigate the plasmon coupling of gold nanoparticle (AuNP) dimers dispersed in a nematic liquid crystal matrix using the polarization z-scan technique. Our experimental setup includes the precise control of incident light polarization through polarization angles of 0°, 45°, and 90°. Two distinct cell orientations are examined: parallel and twisted nematic cells. In parallel-oriented cells, where liquid crystal molecules and AuNPs align with the rubbing direction, we observe a remarkable 2-3-fold increase in the nonlinear absorption coefficient when the polarization of the incident light is parallel to the rubbing direction. Additionally, a linear decrease in the third-order nonlinear absorption coefficient is noted as the polarization angle varies from 0° to 90°. In the case of twisted nematic cells, the NPs do not have any preferred orientation, and the enhancement remains consistent across all polarization angles. These findings conclusively establish that the observed enhancement in the nonlinear absorption coefficient is a direct consequence of plasmon coupling, shedding light on the intricate interplay between plasmonic nanostructures and liquid crystal matrices.

Giant cell tumor of the tendon sheath of the toe: case report of an unusual localization.

INTRODUCTION AND IMPORTANCE: The purpose of this study is to highlight a rare entity of unusual location and to report our therapeutic attitude in this regard, while detailing the diagnostic criteria and therapeutic management. CASE PRESENTATION: We describe the case of a 32 years old woman with a swelling of the big toe initially neglected by the patient, the evolution is marked by a discomfort when wearing shoes, it was a firm mass of 2 cm slightly painful without local inflammatory signs with bone lysis on radiography, The MRI showed an invasion of the flexor and extensor tendons of the hallux, our approach was a carcinological tumor exeresis and arthrodesis while preserving the toe since the pedicle was not invaded, the histological examination confirmed the diagnosis and the evolution is good without tumor recurrence. CLINICAL DISCUSSION: A giant cell tumor of the tendon sheaths (GCTTC) usually presents as a firm slow growing mass, the radiological assessment shows bone erosions, an MRI for extension assessment and histological confirmation are mandatory, malignant degenerations are unusual but should always be investigated, treatment is based on the most complete surgical resection to avoid the risk of recurrence, adjuvant radiotherapy can be done in case of incomplete resection but it is a controversial subject. CONCLUSION: GCTTC are benign tumors that may be locally malignant because of the invasion of noble structures, which makes their complete exeresis difficult. The diagnosis is based on clinical and radiological criteria and requires histological confirmation.

One-stage combined approach en bloc vertebrectomy for primary Ewing's sarcoma of mobile spine in an adult patient: 3 years following aggressive surgery for a rare entity.

Key Clinical Message: Currently, there is no consensus on the optimal management of nonmetastatic Ewing's sarcoma of the mobile spine. However, associated to chemotherapy, aggressive surgery with en bloc wide resection seems to improve local control and survival. Abstract: Primary Ewing's sarcoma (EWS) of non-sacral spine is extremely rare, especially in middle-age. Therapeutic strategy aims: to large tumor resection, to provide spine stability and to avoid recurrence through chemo and radiotherapy. We report a case of thoracic spine EWS in an adult treated by combined approach en bloc vertebrectomy.

Conservative surgical management of surface osteosarcoma using 3D printing technology: An unusual case report and literature review.

INTRODUCTION AND IMPORTANCE: Surface osteosarcoma, a rare variant of osteosarcoma, poses unique challenges in diagnosis and treatment. This report discusses the application of 3D printing technology in the surgical management of a complex case involving a 27-year-old female patient with surface osteosarcoma in the proximal tibia. CASE PRESENTATION: A 27-year-old female patient presented with a progressively growing mass on her right knee, initially misdiagnosed as a benign bone tumor. Over five years, the lesion expanded from a well-corticated metaphyseal-epiphyseal outgrowth on the proximal tibia to involve the anterior tibial tuberosity. Radiological and histological evaluations confirmed well-differentiated paraosteal surface osteosarcoma. A multidisciplinary team opted for a conservative surgical approach, including resection of the anterior tibial tuberosity and patellar tendon. Precision was enhanced through 3D printing technology, which provided custom cutting guides. The reconstruction involved non-vascularized peroneus and iliac crest bone grafts. CLINICAL DISCUSSION: Accurate differentiation from benign lesions presents challenges. Achieving surgical resection with clear margins is pivotal for favourable outcomes, particularly in young patients. Chemotherapy yields limited benefits in low-grade surface osteosarcomas. Functional prognosis hinges on effective post-resection reconstruction. 3D printing technology facilitates meticulous surgical planning and guidance, enhancing the success of conservative surgical interventions. CONCLUSION: This case underscores the significance of a multidisciplinary approach, accurate diagnosis, and the integration of 3D printing technology in managing surface osteosarcomas. Conservative surgical resection, guided by precise planning and reconstruction, is critical for preserving functionality. Continued research and the adoption of innovative techniques hold promise for improving the quality of life and functional outcomes of individuals grappling with musculoskeletal tumors.

Bone metastases from renal cell carcinoma: 4 years after aggressive surgeries and anti-angiogenic therapy.

Management of bone metastases from renal cell carcinoma (RCC) has significantly changed after the era of targeted therapy that improved the overall survival (OS). Surgical decision-making remains a subject of controversy. We report a case of pelvic bone metastasis from RCC, 2 months after nephrectomy and surgery of a revealing clavicular metastasis.

Reversible Nanoparticle Cubic Lattices in Blue Phase Liquid Crystals.

Blue phases (BPs), a distinct class of liquid crystals (LCs) with 3D periodic ordering of double twist cylinders involving orthogonal helical director twists, have been theoretically studied as potential templates for tunable colloidal crystals. Here, we report the spontaneous formation of thermally reversible, cubic crystal nanoparticle (NP) assemblies in BPs. Gold NPs, functionalized to be highly miscible in cyanobiphenyl-based LCs, were dispersed in BP mixtures and characterized by polarized optical microscopy and synchrotron small-angle X-ray scattering (SAXS). The NPs assemble by selectively migrating to periodic strong trapping sites in the BP disclination lines. The NP lattice, remarkably robust given the small particle size (4.5 nm diameter), is commensurate with that of the BP matrix. At the BP I to BP II phase transition, the NP lattice reversibly switches between two different cubic structures. The simultaneous presence of two different symmetries in a single material presents an interesting opportunity to develop novel dynamic optical materials.

Better Actuation Through Chemistry: Using Surface Coatings to Create Uniform Director Fields in Nematic Liquid Crystal Elastomers.

Controlling the molecular alignment of liquid crystal monomers (LCMs) within nano- and microstructures is essential in manipulating the actuation behavior of nematic liquid crystal elastomers (NLCEs). Here, we study how to induce uniformly vertical alignment of nematic LCMs within a micropillar array to maximize the macroscopic shape change using surface chemistry. Landau-de Gennes numerical modeling suggests that it is difficult to perfectly align LCMs vertically in every pore within a poly(dimethylsiloxane) (PDMS) mold with porous channels during soft lithography. In an untreated PDMS mold that provides homeotropic anchoring of LCMs, a radially escaped configuration of LCMs is observed. Vertically aligned LCMs, a preferred configuration for actuation, are only observed when using a PDMS mold with planar anchoring. Guided by the numerical modeling, we coat the PDMS mold with a thin layer of poly(2-hydroxyethyl methacrylate) (PHEMA), leading to planar anchoring of LCM. Confirmed by polarized optical microscopy, we observe monodomains of vertically aligned LCMs within the mold, in agreement with modeling. After curing and peeling off the mold, the resulting NLCE micropillars showed a relatively large and reversible radial strain (∼30%) when heated above the nematic to isotropic transition temperature.

Use of topological defects as templates to direct assembly of colloidal particles at nematic interfaces.

In this work, we experimentally investigate the ability of topological defects to guide interfacial assembly of spherical particles with homeotropic anchoring confined to nematic interfaces. We propose two different systems: In the first one, particles are trapped at an air/nematic interface where they spontaneously form various 2D patterns. We demonstrate that the phase transition between these patterns can be controlled by defects formed in the nematic bulk. In the second system, we explore the behavior of particles at the surface of bipolar nematic drops. We found that particles assemble into linear chains and interact with surface defects at the North and South poles of the drop, giving rise to the formation of star structures in a self-assembly process. We detail the mechanism that guides the behavior of particles and discuss the role of defects in the formation of the observed patterns.