A Free Energy Model for the Plateau Shear Modulus in Thermosensitive Microgel Suspensions.

Polymer microgels exhibit intriguing macroscopic flow properties arising from their unique microscopic structure. Microgel colloids usually comprise a cross-linked polymer network with a radially decaying density profile, resulting in a dense core surrounded by a fuzzy corona. Notably, microgels synthesized from poly(-isopropylacrylamide) (PNIPAM) are thermoresponsive and capable of adjusting their size and density profile based on temperature.

Polymer Nano-Carrier-Mediated Gene Delivery: Visualizing and Quantifying DNA Encapsulation Using dSTORM.

The success of gene therapy hinges on the effective encapsulation, protection, and compression of genes. These processes deliver therapeutic genes into designated cells for genetic repair, cellular behavior modification, or therapeutic effect induction. However, quantifying the encapsulation efficiency of small molecules of interest like DNA or RNA into delivery carriers remains challenging.

Revisiting the density profile of the fuzzy sphere model for microgel colloids.

Common neutral polymer microgels exhibit an inhomogeneous density profile with a gradual decay that is commonly described using the fuzzy sphere model. The model is based on the idea of convolving the collapsed solid sphere profile with a Gaussian to describe inhomogeneous swelling of the microgel in a good solvent. Here we show that the corresponding density profile in real space used in several recent works - such as in super-resolution microscopy - is different from the fuzzy sphere model, and we explain how to correctly transition between reciprocal space modelling to real space.

Volume Phase Transition of Thermoresponsive Microgels Scrutinized by Dynamic Light Scattering and Turbidity: Correlations Depend on Microgel Homogeneity.

Thermoresponsive microgels experience a volume phase transition triggered by temperature changes, a phenomenon often analyzed using dynamic light scattering to observe overall size alterations via the diffusion coefficient. However, local structural changes are typically assessed using more intricate and expensive techniques like small-angle neutron or X-ray scattering. In our research, we investigate the volume phase transition of poly--isopropylacrylamide (PNIPAM)-based microgels by employing a combination of temperature-dependent dynamic light scattering and simpler, faster, and more efficient attenuation measurements.

IgG and IgM differentiation in a particle-based agglutination assay by control over antigen surface density.

Point-of-care (POC) testing offers fast and on-site diagnostics and can be crucial against many infectious diseases and in screening. One remaining challenge in serological POC testing is the quantification of immunoglobulin G (IgG) and immunoglobulin M (IgM). Quantification of IgG/IgM can be important to evaluate immunity and to discriminate recent infections from past infections and primary infections from secondary infections.

Determining intrinsic potentials and validating optical binding forces between colloidal particles using optical tweezers.

Understanding the interactions between small, submicrometer-sized colloidal particles is crucial for numerous scientific disciplines and technological applications. In this study, we employ optical tweezers as a powerful tool to investigate these interactions. We utilize a full image reconstruction technique to achieve high precision in characterizing particle pairs that enable nanometer-scale measurement of their positions.

Tuning disorder in structurally colored bioinspired photonic glasses.

Colloidal crystals, such as opals, display bright and iridescent colors when assembled from submicron particles. While the brightness and purity of iridescent colors are well suited for ornaments, signaling, and anticounterfeiting, their angle dependence limits the range of their applications. In contrast, colloidal glasses display angle-independent structural color that is tunable by the size and local arrangement of particles.

Structural color from pigment-loaded nanostructures.

Color can originate from wavelength-dependence in the absorption of pigments or the scattering of nanostructures. While synthetic colors are dominated by the former, vivid structural colors found in nature have inspired much research on the latter. However, many of the most vibrant colors in nature involve the interactions of structure and pigment.

Single particle investigation of triolein digestion using optical manipulation, polarized video microscopy, and SAXS.

Hypothesis: Understanding how soft colloids, such as food emulsion droplets, transform based on their environment is critical for various applications, including drug and nutrient delivery and biotechnology. However, the mechanisms behind colloidal transformations within individual oil droplets still need to be better understood.

Experiments: This study employs optical micromanipulation with microfluidics and polarized optical video microscopy to investigate the pancreatic lipase- and pH-triggered colloidal transformations in a single triolein droplet.

Bandgap fluctuations and robustness in two-dimensional hyperuniform dielectric materials.

We numerically study the statistical fluctuations of photonic band gaps in ensembles of stealthy hyperuniform disordered patterns. We find that at low stealthiness, where correlations are weak, band gaps of different system realizations appear over a wide frequency range, are narrow, and generally do not overlap. Interestingly, above a critical value of stealthiness ≳0.

Probing Temperature Responsivity of Microgels and Its Interplay with a Solid Surface by Super-Resolution Microscopy and Numerical Simulations.

Super-resolution microscopy has become a powerful tool to investigate the internal structure of complex colloidal and polymeric systems, such as microgels, at the nanometer scale. An interesting feature of this method is the possibility of monitoring microgel response to temperature changes . However, when performing advanced microscopy experiments, interactions between the particle and the environment can be important.

Transport through Amorphous Photonic Materials with Localization and Bandgap Regimes.

We propose a framework that unifies the description of light transmission through three-dimensional amorphous dielectric materials that exhibit both localization and a photonic bandgap. We argue that direct, coherent reflection near and in the bandgap attenuates the generation of diffuse or localized photons. Using the self-consistent theory of localization and considering the density of states of photons, we can quantitatively describe the total transmission of light for all transport regimes: transparency, light diffusion, localization, and bandgap.

Echo speckle imaging of dynamic processes in soft materials.

We present a laser-speckle imaging technique, termed Echo speckle imaging (ESI), that quantifies the local dynamics in biological tissue and soft materials with a noise level around or below 10% of the measured signal without affecting the spatial resolution. We achieve this through an unconventional speckle beam illumination that creates changing, statistically independent illumination conditions and substantially increases the measurement accuracy. Control experiments for dynamically homogeneous and heterogeneous soft materials and tissue phantoms illustrate the performance of the method.

Inkjet Printing of Structurally Colored Self-Assembled Colloidal Aggregates.

Structurally colored materials offer increased stability, high biocompatibility, and a large variety of colors, which can hardly be reached simultaneously using conventional chemical pigments. However, for practical applications, such as inkjet printing, it is vital to compartmentalize these materials in small building blocks (with sizes ideally below 5 μm) and create "ready-to-use" inks. The latter can be achieved by using photonic balls (PB): spherical aggregates of nanoparticles.

Three-dimensional printing of photonic colloidal glasses into objects with isotropic structural color.

Structural color is frequently exploited by living organisms for biological functions and has also been translated into synthetic materials as a more durable and less hazardous alternative to conventional pigments. Additive manufacturing approaches were recently exploited for the fabrication of exquisite photonic objects, but the angle-dependence observed limits a broader application of structural color in synthetic systems. Here, we propose a manufacturing platform for the 3D printing of complex-shaped objects that display isotropic structural color generated from photonic colloidal glasses.

Optical tweezer platform for the characterization of pH-triggered colloidal transformations in the oleic acid/water system.

Hypothesis: Soft colloidal particles that respond to their environment have innovative potential for many fields ranging from food and health to biotechnology and oil recovery. The in situ characterisation of colloidal transformations that triggers the functional response remain a challenge.

Experiments: This study demonstrates the combination of an optical micromanipulation platform, polarized optical video microscopy and microfluidics in a comprehensive approach for the analysis of pH-driven structural transformations in emulsions.

Microrheological Approach for Probing the Entanglement Properties of Polyelectrolyte Solutions.

The entanglement dynamics and viscoelasticity of polyelectrolyte solutions remain active research topics. Previous studies have reported conflicting experimental results when compared to Dobrynin's scaling predictions derived from the Doi-Edwards (DE) tube model for entangled polymers. Herein, by combining classical bulk shear rheometry with diffusing wave spectroscopy (DWS) microrheometry, we investigate how the key viscoelastic parameters (the specific viscosity η, the plateau modulus , and the ratio of the reptation time to the Rouse time of an entanglement strand τ/τ) depend on the polymer concentration for semidilute entangled (SE) solutions containing poly(sodium styrenesulfonate) with high molecular weight.

Transport properties of optically thin solid dielectrics from frequency correlations of randomly scattered light: publisher's note.

This publisher's note contains a correction to Opt. Lett.47, 1439 (2022)10.

Transport properties of optically thin solid dielectrics from frequency correlations of randomly scattered light.

Frequency-dependent intensity correlation function measurements can be employed to determine the optical turbidity of solid disordered dielectrics. Here we demonstrate a speckle frequency correlation experiment with a focused beam and using an area detector. We show how to apply frequency correlation measurements to optically thin solid samples with the aim of determining the light diffusion coefficient and transport mean free path ℓ*.

Macroporous Silica Foams Fabricated via Soft Colloid Templating.

Macroporous materials with controlled pore sizes are of high scientific and technological interest, due to their low specific weight, as well as unique acoustic, thermal, or optical properties. Solid foams made of titania, silica, or silicon, as representative materials, have been previously obtained with several hundred nanometer pore sizes, by using sacrificial templates such as spherical emulsion droplets or colloidal particles. Macroporous structures in particular are excellent candidates as photonic materials with applications in structural coloration and photonic bandgap devices.

Enhancing the Refractive Index of Polymers with a Plant-Based Pigment.

Polymers are essential components of many nanostructured materials. However, the refractive indices of common polymers fall in a relatively narrow range between 1.4 and 1.

Light scattering from colloidal aggregates on a hierarchy of length scales.

Disordered dielectrics with structural correlations on length scales comparable to visible light wavelengths exhibit interesting optical properties. Such materials exist in nature, leading to beautiful structural non-iridescent color, and they are also increasingly used as building blocks for optical materials and coatings. In this article, we explore the angular resolved single-scattering properties of micron-sized, disordered colloidal assemblies.

Self-motion and heterogeneous droplet dynamics in moderately attractive dense emulsions.

We show that diffusing wave spectroscopy (DWS) is sensitive to the presence of a moderate short-range attraction between droplets in uniform fractionated colloidal emulsions near and below the jamming point associated with monodisperse hard spheres. This moderate interdroplet attraction, induced by micellar depletion, has an energy of about ∼2.4, only somewhat larger than thermal energy.