Particle-stabilized emulsions, also known as Pickering emulsions, have shown promise in areas that require long-term stability with minimum use of surfactants. While most work has focused on densely covered Pickering emulsions, such emulsions are known to retain stability even when the interfaces are sparsely covered with particles. Here, the formation, dynamics, and stability of poorly covered model Pickering emulsions are studied in a controlled manner by utilizing a microfluidic platform. The formed Pickering emulsions remain highly stable, over at least 12 h, even with a surface area coverage below 3%. By directly visualizing the droplet interface at various stages, the exceptional stability is attributed to the highly spatially heterogeneous distribution of adsorbed particles which exclusively form particle bridges at the contact point between the droplets. Remarkably, these bridges are assembled in the form of crowns between the droplet interfaces, as visualized by confocal microscopy. The assembly behavior of the adsorbed particles in response to hydrodynamic forces and the formation of non-uniform particle distribution are discussed by analyzing the different forces present during emulsification, corroborated by numerical simulations. In conclusion, using a lab-on-a-chip approach, this work provides further understanding toward the fabrication of Pickering emulsions via preferential interfacial localization of particles.

Thrips are one of the most challenging pests in agricultural crops, including Chrysanthemum. In this study we tested via two plant assays whether solutions containing sticky rice germ oil (RGO) droplets could effectively trap thrips and lower thrips damage on Chrysanthemum. In the first assay, we additionally assessed the metabolomic effects of these RGO droplet sprays and thrips presence on plant chemistry via 1H NMR and headspace GC-MS on multiple timepoints to investigate which plant metabolites were affected by spraying and their potential relation to plant resistance against thrips. In the second assay, we tested the individual RGO solution constituents against thrips. Our results suggested that the adhesive RGO droplets were not effective as a physical trap as only three out of 600 adult thrips were caught at the achieved coverage. However, average thrips damage was still reduced up to 50% and no negative effects on plant growth were observed up to 25 days. Results from the second plant assay indicated that the individual constituents of the solution containing RGO droplets may have direct effects against thrips. Metabolomics analysis of sprayed leaves via headspace GC-MS and 1H NMR indicated that fatty acids and several volatile compounds such as 4(10)-thujene (sabinene), eucalyptol, cis-4-thujanol, and isocaryophyllene were highest on day 10, while sucrose, malic acid, o-Cymene, and 3-Methyl-2-butenoic acid were highest on day 25. Plants with thrips showed higher flavonoid, carbohydrate and glutamine acetic acid levels, and lower fatty acids and malic acid levels. RGO application increased the levels of fatty acids and alcohols present on top of and inside the Chrysanthemum leaves, while decreasing the concentrations of volatile compounds such as eucalyptol, chrysanthenone and eugenol in the Chrysanthemum leaves. Most interestingly, the thrips effect on the plant metabolome was no longer visible in RGO treated plants at the later harvesttime, suggesting that RGO application may overrule or prevent the metabolomic effects of thrips infestation. In conclusion, our study provides new information on how the application of a new plant-based plant protection product affects insect herbivores and alters crop phytochemistry for improved herbivore resistance.

Titanium dioxide is the world's most widely used pigment; however, increased cost and potential environmental concerns have driven a need for a sustainable replacement. The study has developed a scalable method to produce more sustainable photonic whiteners with application in paint and other dispersion formulations. Bio-resourced zein protein nanoparticles are synthesized and used as sacrificial templates within a silica matrix. These micron-sized photonic whiteners exhibit morphologically dependent whitening capabilities when incorporated into paint films. When the silica content is insufficient, an open structure forms, while an excess of silica content results in fewer interfaces and reduced scattering efficiency, leading to suboptimal whitening performance. An ideal ratio of silica to zein nanoparticles ensures optimal whitening properties comparable to commercially available whitener alternatives to titanium dioxide. Further analysis reveals a non-uniform internal morphology of the photonic whiteners, with a silica-void network dispersed within a solid silica matrix. This morphology provides an innovative criterion for optimizing the whitening performance of photonic structures beyond composition. Titanium dioxide is the most widely used pigment; however, increased cost and potential environmental concerns necessitate a sustainable replacement. The authors fabricate photonic whiteners using bio-resourced zein protein nanoparticles as sacrificial templates within a micron diameter, spherical, silica matrix. An ideal ratio of silica to zein nanoparticles achieves optimal whitening properties, comparable to commercially available titania whitener alternatives. image

With a continuous increase in world population and food production, chemical pesticide use is growing accordingly, yet unsustainably. As chemical pesticides are harmful to the environment and developmental resistance in pests is increasing, a sustainable and effective pesticide alternative is needed. Inspired by nature, we mimic one defense strategy of plants, glandular trichomes, to shift away from using chemical pesticides by moving toward a physical immobilization strategy via adhesive particles. Through controlled oxidation of a biobased starting material, triglyceride oils, an adhesive material is created while monitoring the reactive intermediates. After being milled into particles, nanoindentation shows these particles to be adhesive even at low contact forces. A suspension of particles is then sprayed and found to be effective at immobilizing a target pest, thrips, Frankliniella occidentalis . Small arthropod pests, like thrips, can cause crop damage through virus transfer, which is prevented by their immobilization. We show that through a scalable fabrication process, biosourced materials can be used to create an effective, sustainable physical pesticide.

Inkjet printing is a ubiquitous consumer and industrial process that involves concomitant processes of droplet impact, wetting, evaporation, and imbibement into a substrate as well as consequential substrate rearrangements and remodeling. In this work, we perform a study on the interaction between ink dispersions of different composition on substrates of increasing complexity to disentangle the motion of the liquid from the dynamic response of the substrate. We print three variations of pigmented inks and follow the ensuing dynamics at millisecond and micron time and length scales until complete drying using a multiple scattering technique, laser speckle imaging (LSI). Measurements of the photon transport mean free path, l*, for the printed inks and substrates show that the spatial region of information capture is the entire droplet volume and a depth within the substrate of a few mu m beneath the droplet. Within this spatial confinement, LSI is an ideal approach for studying the solid-liquid transition at these small length and time scales by obtaining valid g2 and d2 autocorrelation functions and interpreting these dynamic changes under through kymographs. Our in situ LSI results show that droplets undergo delamination and cracking processes arising during droplet drying, which are confirmed by post mortem SEM imaging. Laser Speckle Imaging is used to follow the concomitant processes during inkjet printing, including droplet impact, wetting, evaporation, and imbibement into a substrate as well as consequential substrate rearrangements and remodeling.

Arthropod pests cause significant problems in agricultural crops all around the world. As chemical pesticide use becomes less desired, there is a need for alternative methods of pest control. Inspired by the natural adhesiveness of arthropod trapping plants, we examined the effectiveness of adhesive droplets made from oxidised and cross-linked plant-derived oils for control of western flower thrips. Two filter paper droplet adhesiveness assays and three detached chrysanthemum leaf assays were carried out to test efficacy against thrips. Suspensions containing adhesive droplets and other constituents were applied to filter papers and leaves via spraying or dipping. On filter papers, droplets made from oxidised rice germ oil (RGO) of different sizes caught 40–93% of thrips. Droplets made of a mixture of sunflower, olive, and linseed oil (MIX) caught up to 94% of thrips. Likewise, adhesive droplet-treated filter papers showed higher thrips mortality than untreated or control solution-treated filter papers. On chrysanthemum leaves, thrips were caught by both RGO (up to 40%) and MIX droplets (up to 20%) and thrips damage and reproduction were reduced. On MIX-treated leaves, thrips mortality was also increased. Within treatments, droplets of different size classes occurred and larger droplets were more effective at catching thrips in general. Droplets were also robust to rinsing with water, which is of importance for their application in horticulture. In conclusion, adhesive droplets made from edible plant oils show potential for use in control of western flower thrips.

The assembly of (nano)particles into compact hierarchical structures yields emergent properties not found in the individual constituents. The formation of these structures relies on a profound knowledge of the nanoscale interactions between (nano)particles, which are often designed by researchers aided by computational studies. These interactions have an effect when the (nano)particles are brought into close proximity, yet relying only on diffusion to reach these closer distances may be inefficient. Recently, physical confinement has emerged as an efficient methodology to increase the volume fraction of (nano)particles, rapidly accelerating the time scale of assembly. Specifically, the high surface area of droplets of one immiscible fluid into another facilitates the controlled removal of the dispersed phase, resulting in spherical, often ordered, (nano)particle assemblies. In this review, we discuss the design strategies, computational approaches, and assembly methods for (nano)particles in confined spaces and the emergent properties therein, such as trigger-directed assembly, lasing behavior, and structural photonic color. Finally, we provide a brief outlook on the current challenges, both experimental and computational, and farther afield application possibilities.

The synthesis of binary nanocrystal superlattices (BNSLs) enables the targeted integration of orthogonal physical properties, such as photoluminescence and magnetism, into a single superstructure, unlocking a vast design space for multifunctional materials. However, the formation mechanism of BNSLs remains poorly understood, restricting the prediction of the structure and properties of superlattices. Here we use a combination of in situ scattering and molecular simulation to elucidate the self-assembly of two common BNSLs (AlB2 and NaZn13) through emulsion templating. Our self-assembly experiments reveal that no intermediate structures precede the formation of the final binary phases, indicating that their formation proceeds through classical nucleation. Using simulations, we find that, despite the formation of AlB2 and NaZn13 typically being attributed to entropy, their self-assembly is most consistent with the nanocrystals possessing short-range interparticle attraction, which we find can accelerate nucleation kinetics in BNSLs. We also find homogeneous, classical nucleation in simulations, corroborating our experiments. These results establish a robust correspondence between experiment and theory, paving the way towards prediction of BNSLs. Unravelling the formation of binary nanocrystal phases is challenging. Here, by combining in situ small-angle X-ray scattering and molecular dynamics simulations, we show that AlB2 and NaZn13 superlattices undergo classical homogeneous nucleation consistent with the presence of short-range attractive interactions guiding the crystallization process.

In recent times, 3D printing technology has revolutionized our ability to design and produce products, but optimizing the print quality can be challenging. The process of extrusion 3D printing involves pressuring molten material through a thin nozzle and depositing it onto previously extruded material. This method relies on bonding between the consecutive layers to create a strong and visually appealing final product. This is no easy task, as many parameters, such as the nozzle temperature, layer thickness, and printing speed, must be fine-tuned to achieve optimal results. In this study, a method for visualizing the polymer dynamics during extrusion is presented, giving insight into the layer bonding process. Using laser speckle imaging, the plastic flow and fusion can be resolved non-invasively, internally, and with high spatiotemporal resolution. This measurement, which is easy to perform, provides an in-depth understanding of the underlying mechanics influencing the final print quality. This methodology was tested with a range of cooling fan speeds, and the results showed increased polymer motion with lower fan speeds and, thus, explained the poor printing quality when the cooling fan was turned off. These findings show that this methodology allows for optimizing the printing settings and understanding the material behavior. This information can be used for the development and testing of novel printing materials or advanced slicing procedures. With this approach, a deeper understanding of extrusion can be built to take 3D printing to the next level.

Energy efficient processes in industry represent a key factor to realize a fast transition to renewable energy sources. In the coatings industry, oven technologies applied for drying and curing, mainly contribute to energy consumption. Substitution of these wasting technologies by near infrared radiation (NIR) in combination with a NIR-absorber represents a promising alternative to reduce the energy use. Here, combining of a NIR-LED with a heptamethine cyanine operating as absorber can significantly accelerate the drying process of a water borne coating as measured by Laser Speckle Imaging (LSI). The combination of cyanine and bis(tert-butyl)iodonium salts as radical initiator results in an initiation system that efficiently works in combination with a NIR-LED to dry the coating followed by crosslinking in the same step. photo-DSC and FTIR measurements confirmed the results obtained. The use of a water compatible photoinitiator system based on a cyanine with sulfonate groups and bis(tert-butyl)iodonium lactate as water soluble coinitiator opened the possibility to eliminate the cosolvent needed for film formation and to create a complete VOC free formulation.

The drying of a multi-component dispersion, such as water-based paint, ink and sunscreen to form a solid film, is a widespread process. Binary colloidal suspensions have proven capable of spontaneous layer formation through size segregation during drying. To design bespoke stratification patterns, a deeper understanding of how these emerge is crucial. Here, we visualize and quantify the spatiotemporally evolving concentration profiles in situ and with high resolution using confocal fluorescence microscopy of custom-designed binary dispersions in a well-defined geometry. Our results conclusively establish two distinct stratification routes, which give rise to three layered structures. A first thin layer develops directly underneath the evaporation front in which large particles are kinetically trapped. At later times, asymmetrical particle interactions lead to the formation of two subsequent layers enriched in small and large particles, respectively. The spatial extent and magnitude of demixing strongly depend on the initial volume fraction. We explain and reproduce the experimental concentration profiles using a theoretical model based on dynamic arrest and higher-order thermodynamic and hydrodynamic interactions. These insights unravel the key mechanisms underlying colloidal auto-stratification in multi-component suspensions, and allow preprogramming of stratification patterns in single-deposition formulations for future applications.

In recent times, 3D printing technology has revolutionized our ability to design and produce products, but optimizing the print quality can be challenging. The process of extrusion 3D printing involves pressuring molten material through a thin nozzle and depositing it onto previously extruded material. This method relies on bonding between the consecutive layers to create a strong and visually appealing final product. This is no easy task, as many parameters, such as the nozzle temperature, layer thickness, and printing speed, must be fine-tuned to achieve optimal results. In this study, a method for visualizing the polymer dynamics during extrusion is presented, giving insight into the layer bonding process. Using laser speckle imaging, the plastic flow and fusion can be resolved non-invasively, internally, and with high spatiotemporal resolution. This measurement, which is easy to perform, provides an in-depth understanding of the underlying mechanics influencing the final print quality. This methodology was tested with a range of cooling fan speeds, and the results showed increased polymer motion with lower fan speeds and, thus, explained the poor printing quality when the cooling fan was turned off. These findings show that this methodology allows for optimizing the printing settings and understanding the material behavior. This information can be used for the development and testing of novel printing materials or advanced slicing procedures. With this approach, a deeper understanding of extrusion can be built to take 3D printing to the next level.

Polymeric elastomers made of bottlebrush chains are soft, solvent-free materials with precisely controllable moduli by network topology. However, fabrication methods of bottlebrush networks with precisely programmable topology are lacking. The aim of this study is to achieve precise control over the modulus of hybrid elastomers containing bottlebrush and linear strands by integrating a versatile experimental synthesis approach with Molecular Dynamics (MD) simulations. In this study, polydimethylsiloxane (PDMS) networks (G' = 10 - 328 kPa) are made by crosslinking prepared and purified bottlebrush molecules where the precursors, side chains and backbone, are synthesized using well-controlled living anionic polymerization. This approach allows independent programming of the crucial topological parameters of bottlebrushes, such as length of both sides chain and backbone and grafting density. In addition to this versatile synthesis, MD simulations reveal the influence of network defects inevitably present in all polymer networks. This novel combining of fabrication method and simulation yields experimentally-measured structural shear and Young's moduli which are in better agreement with theoretical predictions. Importantly, these bottlebrush-containing networks have no solvent or additives and notably, by removing ungrafted side chains impurities before network formation, results in soft, solvent-free elastomers with Young's moduli as low as E similar to 30 kPa with adhesiveness far lower than commercial silicone products of similar stiffness.

We assemble semiconductor CdSe nanoplatelets (NPs) at the air/liquid interface into 2D monolayers several micrometers wide, distinctly displaying nematic order. We show that this configuration is the most favorable energetically and that the edge-to-edge distance between neighboring NPs can be tuned by ligand exchange without disrupting film topology and nanoparticle orientation. We explore the rich assembly phase space by using depletion interactions to direct the formation of 1D nanowires from stacks of NPs. The improved control and understanding of the assembly of semiconductor NPs offers opportunities for the development of cheaper optoelectronic devices that rely on 1D or 2D charge delocalization throughout the assembled monolayers and nanowires.

Polymer networks containing bottlebrush chains are emerging materials with exceptionally soft and highly tunable mechanical properties. However, such materials have not been extensively implemented in functional processing techniques such as three-dimensional (3D) printing. Here, we introduce a new design of soft and solvent-free polydimethylsiloxane (PDMS)-based thermoplastic elastomer which contains dangling and space-filling bottlebrush chains, featuring a yield stress and a rapid recovery after stress removal; both required for high spatial fidelity 3D printing. The developed material is composed of two copolymers; the main building block is a diblock copolymer with linear polystyrene (PS) block and bottlebrush PDMS block (PS-b-bbPDMS) while the second component is PS-b-PDMS-b-PS triblock, self-assembling to a physical network. This design provides independent tunability of each structural parameter on the molecular level, hence, macroscopic control of the materials' mechanical properties. Multiple self-supportive 3D structures with spanning elements are 3D printed at elevated temperatures using a developed material with a low shear modulus of G ' = 3.3 kPa containing 3 : 1 molar ratio of diblock to triblock copolymers without the need for volatile solvent, or post-treatment. This 3D printing compatible design opens new opportunities to utilize the distinctive mechanical properties of bottlebrush materials for applications such as soft tissue scaffolds, sensors, actuators, and soft robots. Designed super-soft and solvent-free bottlebrush thermoplastic elastomer compatible with 3D printing with tunability of each topological parameter at the molecular level.

Drying coatings undergo internal dynamic densification and rearrangement, which are challenging to discern with optical techniques due to their multiple scatterings of light. Experiments such as diffusing wave spectroscopy (DWS) and laser speckle imaging (LSI) leverage these multiple scatterings to reveal the in situ dynamics of the coating. In such experiments, the knowledge of the sample volume that can be accessed and therefore studied is fundamental, especially in cases of micrometer-scale coating thicknesses. In this paper, we present a robust and reliable method using transmission geometry to calculate the parameter l*, defined as the transport light mean-free path, which is strongly related to the volume of the sample that light explores in DWS and LSI experiments. We show how this dynamic parameter can be measured for liquid and solid film samples and, crucially, in the case of time-evolving samples, such as drying coatings of paint or ink, which has not been previously explored. We present a series of model ink samples and discuss the evolution of their densification during drying through quantification of dynamic l*.

Syneresis, the compaction of a material accompanied by fluid expulsion, is a typical mechanical instability which exists among colloidal gel based materials and that negatively affects the quality of relevant applications. We shed light onto the internal dynamics of model colloidal gels undergoing syneresis using Laser Speckle Imaging (LSI). The resulting dynamical maps capture the distinct differences in spatial and temporal relaxation patterns between colloidal gels comprising solid and liquid particles. This indicates different mechanisms of syneresis between the two systems and highlights the importance of the constituent particles and their mobile or restrictive interfaces in the mechanical relaxation of the colloidal gels during syneresis.

Linear-bottlebrush-linear (LBBL) triblock copolymers are emerging systems for topologically-tunable elastic materials. In this paper, a new synthetic methodology is presented to synthesize LBBL polystyrene-block-bottlebrushpolydimethylsiloxane-block-polystyrene (PS-b-bbPDMS-b-PS) triblock copolymer via the "grafting onto" approach where the precursors are individually synthesized through living anionic polymerization and selective coupling reaction. In this two-step approach, polystyrene-block-polymethylvinylsiloxane (PS-b-PMVS) diblock copolymer with a low dispersity couples with another living PS block to form PS-b-PMVS-b-PS triblock copolymer. Secondly, this is followed by grafting of separately prepared monohydride-terminated PDMS chains with controllable grafting density through a hydrosilylation reaction. In addition to fully tunable architectural parameters, this approach permits a quantitative determination of the ratio of diblock and triblock bottlebrush copolymers and consistency between batches, highlighting the feasibility for scaled-up production. These LBBL triblock copolymers self-assemble into soft, low-modulus thermoplastic elastomers, and the precise knowledge of the composition is crucial for correlating microstructure to mechanical properties.

Superparticles made from colloidal nanocrystals have recently shown great promise in bridging the nanoscale and mesoscale, building artificial materials with properties designed from the bottom-up. As these properties depend on the dimension of the superparticle, there is a need for a general method to produce monodisperse nanocrystal superparticles. Here, we demonstrate an approach that readily yields spherical nanocrystal superparticles with a polydispersity as low as 2%. This method relies on the controlled densification of the nanocrystal-containing “source” emulsion by the swelling of a secondary “sink” emulsion. We show that this strategy is general and rapid, yielding monodisperse superparticles with controllable sizes and morphologies, including core/shell structures, within a few minutes. The superparticles show a high optical quality that results in lasing through the whispering-gallery modes of the spherical structure, with an average quality factor of 1600. Assembling superparticles into small clusters selects the wavelength of the lasing modes, demonstrating an example of collective photonic behavior of these artificial solids.