How the use of a short channel can improve the separation efficiency of nanoparticles in asymmetrical flow field-flow fractionation.

The use of a commercially available short length channel (14 cm length) is proposed to improve the efficiency associated to the separation by asymmetrical flow field-flow fractionation of particles in the nanometer range respect to a standard channel (27 cm length). The effect of channel length on elution times, separation efficiency and resolution have been studied. Polystyrene particles between 50 and 500 nm in size have been used to compare the behavior of both channels. Theoretical aspects based on the different contributions on particle diffusion inside the channel during the separation process have been considered to justify the results obtained. Non-equilibrium diffusion contribution to the efficiency has shown to be the most relevant aspect to be controlled during the separation. The increment of the field strength applied through the cross-flow velocityallows the reduction of diffusion while keep elution times constant. The use of the same cross-flow in a channel with a smaller area is the key factor that justifies the better efficiencies observed along the whole size range studied (improvements that reach factors up to 4.7 in experimental efficiency respect to the standard channel were achieved). The separation of polystyrene particles of 100 and 200 nm was achieved with a resolution of 1.20, whereas a 0.66 value was obtained with the standard channel at the same elution times. Channel recoveries have been also compared under optimized conditions to ensure that no side effects are produced, including the separation of mixtures of TiO2 nanoparticles. Similar or even better values were obtained with the short length channel, with recoveries higher than 85% for all the polystyrene particles tested and 75% recovery for the TiO2 nanoparticle mixture, which justifies its use for the separation of nanoparticles, providing better resolutions without compromise elution times or recoveries.

Sheathless Inertial Focusing Chip Combining a Spiral Channel with Periodic Expansion Structures for Efficient and Stable Particle Sorting.

Efficient and reliable manipulation of biological particles is crucial in medical diagnosis and chemical synthesis. Inertial microfluidic devices utilizing passive hydrodynamic forces in the secondary flow have drawn considerable attention for their high throughputs, low costs, and harmless particle manipulation. However, as the dominant mechanism, the inertial lift force is difficult to quantitatively analyze because of the uncertainties of its magnitude and direction. The equilibrium position of particles varies along the migration process, thus inducing the instabilities of particle separation. Herein, we present a designable inertial microfluidic chip combining a spiral channel with periodic expansion structures for the sheathless separation of particles with different sizes. The stable vortex-induced lift force arising from the periodic expansion and the Dean drag force significantly enhanced the focusing process and determined the final equilibrium position. The experimental results showed that over 99% of target particles could be isolated with the high target sample purity of 86.12%. In the biological experiment, 93.5% of the MCF-7, 89.5% of the Hela, and 88.6% of the A549 cells were steadily recovered with excellent viabilities to verify the potential of the device in dealing with biological particles over a broad range of throughputs. The device presented in this study can further serve as a lab-on-chip platform for liquid biopsy and diagnostic analysis.

Effects of two surface acoustic wave sorting chips on particles multi-level sorting.

Particle/cell sorting has great potential in medical diagnosis and chemical analysis. Two kinds of microfluidic sorting chips (sequential sorting chip and direct sorting chip) are designed, which combine hydraulic force and acoustic radiation force to achieve continuous sorting of multiple particles. Firstly, the optimal values of the angle (α) between the interdigital transducer (IDT) and the main channel, the peak-to-peak voltage (Vpp), the main flow velocity (Vmax) and the flow ratio (A) are determined by simulation and experiments, the related optimal parameters were obtained that the α = 15°, Vpp = 25 V, Vmax = 4 mm/s, flow ratio A1 = 0.2, and A2 = 0.5, respectively. Then, the corresponding sorting experiments were carried out using two kinds of sorting chips to sort the polystyrene (PS) particles with diameters of 1 µm, 5 µm, and 10 µm, and the sorting rate and purity of particles were calculated and analyzed. Experimental results show that the two kinds of sorting chips can achieve continuous sorting of multiple particles, and the sorting effect of sequential sorting chip (control flow ratio) is better than that of direct sorting chip. In addition, the sorting chips in our research have the advantages of simple structure, high sorting efficiency, and the ability to sort multiple particles, which can be applied in medical and chemical research fields, such as cell sorting and chemical analysis.

Separation of polystyrene nanoparticles with different coatings using two-dimensional off-line coupling of asymmetrical flow field flow fractionation and capillary electrophoresis.

The successful off-line coupling of asymmetrical flow field flow fractionation (AF4) and capillary electrophoresis (CE) for separation of nanoparticles (NPs) with different surface coatings was shown. We could successfully demonstrate that, in a certain NP size range, hyphenation of both techniques significantly improved the separation of differently coated NPs. Three mixtures of polystyrene nanoparticles (PS-NPs) with comparable core sizes but different coatings (no coating/carboxyl-coated) were studied. Separation in either method resulted in non-baseline resolved or non-separated peaks. In contrast, two-dimensional off-line coupling of AF4 and CE resulted in clearly separated regions in their 2 D plots in case of 20 and 50 nm particle mixtures, whereas the 100 nm NP mixture could not be separated at all. Various factors affecting the separation like hydrodynamic diameter or SDS concentration were discussed.

Functionalized polystyrene microspheres as Cryptosporidium surrogates.

Cryptosporidium, a waterborne protozoan pathogen that can cause gastrointestinal illness, is often found in surface waters that are used to supply drinking water. Filtration is a major process to remove Cryptosporidium in drinking water treatment. However, interactions between oocysts and filter media are still unclear and no satisfactory surrogates have been identified for quantifying their filtration removal in porous media. In the present study, polystyrene microsphere with a size, density, and shape similar to Cryptosporidium was modified with glycoprotein or synthesized biomolecules to mimic the surface properties of live Cryptosporidium oocyst. Deposition kinetics between live Cryptosporidium/modified microspheres and filter media were studied at the molecular scale using a quartz crystal microbalance with dissipation monitoring (QCM-D) and at the laboratory-scale using sand-packed columns. Both QCM-D and column experiments underlined the importance of Cryptosporidium surface charge and hydrophobicity on their attenuation and transport in porous media. As compared to live Cryptosporidium, glycopolymer and zwitterionic polymer co- odified polystyrene microspheres (later called copolymers-modified microspheres) represent comparable surface properties, adsorption kinetics on filter surfaces, and transport and deposition behaviors in filter columns; hence were selected as appropriate Cryptosporidium surrogates. This study improves our understanding on how surface characteristics impact Cryptosporidium transport behaviors in porous media and contributes to our capacity to evaluate the attenuation of Cryptosporidium in natural and engineered aquatic environments.

Poor extraction efficiencies of polystyrene nano- and microplastics from biosolids and soil.

Extraction and quantification of nano- and microplastics from sediments and soils is challenging. Although no standard method has been established so far, flotation is commonly used to separate plastic from mineral material. The objective of this study was to test the efficiency of flotation for the extraction of nano- and microplastics from biosolids and soil. We spiked biosolids and soil samples with polystyrene nano- and microbeads (0.05, 1.0, 2.6, 4.8, and 100 µm diameter). Different extraction methods (w/ and w/o H2O2 digestion) were tested, and plastic beads were separated from mineral particles by flotation in a ZnCl2 solution. Plastic particles were quantified by UV-Vis spectrometry and gravimetrically. While large beads (100 µm) could be quantitatively extracted (∼100%) from both biosolids and soils, smaller beads had low extraction efficiencies (ranging from 5 to 80%, with an average of 20%). Except for the 100 µm beads, oxidation with H2O2 negatively impacted the extraction efficiencies. For the soil, extraction with water only, followed by flotation in a ZnCl2 solution, resulted in relatively high extraction efficiencies (>75%) for beads larger than 1 µm, but low efficiencies (<30%) for the 0.05 and 1.0 µm beads. Our results indicate that while flotation generally works to separate plastic nano- and microbeads in a solution, the challenge is to quantitatively extract nano- and microbeads from a biosolids or soil matrix. Samples high in organic matter content require removal of the organic matter, but the common method of H2O2 oxidation leads to poor extraction efficiencies for nano- and microbeads.

Bridging the scales in high-throughput dielectrophoretic (bio-)particle separation in porous media.

Dielectrophoresis (DEP) is a versatile technique for the solution of difficult (bio-)particle separation tasks based on size and material. Particle motion by DEP requires a highly inhomogeneous electric field. Thus, the throughput of classical DEP devices is limited by restrictions on the channel size to achieve large enough gradients. Here, we investigate dielectrophoretic filtration, in which channel size and separation performance are decoupled because particles are trapped at induced field maxima in a porous separation matrix. By simulating microfluidic model porous media, we derive design rules for DEP filters and verify them using model particles (polystyrene) and biological cells (S. cerevisiae, yeast). Further, we bridge the throughput gap by separating yeast in an alumina sponge and show that the design rules are equally applicable in real porous media at high throughput. While maintaining almost 100% efficiency, we process up to 9 mL min-1, several orders of magnitude more than most state-of-the-art DEP applications. Our microfluidic approach provides new insight into trapping dynamics in porous media, which even can be applied in real sponges. These results pave the way toward high-throughput retention, which is capable of solving existing problems such as cell separation in liquid biopsy or precious metal recovery.

"From the Edge to the Center": Viscoelastic Migration of Particles and Cells in a Strongly Shear-Thinning Liquid Flowing in a Microchannel.

Controlling the fate of particles and cells in microfluidic devices is critical in many biomedical applications, such as particle and cell alignment and separation. Recently, viscoelastic polymer solutions have been successfully used to promote transversal migration of particles and cells toward fixed positions in straight microchannels. When inertia is negligible, numerical simulations have shown that strongly shear-thinning polymer solutions (fluids with a shear viscosity that decreases with increasing flow rates) promote transversal migration of particles and cells toward the corners or toward the centerline in a straight microchannel with a square cross section, as a function of particle size, cell deformability, and channel height. However, no experimental evidence of such shifting in the positions for particles or cells suspended in strongly shear-thinning liquids has been presented so far. In this work, we demonstrate that particle positions over the channel cross section can be shifted "from the edge to the center" in a strongly shear-thinning liquid. We investigate the viscoelasticity-induced migration of both rigid particles and living cells (Jurkat cells and NIH 3T3 fibroblasts) in an aqueous 0.8 wt % hyaluronic acid solution. The combined effect of fluid elasticity, shear-thinning, geometric confinement, and cell deformability on the distribution of the particle/cell positions over the channel cross section is presented and discussed. In the same shear-thinning liquid, separation of 10 and 20 µm particles is also achieved in a straight microchannel with an abrupt expansion. Our results envisage further applications in viscoelasticity-based microfluidics, such as deformability-based cell separation and viscoelastic spacing of particles/cells.

Separation of 300 and 100 nm Particles in Fabry-Perot Acoustofluidic Resonators.

Separation of particles on the order of 100 nm with acoustophoresis has been challenging to date because of the competing natures of the acoustic radiation force and acoustic streaming on the particles. In this work, we present a surface acoustic wave (SAW)-based device that integrates a Fabry-Perot type acoustic resonator into a microfluidic channel to separate submicrometer particles. This configuration enhances the overall acoustic radiation force on the particles and thereby offers controlled manipulation of particles as small as 300 nm. Additionally, SAW-based excitation generates high-frequency acoustic waves in the system relative to bulk acoustic wave (BAW)-based actuation, which suppresses Rayleigh streaming effects on the submicrometer particles. We demonstrate a continuous-flow acoustophoretic separation of 300 and 100 nm particles in our device with a separation efficiency of 86.3%. We also present an analytical stochastic method to model the transport of submicrometer particles in the device and predict the migration trajectories as a function of acoustic and velocity potential field strengths. Our model incorporates particle diffusion, which is important for small particles, and successfully predicts the size-dependent separation modality of our system. This device can be used for several applications in microfluidics that require sorting of the submicrometer particles, and the analytical method can also be extended to predict the particle transport in other systems.

Silica aerogel coated on metallic wire by phase separation of polystyrene for in-tube solid phase microextraction.

In this research, an attempt was made toward synthesizing a sol-gel-based silica aerogel and its subsequent coating on a copper wire by phase separation of polystyrene. Adaption of this new approach enabled us to coat the metallic wire with powder materials. The use of this method for coating, led to the formation of a porous and thick structure of silica aerogel. The coated wire was placed in a needle and used as the sorbent for in-tube solid phase microextraction of chlorobenzenes (CBs). The superhydrophobicity of sorbent on extraction efficiency was investigated by using different ratios of tetraethylorthosilicate/methyltrimethoxysilane. The surface coated with the prepared silica aerogel by the phase separation of polystyrene showed high contact angle, approving the desired superhydrophobic properties. Effects of major parameters influencing the extraction efficiency including the extraction temperature, extraction time, ionic strength, desorption time were investigated and optimized. The limits of detection and quantification of the method under the optimized condition were 0.1-1.2 and 0.4-4.1ngL-1, respectively. The relative standard deviations (RSD%) at a concentration level of 10ngL-1 were between 4 and 10% (n=3). The calibration curves of CBs showed linearity from 1 to100ngL-1. Eventually, the method was successfully applied to the extraction of model compounds from real water samples and relative recoveries varied from 88 to 115%.

Magnetic separation of microparticles by shape.

Accurate separation of microparticles by shape has diverse applications in biology and biotechnology, but is a significant challenge in separation science and engineering. We demonstrate a simple and effective mechanism that can achieve shape-based separation of magnetic particles in microscale flows. In this method, a uniform magnetic field is applied perpendicularly to the flow direction, and causes shape-dependent lateral migration of the particles. Using high-speed imaging, we studied the rotational dynamics of the ellipsoidal particles. It is found that the lateral migration is correlated with the asymmetric rotation of the particles. Different from existing techniques that use magnetic forces, our method uses shape-dependent magnetic torque but zero magnetic force.

Fundamental study of the separation of homopolymers from block copolymers by liquid chromatography with preloaded adsorption promoting barriers.

A fundamental study of the separation of homopolymers from polystyrene-block-polymethylmethacrylate (PS-b-PMMA) by liquid chromatography with preloaded discrete and continuous adsorption promoting barriers was performed. The impact of barrier composition on the separation of block copolymers (BCP) was studied by a dual detection (ultraviolet (UV) and evaporated light scattering (ELSD) detectors) system that enabled monitoring both barrier composition and BCP separation simultaneously. The separation of homopolymers from BCP by preloaded discrete adsorption promoting barriers was validated via a series of control experiments by blending known amounts of homopolymers PS or PMMA with PS-b-PMMA, and the resulting chromatograms were free from co-elution of homopolymers and BCP. Quantitation of homopolymers and BCP by ELSD was also demonstrated. The influence of BCP chemical composition on the separation by preloaded discrete adsorption promoting barriers was investigated. Results showed a PS-b-PMMA having 90wt% PMMA co-eluted with homopolymer PMMA, whereas PS-b-PMMA samples having lower amounts of PMMA block could be separated from homopolymer PMMA, successfully. Attempts at using a preloaded solvent gradient for separating homopolymers from block copolymers were unsuccessful. UV detection of the solvent gradient revealed significant deviation in solvent composition compared to the nominally loaded gradient. This deviation was due to the interaction of strong desorption solvent with column stationary phase. As such, the barrier composition in the preloaded gradient method was not as expected. Therefore, one can obtain undesired separation results by preloaded solvent gradients.

Using capillary electrophoresis to characterize polymeric particles.

Capillary electrophoresis (CE) was used for the characterization of a variety of polymeric micron and sub-micron particles based on size, surface functionality, and binding properties. First, a robust capillary zone electrophoresis (CZE) method was developed for the baseline separation and quantitation of commercially available polystyrene particles with various surface modifications (including amino, carboxylate, and sulfate functional groups) and various sizes (0.2, 0.5, 1.0, and 3.0µm). The separation of DNA-templated polyacrylamide particles from untemplated particles (as used for the Ion Torrent Personal Genome Machine) was demonstrated. Finally, using the 29-base thrombin aptamer and thrombin protein as a model system, a study was undertaken to determine dissociation constants for the aptamer and protein in free solution and when the aptamer was conjugated to a particle, with the goal of better understanding how the use of solid substrates, like particles, affects selection and binding processes. Dissociation constants were determined and were found to be approximately 5-fold higher for the aptamer conjugated to a particle relative to that in free solution.

Micro/nanoparticle separation via curved nano-gap device with enhanced size resolution.

Micro/nanoparticles are widely found in industry and biological field to play important roles and particle size distribution is an important factor to evaluate these particles. Nano-gap device has advantages in size determination for particles in diverse size and/or shape, but it has difficulty in practical use due to severe requirement on instrumental alignment to reproduce the gap profile and non-quantitative sample injection based on capillary action. To solve these problems, curved nano-gap device (CGD) was fabricated from two flat glass plates via a simple microfabrication process to gain enhanced size resolution, and pressure-driven liquid delivery system was coupled to CGD. The gap was precisely controlled by wet etching with hydrofluoric acid on a glass plate to obtain the depth of 35.5±15.0nm on average. CGD utilized glass deflection with 18.1nm elevation/µm lateral distance that achieved practical size resolutions of 14.5nm, which was 15.7% smaller than that of conventional linear nano-gap device. Using CGD, particles from 0.5 to 10µm diameter were trapped and separated. The estimated sizes of the trapped particles matched the suggested values well. Cell sizes were also measured by CGD and the measured values matched with the values found by microscope observation. CGD acquired reproducible instrumental setup that resulted in robust analysis on size of micro/nanoparticles.

Influence of shape and size of the particles on jigging separation of plastics mixture.

Plastics are popular for numerous applications due to their high versatility and favourable properties such as endurance, lightness and cheapness. Therefore the generation of plastic waste is constantly increasing, becoming one of the larger categories in municipal solid waste. Almost all plastic materials are recyclable, but for the recycling to be possible it is necessary to separate the different types of plastics. The aim of this research was to evaluate the performance of the jig separation of bi-component plastic mixtures. For this study six granulated plastics had been used: Polystyrene (PS), Polymethyl methacrylate (PMMA), Polyethylene Terephthalate (PET-S, PET-D) and Polyvinyl Chloride (PVC-M, PVC-D). Plastics mixtures were subjected to jigging in a laboratorial Denver mineral jig. The results showed that the quality of the jigging separation varies with the mixture, the density differences and with the size and shape of the particles. In the case of particles with more regular shapes the quality of separation of bi-component plastic mixtures improved with the increase of the particle size. For lamellar particles the influence of particle size was minimal. In general, the beneficiation of plastics with similar densities was not effective, since the separation efficiency was lower than 25%. However, in bi-component plastic mixtures that join a low density plastic (PS) with a high density one (PMMA, PET-S, PET-D, PVC-M and PVC-D), the quality of the jigging separation was greatly improved. The PS grade in the sunk was less than 1% for all the plastic mixtures. Jigging proved to be an effective method for the separation of bi-component plastic mixtures. Jigging separation will be enhanced if the less dense plastic, that overflows, has a lamellar shape and if the denser plastic, that sinks, has a regular one.

Dielectrophoretic manipulation of particle mixtures employing asymmetric insulating posts.

A novel scheme for particle separation with insulator-based dielectrophoresis (iDEP) was developed. This technique offers the capability for an inverted order in particle elution, where larger particles leave the system before smaller particles. Asymmetrically shaped insulating posts, coupled with direct current (DC) biased low-frequency alternating current (AC) electric potentials, were used to successfully separate a mixture of 500 nm and 1 µm polystyrene particles (size difference of 0.5 µm in diameter). In this separation, the 1 µm particles were eluted first, demonstrating the discriminatory potential of this methodology. To extend this technique to biological samples, a mixture containing Saccharomyces cerevisiae cells (6.3 µm) and 2 µm polystyrene particles was also separated, with the cells being eluted first. The asymmetric posts featured a shorter sharp half and a longer blunt half; this produced an asymmetry in the forces exerted on the particles. The negative DC offset produced a net displacement of the smaller particles toward the upstream direction, while the post asymmetry produced a net displacement of the larger particles toward the downstream direction. This new iDEP approach provides a setup where larger particles are quickly concentrated at the outlet of the post array and can be released first when in a mixture with smaller particles. This new scheme offers an extra set of parameters (alternating current amplitude, DC offset, post asymmetry, and shape) that can be manipulated to obtain a desired separation. This asymmetric post iDEP technique has potential for separations where it is important to quickly elute and enrich larger and more fragile cells in biological samples.

Multidetector thermal field-flow fractionation as a unique tool for the tacticity-based separation of poly(methyl methacrylate)-polystyrene block copolymer micelles.

Poly(methyl methacrylate)-polystyrene (PMMA-PS) micelles with isotactic and syndiotactic coronas are prepared in acetonitrile and subjected to thermal field-flow fractionation (ThFFF) analysis at various conditions of increasing temperature gradients. It is shown for the first time that multidetector ThFFF provides comprehensive information on important micelle characteristics such as size (Dh), shape (Rg/Rh), aggregation number (Z), thermal diffusion (DT) and Soret coefficients (ST) as a function of temperature from a single injection. Moreover, it is found that micelles exhibit a unique decreasing trend in DT as a function of temperature which is independent of the tacticity of the corona and the micelle preparation method used. It is also demonstrated that ThFFF can monitor micelle to vesicle transitions as a function of temperature. In addition to ThFFF, it is found from DLS analysis that the tacticity of the corona influences the critical micelle concentration and the magnitude to which micelles expand/contract with temperature. The tacticity does not, however, influence the critical micelle temperature. Furthermore, the separation of micelles based on the tacticity of the corona highlight the unique capabilities of ThFFF.

Separation of linear synthetic polymers in non-aqueous capillary zone electrophoresis using cationic surfactant.

A method for separating water-insoluble and neutral synthetic polymers using non-aqueous capillary zone electrophoresis (NACZE) was developed. The non-aqueous solvent system comprising a mixture of tetrahydrofuran, acetonitrile, and ethanol containing cetyltrimethylammonium chloride was used for solubilizing and conferring positive charges to the polymers. A mixture of polystyrene (PS, Mn=6500) and polybutadiene (PBD, Mn=5900) was successfully separated by the NACZE method using cationic surfactants. Evaluation of the effect of the molecular weight of the polymers on the electrophoretic behavior demonstrated that PSs with different molecular weights (Mn=6500, 10,200, 19,600, 200,000) were co-eluted as a single peak. That is, the apparent electrophoretic mobility of the PSs was independent of the molecular weight. In contrast, evaluation of PBD and polycarbonate (PC) demonstrated that the solubility of polymers in the medium affected the apparent electrophoretic mobility of the polymers, where low solubility resulted in reduced apparent electrophoretic mobility. Using the proposed method, poly(styrene-co-methylmethacrylate)s with different compositions were successfully separated.

Particle separation using virtual deterministic lateral displacement (vDLD).

We present a method for sensitive and tunable particle sorting that we term virtual deterministic lateral displacement (vDLD). The vDLD system is composed of a set of interdigital transducers (IDTs) within a microfluidic chamber that produce a force field at an angle to the flow direction. Particles above a critical diameter, a function of the force induced by viscous drag and the force field, are displaced laterally along the minimum force potential lines, while smaller particles continue in the direction of the fluid flow without substantial perturbations. We demonstrate the effective separation of particles in a continuous-flow system with size sensitivity comparable or better than other previously reported microfluidic separation techniques. Separation of 5.0 µm from 6.6 µm, 6.6 µm from 7.0 µm and 300 nm from 500 nm particles are all achieved using the same device architecture. With the high sensitivity and flexibility vDLD affords we expect to find application in a wide variety of microfluidic platforms.

Microfluidic approach to the formation of internally porous polymer particles by solvent extraction.

We report the controlled formation of internally porous polyelectrolyte particles with diameters ranging from tens to hundreds of micrometers through selective solvent extraction using microfluidics. Solvent-resistant microdevices, fabricated by frontal photopolymerization, encapsulate binary polymer (P)/solvent (S1) mixtures by a carrier solvent phase (C) to form plugs with well-defined radii and low polydispersity; the suspension is then brought into contact with a selective extraction solvent (S2) that is miscible with C and S1 but not P, leading to the extraction of S1 from the droplets. The ensuing phase inversion yields polymer capsules with a smooth surface but highly porous internal structure. Depending on the liquid extraction time scale, this stage can be carried out in situ, within the chip, or ex situ, in an external S2 bath. Bimodal polymer plugs are achieved using asymmetrically inverted T junctions. For this demonstration, we form sodium poly(styrenesulfonate) (P) particles using water (S1), hexadecane (C), and methyl ethyl ketone (S2). We measure droplet extraction rates as a function of drop size and polymer concentration and propose a simple scaling model to guide particle formation. We find that the extraction time required to form particles from liquid droplets does not depend on the initial polymer concentration but is rather proportional to the initial droplet size. The resulting particle size follows a linear relationship with the initial droplet size for all polymer concentrations, allowing for the precise control of particle size. The internal particle porous structure exhibits a polymer density gradient ranging from a dense surface skin toward an essentially hollow core. Average particle porosities between 10 and 50% are achieved by varying the initial droplet compositions up to 15 wt % polymer. Such particles have potential applications in functional, optical, and coating materials.