Concentration Of Nanospheres Research Articles

A smart material: Multi-stimulus-responsive composite microspheres prepared via RAFT polymerization as recyclable pickering emulsifiers and their application in stabilizing real oil phases

The development of smart composites to sustainably separate and recover oil from oily water had attracted much attention. In this study, tri-block (P(LMA-b-NIPAM-b-AA)) polymer brushes were controllably “grown on” the Fe3O4 surface by three-step surface-initiated reversible addition fragmentation chain transfer (SI-RAFT) polymerization to prepare Fe3O4-P(LMA-b-NIPAM-b-AA) (MNPLNA) magnetic nanospheres with interfacial activity. The MNPLNA nanospheres were characterized to demonstrate the triple response of pH, temperature and magnetism. Meanwhile, the comparison experiments showed that the MNPLNA nanospheres with tri-block structure had excellent interfacial activity. Then, the O/W type of Pickering emulsion was prepared by using MNPLNA nanospheres as the particle emulsifier. The size variation pattern of Pickering emulsion was comprehensively investigated by adjusting the concentration of nanospheres, oil-water ratio, electrolyte concentration and polarity of oil phase. Pickering emulsions were controllably separated by the action of an external magnetic field, and could be reversibly switched at least 10 cycles between emulsified and broken states under the trigger of pH and temperature. In addition, MNPLNA nanospheres exhibited excellent emulsification properties for stabilizing variety of real oil phases (e.g., canola oil, kerosene, diesel and crude oil). Based on this, MNPLNA nanospheres were applied as smart multifunctional materials in simulated kerosene-containing wastewater separation. MNPLNA nanospheres could be used to recover kerosene with high recovery rate after 10 separation cycles under the stepwise action of pH, temperature and magnetic field.

Electrophoretic deposition of silk fibroin coatings with pre-defined architecture to facilitate precise control over drug delivery

The therapeutic precision and clinical applicability of drug-eluting coatings can be substantially improved by facilitating tunable drug delivery. However, the design of coatings which allows for precise control over drug release kinetics is still a major challenge. Here, a double-layered silk fibroin (SF) coating system was constructed by sequential electrophoretic deposition. A mixture of dissolved Bombyx mori SF (bmSF) molecules and pre-made bmSF nanospheres at different ratios was deposited as under-layer. Subsequently, this underlayer was covered by a top-layer comprising Antheraea pernyi SF (apSF) molecules (rich in arginylglycylaspartic acid, RGD) to improve the cellular response of the resulting double-layered coatings. Additionally, model drug doxycycline was either pre-mixed with dissolved bmSF molecules or pre-loaded into pre-made bmSF nanospheres at the same amount before their mixing and deposition. The thickness and nanosphere content of the under-layer architecture were proportional to the deposition time and nanosphere concentration in precursor mixtures, respectively. The surface topography, wettability, degradation rate and adhesion strength were comparable within the double-layered coating system. As expected, RGD-rich apSF top-layer improved cell adhesion, spreading and proliferation compared with bmSF top-layer. Furthermore, the amount and duration of drug release increased linearly with increasing nanosphere concentration at fixed deposition time, whereas drug release amount increased linearly with increasing deposition time. These results indicate that the dosage and kinetics of loaded drugs can be quantitatively tailored by altering nanosphere concentration and deposition time as main processing parameters. Overall, this study illustrates the strong potential of pre-defining coating architecture to facilitate control over drug delivery.

ENERGETICALLY AND STERICALLY FAVORABLE ASSEMBLY OF IDENTICAL GOLD NANORODS WITH VARYING CONCENTRATIONS OF NANOSPHERES

Gold nanorod ribbon-like arrays as well as shape-separation effect of rods from sphere-like nanoparticles have been evaluated for identical nanorod suspension with various concentration of nanospheres. These sphere-rod mixtures are prepared with help of different amounts of AgNO3. Deposits of nanoparticles at various positions of the coffee-stain ring are observed in different arrangements. For instance, face-to-face aligned nanorods get settled in ribbon-like superstructures and these arrays are observed to be self-separated from spheres. Self-assembly and shape-separation effect are observed more systematic at the outer-edges than the inner-region of the coffee-stain ring. Experimentally, it has been observed that face-to-face formation of nanorods in suspension is energetically more probable arrangement. As the separation between two nanorods increases, the depth of potential well decreases, indicating that the upper layers of nanorods are more under the influence of lower placed nanorods than those placed in the same plane. Energetically and sterically, more feasible arrangements are observed.

Potential Use of Silica Nanoparticles for the Microbial Stabilisation of Wine: An In Vitro Study Using Oenococcus oeni as a Model.

The emerging trend towards the reduction of SO2 in winemaking has created a need to look for alternative methods to ensure the protection of wine against the growth of undesired species of microorganisms and to safely remove wine microorganisms. This study describes the possible application of silica nanospheres as a wine stabilisation agent, with Oenococcus oeni (DSM7008) as a model strain. The experiment was conducted firstly on model solutions of phosphate-buffered saline and 1% glucose. Their neutralising effect was tested under stirring with the addition of SiO2 (0.1, 0.25, and 0.5 mg/mL). Overall, the highest concentration of nanospheres under continuous stirring resulted in the greatest decrease in cell counts. Transmission electron microscope (TEM) and scanning electron microscopy (SEM) analyses showed extensive damage to the bacterial cells after stirring with silica nanomaterials. Then, the neutralising effect of 0.5 mg/mL SiO2 was tested in young red wine under stirring, where cell counts were reduced by over 50%. The obtained results suggest that silica nanospheres can serve as an alternative way to reduce or substitute the use of sulphur dioxide in the microbial stabilisation of wine. In addition, further aspects of following investigations should focus on the protection against enzymatic and chemical oxidation of wine.

Biocompatible Spherical Gold Nanoparticles Synthesis in Aqueous Tetraethylene Oxide Solution and Their Cellular Uptake.

Small well-defined spherical gold nanoparticles were synthesized by a simple non-physical method based on a mixture of gold salt, tetraethylene oxide and water, free of any additional reducing chemical agent or physical method. The ratio of tetraethylene oxide to water was optimized to achieve a fast synthesis within 30 min. Transmission electron microscopy images showed well dispersed gold nanospheres with a size ranging from 10 to 15 nm. XPS was used to confirm the oxidation state of gold nanoparticles and the oxidation products from tetraethylene oxide after the reaction. This new protocol performed in sustainable and biocompatible conditions is complementary to the current methods used to synthesize gold nanospheres. In order to use these particles in biological samples, we correlated the atomic absorption with the colorimetric concentration of nanospheres in solution. After 24 h of incubation of cancer or neuronal cell lines with these nanoparticles, transmission electron microscopy images showed similar cellular uptake in both cell lines, especially in cytoplasmic vesicular structures.

Extracellular vesicle measurements with nanoparticle tracking analysis – An accuracy and repeatability comparison between NanoSight NS300 and ZetaView

ABSTRACTThe expanding field of extracellular vesicle (EV) research needs reproducible and accurate methods to characterize single EVs. Nanoparticle Tracking Analysis (NTA) is commonly used to determine EV concentration and diameter. As the EV field is lacking methods to easily confirm and validate NTA data, questioning the reliability of measurements remains highly important. In this regard, a comparison addressing measurement quality between different NTA devices such as Malvern’s NanoSight NS300 or Particle Metrix’ ZetaView has not yet been conducted. To evaluate the accuracy and repeatability of size and concentration determinations of both devices, we employed comparative methods including transmission electron microscopy (TEM) and single particle interferometric reflectance imaging sensing (SP-IRIS) by ExoView. Multiple test measurements with nanospheres, liposomes and ultracentrifuged EVs from human serum and cell culture supernatant were performed. Additionally, serial dilutions and freeze-thaw cycle-dependent EV decrease were measured to determine the robustness of each system. Strikingly, NanoSight NS300 exhibited a 2.0–2.1-fold overestimation of polystyrene and silica nanosphere concentration. By measuring serial dilutions of EV samples, we demonstrated higher accuracy in concentration determination by ZetaView (% BIAS range: 2.7–8.5) in comparison with NanoSight NS300 (% BIAS range: 32.9–36.8). The concentration measurements by ZetaView were also more precise (% CV range: 0.0–4.7) than measurements by NanoSight NS300 (% CV range: 5.4–10.7). On the contrary, quantitative TEM imaging indicated more accurate EV sizing by NanoSight NS300 (% DTEM range: 79.5–134.3) compared to ZetaView (% DTEM range: 111.8–205.7), while being equally repeatable (NanoSight NS300% CV range: 0.8–6.7; ZetaView: 1.4–7.8). However, both devices failed to report a peak EV diameter below 60 nm compared to TEM and SP-IRIS. Taken together, NTA devices differ strongly in their hardware and software affecting measuring results. ZetaView provided a more accurate and repeatable depiction of EV concentration, whereas NanoSight NS300 supplied size measurements of higher resolution.

Electrodeposited Nanoporous Polypyrrole Layers for Controlled Drug Release

Nanostructured layers for controlled drug release are fabricated via direct electrochemical codeposition of polymethylmethacrylate (PMMA) nanospheres (NSs) with polypyrrole (PPy). After codeposition, NSs are etched from the matrix to leave a nanoporous PPy layer. Concentration of NSs in the composite, and the resulting concentration of porosities in the etched layer, is optimized varying deposition current density. A maximum concentration of NSs of about 49% vol., corresponding to a loose random sphere packing, is obtained. Complete dissolution of PMMA NSs upon exposure to a mixture of two solvents is demonstrated. Nanoporous layers are loaded with rhodamine B to check their drug release behavior, which is compared with corresponding bulk PPy layers. Nanoporous coatings covered with a bulk PPy capping layer show a 77% improvement in released Rhodamine B with respect to non-nanostructured PPy.

Anomalous stimulated Brillouin scattering in aqueous suspension of polystyrene nanospheres

For the first time, stimulated Brillouin scattering (SBS) spectra have been measured for a suspension of dielectric nanoparticles in water. We observed anomalous dependence of SBS spectra on the concentration of polystyrene nanospheres (74 nm diameter). The nonlinear five-fold increase in the SBS threshold was determined for the nanosphere concentration range of 109 to 1015 cm−3.

Effect of Cotton Cationization Using Copolymer Nanospheres on Ink-Jet Printing of Different Fabrics.

In this study, the cationic Poly[Styrene-Butyl acrylate-(P-vinylbenzyl trimethyl ammonium chloride)] P(St-BA-VBT) nanospheres with N+(CH3)3 functional groups were successfully synthesized by soap-free emulsion polymerization and applied to different fabrics by pad-cure process. After the pad-cure process, the nanospheres were deposited on the surface of the modified cotton fibers successfully without forming a continuous film structure. The X-ray Photoelectron Spectroscopy (XPS) and the Fourier transform infrared (FTIR) results demonstrated that P(St-BA-VBT) nanospheres were adsorbed on the surface of cotton fibers successfully. The excellent color strength value and outline sharpness of the plain, twill, and honeycomb fabrics can be achieved when the nanosphere concentration, sodium bicarbonate, and steaming time were 1 g/L, 10 g/L, and 6 min, respectively. The plain fabrics exhibited the smallest color strength (K/S) values and the best outline sharpness, followed by twill and honeycomb fabrics, which displayed the largest K/S values and the worst outline sharpness after the same treatment. Besides, all the three fabrics showed excellent rubbing fastness and washing fastness. The cationic P(St-BA-VBT) nanospheres modification of the cotton fabrics provides a novel potential approach to obtain good printing efficiency without affecting the tensile breaking strength of cotton fabrics significantly.

Reactive Pad-Steam Dyeing of Cotton Fabric Modified with Cationic P(St-BA-VBT) Nanospheres.

The Poly[Styrene-Butyl acrylate-(P-vinylbenzyl trimethyl ammonium chloride)] P(St-BA-VBT) nanospheres with N+(CH3)3 functional groups were successfully prepared and applied to modify cotton fabrics using a pad-dry process. The obtained cationic cotton fabrics were dyed with pad-steam dyeing with reactive dye. The results show that the appropriate concentration of nanospheres was 4 g/L. The sodium carbonate of 25 g/L and steaming time of 3 min were suitable for dyeing cationic cotton with 25 g/L of C.I. Reactive Blue 222. The color strength and dye fixation rates of dyed cationic cotton fabrics increased by 39.4% and 14.3% compared with untreated fabrics. Moreover, sodium carbonate and steaming time were reduced by 37.5% and 40%, respectively. The rubbing and washing fastness of dyed fabrics were equal or higher 3 and 4–5 grades, respectively. Scanning electron microscopy (SEM) images revealed that the P(St-BA-VBT) nanospheres randomly distributed and did not form a continuous film on the cationic cotton fiber surfaces. The X-ray photoelectron spectroscopy (XPS) analysis further demonstrated the presence of cationic nanospheres on the fiber surfaces. The cationic modification did not affect the breaking strength of cotton fabrics.

Soft/Hard-Coupled Amphiphilic Polymer Nanospheres for Water Lubrication.

Amphiphilic polymer nanospheres of poly(3-sulfopropyl methacrylate potassium salt- co-styrene) [P(SPMA- co-St)] were prepared by a simple soap-free emulsion polymerization method and used as efficient water lubrication additives to enhance the antiwear behaviors of the Ti6Al4V alloy. The monodisperse and flexible P(SPMA- co-St) bicomponent copolymer nanospheres were synthesized with a controllable manner by adjusting the mass fraction ratio of the monomers, with the hydrophobic polystyrene (PSt) as the hard skeletal carrier component and the hydrophilic PSPMA with a hydration layer structure as the soft lubrication layer in the course of friction. The influences of the monomer concentration, the copolymer nanosphere additive content, the load, and the frequency of the friction conditions on their tribological properties were studied in detail, and a probable antiwear mechanism of the soft/hard-coupled copolymer nanospheres under water lubrication was also proposed. The results show that compared with pure PSt, the P(SPMA- co-St) polymer nanospheres exhibited better antiwear property as an additive for water lubrication, and the friction coefficient and the wear volume first decreased and then increased with the increase of the SPMA content, indicating that the hydrophilic SPMA has a significant effect on lubrication properties owing to its hydration performance. Furthermore, with the increase of polymer nanosphere concentration, the friction coefficient and wear amount also decreased to a stable and low value at a saturation concentration of 1 wt %. The flexible polymer nanospheres with a hydrophilic soft SPMA shell and a rigid PSt core exhibited good friction-reduction and antiwear performance as lubrication additives, indicating their promising and potential applications in water lubrication and biological lubrication.

Fabrication of large area flexible nanoplasmonic templates with flow coating.

We describe the development of a custom-built two-axis flow coater for the deposition of polymeric nanosphere monolayers that could be used in the fabrication of large area nanoplasmonic films. The technique described here has the capability of depositing large areas (up to 7 in. × 10 in.) of self-assembled monolayers of polymeric nanospheres onto polyethylene terephthalate (PET) films. Here, three sets of films consisting of different diameters (ranging from 100 to 300 nm) of polymeric nanospheres were used to demonstrate the capabilities of this instrument. To improve the surface wettability of the PET substrates during wet-deposition, we enhanced the wettability by using a forced air blown-arc plasma treatment system. Both the local microstructure, as confirmed by scanning electron microscopy, describing monolayer and multilayer coverage, and the overall macroscopic uniformity of the resultant nanostructured film were optimized by controlling the relative stage to blade speed and nanosphere concentration. We also show using a smaller nanoparticle template that such monolayers can be used to form nanoplasmonic films. As this flow-coating approach is a scalable technique, large area films such as the ones described here have a variety of crucial emerging applications in areas such as energy, catalysis, and chemical sensing.

Salt-free dyeing of cotton fabrics modified with cationic copolymer nanospheres using an acid dye

Cationic St-BA copolymer nanospheres were prepared through batch cationic emulsion polymerization. The synthesized nanospheres were used to modify cotton fabrics. The modified fabrics were then dyed using an acid dye in the absence of salt. The results show that when the nanosphere concentration was 5 g/l the nanosphere amount on the fibers and the K/S value of dyed fabric reached the maximum value. Prolonging the modification time resulted in increasing of the K/S value until the time was 60 min. Raising the modification temperature from 10 °C to 50 °C led to increasing of the K/S value. The K/S values increased gradually with increasing the modification bath pH value from 2.3 to 9. The addition of sodium chloride in the modification bath resulted in decreasing of the K/S values. CMC pretreatment of the fabric before the nanosphere modification increased the K/S values of dyed fabrics. SEM images revealed that after modification and dyeing many nanospheres deposited on the cotton fiber surfaces and the nanospheres did not form a continuous film on the fiber surface. Therefore, the nanosphere modification and the salt-free dyeing would not obviously affect the permeability and handle of the dyed cotton fabric.

Facile modulation of cell adhesion to a poly(ethylene glycol) diacrylate film with incorporation of polystyrene nano-spheres.

Poly(ethylene glycol) diacrylate (PEGDA) is a common hydrogel that has been actively investigated for various tissue engineering applications owing to its biocompatibility and excellent mechanical properties. However, the native PEGDA films are known for their bio-inertness which can hinder cell adhesion, thereby limiting their applications in tissue engineering and biomedicine. Recently, nano composite technology has become a particularly hot topic, and has led to the development of new methods for delivering desired properties to nanomaterials. In this study, we added polystyrene nano-spheres (PS) into a PEGDA solution to synthesize a nano-composite film and evaluated its characteristics. The experimental results showed that addition of the nanospheres to the PEGDA film not only resulted in modification of the mechanical properties and surface morphology but further improved the adhesion of cells on the film. The tensile modulus showed clear dependence on the addition of PS, which enhanced the mechanical properties of the PEGDA-PS film. We attribute the high stiffness of the hybrid hydrogel to the formation of additional cross-links between polymeric chains and the nano-sphere surface in the network. The effect of PS on cell adhesion and proliferation was evaluated in L929 mouse fibroblast cells that were seeded on the surface of various PEGDA-PS films. Cells density increased with a larger PS concentration, and the cells displayed a spreading morphology on the hybrid films, which promoted cell proliferation. Impressively, cellular stiffness could also be modulated simply by tuning the concentration of nano-spheres. Our results indicate that the addition of PS can effectively tailor the physical and biological properties of PEGDA as well as the mechanical properties of cells, with benefits for biomedical and biotechnological applications.

3D printing biomimetic nanomaterials for highly efficient vascularized bone development

Event Abstract Back to Event 3D printing biomimetic nanomaterials for highly efficient vascularized bone development Benjamin Holmes1*, Michael Plesniak1* and Grace Zhang1, 2, 3 1 The George Washington University, Mechanical and Aerospace Engineering, United States 2 The George Washington University, Department of Biomedical Engineering, United States 3 The George Washington University, Division of Genomic Medicine, Department of Medicine, United States Introduction: Large critical sized bone defects are notoriously hard to regenerate due to the need for such large and complex portions of tissue to have an adequate vascular network. As an emerging tissue fabrication technique, 3D bioprinting offers great precision to control the internal architecture of a scaffold and print complicated structures close in architecture to biological tissue[1]. Thus, the objective of this study is to combine a microvascular 3D printed design with biomimetic nanomaterials (i.e., bone minerals, nanocrystalline hydroxyapatite (nHA) and growth factor loaded nanospheres) for highly efficient fluid perfusion and enhanced vascularized bone regeneration. Materials and Methods: Two types of scaffolds with both large (500 µm radius) and small (250 µm radius) fluid microchannels (Figure 1) were designed and 3D printed via fused deposition molding printing from biocompatible polylactic acid (PLA). Biomimetic osteogenic nHA and angiogenic vascular endothelial growth factor (VEGF) loaded PLGA nanospheres were fabricated and then conjugated onto the 3D printed scaffolds using a multi-step aminolysis process. The scaffolds were characterized via scanning electron microscopy (SEM). The VEGF release from the scaffolds was characterized for 7 days. Both human umbilical vein endothelial cell (HUVECs) and human bone marrow mesenchymal stem cell (hMSCs) functions in the 3D printed scaffolds were investigated in vitro. Figure 1; Computer aided designs (CAD) of large (left) and right (small) microvascular channel bone scaffolds. Results and Discussion: SEM showed that the conjugation of nanomaterials had a noticeable effect on the nano-topography when compared to untreated PLA. 7 day VEGF release study showed a slow release rate after 48 hours on scaffolds with VEGF encapsulated nanospheres, when compared to bare VEGF samples. In addition, the scaffolds with larger microchannels and a smaller PLGA nanosphere concentration both provide a more efficient mechanism for HUVEC cell invasion and proliferation. Figure 2 shows hMSC 3 week differentiation on scaffolds with pre-cultured HUVEC vascular networks. Figure 2; 1, 2 and 3 week calcium deposition of hMSCs cultured on scaffolds which have been pre-cultured with HUVECs for 1 week. Data are ± standard error of the mean, N=3; *p<0.05 when compared to all other groups at weeks 1 and 2, respectively; **p<0.05 when compared to scaffolds with large and small microchannels at week 1; ***p<0.05 when compared to scaffolds with small microchannels at week 3; and #p<0.05 when compared to all other groups at week 3. Excellent calcium deposition was exhibited on scaffolds with both VEGF loaded PLGA nanospheres and nHA. Yet, higher values in calcium were seen on samples with only PLGA nanospheres, when compared to plain PLA controls. A similar trend could be observed for collagen type I synthesis on scaffolds. In both cases, higher amount of bone matrix deposited can be attributed to the presence of nHA, but it can also be inferred that the presence of VEGF and HUVECs induced cell to cell interactions which also lead to faster bone tissue formation. Conclusion: Based on these results, it can be inferred that the use of a drug loaded nanoparticle delivery system, along with nHA, a bioactive conjugation method and highly efficient 3D printed micro designs for cell growth, infiltration and fluid perfusion can yield a highly effective method for the enhanced growth of vascularized bone.

Adsorption of P(St-co-DMHB-co-BA) n+·Br n - nanoscale particles onto cotton fiber surfaces: A study by conductometric titration

A more sensitive and accurate method for measuring very low concentration of cationic copolymer nanospheres is established by measuring the conductivity of cationic nanosphere dispersion. The effect of the nanosphere concentration on the conductivity was investigated during the adsorption process. The results indicate that the relationship between the concentration of nanospheres and bromide ions is coincidence with linear relation. At very low nanosphere concentrations, the conductivity increases with increasing the nanosphere concentration, exhibiting a linear relationship. However, the limiting molar conductivity of nanosphere decreases with increasing nanosphere concentration. The obtained adsorption data were fitted to the Langmuir adsorption isotherm. The SEM images show that the nanospheres form a uniform monolayer on cotton fiber surfaces. The saturated amount of the nanospheres on the cotton fibers is 63.49 mg/g.

Synthesis of poly(2-(2-methoxyethoxy)ethyl methacrylate) hydrogel using starch-based nanosphere cross-linkers

Biodegradable thermosensitive hydrogels have attracted great interest because of their potential in biomedical applications. Herein, we present a novel, thermoresponsive poly(2-(2-methoxyethoxy)ethyl methacrylate) hydrogels with starch-based nanospheres as cross-linkers (NMH). NMHs exhibit a narrow lower critical phase transition temperature (LCST) range and high mechanical strength compared with conventional, small molecular cross-linked hydrogels (CMH). Fourier transform infrared (FT-IR) spectroscopy confirms that the NMHs are degradable in aqueous medium. The phase transition temperature of the NMHs is ∼4°C compared with ∼25°C for CMH. The NMHs can sustain strength of 12.2MPa, 10 times more than that of CMH. Moreover, the deswelling rate of NMHs is faster than CMH. The different concentrations of nanospheres can efficiently regulate the various properties of NMHs. The NMHs have excellent properties because of its even network structure formed by nanosphere cross-linkers.

Acoustic pressure pulses from laser-irradiated suspensions containing gold nanospheres in water: Experimental and theoretical study

We present a physical model that describes the acoustic pressure pulses from diluted suspensions of metal nanospheres in a liquid medium irradiated by laser pulses. The experimental measurements of the photoacoustic signals are also reported, where the suspensions of 8-nm gold nanospheres in water at different concentrations and different temperatures were irradiated by 0.8-ns laser pulses. We mainly investigate how the nanosphere concentration and the suspension temperature influence the photoacoustic responses. The estimations from our model are found to be in good agreement with the results from the experiments.

Sensing nanoparticles using a double nanohole optical trap

We use a double nanohole (DNH) optical trap to quantify the size and concentration of nanoparticles in solution. The time to trap shows a linear dependence with nanosphere size and a -2/3 power dependence with nanosphere concentration, which is in agreement with simple microfluidic considerations. The DNH approach has size-specificity on the order of a few nanometers, which was used to selectively quantify particles of a single size within a heterogeneous solution. By looking at individual trapping events, it is in principle possible to extend this approach to the ultimate limit of a single particle concentration, while also being able to operate at high concentrations in the same configuration. In addition, the DNH trap allows us to hold onto individual particles and thereby study constituents of a heterogeneous mixture. By repeating the trapping measurements on spherical particles of different refractive index, we found that the transmission step that indicates trapping scales empirically with the Clausius-Mossotti factor. This approach may be applied to several sensing applications, such as in the study of virus populations, where concentrations vary over many orders of magnitude.

Design and fabrication of a superhydrophobic glass surface with micro-network of nanopillars

The wetting property of a superhydrophobic glass surface with a micro-network of nanopillars fabricated from colloidal lithography and plasma etching is investigated in this paper. The micro-network distribution of nanospheres can be modulated by diluting the nanosphere concentration and controlling the spin rate. The micro-network of nanospheres spun on the glass surface serves as a mask for nanopillars during the plasma etching process. After the fabrication, the nano-structured surface is treated with fluoroalkylsilane self-assembled monolayers to obtain superhydrophobicity. Among several spin rates, the minimum colloidal network area density from a 100nm polystyrene nanosphere solution diluted to 0.026% was found at a spin rate of 4000rpm. The sample with the lowest network area density shows a good quality of superhydrophobicity, having the highest water contact angle and the lowest sliding angle among samples with other network area densities. In particular, samples with a micro-network of pillars also showed mechanical robustness against finger rubbing. To assess the superhydrophobic behavior in-depth, a size-dependent contact angle equation is proposed for use with a high contact angle (>135°) and with a Bo (Bond number)≪1. Furmidge’s sliding angle equation is also modified; it is derived considering a static contact angle to simplify the prediction of the sliding angle. The contact and sliding angle measurements from samples with a micro-network of nanopillars show good agreement with the proposed equations.