Dry Brush Research Articles

Dry brush model for robotic painting

Dry brush model for robotic painting

Soiling, cleaning, and abrasion: The results of the 5-year photovoltaic glass coating field study

External contamination (“soiling”) of the incident surface is a major limiting factor for solar technologies. A 5-year field glass coupon study was conducted to better understand external contamination and its effects; compare cleaning methods and the use of preventative coatings; and explore the abrasion resulting from cleaning to advise on accelerated abrasion testing. Test sites included the cities of Dubai (UAE), Kuwait City (Kuwait), Mesa (AZ), Mumbai (India), and Sacramento (CA). Through the 5-year cumulative study, dry brush, water spray, and wet sponge and squeegee cleaning methods were compared to no cleaning. Optical microscopy was used to obtain images, including representative color images, grayscale images for object analysis, and oblique images for coating integrity assessment. A thresholding protocol was developed to analyze and distinguish specimens using the ImageJ software. Optical performance was quantified using a spectrophotometer, including comprehensive optical characterization (transmittance, reflectance, and absorptance in addition to forward- and back-scattering). Atomic force microscopy was used to verify the abrasion damage morphology, including the width and depth of surface scratches. Analysis of the results included correlation of optical performance and particle area coverage, rank order (by coating or location), and the acceleration factor for abrasion damage. The efficacy of external cleaning was more readily distinguished from the effectiveness of antisoiling coatings. The acceleration factor for dry brush cleaning of a porous silica coating was found to be on the order of unity.

Synergistic effects of dry-brush compatibility and shear stress on rapid alignment of lamellar microstructures for block copolymer reflectors

Because of the high viscosity of severe chain entanglements, a time-consuming process of aligning microstructural orientation in high molecular-weight (Mw) block copolymer photonic crystal films imposed limitations on efficient mass production. In this study, the effective alignment of the block copolymer microstructures in the film state can be carried out within approximately a few minutes. This achievement was realized through the synergistic localized compatibility of dry brush and shear stress during the spin-casting process. The orientation and orderliness of the microphase-separated lamellar structure in as-spun poly(styrene)-block-poly(4-vinylpyridine) (PS-b-P4VP) films can be meticulously controlled by introducing blends with PS homopolymer (hPS) of varying Mws (Mw,hPS) and cholesteric liquid crystal mesogen (Chol). Within the ternary blended films of hPS/PS-b-P4VP(Chol), the wet-brush miscibility by blending low-Mw hPS with a small molecular weight ratio (α) of Mw,hPS to Mw,bPS (Mw of the PS block chain) of α <1 results in the formation of disoriented lamellar structures, whereas dry-brush localization by introducing high-Mw hPS with α∼0.9 yields highly parallel-aligned lamellar structures to the substrate after spin casting, even with a massive quantity of additive hPS (∼59 wt%). The dry-brush compatibility can be demonstrated by morphological observation in the ternary blended film after extraction of the hPS. As a result, without any further efforts, such as additional solvent or thermal annealing treatments, the as-spun ternary blended film can exhibit visible structural colorations with controlled wavelengths by alternating the quantity of hPS. This provides an accessible solution for rapidly producing flexible photonic crystals featuring tunable photonic band gaps.

Abrasion resistance of spray coated anti-soiling coatings during waterless cleaning of PV modules

Dust deposition on photovoltaic (PV) modules leads to remarkably high energy loss, which has an enormous economic impact on PV plants. Anti-soiling coatings have been extensively studied as a cost-effective dust mitigation strategy in the PV market. However, such coatings applied to the top surface of the PV modules should be resilient to environmental stressors. Coated modules would also need periodic cleaning; thus, such anti-soiling coating must be abrasion-resistant. This article investigated the abrasion-resistant property of 4 types of commercial hydrophobic anti-soiling coatings. The study emulates the effects of different brush designs on the degradation of anti-soiling coatings under low soiling conditions. The samples were subjected to dry brush cleaning. We tested the samples with 3 different brush designs (linear brush 1, linear brush 2 and rotary brush) with a varying packing density of brush bristles. Linear brush 1 had 3.5 times higher packing density of brush bristles than linear brush 2 and rotary brush. By increasing the packing density of brush bristles by 3.5 times, the degradation rates were enhanced by factors varying from 1.2 X to 4.4 X in coated samples when cleaned with linear brush 1, compared to linear brush 2 and rotary brush. Phenylsilicone based coating shows higher degradation rates (varying from 2.9 X to 11.2 X) than fluoropolymer-based coatings. The result indicates a decline of the anti-soiling property as we see an increase in roll-off angle (compared to Mumbai, India’s tilt angle = 19º) with the increase in number of cycles. The results also show that compared to the structural brush design, the packing density of the brush bristle has a strong impact on the coating life. However, the actual coating life in the field would also be dependent on other environmental factors like the amount of dust deposit, moisture etc.

Comparison of the AmpFire and MA-6000 polymerase chain reaction platforms for high-risk human papillomavirus testing in cervical precancer screening

High-risk human papillomavirus (hr-HPV) testing for primary cervical precancer screening offers an opportunity to improve screening in low-middle income countries (LMICs). This study aimed to compare the analytic performances of the AmpFire and MA-6000 platforms for hr-HPV DNA testing in three groups of women screened for hr-HPV types in Ghana: group 1 with 33 GeneXpert-archived ThinPrep/liquid-based samples subjected to both tests, group 2 with 50 AmpFire-archived dry brush samples subjected to MA-6000 testing, and group 3 involving 143 cotton swab samples simultaneously subjected to both tests without archiving. The overall agreement rates were 73 %, 92 %, and 84 %, for groups 1–3, respectively, and 84 % (95 % CI, 78.6–88.6) for the entire group. Neither AmpFire nor MA-6000 was more likely to test hr-HPV positive in all three groups and the combined group. Group 1 showed fair agreement without statistical significance (κ = 0.224, 95 % CI, −0.118 to 0.565), while group 3 showed significant moderate agreement (κ = 0.591, 95% CI, 0.442–0.741). Group 2 showed an almost perfect significant level of agreement (κ = 0.802; 95 % CI, 0.616–0.987). Thus, both platforms showed statistically significant moderate to near-perfect agreement for detecting hr-HPV in cervicovaginal samples, with variation according to archiving conditions and duration between sample collection and retesting. For LMICs using these platforms for COVID-19 testing, as the COVID-19 pandemic subsides, the platforms can become available for running other tests such as hr-HPV DNA testing for cervical precancer screening.

Hydrophilic Aldehyde-Functional Polymer Brushes: Synthesis, Characterization, and Potential Bioapplications.

Surface-initiated activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP) is used to polymerize a cis-diol-functional methacrylic monomer (herein denoted GEO5MA) from planar silicon wafers. Ellipsometry studies indicated dry brush thicknesses ranging from 40 to 120 nm. The hydrophilic PGEO5MA brush is then selectively oxidized using sodium periodate to produce an aldehyde-functional hydrophilic PAGEO5MA brush. This post-polymerization modification strategy provides access to significantly thicker brushes compared to those obtained by surface-initiated ARGET ATRP of the corresponding aldehyde-functional methacrylic monomer (AGEO5MA). The much slower brush growth achieved in the latter case is attributed to the relatively low aqueous solubility of the AGEO5MA monomer. X-ray photoelectron spectroscopy (XPS) analysis confirmed that precursor PGEO5MA brushes were essentially fully oxidized to the corresponding PAGEO5MA brushes within 30 min of exposure to a dilute aqueous solution of sodium periodate at 22 °C. PAGEO5MA brushes were then functionalized via Schiff base chemistry using an amino acid (histidine), followed by reductive amination with sodium cyanoborohydride. Subsequent XPS analysis indicated that the mean degree of histidine functionalization achieved under optimized conditions was approximately 81%. Moreover, an XPS depth profiling experiment confirmed that the histidine groups were uniformly distributed throughout the brush layer. Surface ζ potential measurements indicated a significant change in the electrophoretic behavior of the zwitterionic histidine-functionalized brush relative to that of the non-ionic PGEO5MA precursor brush. The former brush exhibited cationic character at low pH and anionic character at high pH, with an isoelectric point being observed at around pH 7. Finally, quartz crystal microbalance studies indicated minimal adsorption of a model globular protein (BSA) on a PGEO5MA brush-coated substrate, whereas strong protein adsorption via Schiff base chemistry occurred on a PAGEO5MA brush-coated substrate.

Fouling Resistance and Release Properties of Poly(sulfobetaine) Brushes with Varying Alkyl Chain Spacer Lengths and Molecular Weights

We examined the effects of alkyl carbon spacer length (CSL) and molecular weight on fouling resistance and release properties of zwitterionic poly(sulfobetaine methacrylate) brushes. Using surface-initiated atom transfer radical polymerization, we synthesized two series of brushes with CSL = 3 and 4 and molecular weight from 19 to 1500 kg ·mol-1, corresponding to dry brush thickness from around 6 to 180 nm. The brush with CSL = 3 was nearly completely wet with water (independent of molecular weight), whereas the brush with CSL = 4 exhibited a strong increase in water contact angle with molecular weight. Though the two-brush series had distinct wetting properties, both series of brushes exhibited similarly great resistance against fouling by Staphylococcus epidermidis bacteria and Aspergillus niger fungi spores when submerged in water, indicating that neither molecular weight nor CSL strongly affected the antifouling behavior. We also compared the efficacy of brushes against fouling by fungi and silicon oil in air. Brushes grafted to filter paper were strongly fouled by fungi and silicon oil in air. Grafting the polymers to the filter paper, however, greatly enhanced removal of the foulant upon rinsing. The removal of fungi and silicon oil when rinsed with a salt solution was enhanced by 219 and 175%, respectively, as compared to a blank filter paper control. Thus, our results indicate that these zwitterionic brushes can promote foulant removal for dry applications in addition to their well-known fouling resistance in submerged conditions.

Brushed creation of liquid marbles

A method where particulates are transferred via a cosmetic brush onto liquid drops created on a highly non-wetting substrate with a hole to generate talc and graphite liquid marbles (LMs) and talc-graphite Janus liquid marbles is described. van der Waals forces facilitated the attachment of particulates to the dry brush bristles. Subsequently, the surface tension forces that developed from particle interaction with water (which were O(102) higher than the van der Waals forces) could then engender transfer of the particulates to the liquid-gas interface of the drop. Forces below 1 mN applied by a dangling foil on the LM ensured preservation of the drop shape when the force was removed. During the application of this force, the contact angles at the contact lines behaved differently from sessile drops that are inclined on surfaces. This preparation method portends the ability to automate the creation of LMs and Janus LMs for various applications.

Compatibilization of Immiscible Polymer Blends Using Block Copolymer: Influence of the Dry Brush Model Modifications on Model Results

AbstractThe compatibilization of polymer blends using a copolymer can be estimated, among other, using simple theoretical models based on Leibler's mean field theory and its modification by Noolandi. The case when copolymer chain is shorter than homopolymer chains can be described in the “dry brush” approximation for high concentration of the copolymer in the interfacial layer and in the approximation for the low copolymer concentration in the interfacial layer. Since, there is a discontinuity between results provided by them, the effect of several modifications of the dry brush approximation has been studied. None of the tried modifications shifts results closer to the approximation of the low copolymer concentration.

A Comparative Evaluation of Different Methods PF Cleaning and Preparing Occlusal Fissures, Before Placement of Pit and Fissure Sealant: A Stereomicroscopic Study

Aim and objective The study was aimed to comparatively evaluate the effect of different methods of cleaning and preparation of occlusal surfaces on microleakage of pit and fissure sealant. Materials and method: Eighty (80) sound extracted premolars served as samples and were divided into four categories according to the method of cleaning and preparation of occlusal surfaces. Prior to sealant placement. The groups were: A Dry Brush, B Pumice Slurry Air Polishing and D Prophylaxis Paste. In each group, subsequent to cleaning of occlusal surfaces with the method assigned to, pit and fissure sealant was applied. The samples were then kept in an incubator, thermocycled and then immersed in methylene blue dye. Each tooth was sectioned longitudinally into two halves and observed under stereomicroscope for microleakage using a criteria given by Cooley et al. Statistical analysis: Discrete microleakage score of groups is summarized in number (n) and percentage (%).Result: Comparing the microleakage score of four groups, χ2 test showed significantly different microleakage score among the groups (χ2 =33.96, P &lt;0.001). Conclusion: Microleakage score showed both pumice slurry (Group B) and especially air polishing (Group C) to be significantly more superior than prophylaxis paste (Group D) and dry brush (Group A).&#x0D;

Evaluation of dry specimen transport and processing time using an isothermal amplification high-risk human papillomavirus assay

BackgroundDry specimen transport has shown equivalence to traditional liquid transport using a novel high-risk Human papillomavirus assay. Considering that dry transport might cross obstacles during cervical cancer screening in low and middle resource settings, this study was designed evaluate different processing time of dry specimen transport using the same isothermal amplification hrHPV assay. MethodsThere were 564 women between the ages of 30–55 recruited from colposcopy clinic. For each patient, two endocervical samples were collected and placed into empty collection tubes by physician. Samples were stored at room temperature until analyzed for hrHPV using the AmpFire assay at two time points: 2 days and 2 weeks. 511 of the 564 participants with positive hrHPV were provided colposcopy exam and quadrant biopsy. ResultsA total of 1128 endocervical samples from 564 patients were detected by the Ampfire assay. Good agreement was found between two time periods (Kappa ​± ​Standard error ​= ​0.67 ​± ​0.04). Sensitivity (2days/2weeks) for CIN2+ was 95.28% (95% CI: 92.14%–98.42%) vs 90.57% (CI (86.65%–94.49%) and specificity (2days/2weeks) was 22.47% (CI 19.33%–25.61%) vs 28.15% (CI 24.23%–32.07%) respectively. The difference for Ampfire HPV detection in sensitivity for CIN2+ for the two time periods was not significant (P ​= ​0.227), while the difference in specificity for CIN2+ was significant (P ​= ​0.001). The difference in Ct values 29.23 (CI 28.15–30.31) and 29.27 (CI 28.19–30.35) between two time points was not significant (P ​= ​0.164). ConclusionProcessing dry brush specimens can be delayed up to 2 weeks. Using the AmpFire assay platform which supports cervical cancer prevention programs in low-to-middle-income countries (LMICs).

Testing for Sexually Transmitted Infection Using Wet and Dry Self-Collected Brush Samples Among Women in Mombasa, Kenya.

We compared detection of Chlamydia trachomatis , Neisseria gonorrhoeae , and Trichomonas vaginalis using dry and wet self-collected samples using brushes among females who engage in sex work in Mombasa, Kenya. Detection of T. vaginalis and N. gonorrhoeae in dry and wet samples was similar, but C. trachomatis detection in dry samples appeared lower.

Possible Link Between Climate Change and Extraordinary Wildfires in Australia, the Amazon and Western United States

Areas with dry climates have recently become more vulnerable to wildfires as the soil and air moisture have been changing because of greenhouse gasses in the atmosphere. Areas especially impacted are Australia, the Amazon, and western United States. The common factors at these locations are a dry environment and brush or forests fueling the fires once they start. As the climate continues to change, less moisture is present in the ground in these areas. This proliferates the susceptibility to wildfire. Prevention methods for inhibiting wildfires include reducing our carbon footprint, using care around campfires and other causes of wildfire, as well as routine thinning and removal of excess vegetation. The purpose of this study was to determine whether there is a link between Climate Change and the extraordinary magnitude, intensity, and frequency of recent wildfires. Although it is not possible to link all these wildfires directly and undeniably to Climate Change, the data examined clearly point to a strong possibility that such a link exists.

Determining the prevalence of high-risk human papillomavirus infection using a novel cervical precancer screening approach in incarcerated women at the Nsawam Medium Security Prison, Ghana

BackgroundAcross Ghana, females comprise 1.2% of the entire prison population (n = 15,463). Cervical cancer screening services are however nonexistent and the prevalence of high-risk human papillomavirus (hr-HPV) and cervical precancer is undocumented. We aimed to screen and treat inmates for cervical precancer and determine the prevalence of hr-HPV using the novel AmpFire HPV detection system combined with colposcopy by trained nurses using a mobile colposcope (the Enhanced Visual Assessment (EVA) system).MethodsA descriptive cross-sectional study design was employed, involving all incarcerated women at the Nsawam Medium Security Prison, Ghana. After counselling and informed consent, women underwent a structured questionnaire-based interview entered into a Microsoft Excel spreadsheet. Women were co-tested for cervical pre-cancer and hr-HPV by two trained nurses using dry brush cervical samples for 15 hr-HPV types (AmpFire HPV test) after which mobile colposcopy with the EVA system was performed. EVA images were reviewed by a gynaecologist. Frequencies and percentages were used to describe categorical data, while means, standard deviations, medians and interquartile ranges (IQRs) were used to describe continuous data.Results75% of the women were convicts with a median sentence of 5 years (IQR: 2–10 years). Their mean age was 41.1 years (standard deviation: 15.5 years, range: 19–97 years). The self-reported prevalence rate of HIV was 13.1% (95% confidence interval (CI): 7.5%–21.9%), all of whom were receiving treatment. The hr-HPV prevalence rate was 47.6% (CI: 36.9%–58.3%) in the general population of imprisoned women and 63.6% (CI: 35.4%–84.8%) among HIV positive women. Six percent (6%) had lesions on the cervix, of which 3.6% were treated with thermal coagulation and 2.4% were treated with loop electrosurgical excision procedure. The average age of hr-HPV positive women was 37.8 years.ConclusionsThere is a high prevalence of hr-HPV infection among women in custody at the Nsawam Medium Security Prison. These women will benefit from structured cervical cancer prevention services, including treatment for abnormalities that are picked up during such screening.

Analysis of the effect of the interaction parameters of copolymer blocks on their efficiency in reducing the interfacial tension between the components of immiscible polymer blends

Block and graft copolymers with blocks that are identical to, miscible with or adhere to related components of a polymer blend can serve as compatibilizers. The relatively simple models established by Leibler and Noolandi provide the basis for addressing the influence of partial interaction parameters between the individual segments of two homopolymers and one copolymer and the influence of the copolymer block length ratio on the compatibilization efficiency. The maximum compatibilization efficiency for both the wet and dry brush formulae is obtained for a slightly longer chain of units compatible with the dispersed phase than that compatible with the matrix. A negative interaction parameter between a copolymer block and any homopolymer leads to lower copolymer contents at the interface and thus to a weaker compatibilization effect. If the units of one block of copolymer are miscible with one of the homopolymers and the units of the second block are immiscible with the second homopolymer, the copolymer content at the interface is lower than that when the mentioned interaction parameters are zero, and the compatibilization effect becomes weaker.

Effect of different placement techniques on color stability and surface roughness of resin composites

Abstract Introduction Longevity and clinical success of dental restorations can be influenced by many factors during the restorative procedures. Objective This study aimed to evaluate the influence of different placement techniques on color stability and surface roughness of two resin composites. Material and method The groups of specimens (n=10) were divided according to resin composite (FiltekTM Z250 XT and FiltekTM Z350 XT) and placement technique: Mylar strip, spatula, dry brush, modeling liquid, and surface sealant. Color stability and surface roughness were accessed using a spectrophotometer (CIELab color space) and a rugosimeter (standard cutoff of 0.8 mm), respectively, after water storage. Subsequently, the specimens were immersed in coffee for 48 h and final color was measured. The data were analyzed using ANOVA and the Tukey’s post hoc test (α=5%) and the correlation between surface roughness (Ra) and color change (∆Eab) was assessed using the Pearson’s correlation coefficient. Result The different placement techniques influenced Ra and ∆Eab on both resin composites. The groups treated with surface sealant showed greater difference in ∆Eab for both resin composites. The FiltekTM Z250 XT resin showed greater color stability compared with the FiltekTM Z350 XT resin regardless of the placement technique used. Ra of each placement technique was similar among the resin composites except for the FiltekTM Z350 XT modeling liquid group, which presented lower Ra values compared with those of FiltekTM Z250 XT. A correlation between Ra and staining was identified (p=0.268). Conclusion Color stability and Ra are influenced by different placement techniques.

Gradient dynamics model for drops spreading on polymer brushes

When a liquid drop spreads on an adaptive substrate the latter changes its properties what may result in an intricate coupled dynamics of drop and substrate. Here we present a generic mesoscale hydrodynamic model for such processes that is written as a gradient dynamics on an underlying energy functional. We specify the model details for the example of a drop spreading on a dry polymer brush. There, liquid absorption into the brush results in swelling of the brush causing changes in the brush topography and wettability. The liquid may also advance within the brush via diffusion (or wicking) resulting in coupled drop and brush dynamics. The specific model accounts for coupled spreading, absorption and wicking dynamics when the underlying energy functional incorporates capillarity, wettability and brush energy. After employing a simple version of such a model to numerically simulate a droplet spreading on a swelling brush we conclude with a discussion of possible model extensions.

Real-Time Measurement of Polymer Brush Dynamics Using Silicon Photonic Microring Resonators: Analyte Partitioning and Interior Brush Kinetics.

Polymer brushes are found in biomedical and industrial technologies, where they exhibit functionalities considerably dependent on polymer brush-solvent-analyte interactions. It remains a difficult challenge to quickly analyze solvent-swollen polymer brushes, both at the solvent-polymer brush interface and in the brush interior, as well as to monitor the kinetics of interaction of solvent-swollen brushes with key analytes. Here, we demonstrate the novel use of silicon photonic microring resonators to characterize in situ swollen polymer brush-analyte interactions. By monitoring resonant wavelength shifts, we find that brush-solvent-analyte interaction parameters can be extracted from a single set of data or from successive analyte introductions using a single brush-coated sensor. The partition coefficient of three industrially relevant plasticizers into hydrophobic and hydrophilic brushes was determined and found to be in agreement with known solubility trends. We found that the diffusion coefficient of the plasticizer into the brush decreases as brush thickness increases, supporting a model of a dense inner brush layer and diffuse outer layer. pKa's of pH-sensitive brushes were determined on the microring resonator platform; upon increasing the dry brush thickness, the pKa for poly(2-dimethylamino ethyl methacrylate) decreased from 8.5 to approach the bulk material pKa of 7.3 and showed dependence on the presence and concentration of salt. These proof-of-concept experiments show how the surface-sensitive nature of the microring resonator detection platform provides valuable information about the interaction of the polymer brushes with the solvents and analytes, not easily accessed by other techniques.

Etching of sub-10 nm half-pitch high chi block copolymers for directed self-assembly (DSA) application

Directed Self-Assembly of block copolymers is a lithographic technique being developed to reach sub-10 nm technological nodes. Recently, high chi block copolymers have been developed to achieve higher resolution. In this paper, the high chi system investigated is a modified polystyrene-b-poly(methyl methacrylate)(PS-b-PMMA) presenting a pitch of 18 nm. One critical step for its integration is the PMMA removal selectively to the PS. Two approaches to remove the PMMA phase are presented, highlighting the challenges encountered due to its smaller dimensions. The first one is a full dry approach based on a CH4/N2 chemistry, which presents some bridge formation due to intensive sidewalls passivation and to a species confinement effect accentuated by the small 9-nm critical dimension of the lines. Therefore, the main high chi PS-b-PMMA dry etching difficulties come from the trade-off between obtaining high selectivity and avoiding bridge formation. The second approach is a mixed wet and dry PMMA removal process based on UV exposure followed by solvent rinse. An Ar/O2 dry brush layer opening was developed and the pattern transfer into the SiO2 and Si underlayers is demonstrated for the high chi PS-b-PMMA.

Grafting-Induced Structural Ordering of Lactide Chains.

The structure of a grafted layer of lactide chains in the “dry brush” regime immersed in a melt of chemically similar polymer was examined while varying graft lengths. To this end, microsecond atomistic molecular dynamics simulations were performed. Almost no influence of graft length on the fraction of the grafted chains backfolded to the grafting surface was found. However, a structural ordering was unexpectedly observed in the system when the length of the grafted lactide chains was close to approximately 10 Kuhn segments. This ordering of the grafts is characterized by the formation of helical fragments whose structure is in good agreement with the experimental data for the α crystal of the lactide chains. Both the backfolding and the structural ordering may be viewed as the initial stage of the crystallization of the layer of grafted lactide chains. In contrast to the known behavior for conventional polymer brushes in the “dry brush” regime, the structure of the grafted lactide chains can be either amorphous or ordered, depending on the graft length N and the grafting density σ when their product Nσ is fixed.