Insights into the Mechanical Properties of Ultrathin Perfluoropolyether-Silane Coatings.

Ultrathin perfluoropolyether-silane (PFPE-silane) films offer excellent functionality as antifingerprint coatings for display touchscreens due to their oleophobic, hydrophobic, and good adhesion properties. During smartphone use, PFPE-silane coatings undergo many abrasion cycles which limit the coating lifetime, so a better understanding of how to optimize the film structure for improved mechanical durability is desired. However, the hydrophobic and ultrathin (1-10 nm) nature of PFPE-silane films renders them very difficult to experimentally characterize. In this study, the cohesive fracture energy and elastic modulus, which are directly correlated with hardness and better wear resistance of 3.5 nm-thick PFPE-silane films were, respectively, measured by double cantilever beam testing and atomic force microscopy indentation. Both the cohesive fracture energy and modulus are shown to be highly dependent on the underlying film structure. Both values increase with optimal substrate conditions and a higher number of silane groups in the PFPE-silane precursor. The higher cohesive fracture energy and modulus values are suggested to be the result of the changes in the film chemistry and structure, leading to higher cross-linking density. Therefore, future work on optimizing PFPE-silane film wear resistance should focus on pathways to improve the cross-linking density. Subcritical fracture testing in humid environments reveals that humidity negatively affects the fracture properties of PFPE-silane films.

Utility of chest x-ray for tracheostomy tube placement in pediatric patients.

Objective: To evaluate the utility of ordering chest x-rays after pediatric tracheostomy tube placement in identifying acute, post-operative complications and how it impacts clinical decision-making. Methods: In this retrospective cohort study, we identified tracheostomies performed in 139 pediatric patients through CPT codes over a 5-year period from 2013 to 2018. Manual chart review was performed for demographic and clinical characteristics, pre-procedure and post-procedure chest x-ray interpretations, and the presence of complications. Each complication was reviewed to see if action was taken due to post-procedure chest x-ray findings. Multivariable logistic regression was performed to determine associations with changes in pre-procedure versus post-procedure chest x-rays. Results: In a cohort of 139 pediatric patients with pre-procedure and post-procedure chest x-rays, 40 (28.8%) of patients had new significant post-procedure chest x-ray findings compared to pre-procedure chest x-ray findings. Of these 40 instances of changes in pre-procedure versus post-procedure chest x-ray findings, only eight resulted in action being taken due to the observed findings. Among these eight instances of action being taken, only one instance involved in invasive action being taken with a bronchoscopy. With multivariable regression analysis, patient age, race, gender, and the presences of genetic syndromes, were not found to be significant risk factors in predicting changes in pre-procedure versus post-procedure chest x-ray. Conclusion: In our study, post-procedure chest x-ray after tracheostomy tube placement did not significantly impact clinical decision making. It may be worth reconsidering the value in routine chest x-rays after tracheostomy tube placement in pediatric patients.

Tethered platelet capture provides a mechanism for restricting circulating platelet activation to the wound site.

Background: Puncture wounding is a longstanding challenge to human health for which understanding is limited, in part, by a lack of detailed morphological data on how the circulating platelet capture to the vessel matrix leads to sustained, self-limiting platelet accumulation. Objectives: The objective of this study was to produce a paradigm for self-limiting thrombus growth in a mouse jugular vein model. Methods: Data mining of advanced electron microscopy images was performed from authors' laboratories. Results: Wide-area transmission electron mcrographs revealed initial platelet capture to the exposed adventitia resulted in localized patches of degranulated, procoagulant-like platelets. Platelet activation to a procoagulant state was sensitive to dabigatran, a direct-acting PAR receptor inhibitor, but not to cangrelor, a P2Y12 receptor inhibitor. Subsequent thrombus growth was sensitive to both cangrelor and dabigatran and sustained by the capture of discoid platelet strings first to collagen-anchored platelets and later to loosely adherent peripheral platelets. Spatial examination indicated that staged platelet activation resulted in a discoid platelet tethering zone that was pushed progressively outward as platelets converted from one activation state to another. As thrombus growth slowed, discoid platelet recruitment became rare and loosely adherent intravascular platelets failed to convert to tightly adherent platelets. Conclusions: In summary, the data support a model that we term Capture and Activate, in which the initial high platelet activation is directly linked to the exposed adventitia, all subsequent tethering of discoid platelets is to loosely adherent platelets that convert to tightly adherent platelets, and self-limiting, intravascular platelet activation over time is the result of decreased signaling intensity.

Massively Parallel Selection of NanoCluster Beacons.

NanoCluster Beacons (NCBs) are multicolor silver nanocluster probes whose fluorescence can be activated or tuned by a proximal DNA strand called the activator. While a single-nucleotide difference in a pair of activators can lead to drastically different activation outcomes, termed polar opposite twins (POTs), it is difficult to discover new POT-NCBs using the conventional low-throughput characterization approaches. Here, a high-throughput selection method is reported that takes advantage of repurposed next-generation-sequencing chips to screen the activation fluorescence of ≈40 000 activator sequences. It is found that the nucleobases at positions 7-12 of the 18-nucleotide-long activator are critical to creating bright NCBs and positions 4-6 and 2-4 are hotspots to generate yellow-orange and red POTs, respectively. Based on these findings, a "zipper-bag" model is proposed that can explain how these hotspots facilitate the formation of distinct silver cluster chromophores and alter their chemical yields. Combining high-throughput screening with machine-learning algorithms, a pipeline is established to design bright and multicolor NCBs in silico.

Venous puncture wound hemostasis results in a vaulted thrombus structured by locally nucleated platelet aggregates.

Primary hemostasis results in a platelet-rich thrombus that has long been assumed to form a solid plug. Unexpectedly, our 3-dimensional (3D) electron microscopy of mouse jugular vein puncture wounds revealed that the resulting thrombi were structured about localized, nucleated platelet aggregates, pedestals and columns, that produced a vaulted thrombus capped by extravascular platelet adherence. Pedestal and column surfaces were lined by procoagulant platelets. Furthermore, early steps in thrombus assembly were sensitive to P2Y12 inhibition and late steps to thrombin inhibition. Based on these results, we propose a Cap and Build, puncture wound paradigm that should have translational implications for bleeding control and hemostasis.

Open-Air Plasma-Deposited Multilayer Thin-Film Moisture Barriers.

Emerging moisture sensitive devices require robust encapsulation strategies to inhibit water ingress and prevent premature failure. A scalable, open-air plasma process has been developed to deposit alternating layers of conformal organosilicate and dense SiO2 thin-film barriers to prevent moisture ingress. The in situ low-temperature process is suitable for direct deposition on thermally sensitive devices and is compatible with flexible polymeric substrates. Using optical calcium testing, low water vapor transmission rates on the order of 10-3 g/m2/day at an accelerated aging condition of 38 °C and 90% relative humidity (RH) are achieved. Using moisture-sensitive perovskite devices as a representative moisture-susceptible device, devices retain over 80% of their initial performance for over 660 h in a 50 °C 50% RH accelerated aging environment. The ability of the multilayer barrier to enable device resistance to humid environments is crucial toward realizing longer operating lifetimes.

Convolutional neural networks to automate the screening of malaria in low-resource countries.

Malaria is an infectious disease caused by Plasmodium parasites, transmitted through mosquito bites. Symptoms include fever, headache, and vomiting, and in severe cases, seizures and coma. The World Health Organization reports that there were 228 million cases and 405,000 deaths in 2018, with Africa representing 93% of total cases and 94% of total deaths. Rapid diagnosis and subsequent treatment are the most effective means to mitigate the progression into serious symptoms. However, many fatal cases have been attributed to poor access to healthcare resources for malaria screenings. In these low-resource settings, the use of light microscopy on a thin blood smear with Giemsa stain is used to examine the severity of infection, requiring tedious and manual counting by a trained technician. To address the malaria endemic in Africa and its coexisting socioeconomic constraints, we propose an automated, mobile phone-based screening process that takes advantage of already existing resources. Through the use of convolutional neural networks (CNNs), we utilize a SSD multibox object detection architecture that rapidly processes thin blood smears acquired via light microscopy to isolate images of individual red blood cells with 90.4% average precision. Then we implement a FSRCNN model that upscales 32 × 32 low-resolution images to 128 × 128 high-resolution images with a PSNR of 30.2, compared to a baseline PSNR of 24.2 through traditional bicubic interpolation. Lastly, we utilize a modified VGG16 CNN that classifies red blood cells as either infected or uninfected with an accuracy of 96.5% in a balanced class dataset. These sequential models create a streamlined screening platform, giving the healthcare provider the number of malaria-infected red blood cells in a given sample. Our deep learning platform is efficient enough to operate exclusively on low-tier smartphone hardware, eliminating the need for high-speed internet connection.

Fully stretchable active-matrix organic light-emitting electrochemical cell array.

Intrinsically and fully stretchable active-matrix-driven displays are an important element to skin electronics that can be applied to many emerging fields, such as wearable electronics, consumer electronics and biomedical devices. Here, we show for the first time a fully stretchable active-matrix-driven organic light-emitting electrochemical cell array. Briefly, it is comprised of a stretchable light-emitting electrochemical cell array driven by a solution-processed, vertically integrated stretchable organic thin-film transistor active-matrix, which is enabled by the development of chemically-orthogonal and intrinsically stretchable dielectric materials. Our resulting active-matrix-driven organic light-emitting electrochemical cell array can be readily bent, twisted and stretched without affecting its device performance. When mounted on skin, the array can tolerate to repeated cycles at 30% strain. This work demonstrates the feasibility of skin-applicable displays and lays the foundation for further materials development.

A review of principles in design and usability testing of tactile technology for individuals with visual impairments.

To lay the groundwork for devising, improving, and implementing new technologies to meet the needs of individuals with visual impairments, a systematic literature review was conducted to: a) describe hardware platforms used in assistive devices, b) identify their various applications, and c) summarize practices in user testing conducted with these devices. A search in relevant EBSCO databases for articles published between 1980 and 2014 with terminology related to visual impairment, technology, and tactile sensory adaptation yielded 62 articles that met the inclusion criteria for final review. It was found that while earlier hardware development focused on pin matrices, the emphasis then shifted toward force feedback haptics and accessible touch screens. The inclusion of interactive and multimodal features has become increasingly prevalent. The quantity and consistency of research on navigation, education, and computer accessibility suggest that these are pertinent areas of need for the visually impaired community. Methodologies for usability testing ranged from case studies to larger cross-sectional studies. Many studies used blindfolded sighted users to draw conclusions about design principles and usability. Altogether, the findings presented in this review provide insight on effective design strategies and user testing methodologies for future research on assistive technology for individuals with visual impairments.

Solid Electrolyte Lithium Phosphous Oxynitride as a Protective Nanocladding Layer for 3D High-Capacity Conversion Electrodes.

Materials that undergo conversion reactions to form different materials upon lithiation typically offer high specific capacity for energy storage applications such as Li ion batteries. However, since the reaction products often involve complex mixtures of electrically insulating and conducting particles and significant changes in volume and phase, the reversibility of conversion reactions is poor, preventing their use in rechargeable (secondary) batteries. In this paper, we fabricate and protect 3D conversion electrodes by first coating multiwalled carbon nanotubes (MWCNT) with a model conversion material, RuO2, and subsequently protecting them with conformal thin-film lithium phosphous oxynitride (LiPON), a well-known solid-state electrolyte. Atomic layer deposition is used to deposit the RuO2 and the LiPON, thus forming core double-shell MWCNT@RuO2@LiPON electrodes as a model system. We find that the LiPON protection layer enhances cyclability of the conversion electrode, which we attribute to two factors. (1) The LiPON layer provides high Li ion conductivity at the interface between the electrolyte and the electrode. (2) By constraining the electrode materials mechanically, the LiPON protection layer ensures electronic connectivity and thus conductivity during lithiation/delithiation cycles. These two mechanisms are striking in their ability to preserve capacity despite the profound changes in structure and composition intrinsic to conversion electrode materials. This LiPON-protected structure exhibits superior cycling stability and reversibility as well as decreased overpotentials compared to the unprotected core-shell structure. Furthermore, even at very low lithiation potential (0.05 V), the LiPON-protected electrode largely reduces the formation of a solid electrolyte interphase.

Experimental and computational investigations of the interactions between model organic compounds and subsequent membrane fouling.

The formation of aggregates of sodium alginate and bovine serum albumin (BSA) (as representative biopolymers) with humic acid were detected by Liquid Chromatography (LC) UV254 response in the biopolymer region for mixture solutions. BSA interaction with humic acid showed that aggregation occurred both in the presence and absence of calcium, suggesting that multivalent ions did not play a part in the aggregation process. Similar analyses of the alginate interaction with humic acid also showed a positive interaction, but only in the presence of calcium ions. The fouling characteristics for the BSA-humic acid mixture appeared to be significantly greater than the fouling characteristics of the individual solutions, while for the sodium alginate-humic acid mixture, the fouling rate was similar to that of the sodium alginate alone. The effectiveness of hydraulic backwashing, 10-15% reversibility, was observed for the BSA-humic acid mixture, while the % reversibility was 20-40% for the sodium alginate-humic acid mixture. Increased humic acid and DOC rejection were observed for both BSA-humic acid and sodium alginate-humic acid solutions compared to the individual solutions, indicating that the biopolymer filter cakes were able to retain humic acids. When compared with BSA-humic acid mixture solution, greater removal of humic acid was observed for alginate-humic mixture, suggesting that sodium alginate may have a greater capacity for associations with humic acid when in the presence of calcium than BSA. Complementary molecular dynamics simulations were designed to provide insights into the specific mechanisms of interaction between BSA and humic acid, as well as between alginate and humic acid. For the BSA-humic acid system; electrostatic, hydrophobic and hydrogen bonding were the dominant types of interactions predicted, whilst divalent ion-mediated bonding was not identified in the simulations, which supported the LC-results. Similarly for the alginate-humic acid system, the interactions predicted were divalent ion-mediated interactions only and this was also supported the LC results. This work suggests that LC-UV254 might be used to identify aggregated biopolymers, and that combined with current characterisation techniques, be used to better explain performance variations between water sources.

Effect of IX dosing on polypropylene and PVDF membrane fouling control.

The performance of ion exchange (IX) resin for organics removal from wastewater was assessed using advanced characterisation techniques for varying doses of IX. Organic characterisation using liquid chromatography with a photodiode array (PDA) and fluorescence spectroscopy (Method A), and UV254, organic carbon and organic nitrogen detectors (Method B), was undertaken on wastewater before and after magnetic IX treatment. Results showed partial removal of the biopolymer fraction at high IX doses. With increasing concentration of IX, evidence for nitrogen-containing compounds such as proteins and amino acids disappeared from the LC-OND chromatogram, complementary to the fluorescence response. A greater fluorescence response of tryptophan-like proteins (278 nm/343 nm) for low IX concentrations was consistent with aggregation of tryptophan-like compounds into larger aggregates, either by self-aggregation or with polysaccharides. Recycling of IX resin through multiple adsorption steps without regeneration maintained the high level of humics removal but there was no continued removal of biopolymer. Subsequent membrane filtration of the IX treated waters resulted in complex fouling trends. Filtration tests with either polypropylene (PP) or polyvinylidene fluoride (PVDF) membranes showed higher rates of initial fouling following treatment with high IX doses (10 mL/L) compared to filtration of untreated water, while treatment with lower IX doses resulted in decreased fouling rates relative to the untreated water. However, at longer filtration times the rate of fouling of IX treated waters was lower than untreated water and the relative fouling rates corresponded to the amount of biopolymer material in the feed. It was proposed that the mode of fouling changed from pore constriction during the initial filtration period to filter cake build up at longer filtration times. The organic composition strongly influenced the rate of fouling during the initial filtration period due to competitive adsorption processes, while at longer filtration times the rate of fouling appeared to depend upon the amount of biopolymer material in the feed water.

Characterisation of organic matter in IX and PACl treated wastewater in relation to the fouling of a hydrophobic polypropylene membrane.

Extensive organic characterisation of a wastewater using liquid chromatography with a photodiode array and fluorescence spectroscopy (Method A), and UV(254) and organic carbon detector (Method B) was undertaken, as well as with fluorescence excitation emission spectroscopy (EEM). Characterisation was performed on the wastewater before and after ion exchange (IX) treatment and polyaluminium chlorohydrate (PACl) coagulation, and following microfiltration of the wastewater and pre-treated wastewaters. Characterisation by EEM was unable to detect biopolymers within the humic rich wastewaters and was not subsequently used to characterise the MF permeates. IX treatment preferentially removed low molecular weight (MW) organic acids and neutrals, and moderate amounts of biopolymers in contrast to a previous report of no biopolymer removal with IX. PACl preferentially removed moderate MW humic and fulvic acids, and large amounts of biopolymers. PACl showed a great preference for removal of proteins from the biopolymer component in comparison to IX. An increase in the fluorescence response of tryptophan-like compounds in the biopolymer fraction following IX treatment suggests that low MW neutrals may influence the structure and/or inhibit aggregation of organic compounds. Fouling rates for IX and PACl treated wastewaters had high initial fouling rates that reduced to lower fouling rates with time, while the untreated Eastern Treatment Plant (ETP) wastewater displayed a consistent, high rate of fouling. The results for the IX and PACl treated wastewaters were consistent with the long-term fouling rate being determined by cake filtration while both pore constriction and cake filtration contributed to the higher initial fouling rates. Higher rejection of biopolymers was observed for PACl and IX waters compared to the untreated ETP water, suggesting increased adhesion of biopolymers to the membrane or cake layer may lead to the higher rejection.