Ultrahigh electrical conductivity in solution-sheared polymeric transparent films

With consumer electronics transitioning toward flexible products, there is a growing need for high-performance, mechanically robust, and inexpensive transparent conductors (TCs) for optoelectronic device integration. Herein, we report the scalable fabrication of highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) thin films via solution shearing. Specific control over deposition conditions allows for tunable phase separation and preferential PEDOT backbone alignment, resulting in record-high electrical conductivities of 4,600 ± 100 S/cm while maintaining high optical transparency. High-performance solution-sheared TC PEDOT:PSS films were used as patterned electrodes in capacitive touch sensors and organic photovoltaics to demonstrate practical viability in optoelectronic applications.Conductive films of high optical transparency are required in a myriad of applications, including electromagnetic shielding, antistatic layers, lighting displays, touch sensors, and as electrodes for photovoltaics (1, 2). As flexible, lightweight displays for televisions and portable consumer electronics become closer to reality, emerging transparent conductors (TCs) need to be mechanically robust (3). An ideal TC, therefore, should have a sheet resistance <100 Ω/□, transmissivity greater than 0.90, and be inherently flexible, all while remaining inexpensive to process on a mass scale (4).Indium tin oxide (ITO) is the most widely used TC material due to the combination of low sheet resistance and high transparency when grown on a variety of substrates. Although common to use, ITO is an expensive material due to the requirement for vacuum deposition and a number of postprocessing steps (5). For example, in organic photovoltaic (OPV) modules ITO was estimated to represent 24% of the module cost (6). However, alternative transparent conductor materials, such as poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) are estimated to comprise only ∼1% of an OPV module cost. Additionally, ITO is not compatible with flexible applications, because small applied strains of as little as 4.5% lead to an order of magnitude increase in the resistance (7).In recent years there have been a number of emerging TC materials studied in the literature ranging from metal nanowires (Au, Ag, Cu) (8–11), conducting carbon allotropes (graphene, carbon nanotubes) (12–15), conducting polymers (16, 17), and other hybrid approaches (18). Recent attempts using metal nanotroughs by Wu et al. have resulted in superior optoelectronic properties with a sheet resistance of 2 Ω/□ at 90% transmission (19). The use of metal mesoscale grids further enhanced the properties of metal nanowires electrodes to a sheet resistance of 0.36 Ω/□ at 92% transmission (20). Although metal nanowires combine low resistance and high transparency, they have inferior flexibility and stretchability compared with polymer-based TCs (3).PEDOT:PSS consists of insoluble PEDOT that is charge stabilized by PSS (Fig. 1A), which affords good solubility in aqueous formulations. Within these solutions, PEDOT:PSS forms micelles where hydrophilic PSS is in contact with water and hydrophobic PEDOT is located in the micelle core (21). Upon spin-coating from solution, the micelles are deposited as a film and can have conductivities on the order of ∼1 S/cm (22). Subsequent annealing, treatment with cosolvents, and postprocessing steps can increase the conductivity of films to over 3,000 S/cm (23, 24). High-performing spin-cast PEDOT:PSS TCs have reached a sheet resistance of 46 Ω/□ at 90% transmission (25, 26). Furthermore, it is compatible with flexible electronics as films can withstand over 90% applied strain without electrical breakdown (7).Open in a separate windowFig. 1.Schematic of solution shearing process. (A) Chemical structure of PEDOT:PSS. (B) Schematic of the solution shearing design and (C) patterning PEDOT:PSS via selective patterning of solvent wetting and dewetting regions.There is a wide variety of solution processing techniques used to deposit uniform, low-roughness films (27). Spin-casting is a popular laboratory-scale deposition technique due to its simplicity and ability to deposit high-quality films with a variety of materials. However, it is a batch process that is difficult to implement on a continuous mass production scale. Furthermore, it is difficult to use elevated substrate temperatures during spin-coating, a parameter that may play a role in the final film characteristics. Contrarily, scalable fabrication through solution shearing allows for tunable deposition conditions which enable enhanced kinetic control resulting in large impacts on the electrical performance of organic electronics (28–30).In this work we use solution shearing to fabricate high-performance TC PEDOT:PSS films (Fig. 1B). Tunable control of PEDOT backbone orientation, local ordering, and phase separation is demonstrated via precise control of the deposition parameters. Record-high PEDOT:PSS conductivities of 4,600 ± 100 S/cm are obtained and reach a sheet resistance of 17 ± 1 Ω/□ at 97.2 ± 0.4% transmission. A patterning method (Fig. 1C) is also developed which enables the use of high-conductivity transparent conductive films in capacitive pressure sensors and OPV devices.     

An endogenous glycosylphosphatidylinositol-specific phospholipase D releases basic fibroblast growth factor-heparan sulfate proteoglycan complexes from human bone marrow cultures

Basic fibroblast growth factor (bFGF) is a hematopoietic cytokine that stimulates stromal and stem cell growth. It binds to a glycosylphosphatidylinositol (GPI)-anchored heparan sulfate proteoglycan on human bone marrow (BM) stromal cells. The bFGF- proteoglycan complex is biologically active and is released by addition of exogenous phosphatidylinositol-specific phospholipase C. In this study, we show the presence of an endogenous GPI-specific phospholipase D (GPI-PLD) that releases the bFGF-binding heparan sulfate proteoglycan and the variant surface glycoprotein (a model GPI-anchored protein) from BM cultures. An involvement of proteases in this process is unlikely, because released proteoglycan contained the GPI anchor component, ethanol-amine, and protease inhibitors did not diminish the release. The mechanism of release is likely to involve a GPI-PLD and not a GPI-specific phospholipase C, because the release of variant surface glycoprotein did not reveal an epitope called the cross- reacting determinant that is exposed by phospholipase C-catalyzed GPI anchor cleavage. In addition, phosphatidic acid (which is specifically a product of GPI-PLD-catalyzed anchor cleavage) was generated during the spontaneous release of the GPI-anchored variant surface glycoprotein. We also detected GPI-PLD-specific enzyme activity and mRNA in BM cells. Therefore, we conclude that an endogenous GPI-PLD releases bFGF-heparan sulfate proteoglycan complexes from human BM cultures. This mechanism of GPI anchor cleavage could be relevant for mobilizing biologically active bFGF in BM. An endogenous GPI-PLD could also release other GPI-anchored proteins important for hematopoiesis and other physiologic processes.     

A common genetic variation in the 3'-untranslated region of the prothrombin gene is associated with elevated plasma prothrombin levels and an increase in venous thrombosis

We have examined the prothrombin gene as a candidate gene for venous thrombosis in selected patients with a documented familial history of venous thrombophilia. All the exons and the 5'- and 3'-UT region of the prothrombin gene were analyzed by polymerase chain reaction and direct sequencing in 28 probands. Except for known polymorphic sites, no deviations were found in the coding regions and the 5'-UT region. Only one nucleotide change (a G to A transition) at position 20210 was identified in the sequence of the 3'-UT region. Eighteen percent of the patients had the 20210 AG genotype, as compared with 1% of a group of healthy controls (100 subjects). In a population-based case-control study, the 20210 A allele was identified as a common allele (allele frequency, 1.2%; 95% confidence interval, 0.5% to 1.8%), which increased the risk of venous thrombosis almost threefold odds ratio, 2.8; 95% confidence interval, 1.4 to 5.6. The risk of thrombosis increased for all ages and both sexes. An association was found between the presence of the 20210 A allele and elevated prothrombin levels. Most individuals (87%) with the 20210 A allele are in the highest quartile of plasma prothrombin levels (> 1.15 U/mL). Elevated prothrombin itself also was found to be a risk factor for venous thrombosis.     

Blastomycosis in a young African man presenting with a pleural effusion

Blastomyces dermatitidis is a dimorphic fungus endemic to northwestern Ontario, Manitoba and some parts of the United States. The fungus is also endemic to parts of Africa. Pulmonary and extrapulmonary findings of a 24-year-old African man who presented with weight loss, dry cough and chronic pneumonia not resolving with antibiotic treatment are presented. The unusual occurrence of pulmonary blastomycosis associated with skin lesions and a moderate pleural effusion is reported.     

Species-dependent variations in erythrocyte membrane skeletal proteins

Two mammalian species (porcine and murine) have erythrocytes that are being widely used to study membrane protein synthesis and red cell aging. Erythrocytes of these species however, are significantly smaller than those of the human. Before results obtained from study of these red cells can be applied to human cells, the membrane skeleton of these species must be investigated to determine if the skeletal elements are equivalent. Both pig and mouse bands 4.1b were of lower molecular weight than human 4.1b, and the a/b ratio was lower. In each species, 4.1a and b were sequence-related phosphoproteins, and yielded substantially different one-dimensional peptide maps. Band 3 of pig and mouse erythrocytes had a higher molecular weight than human band 3 and also had differing one-dimensional peptide maps after limited proteolytic cleavage with three different enzymes. In each species, free band 3 and band 3 bound to the membrane skeleton had identical peptide maps. Other major membrane skeletal components (spectrin, actin, and bands 2.1 and 4.2) seem to be very similar in molecular weight in various species. These results demonstrate that the molecular weights and relative proportions of the membrane skeletal elements are species dependent.     

Comparison of the effects of ether and restraint stress on the activity of tuberoinfundibular dopaminergic neurons in female and male rats

The purpose of the present study was to characterize the acute inhibitory effects of restraint stress on the activity of tuberoinfundibular dopamine (DA) neurons as estimated by measuring concentrations of 3,4-dihydroxyphenylacetic acid (DOPAC) in the median eminence. The time course of the effects of two types of physical restraint (immobilization in the supine position or confinement in an acrylic cylindrical tube) was determined in unanesthetized and diethylether (ether)-exposed female and male rats. The combination of brief (2 min) exposure to ether followed by 10 and 20 min of supine restraint increased concentrations of prolactin in plasma and decreased DOPAC concentrations in median eminence of both female and male rats. Thirty minutes of supine restraint decreased DOPAC concentrations in the median eminence of female rats that were not exposed to ether, and brief exposure to ether enhanced this effect. By contrast, 30 min of supine restraint failed to alter DOPAC concentrations in the median eminence in either unanesthetized or ether-exposed male rats. Tube restraint in the absence of ether failed to alter DOPAC concentrations in the median eminence of either female or male rats; but in female rats preexposed to ether, 30 min of tube restraint decreased DOPAC concentrations in the median eminence. On the other hand, in the absence of physical restraint, 2 min ether exposure caused a transient increase in prolactin secretion and a concurrent decrease of DOPAC concentrations in median eminence of both female and male rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

Identification of the molecular defect in the erythrocyte membrane skeleton of some kindreds with hereditary spherocytosis

We have localized the molecular alteration in the membrane skeleton of two of four kindreds with hereditary spherocytosis (HS) to an alteration in the spectrin-protein-4.1 interaction due to a defective spectrin molecule. The defective spectrin-protein-4.1 interaction in these kindreds (referred to as type I HS) leads to a weakened spectrin- protein-4.1-actin ternary complex, which in turn may lead to the friable membrane skeleton and suggested membrane instability related to this disorder. Type I HS spectrin binds approximately 63% as much protein-4.1 as normal spectrin (with equal affinity). This defect does not correlate with splenic function or erythrocyte age in the circulation. However, the approximately 37% reduction in binding of protein-4.1 to HS spectrin approaches the theoretical value of 50% expected in this autosomal dominant disorder. All other type I membrane skeletal interactions (spectrin-syndein, spectrin heterodimer- heterodimer, syndein-band-3) were found to be normal. It would appear therefore that the defective HS spectrin-protein-4.1 interaction in type I hereditary spherocytosis may be the primary molecular defect rather than a secondary phenomena.     

Type IIB Tampa: a variant of von Willebrand disease with chronic thrombocytopenia, circulating platelet aggregates, and spontaneous platelet aggregation

Type IIB von Willebrand disease is characterized by enhanced ristocetin- induced platelet aggregation and absence of large von Willebrand factor multimers from plasma. An alteration of the von Willebrand factor molecule resulting in increased reactivity with platelets appears to be the basis for these abnormalities. We have now identified a new variant of type IIB von Willebrand disease in a family in which the four affected members also have chronic thrombocytopenia, in vivo platelet aggregate formation, and spontaneous platelet aggregation in vitro. In spite of repeatedly prolonged bleeding times and persistent thrombocytopenia, their bleeding diathesis is only moderate.