Controlling spatial distribution of functional lipids in a supported lipid bilayer prepared from vesicles.

Conjugating biomolecules, such as antibodies, to bioconjugate moieties on lipid surfaces is a powerful tool for engineering the surface of diverse biomaterials, including cells and nanoparticles. We developed supported lipid bilayers (SLBs) presenting well-defined spatial distributions of functional moieties as models for precisely engineered functional biomolecular-lipid surfaces. We used quartz crystal microbalance with dissipation (QCM-D) and atomic force microscopy (AFM) to determine how vesicles containing a mixture of 1,2-dipalmitoyl-sn-glycero-3-phosphatidylcholine (DPPC) and 1,2-distearoyl-sn-glycero-3-phosphoethanolamine-N-[azido(polyethylene glycol)-2000] (DSPE-PEG-N3) form SLBs as a function of the lipid phase transition temperature (Tm). Above the DPPC Tm, DPPC/DSPE-PEG-N3 vesicles form SLBs with functional azide moieties on SiO2 substrates via vesicle fusion. Below this Tm, DPPC/DSPE-PEG-N3 vesicles attach to SiO2 intact. Intact DPPC/DSPE-PEG-N3 vesicles on the SiO2 surfaces fuse and rupture to form SLBs when temperature is brought above the DPPC Tm. AFM studies show uniform and complete DPPC/DSPE-PEG-N3 SLB coverage of SiO2 surfaces for different DSPE-PEG-N3 concentrations. As the DSPE-PEG-N3 concentration increases from 0.01 to 6 mol%, the intermolecular spacing of DSPE-PEG-N3 in the SLBs decreases from 4.6 to 1.0 nm. The PEG moiety undergoes a mushroom to brush transition as DSPE-PEG-N3 concentration varies from 0.1 to 2.0 mol%. Via copper-free click reaction, IgG was conjugated to SLB surfaces with 4.6 nm or 1.3 nm inter-DSPE-PEG-N3 spacing. QCM-D and AFM data show; 1) uniform and complete IgG layers of similar mass and thickness on the two types of SLB; 2) a higher-viscosity/less rigid IgG layer on the SLB with 4.6 nm inter-DSPE-PEG-N3 spacing. Our studies provide a blueprint for SLBs modeling spatial control of functional macromolecules on lipid surfaces, including surfaces of lipid nanoparticles and cells.

pH-Mediated Size-Selective Adsorption of Gold Nanoparticles on Diblock Copolymer Brushes.

Precise control of nanoparticles at interfaces can be achieved by designing stimuli-responsive surfaces that have tunable interactions with nanoparticles. In this study, we demonstrate that a polymer brush can selectively adsorb nanoparticles according to size by tuning the pH of the buffer solution. Specifically, we developed a facile polymer brush preparation method using a symmetric polystyrene-b-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer deposited on a grafted polystyrene layer. This method is based on the assembly of a PS-b-P2VP thin film oriented with parallel lamellae that remains after exfoliation of the top PS-b-P2VP layer. We characterized the P2VP brush using X-ray reflectivity and atomic force microscopy. The buffer pH is used to tailor interactions between citrate-coated gold nanoparticles (AuNPs) and the top P2VP block that behaves like a polymer brush. At low pH (∼4.0) the P2VP brushes are strongly stretched and display a high density of attractive sites, whereas at neutral pH (∼6.5) the P2VP brushes are only slightly stretched and have fewer attractive sites. A quartz crystal microbalance with dissipation monitored the adsorption thermodynamics as a function of AuNP diameter (11 and 21 nm) and pH of the buffer. Neutral pH provides limited penetration depth for nanoparticles and promotes size selectivity for 11 nm AuNP adsorption. As a proof of concept, the P2VP brushes were exposed to various mixtures of large and small AuNPs to demonstrate selective capture of the smaller AuNPs. This study shows the potential of creating devices for nanoparticle size separations using pH-sensitive polymer brushes.

Polymer-Grafted, Gold Nanoparticle-Based Nano-Capsules as Reversible Colorimetric Tensile Strain Sensors.

Colloidal colorimetric microsensors enable the in-situ detection of mechanical strains within materials. Enhancing the sensitivity of these sensors to small scale deformation while enabling reversibility of the sensing capability would expand their utility in applications including biosensing and chemical sensing. In this study, we introduce the synthesis of colloidal colorimetric nano-sensors using a simple and readily scalable fabrication method. Colloidal nano sensors are prepared by emulsion-templated assembly of polymer-grafted gold nanoparticles (AuNP). To direct the adsorption of AuNP to the oil-water interface of emulsion droplets, AuNP (≈11nm) are functionalized with thiol-terminated polystyrene (PS, Mn  = 11k). These PS-grafted gold nanoparticles are suspended in toluene and subsequently emulsified to form droplets with a diameter of ≈30µm. By evaporating the solvent of the oil-inwater emulsion, we form nanocapsules (AuNC) (diameter < 1µm) decorated by PS-grafted AuNP. To test mechanical sensing, the AuNC are embedded in an elastomer matrix. The addition of a plasticizer reduces the glass transition temperature of the PS brushes, and in turn imparts reversible deformability to the AuNC. The plasmonic peak of the AuNC shifts towards lower wavelengths upon application of uniaxial tensile tension, indicating increased inter-nanoparticle distance, and reverts back as the tension is released.

A 3-Fluoropyridine Manipulating the Aggregation and Fibril Network of Donor Polymers for Eco-Friendly Solution-Processed Versatile Organic Solar Cells.

The development of eco-friendly solvent-processed organic solar cells (OSCs) suitable for industrial-scale production should be now considered the imperative research. Herein, asymmetric 3-fluoropyridine (FPy) unit is used to control the aggregation and fibril network of polymer blends. Notably, terpolymer PM6(FPy = 0.2) incorporating 20% FPy in a well-known donor polymer poly[(2,6-(4,8-bis(5-(2-ethylhexyl-3-fluoro)thiophen-2-yl)-benzo[1,2-b:4,5-b']dithiophene))-alt-(5,5-(1',3'-di-2-thienyl-5',7'-bis(2-ethylhexyl)benzo[1',2'-c:4',5'-c']dithiophene-4,8-dione)] (PM6) can reduce the regioregularity of the polymer backbone and endow them with much-enhanced solubility in eco-friendly solvents. Accordingly, the excellent adaptability for fabricating versatile devices based on PM6(FPy = 0.2) by toluene processing is demonstrated. The resulting OSCs exhibit a high power conversion efficiency (PCE) of 16.1% (17.0% by processed with chloroform) and low batch-to-batch variation. Moreover, by controlling the donor-to-acceptor weight ratio at 0.5:1.0 and 0.25:1.0, semi-transparent OSCs (ST-OSCs) yield significant light utilization efficiencies of 3.61% and 3.67%, respectively. For large-area (1.0 cm2 ) indoor OSC (I-OSC), a high PCE of 20.6% is achieved with an appropriate energy loss of 0.61 eV under a warm white light-emitting diode (3,000 K) with the illumination of 958 lux. Finally, the long-term stability of the devices is evaluated by investigating their structure-performance-stability relationship. This work provides an effective approach to realizing eco-friendly, efficient, and stable OSCs/ST-OSCs/I-OSCs.

Zwitterionic surface chemistry enhances detachment of bacteria under shear.

The ubiquitous nature of microorganisms, especially of biofilm-forming bacteria, makes biofouling a prevalent challenge in many settings, including medical and industrial environments immersed in liquid and subjected to shear forces. Recent studies have shown that zwitterionic groups are effective in suppressing bacteria and protein adhesion as well as biofilm growth. However, the effect of zwitterionic groups on the removal of surface-bound bacteria has not been extensively studied. Here we present a microfluidic approach to evaluate the effectiveness in facilitating bacteria detachment by shear of an antifouling surface treatment using (3-(dimethyl;(3-trimethoxysilyl)propyl)ammonia propane-1-sulfonate), a sulfobetaine silane (SBS). Control studies show that SBS-functionalized surfaces greatly increase protein (bovine serum albumin) removal upon rinsing. On the same surfaces, enhanced bacteria (Pseudomonas aeruginosa) removal is observed under shear. To quantify this enhancement a microfluidic shear device is employed to investigate how SBS-functionalized surfaces promote bacteria detachment under shear. By using a microfluidic channel with five shear zones, we compare the removal of bacteria from zwitterionic and glass surfaces under different shear rates. At times of 15 min, 30 min, and 60 min, bacteria adhesion on SBS-functionalized surfaces is reduced relative to the control surface (glass) under quiescent conditions. However, surface-associated bacteria on the SBS-functionalized glass and control show similar percentages of live cells, suggesting minimal intrinsic biocidal effect from the SBS-functionalized surface. Notably, when exposed to shear rates ranging from 104 to 105 s-1, significantly fewer bacteria remain on the SBS-functionalized surfaces. These results demonstrate the potential of zwitterionic sulfobetaine as effective antifouling coatings that facilitate the removal of bacteria under shear.

A Single Crystal 2D Hexagonal Array in a Centimeter Scale with a Self-Directed Assembly of Diblock Copolymer Spheres.

The creation of a single-grain two-dimensional (2D) nanoarray over a large area (∼1 cm2) has been only realized with expensive lithographic fabrication involving a complicated multichemical process. In this work, we report the production of a highly aligned single-grain 2D crystalline nanoarray over a centimeter-scale large area with a concept of self-directed assembly (SDA) in block copolymer (BCP) thin films. No lithographic guiding pattern is employed in SDA. A sphere-forming BCP is first transformed to transient-cylinders and aligned with shear. The aligned cylinders act as a guiding pattern to restore the sphere-morphology producing a single-grain 2D crystalline array with the following solvent vapor annealing. The SDA process has two governing parameters: orientational order of guiding patterns in the first step and the lattice matching between the transient guiding cylinders and the restored spheres. The successful application of SDA yields a single-grain of 2D crystalline hexagonal nanoarray with an exceptional long-range order, which is confirmed by employing image treating algorithms and grazing incidence small-angle X-ray scattering (GISAXS) measurements. The suggested SDA strategy is found to be effective for large-scale nanopatterning with no lithographic tools.

Biosynthesis of aliphatic plastic monomers with amino residues in Yarrowia lipolytica.

Introduciton: The α,ω-diamines (NH2-(CH2)n-NH2) and ω -amino fatty acids (NH2-(CH2)n-COOH) have been widely used as building blocks in polymerindustries. Medium- to long-chain (C8 to C18) fatty acid monomers with amino residues are almost exclusively produced via chemical processes that generate hazardous waste and induce severe environmental problems, such as global warming and pollution. Here, we present the construction platformstrains of Yarrowia lipolytica a cheese-ripening yeast, for direct biotransformation of hydrocarbons into medium- to long-chain α,ω-diamines and ωamino fatty acids using metabolic engineering of endogenous fatty acid ω- and ß-oxidation pathways and introducing heterologous ω-transaminase in Y. lipolytica. Methods: We deleted six genes encoding the acyl-CoA oxidase (ACO1-6) and four fatty aldehyde dehydrogenase genes (FALDH1-4), which catalyze fatty acid ß-oxidation and downstream oxidation of fatty aldehydes in Y. lipolytica, respectively. The ω-transaminase from Chromobacterium violaceum DSM30191 was introduced into the genome of the ΔPOX ΔFALDH strain under the control of Y. lipolytica-derived EXP1 promoters. Results and Discussion: The ΔPOX ΔFALDH strains with ω-CvTA successfully accumulated the corresponding C12 αω-diamines into a shaking culture medium with dodecane or dodecanol. In addition, these strains accumulated C12 ω-amino fatty acids from dodecanoic acid. With the commercially available α,ω-diacid bioprocess, this yeast biosynthesis producing medium- and longchain α,ω-diamines and ω-amino fatty acids could complete the yeast platform technology generating all medium- and long-chain aliphatic polyamide monomers, α,ω-biofunctionalized with one or both carboxylic acid and amino residues.

Cu(In,Ga)Se2 Solar Cells Integrated with Subwavelength Structured Cover Glass Fabricated by One-Step Self-Masked Etching.

We report an anti-reflective cover glass for Cu(In,Ga)Se2 (CIGS) thin film solar cells. Subwavelength structures (SWSs) were fabricated on top of a cover glass using one-step self-masked etching. The etching method resulted in dense whiskers with high aspect ratio. The produced structure exhibited excellent anti-reflective properties over a broad wavelength range, from the ultraviolet to the near infrared. Compared to a flat-surface glass, the average transmittance of the glass integrated with the SWSs improved from 92.4% to 95.2%. When the cover glass integrated with the SWSs was mounted onto the top of a CIGS device, the short-circuit current and the efficiency of the solar cell were enhanced by 4.38 and 6%, respectively, compared with a CIGS solar cell without cover glass.

Luminescent down-shifting CsPbBr3 perovskite nanocrystals for flexible Cu(In,Ga)Se2 solar cells.

To overcome the parasitic absorption of ultraviolet (UV) light in the transparent conductive oxide (TCO) layer of flexible Cu(In,Ga)Se2 (CIGS) thin film solar cells, a CsPbBr3 perovskite nanocrystal based luminescent down-shifting (LDS) layer was integrated on CIGS solar cells fabricated on a stainless steel foil. The CsPbBr3 perovskite nanocrystal absorbs solar irradiation at wavelengths shorter than 520 nm and emits photons at a wavelength of 532 nm. These down-shifted photons pass the TCO layer without parasitic absorption and are absorbed in the CIGS absorber layer where they generate photocurrent. By minimizing the parasitic absorption in the TCO layer, the external quantum efficiency (EQE) of the CIGS solar cell with the CsPbBr3 perovskite nanocrystal layer is highly improved in the UV wavelength range between 300 and 390 nm. Additionally, in the wavelength range between 500 and 1100 nm, the EQE is improved since the surface reflectance of the CIGS device with the CsPbBr3 perovskite LDS layer was reduced. This is because the CsPbBr3 perovskite nanocrystal layer, which has an effective refractive index of 1.82 at a wavelength of 800 nm, reduces the large refractive index mismatch between air (nair = 1.00) and the TCO layer (nZnO = 1.96 at a wavelength of 800 nm). Both the short circuit current density and power conversion efficiency of the flexible CIGS solar cell integrated with the CsPbBr3 perovskite are improved by 4.5% compared with the conventional CIGS solar cell without the CsPbBr3 perovskite LDS layer.

Enhanced Light Harvesting in Photovoltaic Devices Using an Edge-Located One-Dimensional Grating Polydimethylsiloxane Membrane.

In streamlined multipurpose applications for light management and protection, encapsulants are merged with photonic crystal structures into solar modules. We present an edge-located 1D grating, attachable polymer on the top of a photovoltaic module to provide a strategy for capturing solar light and improving cell efficiency. Large-area solar arrays suffer from space utilization problems due to nonactive area. The introduction of periodically patterned gratings with specific geometric range is highly preferred to redirect the light toward photovoltaic active areas. To realize optimized broadband light diffraction for solar devices, the theoretical analysis of one-dimensional line patterned diffraction gratings was performed through wave-optic-based simulation. Based on the experimental results, the replica molding-based patterning method was adopted to fabricate the grating polymer for low-cost thin-film production. Also, we demonstrated enhanced light collection by grating patterned encapsulants with improved current density in comparison to the performance of a flat surface.

Shear-solvo defect annihilation of diblock copolymer thin films over a large area.

Achieving defect-free block copolymer (BCP) nanopatterns with a long-ranged orientation over a large area remains a persistent challenge, impeding the successful and widespread application of BCP self-assembly. Here, we demonstrate a new experimental strategy for defect annihilation while conserving structural order and enhancing uniformity of nanopatterns. Sequential shear alignment and solvent vapor annealing generate perfectly aligned nanopatterns with a low defect density over centimeter-scale areas, outperforming previous single or sequential combinations of annealing. The enhanced order quality and pattern uniformity were characterized in unprecedented detail via scattering analysis and incorporating new mathematical indices using elaborate image processing algorithms. In addition, using an advanced sampling method combined with a coarse-grained molecular simulation, we found that domain swelling is the driving force for enhanced defect annihilation. The superior quality of large-scale nanopatterns was further confirmed with diffraction and optical properties after metallized patterns, suggesting strong potential for application in optoelectrical devices.

Fabrication of gold nanowires in micropatterns using block copolymers.

In this work, we introduce a facile method for fabricating well-aligned gold nanowires in a desired microstructure by combining the shear alignment of block copolymer (BCP) cylinders with a conventional lithography process. The aligned line patterns in a long-range order were firstly created with the shear alignment of cylinder-forming polystyrene-block-poly(2-vinylpyridine) thin films; then, gold was loaded to create metal nanowires. We directly employed photolithography on the nanopatterns, which simplified many fabrication steps. Furthermore, the combination of BCP assembly and photolithography allows for the independent control of nanopatterns and micropatterns, providing an opportunity to increase the nanopatterns' versatility.

Ultrawide Spectral Response of CIGS Solar Cells Integrated with Luminescent Down-Shifting Quantum Dots.

Conventional Cu(In1-x,Gax)Se2 (CIGS) solar cells exhibit poor spectral response due to parasitic light absorption in the window and buffer layers at the short wavelength range between 300 and 520 nm. In this study, the CdSe/CdZnS core/shell quantum dots (QDs) acting as a luminescent down-shifting (LDS) layer were inserted between the MgF2 antireflection coating and the window layer of the CIGS solar cell to improve light harvesting in the short wavelength range. The LDS layer absorbs photons in the short wavelength range and re-emits photons in the 609 nm range, which are transmitted through the window and buffer layer and absorbed in the CIGS layer. The average external quantum efficiency in the parasitic light absorption region (300-520 nm) was enhanced by 51%. The resulting short circuit current density of 34.04 mA/cm2 and power conversion efficiency of 14.29% of the CIGS solar cell with the CdSe/CdZnS QDs were improved by 4.35 and 3.85%, respectively, compared with those of the conventional solar cells without QDs.

Controlled Segmentation of Metal Nanowire Array by Block Copolymer Lithography and Reversible Ion Loading.

Spatial arrangement of 1D nanomaterials may offer enormous opportunities for advanced electronics and photonics. Moreover, morphological complexity and chemical diversity in the nanoscale components may lead to unique properties that are hardly anticipated in randomly distributed homogeneous nanostructures. Here, controlled chemical segmentation of metal nanowire arrays using block copolymer lithography and subsequent reversible metal ion loading are demonstrated. To impose chemical heterogeneity in the nanowires generated by block copolymer lithography, reversible ion loading method highly specific for one particular polymer block is introduced. Reversibility of the metal ion loading enables area-selective localized replacement of metal ions in the self-assembled patterns and creates segmented metal nanowire arrays with different metallic components. Further integration of this method with shear aligning process produces high aligned segmented metal nanowire array with desired local chemical compositions.

All-solid-state reduced graphene oxide supercapacitor with large volumetric capacitance and ultralong stability prepared by electrophoretic deposition method.

Portable energy storage devices have gained special attention due to the growing demand for portable electronics. Herein, an all-solid-state supercapacitor is successfully fabricated based on a poly(vinyl alcohol)-H3PO4 (PVA-H3PO4) polymer electrolyte and a reduced graphene oxide (RGO) membrane electrode prepared by electrophoretic deposition (EPD). The RGO electrode fabricated by EPD contains an in-plane layer-by-layer alignment and a moderate porosity that accommodate the electrolyte ions. The all-solid-state RGO supercapacitor is thoroughly tested to give high specific volumetric capacitance (108 F cm(-3)) and excellent energy and power densities (7.5 Wh cm(-3) and 2.9 W cm(-3), respectively). In addition, the all-solid-state RGO supercapacitor exhibits an ultralong lifetime for as long as 180 days (335 000 cycles), which is an ultrahigh cycling capability for a solid-state supercapacitor. The RGO is also tested for being used as a transparent supercapacitor electrode demonstrating its possible use in various transparent optoelectronic devices. Due to the facile scale-up capability of the EPD process and RGO dispersion, the developed all-solid-state supercapacitor is highly applicable to large-area portable energy storage devices.

Electromagnetic interference (EMI) transparent shielding of reduced graphene oxide (RGO) interleaved structure fabricated by electrophoretic deposition.

Here we introduce the electromagnetic shielding effectiveness (SE) of reduced graphene oxide (RGO) sheets interleaved between polyetherimide (PEI) films fabricated by electrophoretic deposition (EPD). Incorporating only 0.66 vol % of RGO, the developed PEI/RGO composite films exhibited an electromagnetic interference shielding effectiveness (EMI SE) at 6.37 dB corresponding to ∼50% shielding of incident waves. Excellent flexibility and optical transparency up to 62% of visible light was demonstrated. It was achieved by placing the RGO sheets in the localized area as a thin film (ca. 20 nm in thickness) between the PEI films (ca. 2 µm) to be an interleaved and alternating structure. This unique interleaved structure without any delamination areas was fabricated by a successive application of cathodic and anodic EPD of both RGO and PEI layers. The EPD fabrication process was ensured by an alternating deposition of the quarternized-PEI drops and RGO, each taking positive and negative charges, respectively, in the water medium. We believe that the developed facile fabrication method of RGO interleaved structure with such low volume fraction has great potential to be used as a transparent EMI shielding material.

Peroneal neuropathy after tibio-fibular fracture.

OBJECTIVE: To investigate the injury mechanism in patients who had peroneal neuropathy after a tibio-fibular fracture and the correlation between tibio-fibular fracture location and the severity of the peroneal neuropathy by using electrodiagnosis. METHOD: Thirty-four patients with peroneal neuropathy after a tibio-fibular fracture were recruited for this study. Their medical records, radiologic and electrodiagnostic findings were investigated retrospectively. They were divided into 2 groups according to the existence of a fibular head fracture. The group of patients without the fibular head fracture was further classified according to the criteria of Orthopedic Trauma Association (OTA) classification. The differences between the two groups in the severity of the neuropathy and electrodiagnostic findings were evaluated. RESULTS: Nine cases (26.5%) had tibio-fibular fractures with a coexisting fibular-head fracture and 25 cases (73.5%) had tibio-fibular fractures without fractures in the fibular-head area. There was no statistical significance in the correlation between the existence of the fibular head fracture and the severity of the electrodiagnostic findings. Neither was there any statistically significant relationship between the site of the tibio-fibular fracture and the severity of the peroneal neuropathy (p>0.05). CONCLUSION: This study showed there were numerous cases with common peroneal neuropathy after tibiofibular fracture without a coexisting fibular-head fracture, which shows the importance of indirect nerve injury mechanisms as well as that of direct nerve injury as a cause of peroneal neuropathy. In addition, this study showed that there was no statistically significant correlation between the site of tibio-fibular fracture and the severity of peroneal neuropathy.