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A simple layer-stacking technique to generate biomolecular and mechanical gradients in photocrosslinkable hydrogels
摘要： Physicochemical and biological gradients are desirable features for hydrogels to enhance their relevance to biological environments for three-dimensional (3D) cell culture. Therefore, simple and efficient techniques to generate chemical, physical and biological gradients within hydrogels are highly desirable. This work demonstrates a technique to generate biomolecular and mechanical gradients in photocrosslinkable hydrogels by stacking and crosslinking prehydrogel solution in a layer by layer manner. Partial crosslinking of the hydrogel allows mixing of prehydrogel solution with the previous hydrogel layer, which makes a smooth gradient profile, rather than discrete layers. This technique enables the generation of concentration gradients of bovine serum albumin in both gelatin methacryloyl (GelMA) and poly(ethylene glycol) diacrylate hydrogels, as well as mechanical gradients across a hydrogel containing varying gel concentrations. Fluorescence microscopy, mechanical testing, and scanning electron microscopy show that the gradient profiles can be controlled by changing both the volume and concentration of each layer as well as intensity of UV exposure. GelMA hydrogel gradients with different Young’s moduli were successfully used to culture human fibroblasts. The fibroblasts migrated along the gradient axis and showed different morphologies. In general, the proposed technique provides a rapid and simple approach to design and fabricate 3D hydrogel gradients for in vitro biological studies and potentially for in vivo tissue engineering applications.
关键词： 3D cell culture,Gelatin methacryloyl,Photocrosslinkable hydrogel,Poly(ethylene glycol) diacrylate,Gradient
更新于2025-11-21 11:24:58
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Transparent Platinum Counter Electrode Prepared by Polyol Reduction for Bifacial, Dye-Sensitized Solar Cells
摘要： Pt catalytic nanoparticles on F-doped SnO2/glass substrates were prepared by polyol reduction below 200 °C. The polyol reduction resulted in better transparency of the counter electrode and high power-conversion efficiency (PCE) of the resultant dye-sensitized solar cells (DSSCs) compared to conventional thermal reduction. The PCEs of the DSSCs with 5 μm-thick TiO2 photoanodes were 6.55% and 5.01% under front and back illumination conditions, respectively. The back/front efficiency ratio is very promising for efficient bifacial DSSCs.
关键词： dye-sensitized solar cell,platinum,bifacial,ethylene glycol,counter electrode
更新于2025-11-21 11:01:37
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Formation of a keratin layer with silk fibroin-polyethylene glycol composite hydrogel fabricated by digital light processing 3D printing
摘要： Silk fibroin (SF)-incorporated 4-arm polyethylene glycol acrylate (PEG4A) was used as a bioink for digital light processing three-dimensional printing. A visible range of light was adopted for the process to assure the safety of the cells in the bioink. Fibroblast cells were embedded in the printed hydrogels, and the keratinocyte cells were cultured at the surfaces of the hydrogels. The proliferation of cells with the bioink materials, PEG4A and SF-PEG4A, and the toxicity of these materials, were verified by live/dead and alamarBlue assays. The primary human keratinocytes on the SF-PEG4A hydrogel scaffold generated a keratin layer by the tissue culture at the air-liquid interface, promoting maturation and stratification. SF-polyethylene glycol hydrogels showed higher cell proliferation and cell spreading, and the thicker keratin layer was formed with SF-PEG4A hydrogels compared with PEG4A hydrogels.
关键词： Digital light processing,Silk fibroin,3D printing,4-arm polyethylene glycol acrylate,Keratin
更新于2025-09-23 15:23:52
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Fabrication of octagonal and dodecagonal single crystal Si micropyramids via etching without using a pre-patterned mask
摘要： Surface texturing of Si has attracted signi?cant attention over the past decades as micro/nano patterns allow for preferred opto-electronic and electrochemical properties. Here a new fabrication method, based on etching in aqueous NaOH-polyethylene glycol solution is presented, which allows the formation of novel eight and twelve sided Si micropyramids. Particularly, the presence of NaOH resulted in the formation of four sided facets along intersecting {111} planes, while with continuous etching the high molar mass polyethylene glycol resulted in the formation of four additional facets identi?ed to be (212) planes producing octagonal pyramids. Further etching of these octagonal pyramids lead to the formation of twelve-sided pyramids. Eight-faceted (octagonal) pyramids have been reported in the literature, but only through the use of photolithography, while twelve-faceted (dodecagonal) pyramids have not been observed for any type of crystal.
关键词： Pyramids,Octagon,Si patterning,Etching,Polyethylene glycol,Dodecagon
更新于2025-09-23 15:23:52
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Development of Graphitic Domains in Carbon Foams for High Efficient Electro/Photo-to-Thermal Energy Conversion Phase Change Composites
摘要： In this research work, hierarchical porous carbon foams (CFs) with high surface area and three dimensionally (3D) interconnected macro/meso/microporous structures were prepared through pyrolysis of stabilized poly(acrylonitrile-co-divinylbenzene) P(AN-co-DVB) polyHIPE foams at 900 °C under nitrogen atmosphere. The prepared CFs revealed high surface area (540 m2 g-1), semi-ordered nanoporosity, high electrical conductivity (470 S m-1) and high graphitization degree. Further, HR-TEM observation of CFs revealed the formation of graphitic domains in the structures. The obtained CFs were employed for encapsulation of phase change materials (PCMs) e.g. paraffin (PA) and polyethylene glycol (PEG). The prepared PCMs composites revealed the excellent reversible thermal/chemical stability after frequent 200 heating/cooling cycles. Black CF/PA and CF/PEG composites can be promising structures to driven either by applying a small voltage (3-3.6 V) with high electric-to thermal efficiency (up to 85%) or by irradiating with sunlight with high photo-to thermal efficiency (up to around 91%).
关键词： paraffin and poly ethylene glycol,carbon foam,phase change materials
更新于2025-09-23 15:23:52
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[IEEE 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Budapest (2018.7.1-2018.7.5)] 2018 IEEE 2nd International Conference on Dielectrics (ICD) - Bistable Optical Functions of Polyethylene Glycol
摘要： Polyethylene glycol takes both transparent and translucent phases during the phase transition process at around room temperature. This bistability seems useful to create optical devices including 3D displays and tunable random lasers. These devices, however, require a spot-heating technique that controls the phase of each microelement. Self-heating of microelements is achievable if the electric conductivity of the polyethylene glycol is enhanced by the dissolution of alkaline halide salts.
关键词： ionic conduction,bistability,optical functions,polyethylene glycol,phase transition
更新于2025-09-23 15:23:52
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Highly Responsive PEG/Gold Nanoparticle Thin Film Humidity Sensor via Inkjet Printing Technology
摘要： In this study, a highly responsive humidity sensor is developed by printing gold nanoparticles (GNP) grafted with a hygroscopic polymer. These GNPs are inkjet printed to form a uniform thin film over an interdigitated electrode with controllable thickness by adjusting the printing parameters. The resistance of the printed GNP thin film decreases significantly upon exposure to water vapor and exhibits a semi-log relationship with relative humidity (RH). The sensor can detect RH variations from 1.8% to 95% with large resistance changes up to 4 order of magnitude with no hysteresis and small temperature dependence. In addition, with a thin thickness, the sensor can reach absorption equilibrium quickly with response and recovery times of ≤1.2 and ≤3 seconds, respectively. The fast response to humidity changes also allows the GNP thin film sensor to distinguish signals from intermittent humidification/dehumidification cycles with a frequency up to 2.5 Hz. The printed sensors on flexible substrates show little sensitivity to bending deformation and can be embedded in a mask for human respiratory detection. In summary, this study demonstrates the feasibility of applying printing technology for the fabrication of thin film humidity sensors, and the developed methodology can be further applied to fabricate many other types of nanoparticle based sensor devices.
关键词： inkjet printing,respiratory monitoring,Humidity sensor,gold nanoparticle,poly(ethylene glycol)
更新于2025-09-23 15:23:52
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Influence of silicon dioxide medium on the structural and electrical properties of nickel zinc ferrite
摘要： Nickel zinc ferrite [(Ni 0:65 Zn 0:35 Fe 2 O 4)x / (SiO 2)1(cid:0)x where, x = 1.0, 0.85, 0.65, 0.50, 0.35, and 0.15] is synthesized using the glyoxylate precursor method. The synthesis, characterization, and electrical study of nickel zinc ferrites/SiO 2 powder with low dielectric constant, very low conductivity, and loss tangent with low frequency dispersion, suitable for good insulators, is reported here. X-ray diffraction, TGA, and FT-IR studies are employed for identifying crystalline phases and structure. Crystallite size is calculated by the Scherrer formula and Williamson–Hall equation and found to fall in the range of 4.9–25 nm. TEM of the samples shows spherical particles of uniform size distribution and the spotty rings of SAED patterns are analyzed for identifying the crystal planes. The study confirms a simple and efficient way to synthesize single-phase nickel zinc ferrite (NZFO) spherical particles of nano size ( (cid:25) 15 nm at 1000 ? C) with lower particle agglomeration in comparison to any other methods. Electrical studies are carried out using an LCR meter. The observed value of dielectric constant falls in the range of 10–80, loss tangent in the range of 0.05–0.4, and electrical conductivity in the range of 10 (cid:0)4 to 10 (cid:0)7 mho m (cid:0)1 . These values are respectively functions of temperature, frequency, and the ferrite content in ferrite/SiO 2 samples. A proper selection of ferrite concentration in the silica medium enables one to prepare NZFO/SiO 2 material of very low loss tangent with dielectric constant in the range of 10–80.
关键词： tetraethyl orthosilicate,dielectric constant,Nickel zinc ferrite,dielectric conductivity,loss tangent,ethylene glycol
更新于2025-09-23 15:21:21
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Novel lanthanidomesogens based on poly(ethylene glycol) cholesterol ether: Liquid crystal phase behavior and luminescence properties
摘要： Biocompatible systems with luminescent properties attract significant interest as they are broadly used in bioanalysis and medical diagnostics. This paper describes new lanthanide liquid crystals based on an oxyethylated amphiphile with a cholesterol fragment (CholEO10). The complex of physicochemical methods (polarizing optical microscopy (POM), X-ray powder diffraction, FTIR-spectroscopy and luminescent analysis) was used to study liquid crystalline, structural and optical properties of these new biomesogens. Their phase behavior was compared with the behavior a lanthanum-containing analogue without a cholesterol fragment in its structure. A rigid hydrophobic fragment was found to exert a strong influence on lyotropic mesomorphism in aqueous media. The phase transition from a lamellar mesophase to a hexagonal one was observed with decrease of the CholEO10/La3+ complex concentration and addition of water. The study of luminescent properties of CholEO10/Ln3+ complexes, where Ln3+ is Dy3+, Tb3+, or Eu3+, revealed that their characteristic emission occurs in the yellow, green and red spectral ranges. Optical characteristics of new mesogens were estimated. Mesogenic CholEO10/Tb3+ and CholEO10/Eu3+ complexes demonstrate longer lifetime of their excited state as compared with the C12EO10/Ln3+/H2O complex.
关键词： Cholesterol derivatives,Liquid crystals,Luminescence,Poly(ethylene glycol),Lanthanide
更新于2025-09-23 15:21:21
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Stretchable Hole Extraction Layer for Improved Stability in Perovskite Solar Cells
摘要： Flexibility and stretchability of solar cells are crucial factors for enhancing their real-life application for wearable devices. Although poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) has been conventionally employed as a hole extraction layer (HEL) in flexible organic or perovskite solar cells, the inherent stretchability of PEDOT:PSS has yet to be convinced. Here, we report a highly stretchable and mechanically stable PEDOT:PSS-based thin film and its application on flexible perovskite solar cells. We synthesized a chemically linked copolymer, P(SS-co-TFPMA), consisting of PSS and tetrafluoropropylmethacrylate (TFPMA), followed by graft-copolymerization with poly(ethylene glycol) methyl ether methacrylate (PEGMA) to form a P(SS-co-TFPMA)-g-PEGMA dopant for the PEDOT HEL. The PEDOT:P(SS-co-TFPMA)-g-PEGMA (PEDOT:PTP) copolymer solution has excellent homogeneity and high phase stability and its developed HEL film exhibits outstanding stretching capability. After stretching of 300%, PEDOT:PTP films sustain conductivity of over 80% of its original conductivity whereas the conventional PEDOT:PSS films completely lose their conductivity after the strain of 300 %. In addition, the PEDOT:PTP incorporated flexible perovskite solar cells exhibited improved mechanical stability compared with the unassisted cells, retaining 92% of the initial power conversion efficiency after 1500 bending cycles at a 7 mm radius.
关键词： PEDOT:PTP,Stretchable,PEDOT:PSS,Hole extraction layer,Flexible,poly(ethylene glycol)methylacrylate
更新于2025-09-23 15:21:01