Transparent Planar Research Articles

Nearly Panoramic Neuromorphic Vision with Transparent Photosynapses.

Neuromorphic vision based on photonic synapses has the ability to mimic sensitivity, adaptivity, and sophistication of bio-visual systems. Significant advances in artificial photosynapses are achieved recently. However, conventional photosyanptic devices normally employ opaque metal conductors and vertical device configuration, performing a limited hemispherical field of view. Here, a transparent planar photonic synapse (TPPS) is presented that offers dual-side photosensitive capability for nearly panoramic neuromorphic vision. The TPPS consisting of all two dimensional (2D) carbon-based derivatives exhibits ultra-broadband photodetecting (365-970nm) and ≈360° omnidirectional viewing angle. With its intrinsic persistent photoconductivity effect, the detector possesses bio-synaptic behaviors such as short/long-term memory, experience learning, light adaptation, and a 171% pair-pulse-facilitation index, enabling the synapse array to achieve image recognition enhancement (92%) and moving object detection.

An autonomous power temperature sensor based on window-integrated transparent PV using sustainable luminescent carbon dots.

The energy efficiency of buildings can be significantly improved through the use of renewable energy sources. Luminescent solar concentrators (LSCs) appear to be a solution for integrating photovoltaic (PV) devices into the structure of buildings (windows, for instance) to enable low-voltage devices to be powered. Here, we present transparent planar and cylindrical LSCs based on carbon dots in an aqueous solution and dispersed in organic-inorganic hybrid matrices, which present photoluminescent quantum yield values up to 82%, facilitating an effective solar photon conversion. These LSCs showed the potencial for being incorporated as building windows due to an average light transmittance of up to ∼91% and color rendering index of up to 97, with optical and power conversion efficiency values of 5.4 ± 0.1% and 0.18 ± 0.01%, respectively. In addition, the fabricated devices showed temperature sensing ability enabling the fabrication of an autonomous power mobile temperature sensor. Two independent thermometric parameters were established based on the emission and the electrical power generated by the LSC-PV system, which could both be accessed by a mobile phone, enabling mobile optical sensing through multiparametric thermal reading with relative sensitivity values up to 1.0% °C-1, making real-time mobile temperature sensing accessible to all users.

Correction to “Highly Transparent Planar Dipole Using Liquid Ionized Salt-Water Under Surface Tension Condition for UHD TV Applications” [Jan 21 35-42

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Highly Transparent Planar Dipole Using Liquid Ionized Salt Water Under Surface Tension Condition for UHD TV Applications

In this article, a feasibility study on an optically transparent planar dipole antenna using liquid salt water at wide ultra-high frequency (UHF) band (470-771 MHz) for application in external antenna of ultra-high-definition television (UHD TV) is presented. The most significant reason behind using liquid salt water for transparent antenna applications is its excellent average optical transparency (OTav) (>95% at salinity of 40 ppt) compared with other typical solid transparent thin-film electrodes such as indium tin oxide (>73%) or multilayer films (>78%). Each conductive arm of the proposed dipole is constructed from a salt-water layer held between two clear planar acrylic layers (ε <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">r</sub> = 2.61, tan δ = 0.01, OT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">av</sub> > 90%) (acrylic/salt water/acrylic; ASA) due to surface tension. To investigate the electrical and optical properties of the ASA structure, we analyze the surface tension to determine the thickness of the salt-water layer that finalizes its sheet resistance and OT <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">av</sub> . The average gain and efficiency of the antenna are 1.72 dBi and 74%, respectively, in the operating UHF band. This makes the proposed antenna a good candidate for application as a transparent external antenna in UHD TVs and proves that it is possible to use salt water for high-frequency devices.

In Operando Optical Visualization of Br5 - electrochemistry with a Planar Glass Battery for Zn/Br Flow Batteries

Zn/Br flow batteries are one of the promising technologies for stationary energy storage. Bromine complexing agents have been used to form phase-separated liquid polybromide charging products. However, dynamic and microscopic understandings of the nucleation and growth of the polybromides are limiteddue to the beam-sensitivity and complexity of these compounds and their surrounding electrolytes. In this communication, we report an in operando platform composed of dark field light microscopy and a transparent planar electrochemical cell to dynamically reveal the electrochemical nucleation and formation of polybromides. Using our platform, we confirm the liquid nature, reveal the pinning effect (strong interaction with Pt), memory effect (surface residual), self-discharge of the polybromide product, and discover over-oxidation as a side reaction for ZBB. We also conclude that the electrochemically formed droplets are mainly MEPBr5,rather than previously reported MEPBr3 with in situ Raman spectroscopy. These results provide mechanistic insightsinto the role of ionic liquid complexing agents and Zn/Br battery design. The in operando visualization platform can also be applied to study other unstable or transient products or intermediates in electrochemical reactions in ambient environment.

Dark Field Scattering Spectroelectrochemistry of Single Au Nanoparticles at Transparent Planar and Micro-Sized Electrodes

Noble metallic nanoparticles (NPs) (e.g., Au, Ag, Cu, Ni, and Pt have interesting catalytic and optical properties playing important role in electrocatalysis and spectroscopy enhancement. Ensemble averaging methods are usually applied to characterizing these properties. It remains extremely challenging to resolve electrochemical events of single catalytic NP using conventional quantitative analysis methods. In this study, we present very preliminary results of a spectroelectrochemistry study of single Au NPs at transparent planar electrode and ultramicroelectrode (UME). Our goal of this study is to resolve the electrocatalytic property of single Au NPs with combined methods of electrochemistry and dark field light scattering (DFS). Hydrazine oxidation reaction is used as a model system to characterize the catalytic characteristics of single Au NPs coated onto at a planer indium-tin-oxide (ITO) surface and ITO UMEs. Dark-field spectroelectrochemical study of Au NPs reveals the formation of nitrogen gas from NPs surface accompanied with a decrease in light scattering intensity. Spectroelectrochemistry method used in this work can potentially resolve local redox reactions catalyzed by metallic NPs at the nanometer scales.

Dark Field Scattering Spectroelectrochemistry of Single Au Nanoparticles at Transparent Planar and Micro-Sized Electrodes

Boron dipyrromethene (BODIPY) molecules with donor-acceptor configurations are of great interests for harvesting and converting solar energy in a solar cell. Au nanoparticles have been applied to enhance solar energy harvesting and conversion efficiency of organic solar cells because of their surface plasmon properties for increasing light absorption cross-section of an organic dye. Electrochemical properties of single BODIPY dyes and plasmonic Au nanoparticles (NPs) are studied using combined optical and electrochemical methods to reveal their structure-function relationship at the nanometer scale. Our study shows a heterogeneous half redox potential distribution for the BODIPY molecules embedded in polystyrene film because of the heterogeneity in their charge transfer rates. Single molecules adsorbed onto a TiO2 surface with ordered nanostructures show surprising fluorescence blinking activity with the shortest ON duration time in comparison to bare glass and indium-doped tin oxide (ITO) surfaces. Dark field scattering (DFS), photoluminescence (PL), and electrogenerated chemiluminescence (ECL) are used to probe local redox reactions of single Au nanoparticles at transparent planar and micro-sized electrode. Our study shows that these optical responses at individual plasmonic NPs are strongly dependent on particle size, and are affected by the local chemical and charge transfer environment of the NPs.

Flexible, Stretchable, and Transparent Planar Microsupercapacitors Based on 3D Porous Laser-Induced Graphene.

The graphene with 3D porous network structure is directly laser-induced on polyimide sheets at room temperature in ambient environment by an inexpensive and one-step method, then transferred to silicon rubber substrate to obtain highly stretchable, transparent, and flexible electrode of the all-solid-state planar microsupercapacitors. The electrochemical capacitance properties of the graphene electrodes are further enhanced by nitrogen doping and with conductive poly(3,4-ethylenedioxythiophene) coating. With excellent flexibility, stretchability, and capacitance properties, the planar microsupercapacitors present a great potential in fashionable and comfortable designs for wearable electronics.

Design of an Optically Transparent Reflectarray for Solar Applications Using Indium Tin Oxide

Optically transparent planar antennas made of transparent conductive oxide (TCO) have attracted considerable attention in research over the years, particularly for solar panel applications. However, their design has proved difficult due to their inherent conductor losses. This paper focuses on the design of an optically transparent reflectarray using indium tin oxide, which is a type of TCO. The design is composed of subwavelength rectangular patch elements that exhibit 272° of phase range and mitigate conductor losses in reflectarray operation. This paper examines the behavior and response of lossy reflectarray unit cells and investigates different techniques to reduce the impact of loss in TCO reflectarray designs, primarily using different patch geometries and subwavelength elements. The proposed element design is simulated and experimentally characterized. A full reflectarray prototype operating at 26 GHz is successfully demonstrated and fabricated, with the simulated and experimental results in good agreement.

Transparent Synchronous Electrostatic Actuator for Long-Stroke Planar Motion

This paper reports a development of a transparent planar electrostatic actuator, which is useful for constructing interactive human–computer interfaces on flat panel displays. The actuator is a pair of transparent plastic films with strip electrodes in three-phase connections. Half of the electrodes in each film are X electrodes, and the rest are Y electrodes; electrostatic forces excited by applying three-phase voltage to these electrodes drive the actuator at speeds proportional to the excitation frequency. The stator film of the actuator has its X and Y electrodes alternately arranged in a four-by-four checkerboard pattern. The slider is a square film with its side twice that of a single square in the stator, with its electrodes separated by diagonal lines. A geometric analysis shows that this electrode arrangement brings position independence of overlapping areas of electrodes. The position independence gives the actuator a uniform thrust force characteristic required for long-stroke planar motion. Based on this concept, we fabricated a prototype by screen-printing. The prototype could exert approximately 100-mN thrust force with an excitation by a pair of 500-V three-phase voltages, and could travel along straight and curved paths within a 132 mm by 132 mm movable range.

The Effect of CB15 on Cholesteric Liquid Crystal’s Thermal-Optical Properties

A kind of Cholesteric Liquid Crystal was prepared by mixing CB15 with Nematic Liquid Crystal 1717. The influence of CB15 content on the CLC texture, pitch length and thermal optical properties were investigated. The results indicated that the CB15 content affected significantly the CLC texture and the content in the region of 8.0-12.0 wt% were optimal condition for realizing the thermally erase in which texture could be easily changed from scatting focal conic texture to transparent planar one.

Circular Dichroism Analysis of Cyclic β-Helical Peptides Adsorbed on Planar Fused Quartz

Conformational changes of three cyclic β-helical peptides upon adsorption onto planar fused-quartz substrates were detected and analyzed by far-ultraviolet (UV) circular dichroism (CD) spectroscopy. In trifluoroethanol (TFE), hydrophobic peptides, Leu β and Val β, form left- and right-handed helices, respectively, and water-soluble peptide WS β forms a left-handed helix. Upon adsorption, CD spectra showed a mixture of folded and unfolded conformations for Leu β and Val β and predominantly unfolded conformations for WS β. X-ray photoelectron spectroscopy (XPS) provided insight about the molecular mechanisms governing the conformational changes, revealing that ca. 40% of backbone amides in Leu β and Val β were interacting with the hydrophilic substrate, while only ca. 15% of the amines/amides in WS β showed similar interactions. In their folded β-helical conformations, Leu β and Val β present only hydrophobic groups to their surroundings; hydrophilic surface groups can only interact with backbone amides if the peptides change their conformation. Conversely, as a β helix, WS β presents hydrophilic side chains to its surroundings that could, in principle, interact with hydrophilic surface groups, with the peptide retaining its folded structure. Instead, the observed unfolded surface conformation for WS β and the relatively small percentage of surface-bound amides (15 versus 40% for Leu β and Val β) suggest that hydrophilic surface groups induce unfolding. Upon this surface-induced unfolding, WS β interacts with the surface preferentially via hydrophilic side chains rather than backbone amides. In contrast, the unfolded β-hairpin-like form of WS β does not irreversibly adsorb on fused quartz from water, highlighting that solvation effects can be more important than initial conformation in governing peptide adsorption. Both label-free methods demonstrated in this work are, in general, applicable to structural analysis of a broad range of biomolecules adsorbed on transparent planar substrates, the surface properties of which could be customized.

Advanced bistable cholesteric light shutter with dual frequency nematic liquid crystal

In this paper, a direct switching between a transparent (or reflecting) planar (P) state to an opaque (or transparent) focal conic (FC) state and vice-versa of a polymer free bistable cholesteric light shutter without any homogeneous polyimide (PI) layer, is demonstrated based on the sign inversion of dielectric anisotropy of dual frequency liquid crystal (DFLC). The direct switching was achieved by applying square wave field at low (1 kHz) and high (50 kHz) frequency. As a result, the DFLC light shutter sustains bistable bright and dark states in electric field off state and exhibits excellent electro-optic performance. The direct switching from the FC to P states not only supports more uniform P state but also significantly reduces switching voltage by eliminating the high field homeotropic (H) state required for the switching in the conventional polymer stabilized cholesteric texture (PSCT) light shutter. The driving voltage applied to make a transition from the P to FC one is relatively low (3Vp-p/µm). Further, switching time from FC to P state was reduced drastically with homeotropic PI layer. Results show that dual frequency cholesteric liquid crystal (DFCLC) light shutter holds a great promise for use in energy efficient display devices and switchable windows.

Quantitative measurement and visualization of biofilm O 2 consumption rates in membrane filtration systems

There is a strong need for techniques enabling direct assessment of biological activity of biofouling in membrane filtration systems. Here we present a new quantitative and non-destructive method for mapping O 2 dynamics in biofilms during biofouling studies in membrane fouling simulators (MFS). Transparent planar O 2 optodes in combination with a luminescence lifetime imaging system were used to map the two-dimensional distribution of O 2 concentrations and consumption rates inside the MFS. The O 2 distribution was indicative for biofilm development. Biofilm activity was characterized by imaging of O 2 consumption rates, where low and high activity areas could be clearly distinguished. The spatial development of O 2 consumption rates, flow channels and stagnant areas could be determined. This can be used for studies on concentration polarization, i.e. salt accumulation at the membrane surface resulting in increased salt passage and reduced water flux. The new optode-based O 2 imaging technique applied to MFS allows non-destructive and spatially resolved quantitative biological activity measurements (BAM) for on-site biofouling diagnosis and laboratory studies. The following set of complementary tools is now available to study development and control of biofouling in membrane systems: (i) MFS, (ii) sensitive pressure drop measurement, (iii) magnetic resonance imaging, (iv) numerical modelling, and (v) biological activity measurement based on O 2 imaging methodology.

Virtual display design using waveguide hologram in conical mounting configuration

An improved virtual display is proposed by using a waveguide holographic configuration with two total internal reflection holographic gratings in conical mounting and two volume hologram in classical mounting recorded on a single transparent planar waveguide. Using this compact configuration, efficiency can be dramatically improved and assembly is easy to be realized. The main principle and the method of intensity uniformity control are present in the paper. The analysis and simulation results are also explained. The virtual display system design shows good optical performance with 25 deg. field of view, a large pupil about 43 mm, little distortion less than 1%, and low aberration. The configuration can be used to a portable or wearable display.

A simple optode based method for imaging O 2 distribution and dynamics in tap water biofilms

A ratiometric luminescence intensity imaging approach is presented, which enables spatial O 2 measurements in biofilm reactors with transparent planar O 2 optodes. Optodes consist of an O 2 sensitive luminescent dye immobilized in a 1–10 μm thick polymeric layer on a transparent carrier, e.g. a glass window. The method is based on sequential imaging of the O 2 dependent luminescence intensity, which are subsequently normalized with luminescent intensity images recorded under anoxic conditions. We present 2-dimensional O 2 distribution images at the base of a tap water biofilm measured with the new ratiometric method and compare the results with O 2 distribution images obtained in the same biofilm reactor with luminescence lifetime imaging. Using conventional digital cameras, such simple normalized luminescence intensity imaging can yield images of 2-dimensional O 2 distributions with a high signal-to-noise ratio and spatial resolution comparable or even surpassing those obtained with expensive and complex luminescence lifetime imaging systems. The method can be applied to biofilm growth incubators allowing intermittent experimental shifts to anoxic conditions or in systems, in which the O 2 concentration is depleted during incubation.

Electro-thermal switchable bistable reverse mode polymer stabilized cholesteric texture light shutter

We studied the effects of different UV curing intensities and monomer concentrations on the distortion of polymer network of reverse mode polymer stabilized cholesteric texture (PSCT) after the application of a high voltage pulse perpendicular to the cell substrates. SEM observations indicated that lower intensities of UV irradiation resulted in the formation of more compact polymer networks with smaller voids. The majority of cholesteric liquid crystal was heavily affected by the distorted polymer network, meaning that the stabilized focal conic texture was unable to revert to the planar texture via the annealing treatment. Additionally, as the monomer concentrations increased, the resistance of the polymer network toward a high voltage pulse applied perpendicularly to the cell substrates increased, resulting in less pronounced distortion. With the use of a higher UV curing intensity and a lower monomer concentration, we created an optimized polymer network that could stabilize the scattering focal conic texture after distortion, and revert to the transparent planar texture via the annealing treatment, thereby giving rise to an electro-thermal switchable bistable reverse mode PSCT light shutter. It exhibited excellent gray scale performance, and the ability to maintain the bright and dark states without the need to apply an electric field, and thereby holds tremendous promise for use in energy efficient and thermally insulating switchable window.

Novel type of combined photopatternable and electro-switchable polymer-stabilized cholesteric materials

A novel type of photopatternable polymer network-stabilized cholesteric materials for creation of electrooptical switching was elaborated. For this purpose cholesteric composites based on a commercial low-molar-mass nematic mixture, a chiral dopant, different amount of polymerizable mesogenic diacrylate (1–6 wt%) and a chiral-photochromic substance consisting cinnamoyl and isosorbide fragments (∼4 wt%) were prepared. A small amount of photoinitiator sensitive mostly to light with wavelength of 365 nm was also added. UV irradiation of the complex mixture with this wavelength light results in the polymerization of the diacrylate and formation of the polymer network stabilizing the initial planar texture in the electrooptical cell. Electrical field application induces a transition from the transparent planar cholesteric texture to a scattered focal conic one; at higher voltage the selective light reflection peak disappears. Irradiation of the cell with shorter wavelength light (313 nm) leads predominantly to the E–Z isomerization of the chiral-photochromic dopant followed by irreversible helix untwisting and to the shift of the selective light reflection from blue to green or red spectral regions. In this case, the competing photopolymerization process almost does not take place. Subsequent irradiation of the cell by longer-wavelength UV light (365 nm) allows one to obtain a polymer network and stabilize the new texture. Electrooptical properties of cells with different values of helix pitch were studied in detail. These data demonstrate the new opportunities for creation of photopatternable electrooptically switchable devices, which can be used in photonics and electrooptics.

Transcutaneous pO2 imaging during tourniquet‐induced forearm ischemia using planar optical oxygen sensors

Oxygen-dependent quenching of luminescence using transparent planar sensor foils was shown to overcome the limitations of the polarographic electrode technique in an animal model. This method was then transferred to a clinical setting to measure the transcutaneous pO(2) (p(tc)O(2)). In six healthy subjects, a cuff on the upper arm was occluded up to 20 mmHg above systolic pressure and released after 8 min. P(tc)O(2) was measured at the lower arm every 30 s before, during, and up to 20 min after cuff occlusion (40 degrees C applied skin temperature) using luminescence lifetime imaging (LLI) of platinum(II)-octaethyl-porphyrin immobilized in a polystyrene matrix. For validation, the polarographic Clark electrode technique was applied in close proximity, and measurements were conducted simultaneously. P(tc)O(2) measurements before (70.8+/-19.1 vs. 66.2+/-7.7 mmHg) and at the end of ischemic (2.7+/-1.2 vs. 3.6+/-1.7 mmHg) and reperfusion phases (72.2+/-3.6 vs. 68.4+/-8.9 mmHg) did not differ significantly using the Clark electrode vs. LLI. At both the initial ischemic and the reperfusion phases, the Clark electrode measured a faster decrease or increase, respectively, in p(tc)O(2) because of the oxygen consumption occurring in this method. The presented method provides accurate and reproducible p(tc)O(2) values under changing microcirculatory conditions. The lack of oxygen consumption during measurement allows both a more realistic estimation of p(tc)O(2) than compared with the gold standard and permanent use in regions with critical oxygen supply.

In Vivo Phosphorescence Imaging of pO2 Using Planar Oxygen Sensors

Oxygen-dependent quenching of luminescence of metal porphyrin complexes has been used to image the pO(2) distribution over tumor and normal tissue. An experimental setup is described using a platinum(II)-octaethyl-porphyrin immobilized in a polystyrene matrix as transparent planar sensor. Sensitivity over a broad range is high at low pO(2) values (+/- 0.2 mm Hg at 0 mm Hg; +/- 1.5 mm Hg at 160 mm Hg pO(2)). Due to intrinsically referencing via lifetime encoding there was no modification of the sensor response in vivo in the dorsal skinfold chamber model with amelanotic melanoma (A-MEL-3) in awake hamsters when compared to the in vitro calibration. pO(2) measurements over normal tissue (25.8 +/- 5.1 mm Hg) and tumor tissue (9.2 +/- 5.1 mm Hg) were in excellent agreement with previous results obtained in this model using a surface multiwire electrode. Using the presented method the surface pO(2) distribution can be mapped with a high temporal resolution of approximately 100 ms and a spatial resolution of at least 25 mu m. Moreover, the transparent sensor allows the simultaneous visualization of the underlying microvasculature.