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Abstract Recent developments in flexible circuits and optoelectronic materials have the potential to provide innovative solutions for wearable sensing. The presented work explores how materials from these developments can reduce the complexity of developing flexible optoelectronics. The work uses simplified fabrication methods to develop a large area thin film optoelectronic device using conjugated polymers and Quantum Dots, with the goal of providing evidence that such devices can be developed outside of a clean room facility. Electroluminescence testing using a power source and an imaging spectrometer show that both conductive polymers and Quantum Dots in the functional layer contribute to light emission. High voltages needed for light emission are likely a result of the observed uneven thicknesses in the active layer, which should be the main focus for improvement in continued work. To study flexibility, the effects of cyclic bending using an Instron machine is observed. Visual analysis identifies four main flaw features that can occur from the fabrication process, and that cyclic bending causes cracking only at these flaw features. This work serves as evidence that use of clean room facilities are not necessary to provide significant contributions towards flexible optoelectronic materials development. [ABSTRACT FROM AUTHOR]

Polymer nanocomposite (PNC) films of poly (ethylene oxide) (PEO) and poly (vinyl pyrrolidone) (PVP) blend matrix (50/50 wt%) incorporated with zinc oxide (ZnO) nanoparticles (i.e., (PEO–PVP)– x wt% ZnO; x  = 0, 1, 3 and 5) were prepared and characterized as potential candidates for applications in the next generation optoelectronic and microelectronic devices. The structural properties of these PNCs were investigated by using scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy and the X–ray diffraction (XRD) measurement techniques. The porous spherulites morphology, polymer-polymer and polymer-nanoparticle interactions, and the semicrystalline structures of these materials have been significantly influenced by the incorporated amount of ZnO nanoparticles in the polymer blend matrix. The optical behaviour of the PNC films was studied from ultraviolet–visible (UV–vis) spectroscopy, and the optical parameters viz. optical energy band gap (indirect and direct), Urbach tail energy, refractive index and the ZnO surface plasmon resonance energy were determined. Complex permittivity, electric modulus, electrical conductivity and the impedance spectra of these PNC materials as flexible nanodielectrics have been measured in the frequency range from 20 Hz to 1 MHz by employing the dielectric relaxation spectroscopy (DRS). The DRS results reveal that the ambient temperature values of complex permittivity increase with the increase of ZnO contents up to 3 wt% in the PEO–PVP blend matrix and then it slightly decreases at 5 wt%. The dielectric relaxation process confirms that the polymers cooperative chains segmental dynamics in the blend matrix enhances in presence of ZnO nanoparticles in the complex nanocomposite structures. The temperature dependent study of 3 wt% ZnO containing PNC film reveals that the complex permittivity increase linearly with the increase of temperature, whereas the dielectric relaxation time and electrical conductivity values obey the Arrhenius behaviour. [ABSTRACT FROM AUTHOR]

Polythiophenes are conjugated polymers that are highly promising candidates for use as an active layer in flexible optoelectronic devices. The β-substitution position in the thiophene ring minimizes the occurrence of couplings during polymerization, producing more regular structures and resulting in better properties. The relatively high stability and the possibility of tuning the properties by molecular engineering make polythiophenes one of the most versatile classes of conjugated polymers. In this study, we present an investigation of the influence of two types of polythiophenes on their spectroelectrochemical properties: (i) poly(alcoxythiophenes) (POTs), including poly(3-methoxythiophene) (PMOT) and poly(3,4-ethylenedioxythiophene) (PEDOT), and (ii) poly(3-alkylthiophenes) (PYTs), including poly(3-hexylthiophene) (P3HT) and poly(3-dodecylthiophene) (PDDT). The polymers were electrochemically synthesized by cyclic voltammetry and characterized by infrared spectroscopy. The “in situ” simultaneous optical absorption and fluorescence investigation of the solutions showed new energy state polarons in the redox process. Chronoabsorptometry measurements enabled determination of parameters such as electrochromic efficiency, coulombic efficiency, optical contrast, and switching time of the polymers in the reduced and oxidized states. A switching time of 2 s and an electrochemical efficiency of almost 90 cm2 C−1 are promising for applying these polymers in electrochromic devices. [ABSTRACT FROM AUTHOR]

Sensors have attracted particular attention as analytical devices because of their importance in health and security. The ability to obtain unique functions using molecular design have rapidly advanced the use of organic optoelectronic materials of π-conjugated compounds in electronic sensing devices. A brief introduction to sensors, focusing on organic micro- or nanoassemblies created using state-of-the-art protocols for assembly and their recent development for high-performance electronic sensing devices, is presented. [ABSTRACT FROM AUTHOR]

β-GaO films were grown on c-plane sapphire substrates at different substrate temperatures by metal-organic chemical vapor deposition. The effects of substrate temperature on transparence, optical band gap and photoluminescence of the films were studied systematically. With increasing the substrate temperature, the films structure was changed from amorphous to single orientation β-GaO. The β-GaO films exhibited excellent optical transparency in the ultraviolet and visible regions. The ultraviolet-blue photoluminescence was observed at room temperature. The temperature-dependent photoluminescence was also carried out and the relative intensity of the blue emission with respect to the ultraviolet emission decreased with increasing the measured temperature. The origin of luminescence was discussed. [ABSTRACT FROM AUTHOR]

In this work, we analyze the use of optoelectronic tweezers (OETs) to manipulate 45 μm diameter Sn62Pb36Ag2 solder beads with light-induced dielectrophoresis force and we demonstrate high positioning accuracy. It was found that the positional deviation of the solder beads increases with the increase of the trap size. To clarify the underlying mechanism, simulations based on the integration of the Maxwell stress tensor were used to study the force profiles of OET traps with different sizes. It was found that the solder beads felt a 0.1 nN static friction or stiction force due to electrical forces pulling them towards the surface and that this force is not dependent on the size of the trap. The stiction limits the positioning accuracy; however, we show that by choosing a trap that is just larger than the solder bead sub-micron positional accuracy can be achieved. [ABSTRACT FROM AUTHOR]

2D ternary semiconductor single crystals, an emerging class of new materials, have attracted significant interest recently owing to their great potential for academic interest and practical application. In addition to other types of metal dichalcogenides, 2D tin dichalcogenides are also important layered compounds with similar capabilities. Yet, multi-elemental single crystals enable to assist multiple degrees of freedom for dominant physical properties via ratio alteration. This study reports the growth of single crystals Se-doped SnS2 or SnSSe alloys, and demonstrates their capability for the fabrication of phototransistors with high performance. Based on exfoliation from bulk high quality single crystals, this study establishes the characteristics of few-layered SnSSe in structural, optical, and electrical properties. Moreover, few-layered SnSSe phototransistors are fabricated on both rigid (SiO2/Si) and versatile polyethylene terephthalate substrates and their optoelectronic properties are examined. SnSSe as a phototransistor is demonstrated to exhibit a high photoresponsivity of about 6000 A W−1 with ultra-high photogain [ABSTRACT FROM AUTHOR]

ZnO films on Al2O3 (112 $\bar2$0) with excellent transport properties were grown using metalorganic chemical vapor deposition (MOCVD) with a high speed rotating disk and a separated showerhead. Diisopropylzinc and tert -butanol were used as Zn and O precursors, respectively. Hall-effect measurements revealed that the ZnO films in this work showed a high mobility of 140 cm2/Vs and a low carrier concentration of 1.5×1017 cm-3, both of which are comparable to those grown by molecular beam epitaxy or pulsed laser deposition. This report should open a way to the mass production of single crystalline ZnO films which should be usable for optoelectronic devices. (© 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [ABSTRACT FROM AUTHOR]

Injection and extraction of charges through ohmic contacts are required for efficient operation of semiconductor devices. Treatment using polar non-solvents switches polar anode surfaces, including PEDOT:PSS and ITO, from barrier-limited hole injection and extraction to ohmic behaviour. This is caused by an in-situ modification of the anode surface that is buried under a layer of organic semiconductor. The exposure to methanol removes polar hydroxyl groups from the buried anode interface, and permanently increases the work function by 0.2-0.3 eV. In the case of ITO/PEDOT:PSS/PBDTTT-CT:PC71BM/Al photovoltaic devices, the higher work function promotes charge transfer, leading to p-doping of the organic semiconductor at the interface. This results in a two-fold increase in hole extraction rates which raises both the fill factor and the open-circuit voltage, leading to high power conversion efficiency of 7.4%. In ITO/PEDOT:PSS/F8BT/Al polymer light-emitting diodes, where the organic semiconductor's HOMO level lies deeper than the anode Fermi level, the increased work function enhances hole injection efficiency and luminance intensity by 3 orders of magnitude. In particular, hole injection rates from PEDOT:PSS anodes are equivalent to those achievable using MoO3. These findings exemplify the importance of work function control as a tool for improved electrode design, and open new routes to device interfacial optimization using facile solvent processing techniques. Such simple, persistent, treatments pave the way towards low cost manufacturing of efficient organic optoelectronic devices. [ABSTRACT FROM AUTHOR]

We demonstrate rectifying Schottky diodes fabricated using as-grown single-walled carbon nanotubes (SWNT) ensembles, without removing the metallic SWNTs, for optoelectronic device applications. The SWNTs are contact by a low work-function metal through a high-bandgap charge-blocking layer (ZnO) resulting in highly-nonlinear current-voltage properties compared to control ensemble SWNT devices, fabricated without a charge-blocking layer, which show resistive behaviour. This significant improvement in diode behaviour is obtained by reducing source-drain leakage from the metallic SWNTs using the charge-blocking layer which channels charge transport via the semiconducting SWNTs. Moreover, we explore an alternative method of creating the charge barrier layer via oxidizing a thin film of Zn deposited on directly on the SWNTs which could potentially reduce cost and increasing scalability of this technique to obtain highly rectifying diodes from as-grown ensemble SWNTs. [ABSTRACT FROM AUTHOR]

Water/alcohol-soluble conjugated polymers (WSCPs) and small molecules (WSCSs) are materials that can be processed from water or other polar solvents. They provide good opportunities to fabricate multilayer organic optoelectronic devices without interface mixing by solution processing, and exhibit a promising interface modification ability for metal or metal oxide electrodes to greatly enhance the device performance of solar cells. Moreover, owing to their intriguing processability, WSCPs and WSCSs have great potential for applying environmentally friendly processing technologies to fabricate solar cells. In this review, the authors give an overview of recent developments in WSCPs and WSCSs, including their molecular design, material synthesis, functional principles and application as interface modification layers and photoactive components in emerging photovoltaic technologies such as organic/polymer solar cells, organic–inorganic hybrid solar cells and dye-sensitised solar cells. [ABSTRACT FROM AUTHOR]

The design, synthesis, and characterization of new organic semiconductors (OSCs) are important aspects for the development of next-generation optoelectronic devices. Structurally, organic semiconductors based on π-conjugated molecules can be easily modified via rational synthesis to tune multi-level self-assembled structures and discover novel chemical, optical, and electronic properties. Heteroarenes, which contain chalcogens and nitrogens in fused aromatic rings, are being developed as promising semiconducting materials for applications in a variety of electronic devices due to their outstanding optoelectronic properties. We highlight recent approaches toward realizing high performance p-channel field effect transistors based on linear heteroacenes and heteroatom annulated polycyclic aromatics (PAHs) as key functional components. These comprehensive, but carefully orchestrated approaches simultaneously address (i) practical synthesis, (ii) tunable self-assembled packing arrangement as well as (iii) high electronic performance. [ABSTRACT FROM AUTHOR]

Organic and printed electronics technologies require conductors with a work function that is sufficiently low to facilitate the transport of electrons in and out of various optoelectronic devices. We show that surface modifiers based on polymers containing simple aliphatic amine groups substantially reduce the work function of conductors including metals, transparent conductive metal oxides, conducting polymers, and graphene. The reduction arises from physisorption of the neutral polymer, which turns the modified conductors into efficient electron-selective electrodes in organic optoetectronic devices. These polymer surface modifiers are processed in air from solution, providing an appealing alternative to chemically reactive low-work function metals. Their use can pave the way to simplified manufacturing of tow-cost and large-area organic electronic technologies. [ABSTRACT FROM AUTHOR]

In machining as a result of the cutting motion, the surface of workpiece will be influenced by cutting parameters, cutting force and vibrations etc. But the effects of vibrations have been paid less attention. Thus, by monitoring the machined surface topography of the workpiece and extracting the relevant information the cutting process and tool wear state should be able to be monitored and quantified. In a automated manufacturing systems, an accurate detection of the tool conditions under given cutting conditions so that worn tools can be identified and replaced in time. This work is aimed at to predict the effects of displacements due to vibration during face milling and to examine the surface topography of different workpiece materials so as to develop a base for on-line tool condition monitoring system. First part consists of a data acquisition and signal processing using acousto optic emission sensor (i.e., laser doppler vibrometer) for on line tool condition monitoring and the second part of the work presents the vision based surface topography analysis of machined surfaces during the progression of the tool wear. The encouraging results of the work paves the way for the development of a real-time, low-cost, and reliable tool-condition-monitoring system. [ABSTRACT FROM AUTHOR]

Abstract: The current state of focal plane arrays (FPAs) made from quantum well infrared photodetectors (QWIPs) is presented. In the last decade, QWIP technology has successfully transitioned at several companies from research and development to manufacturing and, today, represents a commercial success in cooled high-performance longwave infrared imaging. Technical performance metrics such as quantum efficiency, temporal and spatial noise, maximum frame rate and operating temperature, array uniformity and pixel operability, and manufacturing reproducibility are presented. [Copyright &y& Elsevier]

Abstract: Solid-state photomultipliers (SSPMs) are a compact, lightweight, potentially low-cost alternative to a photomultiplier tube for a variety of scintillation detector applications, including digital-dosimeter and medical-imaging applications. Manufacturing SSPMs with a commercial CMOS process provides the ability for rapid prototyping, and facilitates production to reduce the cost. RMD designs CMOS SSPM devices that are fabricated by commercial foundries. This work describes the characterization and performance of these devices for scintillation detector applications. This work also describes the terms contributing to device noise in terms of the excess noise of the SSPM, the binomial statistics governing the number of pixels triggered by a scintillation event, and the background, or thermal, count rate. The fluctuations associated with these terms limit the resolution of the signal pulse amplitude. We explore the use of pixel-level signal conditioning, and characterize the performance of a prototype SSPM device that preserves the digital nature of the signal. In addition, we explore designs of position-sensitive SSPM detectors for medical imaging applications, and characterize their performance. [ABSTRACT FROM AUTHOR]

Machining of Kevlar laminates with conventional methods results in poor end-product quality and excessive specific energy requirement for machining. However, laser machining has considerable advantages over the conventional methods due to precision and rapid processing. In the present study, laser hole cutting into Kevlar laminates with different thicknesses and properties is carried out. The laser output power, frequency, and cutting speed are varied during the hole-cutting experiments. The specific energy requirements for cutting, thermal efficiency of the cutting process, and kerf width are formulated and predicted for various laser parameters and Kevlar properties. The cut quality is associated with the damage size around the holes cut and statistical analysis is carried out to examine the affecting parameters on the damaged size. It is found that specific energy requirement is significantly lower than that of the conventional drilling method. The damage size is affected significantly by the laser irradiated power. The quality of holes, as judged by the percentage of damage size around the cut edges cut by a laser beam, is considerably improved compared to the conventional methods. [ABSTRACT FROM AUTHOR]

This paper presents a novel reverse engineering digitizing system for full part geometry, which is based on a cross-sectional imaging device built in a NC milling machine. The system successively captures a picture for each planar cross-section contour of the part by end-milling and CCD imaging, and builds the geometry for both external and internal surfaces of the complex 3D part based on a set of the vectored cross-sectional contours. The system mainly consists of three components: a NC milling machine, a cross-sectional imaging device and a computer control unit. Some issues involving the principle and process flow of the system, encasing materials, cross-sectional imaging and NC code generation, etc. are described in detail. Built on an existing NC milling machine, a portable device for capturing the cross-sectional images is designed, which includes an isolated light source, a digital camera, a protective case, a rigid arm and a robust tripod. The device, connected to a computer control unit, serves as a highly flexible accessory for the NC milling machine, constructing the cross-sectional imaging system for reverse engineering. Furthermore, the error analysis and accuracy assessment of the system are also addressed. A typical case is discussed in detail to illustrate the applications of the system. Such a re-configurable digitizing system for reverse engineering offers a number of advantages, such as the functional extension of an existing NC milling machine, low costs, and rapid construction. As a result, this system provides a feasible and useful scheme for many enterprises to construct their own reverse measuring system based on existing equipment to aid in rapid product development and extend the function of existing equipment. [ABSTRACT FROM AUTHOR]

Sub-ppm hydrogen chloride (HCl) and water vapour (H2O) monitoring using photoacoustic spectroscopy in optical fibre manufacturing is reported. The development and performance of a sensor based on an acoustic resonant configuration is described, and on-site measurements are presented. Two DFB lasers emitting in the 1370 nm and 1740 nm range were used for the detection of H2O and HCl, respectively. A detection limit (defined for a SNR=3) of 60 ppb for HCl and 40 ppb for H2O was achieved. Contamination sources of the carrier gas used for the fibre preform manufacturing are identified and discussed. [ABSTRACT FROM AUTHOR]

In this paper, a flexible microassembly system based on hybrid manipulation scheme is proposed to apply to the assembly of photonics components such as lensed optical fiber ferrules and laser diode (LD) pumps. In order to achieve both high precision and dexterity in microassembly, we propose a hybrid microassembly system with sensory feedbacks of vision and force. This system consists of the distributed six degrees of freedom (DOF) micromanipulation units, the stereomicroscope, and haptic interface for the force feedback-based microassembly. A hybrid assembly method, which combines the vision-based microassembly and the scaled teleoperated microassembly with force feedback, is proposed. The feasibility of the proposed method is investigated via experimental studies for assembling micro-optoelectrical components. Experimental results show that the hybrid microassembly system is feasible for applications to the assembly of photonic components in the commercial market with better flexibility and efficiency. [ABSTRACT FROM AUTHOR]