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Biological compounds often provide clues to advance material designs. Replicating their molecular structure and functional motifs in artificial materials offers a blueprint for unprecedented functionalities. Here, we report a flexible biomimetic thermal sensing (BTS) polymer that is designed to emulate the ion transport dynamics of a plant cell wall component, pectin. Using a simple yet versatile synthetic procedure, we engineer the physicochemical properties of the polymer by inserting elastic fragments in a block copolymer architecture, making it flexible and stretchable. The thermal response of our flexible polymer outperforms current state-of-the-art temperature sensing materials, including vanadium oxide, by up to two orders of magnitude. Thermal sensors fabricated from these composites exhibit a sensitivity that exceeds 10 mK and operate stably between 15° and 55°C, even under repeated mechanical deformations. We demonstrate the use of our flexible BTS polymer in two-dimensional arrays for spatiotemporal temperature mapping and broadband infrared photodetection.

Silent communication based on biosignals from facial muscle requires accurate detection of its directional movement and thus optimally positioning minimum numbers of sensors for higher accuracy of speech recognition with a minimal person-to-person variation. So far, previous approaches based on electromyogram or pressure sensors are ineffective in detecting the directional movement of facial muscles. Therefore, in this study, high-performance strain sensors are used for separately detecting

Intrinsically stretchable electronics can form intimate interfaces with the human body, creating devices that could be used to monitor physiological signals without constraining movement. However, mechanical strain invariably leads to the degradation of the electronic properties of the devices. Here we show that strain-insensitive intrinsically stretchable transistor arrays can be created using an all-elastomer strain engineering approach, in which the patterned elastomer layers with tunable stiffnesses are incorporated into the transistor structure. By varying the cross-linking density of the elastomers, areas of increased local stiffness are introduced, reducing strain on the active regions of the devices. This approach can be readily incorporated into existing fabrication processes, and we use it to create arrays with a device density of 340 transistors cm–2 and a strain insensitivity of less than 5% performance variation when stretched to 100% strain. We also show that it can be used to fabricate strain-insensitive circuit elements, including NOR gates, ring oscillators and high-gain amplifiers for the stable monitoring of electrophysiological signals. An all-elastomer strain engineering approach, which uses patterned elastomer layers with tunable stiffnesses, can be used to create intrinsically stretchable transistor arrays with a device density of 340 transistors cm–2 and strain insensitivity of less than 5% performance variation when stretched to 100% strain.

The cathode material, high Nickel content Ni0.7Co0.2Mn0.1 (NCM), was synthesized by coprecipitation with NH4OH used as a complexing agent. The prepared materials are made in the formation of spherical particles of Li(Ni0.7Co0.2Mn0.1)O2 of several micrometers in diameter. Al2O3 was coated by an impregnation method and its content was gradually increased to 1, 2 and 5 wt%. As a result, 1 wt% coated Al2O3 compared to pristine NCM exhibited 82% and 80% retention rates at 5 C and 1 wt% Al2O3 coated NCM recovery at 0.2 C after 5 C showed 100%. In addition, capacity retention of 1 wt% NCM+Al gently decreased in 100 cycle life characteristics, and capacity retention of 95% or more was confirmed.

Organic semiconductors (OSCs) are of interest for replacing traditional Si-based semiconductors as their flexibility and transparency enable new applications. The properties of OSC materials greatly depend on their orientation and molecular arrangement, which are strongly dependent on the underlying substrate material. Hence, in this study, in situ ultraviolet photoelectron spectroscopy (UPS) is used to elucidate the effect of the substrate on OSC orientation. Two types of OSCs, namely those with shape anisotropy (pentacene, dinaphtho[2,3-b:2',3'-f]thieno[3,2-b]thiophene, and dibenzothiopheno[6,5-b:6',5'-f]thieno[3,2-b]thiophene) and those with shape isotropy (N,N'-di(1-naphthyl)-N,N'-diphenyl-(1,1'-biphenyl)-4,4'-diamine, tris(4-carbazoyl-9-ylphenyl)amine, and [6,6]-phenyl C71 butyric acid methyl ester), are deposited on different electrode materials. The differences in the UPS spectra of these materials are observed directly. In general, the orientation of anisotropic OSC molecules significantly depends on the substrate properties, while that of the isotropic ones do not. All the anisotropic OSC molecules grown on poly(3,4-ethylenedioxythiophene)-polystyrenesulfonate (PEDOT:PSS) electrodes show a greater degree of molecular ordering than those grown on Au and multiwalled carbon nanotube/PEDOT:PSS electrodes. The molecular arrangements within the OSC/electrode structures are reflected in the energy-level shifts in the corresponding UPS spectra and hence in the electronic configurations. The results of this study should aid the design and synthesis of OSC materials with configurations suitable for organic electronic devices.

Strategies to improve stretchability of polymer semiconductors, such as introducing flexible conjugation-breakers or adding flexible blocks, usually result in degraded electrical properties. In this work, we propose a concept to address this limitation, by introducing conjugated rigid fused-rings with optimized bulky side groups and maintaining a conjugated polymer backbone. Specifically, we investigated two classes of rigid fused-ring systems, namely, benzene-substituted dibenzothiopheno[6,5-b:6',5'-f]thieno[3,2-b]thiophene (Ph-DBTTT) and indacenodithiophene (IDT) systems, and identified molecules displaying optimized electrical and mechanical properties. In the IDT system, the polymer PIDT-3T-OC12-10% showed promising electrical and mechanical properties. In fully stretchable transistors, the polymer PIDT-3T-OC12-10% showed a mobility of 0.27 cm2 V-1 s-1 at 75% strain and maintained its mobility after being subjected to hundreds of stretching-releasing cycles at 25% strain. Our results underscore the intimate correlation between chemical structures, mechanical properties, and charge carrier mobility for polymer semiconductors. Our described molecular design approach will help to expedite the next generation of intrinsically stretchable high-performance polymer semiconductors.

A body area sensor network (bodyNET) is a collection of networked sensors that can be used to monitor human physiological signals. For its application in next-generation personalized healthcare systems, seamless hybridization of stretchable on-skin sensors and rigid silicon readout circuits is required. Here, we report a bodyNET composed of chip-free and battery-free stretchable on-skin sensor tags that are wirelessly linked to flexible readout circuits attached to textiles. Our design offers a conformal skin-mimicking interface by removing all direct contacts between rigid components and the human body. Therefore, this design addresses the mechanical incompatibility issue between soft on-skin devices and rigid high-performance silicon electronics. Additionally, we introduce an unconventional radiofrequency identification technology where wireless sensors are deliberately detuned to increase the tolerance of strain-induced changes in electronic properties. Finally, we show that our soft bodyNET system can be used to simultaneously and continuously analyse a person’s pulse, breath and body movement. By integrating wireless stretchable on-skin sensor tags and flexible readout circuits attached to textiles using an unconventional radiofrequency identification design, a body area sensor network can be created that can continuously analyse a person’s pulse, breathing and body movement.

A solution-processable organic–inorganic hybrid material composed of a polysiloxane urethane acrylate composite (PSUAC) was developed through a dual cross-linking mechanism and satisfies all the requirements for use as a gate dielectric for flexible organic thin-film transistors (OTFTs). PSUACs incorporate the urethane group for promoting adhesion to substrates and the acrylate group for enhancing the degree of cross-linking via a photo-curing reaction. Aluminium acetoacetate is introduced as a thermal curing agent that reacts with the silanols at the end of the PSUA resin, thus realizing a reliable dielectric that is barely affected by the slow polarization induced by moisture absorption. Thin films of the cross-linked PSUAC provided smooth surfaces with a root-mean-square roughness of 6.2 MV cm−1, while the capacitance was only slightly affected by the frequency. A self-assembled monolayer (SAM) of octadecyltrichlorosilane (ODTS) was formed on the cross-linked PSUAC dielectric to provide a hydrophobic surface with a water-contact angle of 107°. OTFTs employing a small-molecule organic semiconductor of dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene (DBTTT) were fabricated using the cross-linked PSUAC as a gate dielectric. These realized a high mobility of 3.3 cm2 V−1 s−1 and an on/off ratio of >107 without any hysteresis in the transfer characteristics. The threshold voltage was shifted by about 2 V in the bias stress measurement conducted for 10 000 s on non-passivated devices exposed in air, verifying the stable characteristics of the gate dielectric layer even without passivation of the device. Flexible OTFTs on a polyimide (PI) substrate were fabricated and identical electrical properties with a mobility of 3.3 cm2 V−1 s−1 were confirmed. PSUAC can be used as a reliable gate dielectric for high-performance OTFT devices including flexible applications.

As a key component in stretchable electronics, semiconducting polymers have been widely studied. However, it remains challenging to achieve stretchable semiconducting polymers with high mobility and mechanical reversibility against repeated mechanical stress. Here, we report a simple and universal strategy to realize intrinsically stretchable semiconducting polymers with controlled multi-scale ordering to address this challenge. Specifically, incorporating two types of randomly distributed co-monomer units reduces overall crystallinity and longer-range orders while maintaining short-range ordered aggregates. The resulting polymers maintain high mobility while having much improved stretchability and mechanical reversibility compared with the regular polymer structure with only one type of co-monomer units. Interestingly, the crystalline microstructures are mostly retained even under strain, which may contribute to the improved robustness of our stretchable semiconductors. The proposed molecular design concept is observed to improve the mechanical properties of various p- and n-type conjugated polymers, thus showing the general applicability of our approach. Finally, fully stretchable transistors fabricated with our newly designed stretchable semiconductors exhibit the highest and most stable mobility retention capability under repeated strains of 1,000 cycles. Our general molecular engineering strategy offers a rapid way to develop high mobility stretchable semiconducting polymers., Designing intrinsically stretchable semiconducting polymers with suitable charge transport and mechanical properties required for stretchable electronic devices remains a challenge. Here, the authors report terpolymer-based semiconductors with intrinsically high stretchability and mobility.

A skin-like electronic health care patch is demonstrated with a stretchable organic light-emitting diode display and photodiode., Skin-like health care patches (SHPs) are next-generation health care gadgets that will enable seamless monitoring of biological signals in daily life. Skin-conformable sensors and a stretchable display are critical for the development of standalone SHPs that provide real-time information while alleviating privacy concerns related to wireless data transmission. However, the production of stretchable wearable displays with sufficient pixels to display this information remains challenging. Here, we report a standalone organic SHP that provides real-time heart rate information. The 15-μm-thick SHP comprises a stretchable organic light-emitting diode display and stretchable organic photoplethysmography (PPG) heart rate sensor on all-elastomer substrate and operates stably under 30% strain using a combination of stress relief layers and deformable micro-cracked interconnects that reduce the mechanical stress on the active optoelectronic components. This approach provides a rational strategy for high-resolution stretchable displays, enabling the production of ideal platforms for next-generation wearable health care electronics.

Intrinsically and fully stretchable active-matrix-driven displays are an important element to skin electronics that can be applied to many emerging fields, such as wearable electronics, consumer electronics and biomedical devices. Here, we show for the first time a fully stretchable active-matrix-driven organic light-emitting electrochemical cell array. Briefly, it is comprised of a stretchable light-emitting electrochemical cell array driven by a solution-processed, vertically integrated stretchable organic thin-film transistor active-matrix, which is enabled by the development of chemically-orthogonal and intrinsically stretchable dielectric materials. Our resulting active-matrix-driven organic light-emitting electrochemical cell array can be readily bent, twisted and stretched without affecting its device performance. When mounted on skin, the array can tolerate to repeated cycles at 30% strain. This work demonstrates the feasibility of skin-applicable displays and lays the foundation for further materials development., To realize a skin-like display for human-electronics interfaces, intrinsically stretchable light-emitting, transistor and device interconnect components are needed. Here, the authors report a fully stretchable transistor driven active-matrix organic light-emitting electrochemical cell array.

The cathode material, high Nickel content Ni

A hybrid gate dielectric material for flexible OTFT is developed by using core–shell nanoparticles (SiO2@PSRXL) where the core and the shell consist of silica nanoparticles and polysiloxane resin, respectively. Since polysiloxane resin contains both thermal- and photo-crosslinkable functional groups, densely-crosslinked thin gate dielectric films can be easily prepared on various substrates by conventional solution casting followed by dual crosslinking. SiO2@PSRXL films exhibit high thermal stability (weight loss at 300 °C is smaller than 3 wt%). The dielectric films made of SiO2@PSRXL show an exceptionally low leakage current and no breakdown voltage up to 4.3 MV cm−1, which are comparable to those of silica dielectrics prepared by CVD. OTFT devices based on dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene (DTBTT) as a semiconductor and SiO2@PSRXL as a gate dielectric exhibit good hole mobility (2.5 cm2 V−1 s−1) and Ion/Ioff ratio (106).

Molecular additives are often used to enhance dynamic motion of polymeric chains, which subsequently alter the functional and physical properties of polymers. However, controlling the chain dynamics of semiconducting polymer thin films and understanding the fundamental mechanisms of such changes is a new area of research. Here, cycloparaphenylenes (CPPs) are used as conjugated molecular additives to tune the dynamic behaviors of diketopyrrolopyrrole-based (DPP-based) semiconducting polymers. It is observed that the addition of CPPs results in significant improvement in the stretchability of the DPP-based polymers without adversely affecting their mobility, which arises from the enhanced polymer dynamic motion and reduced long-range crystalline order. The polymer films retain their fiber-like morphology and short-range ordered aggregates, which leads to high mobility. Fully stretchable transistors are subsequently fabricated using CPP/semiconductor composites as active layers. These composites are observed to maintain high mobilities when strained and after repeated applied strains. Interestingly, CPPs are also observed to improve the contact resistance and charge transport of the fully stretchable transistors. ln summary, these results collectively indicate that controlling the dynamic motion of polymer semiconductors is proved to be an effective way to improve their stretchability.

Wearable and skin electronics benefit from mechanically soft and stretchable materials to conform to curved and dynamic surfaces, thereby enabling seamless integration with the human body. However, such materials are challenging to process using traditional microelectronics techniques. Here, stretchable transistor arrays are patterned exclusively from solution by inkjet printing of polymers and carbon nanotubes. The additive, non-contact and maskless nature of inkjet printing provides a simple, inexpensive and scalable route for stacking and patterning these chemically-sensitive materials over large areas. The transistors, which are stable at ambient conditions, display mobilities as high as 30 cm2 V−1 s−1 and currents per channel width of 0.2 mA cm−1 at operation voltages as low as 1 V, owing to the ionic character of their printed gate dielectric. Furthermore, these transistors with double-layer capacitive dielectric can mimic the synaptic behavior of neurons, making them interesting for conformal brain-machine interfaces and other wearable bioelectronics., The development of novel low-cost fabrication schemes for realizing stretchable transistor arrays with applicability in wearable electronics remains a challenge. Here, the authors report skin-like electronics with stretchable active materials and devices processed exclusively from ink-jet printing.

We studied organic thin film transistors using vacuum-deposited para-sexiphenyl (p-6P) as a sublayer to reduce the surface energy of the dielectric material. The correlation between the growth mode of a thin film of the organic semiconductor dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene and the number of p-6P sublayers could be explained by a surface energy difference resulting from molecular orientation changes in the p-6P layer. A local surface energy difference was confirmed by measuring the adhesion force using a nanomechanical force measurement method.We studied organic thin film transistors using vacuum-deposited para-sexiphenyl (p-6P) as a sublayer to reduce the surface energy of the dielectric material. The correlation between the growth mode of a thin film of the organic semiconductor dibenzothiopheno[6,5-b:6′,5′-f]thieno[3,2-b]thiophene and the number of p-6P sublayers could be explained by a surface energy difference resulting from molecular orientation changes in the p-6P layer. A local surface energy difference was confirmed by measuring the adhesion force using a nanomechanical force measurement method.

Skin-inspired semiconductor that is intrinsically stretchable, self-healable, and strain-sensitive for advanced sensory devices., Skin-like sensory devices should be stretchable and self-healable to meet the demands for future electronic skin applications. Despite recent notable advances in skin-inspired electronic materials, it remains challenging to confer these desired functionalities to an active semiconductor. Here, we report a strain-sensitive, stretchable, and autonomously self-healable semiconducting film achieved through blending of a polymer semiconductor and a self-healable elastomer, both of which are dynamically cross-linked by metal coordination. We observed that by controlling the percolation threshold of the polymer semiconductor, the blend film became strain sensitive, with a gauge factor of 5.75 × 105 at 100% strain in a stretchable transistor. The blend film is also highly stretchable (fracture strain, >1300%) and autonomously self-healable at room temperature. We proceed to demonstrate a fully integrated 5 × 5 stretchable active-matrix transistor sensor array capable of detecting strain distribution through surface deformation.

We report a newly synthesized donor (D)-acceptor (A)type semiconducting copolymer, consisting of thiophene as an electron-donating unit and thiazole as an electron-accepting unit (PQTBTz-TT-C8) for the active layer of the organic field-effect transistors (OFETs). Specifically, this study investigates the structure and electrical property relationships of PQTBTz-TT-C8 with comprehensive analyses on the charge-transporting properties corresponding to the spin rate of the spin coater during the formation of the PQTBTz-TT-C8 film. The crystallinity of PQTBTz-TT-C8 films is examined with grazing incidence X-ray diffraction. Temperature-dependent transfer measurements of the OFETs are conducted to extract the density of states (DOS) and characterize the charge-transport properties. Comparative analyses on charge transports within the framework of the physical model, based on polaron hopping and Gaussian DOS, reveal that the prefactors of both physical charge-transport models are independent of the spin-coating condition for the films. For staggered structural transistors, however, the thickness of the PQTBTz-TT-C8 films, which strongly affect the series resistance along the charge-transfer path in a vertical direction, is changed in accordance with the spin-coating rate. In other words, the spin-coating rate of the PQTBTz-TT-C8 films influences the thickness of the polymer films, yet any significant changes in the crystallinity of the film or electronic coupling between the neighboring molecules upon the spin-coating condition were barely noticeable. Because the PQTBTz-TT-C8 backbone chains inside the thin film are stacked up with the edge-on, the series resistances are changed according to the thickness of the film and thus the performance of the device varies depending on the thickness.

Skin-like electronics that can adhere seamlessly to human skin or within the body are highly desirable for applications such as health monitoring, medical treatment, medical implants and biological studies, and for technologies that include human-machine interfaces, soft robotics and augmented reality. Rendering such electronics soft and stretchable-like human skin-would make them more comfortable to wear, and, through increased contact area, would greatly enhance the fidelity of signals acquired from the skin. Structural engineering of rigid inorganic and organic devices has enabled circuit-level stretchability, but this requires sophisticated fabrication techniques and usually suffers from reduced densities of devices within an array. We reasoned that the desired parameters, such as higher mechanical deformability and robustness, improved skin compatibility and higher device density, could be provided by using intrinsically stretchable polymer materials instead. However, the production of intrinsically stretchable materials and devices is still largely in its infancy: such materials have been reported, but functional, intrinsically stretchable electronics have yet to be demonstrated owing to the lack of a scalable fabrication technology. Here we describe a fabrication process that enables high yield and uniformity from a variety of intrinsically stretchable electronic polymers. We demonstrate an intrinsically stretchable polymer transistor array with an unprecedented device density of 347 transistors per square centimetre. The transistors have an average charge-carrier mobility comparable to that of amorphous silicon, varying only slightly (within one order of magnitude) when subjected to 100 per cent strain for 1,000 cycles, without current-voltage hysteresis. Our transistor arrays thus constitute intrinsically stretchable skin electronics, and include an active matrix for sensory arrays, as well as analogue and digital circuit elements. Our process offers a general platform for incorporating other intrinsically stretchable polymer materials, enabling the fabrication of next-generation stretchable skin electronic devices.

This paper examines the hedging performance with mini gold futures traded on the Korean Exchange (KRX). We use the daily prices of gold and mini gold futures from September 13, 2010 to May 31, 2013. We employ the OLS model and VECM as well as the bivariate GJR-GARCH (1,1) model. Our empirical results maintain that the time varying GJR-GARCH (1,1) model yields better hedging performance than time-invariant OLS or VECM models in the both in-sample and out-of sample periods. We thus recommend that investors consider the asymmetric dynamic hedging model when constructing the minimum-variance hedging portfolio to manage the market risk exposure of gold.

An ion-sensitive organic field-effect transistor (ISOFET) has been fabricated by using poly(3-hexylthiophene) as the semiconductor and polymethylmethacrylate as the gate insulator. With the gate metallization replaced by an Ag/AgCl reference electrode, and following suitable encapsulation, the ISOFETs exhibit transistor behavior in an aqueous environment. Moreover, the devices are shown to respond to changes in pH of the solution. A significant increase in the sensitivity of the ISOFET to H+ ions was found by depositing a Langmuir–Blodgett film of arachidic acid on top of the gate insulator.

The electrical characteristics of pentacene organic thin-film transistors (OTFTs) using cross-linked poly(methyl methacrylate) (PMMA) as the gate dielectric are reported. Ultra-thin films of cross-linked PMMA could be obtained by spin-coating and subsequent irradiation using a 1.515 MeV 4 He + ion beam. The resulting film, with a thickness of 33 nm, possessed a low leakage current density of about 10 −6 A cm −2 for fields up to 2 MV cm −1 . OTFTs incorporating the cross-linked dielectric operated at relatively low voltages, 2 V −1 s −1 , a threshold voltage of −1 V, a sub-threshold slope of 220 mV per decade and an on/off current ratio of 1.0 × 10 6 .

A bootstrapped inverter incorporating pentacene organic thin-film transistors (OTFTs), with poly(methyl methacrylate) as the gate dielectric, has been designed, fabricated and tested. The inverter uses capacitive coupling and bootstrapping effects, and exhibits superior performance to the normal diode-connected load inverter. The pentacene OTFTs used for the inverter possess a field-effect mobility of 0.32 cm2/V/s, a threshold voltage of −10.0 V, a subthreshold slope of 1.5 V per decade and an on/off current ratio of 2.2×106. The inverter has a 30 µs rise time and a 450 µs fall time, at an operating frequency of 1 kHz and 30 V drive voltage.

AMOLEDs (active-matrix organic light emitting diodes) employing poly-Si TFT have been used to integrate peripheral circuits on a glass to reduce the cost through the use of dead space on the glass. The system-on-glass (SOG) development provides enormous challenges to the developers, usually verifying the SOG by transistor-level simulation. IR-drop modeling is needed to reduce the uniformity degradation in the OLED image quality. This paper presents a full panel simulation technique for OLED driver and pixels that is integrated on a glass using the mixed-signals circuit design and the proposed process shows excellent capabilities relating to the capacity and the speed.

Interpixel uniformity is critical to image quality, and is hard to be improved by structural reformation of emissive elements because of nonuniformity in luminance characteristics of subpixels in self-emissive device like the carbon nanotube field emission display (CNT-FED). In this paper, we discuss the improvement of the interpixel uniformity by individually controlling the luminance of all subpixels in a display panel. We propose a prototype CNT-FED with improved interpixel uniformity using luminance correction circuitry. The analysis of interpixel uniformity with the proposed luminance correction circuit shows that the index of interpixel uniformity increases about 8% with only about 10% luminance reduction ratio that is a relatively small penalty compared to the enhancement of the interpixel uniformity. The proposed correction method can also be used to ensure improvement of the interpixel uniformity in large-size CNT-FED panels.

We demonstrate a holographic image reconstructed by a FPD-based complex spatial light modulator (SLM) which is composed of a phase-only SLM and a sheet of beam combiner. A complex SLM which modulates both amplitude and phase independently is necessary for a better image quality with reducing conjugate images. The two-phase encoding method is one of the most practical candidates for the complex SLM. The proposed complex SLM is presented in a phase-only LCD panel which can be manufactured in a conventional LCD process and it was used for generating different phases. The PAL (Parallel-Aligned nematic Liquid crystal) mode is used to modulate the phase without the amplitude change. The film-type beam combiner consists of a prism array and a grating made by a conventional fabrication process. The beam combiner plays a vital role to merge two pixels and to adjust effective complex modulation. In this paper, the holographic image by the proposed complex SLM is verified by the experimental and simulation work in a monochromatic reconstruction. This complex SLM can be scaled up and it is a promising candidate SLM for a large-size holographic 3D display.

The electrical behavior of organic metal-insulator-semiconductor (MIS) structures incorporating a layer of self-assembled metallic nanoparticles is described. These have been based on thermally evaporated pentacene (semiconductor) and spin-coated polymethylmethacrylate (insulator). The MIS devices containing the nanoparticles exhibited significant hysteresis in their capacitance-versus-voltage and conductance-versus-voltage characteristics, which was attributed to the charging and discharging of the nanoparticles. The memory structure reported here offers a useful advance in the development of flexible organic memory structures.

We report on the effect of depositing the ionophore valinomycin onto the polymethylmethacrylate (PMMA) gate insulator of an ion-sensitive organic field-effect transistor (ISOFET) based on poly(3-hexylthiophene). The ionophore was deposited onto the PMMA using the Langmuir-Blodgett (LB) technique; thin films based on pure valinomycin and those in which valinomycin was mixed with arachidic acid were investigated. The pH sensitivity of the reference ISOFET could be improved significantly when the devices were coated with an LB film of arachidic acid. However, the response to was low. By adding a small amount (5% w/w) of the ionophore valinomycin to the fatty acid LB film, an improved response to potassium ions was achieved, but no selectivity over sodium. It was necessary to use an LB membrane of pure valinomycin in order to realise an ISOFET with some selectivity. We suggest that the presence of the ionophore in the fatty acid matrix disrupts the packing of the hydrocarbon chains in the mixed LB film and that the monovalent ion response originates from interactions with the carboxylic acid groups in the fatty acid. In contrast, for the case of the pure valinomycin coating, it is thought that response is controlled by complex formation with the ionophore.

The electrical characteristics of pentacene-based organic thin film transistors (OTFTs) using poly(methyl methacrylate) (PMMA) as the gate dielectric are reported. Uniform pinhole-free and crack-free films of PMMA could be obtained by spin coating, with a lower limit of thickness of about 150 nm. The effects of the insulator thickness and channel dimensions on the performance of the devices have been investigated. Leakage currents, which are present in many polymeric gate dielectrics, were reduced by patterning the pentacene active layer. The resulting devices exhibited minimal hysteresis in their output and transfer characteristics. Optimized OTFT structures possessed a field-effect mobility of 0.33 cm(2) V-1 s(-1), a threshold voltage of -4 V, a subthreshold slope of 1.5 V/decade, and an on/off current ratio of 1.2x10(6).

We report high performance reflective color filters based on one-dimensional metal-dielectric multilayer. Wide viewing angle of ±50°, far beyond that with conventional all-dielectric multilayers, is achieved while maintaining approximately 100% peak reflectance and color reproducibility. Reflectance of 40% in white mode and color gamut of 47% to the United States National Television Systems Committee (NTSC) standard is demonstrated. The proposed color filter is integrated into 3.5-in. color reflective display and shows 30% increase in brightness than conventional dye color filters.

An organic memory device based on a pentacene thin film transistor is demonstrated. Gold nanoparticles have been used as the charge storage elements while a thin film of polymethylmethacrylate formed the gate insulator. The electrical characteristics and the memory behavior of the organic thin film memory transistor (OTFMT) are reported. Under an appropriate gate bias (1 s pulses), the gold nanoparticles are charged and discharged, resulting in significant threshold voltage shifts of the OTFMT. The detailed programing and erasing procedures are reported.