Fully-printed,all-polymer,bendable and highly transparent complementary logic circuits

In this contribution we show a simple approach for the development of all-polymer based complementary logic circuits fabricated by printing on plastic, at low temperature and in ambient conditions. This is achieved by patterning, with a bottom-up approach, solely synthetic carbon-based materials, thus incorporating earth-abundant elements and enabling in perspective the recycling – a critical aspect for low-cost, disposable electronics. Though very simple, the approach leads to logic stages with a delay down to 30 μs, the shortest reported to date for all-polymer circuits, where each single component has been printed. Moreover, our circuits combine bendability and high transparency, favoring the adoption in several innovative applications for portable and wearable large-area electronics.     

Organic light-emitting diodes on shape memory polymer substrates for wearable electronics

Green electrophosphorescent organic light-emitting diodes (OLEDs) with inverted top-emitting structures are demonstrated on bio-compatible shape memory polymer (SMP) substrates for wearable electronic applications. The combination of the unique properties of SMP substrates with the light-emitting properties of OLEDs pave to the way for new applications, including conformable smart skin devices, minimally invasive biomedical devices, and flexible lighting/display technologies. In this work, SMPs were designed to exhibit a considerable drop in modulus when a thermal stimulus is applied, allowing the devices to bend and conform to new shapes when its glass transition temperature is reached. These SMP substrates were synthesized using 1,3,5-triallyl-1,3,5-triazine-2,4,6(1H,3H,5H)-trione (TATATO), trimethylolpropane tris(3-mercaptopropionate) (TMTMP), and tricyclo[5.2.1.0^2,6]decanedimethanol diacrylate (TCMDA), and show a low glass transition temperature of 43 °C, as measured using dynamic mechanical analysis (DMA). The OLEDs fabricated on these substrates exhibit high performance with a maximum efficacy of 33 cd/A measured at a luminance of 1000 cd/m², and a peak luminance of over 30,000 cd/m².     

Flexible Inorganic Ferroelectric Thin Films for Nonvolatile Memory Devices

Next‐generation wearable electronics call for flexible nonvolatile devices for ubiquitous data storage. Thus far, only organic ferroelectric materials have shown intrinsic flexibility and processability on plastic substrates. Here, it is shown that by controlling the heating rate, ferroelectric hafnia films can be grown on plastic substrates. The resulting highly flexible capacitor with a film thickness of 30 nm yields a remnant polarization of 10 µC cm^?2. Bending tests show that the film ferroelectricity can be retained under a bending radius below 8 mm with up to 1000 bending cycles. The excellent flexibility is due to the extremely thin hafnia film thickness. Using the ferroelectric film as a gate insulator, a low voltage nonvolatile vertical organic transistor is demonstrated on a plastic substrate with an extrapolated date retention time of up to 10 years.     

Dose-response functions for historic paper

Paper degradation has been studied extensively over the past few decades from both the conservation and the material science perspectives. This review focuses on the quantifiable impacts of the environment and material composition, from the viewpoint of long-term storage of historic paper-based collections. Therefore, temperature, relative humidity and their variation, and pollution are of major interest while photoinitiated processes are covered only briefly.New experiments comparing the effects of the most abundant indoor pollutants (NO₂, acetic acid and formaldehyde) and the effects of fluctuating temperature and relative humidity are also presented as part of the discussion. This work highlights the need for revision of the existing dose-response (damage) functions for paper and their further development.     

Novel Eco‐Friendly Starch Paper for Use in Flexible,Transparent, and Disposable Organic Electronics

An eco‐friendly biodegradable starch paper is introduced for use in next‐generation disposable organic electronics without the need for a planarizing layer. The starch papers are formed by starch gelatinization using a very small amount of 0.5 wt% polyvinyl alcohol (PVA), a polymer that bound to the starch, and 5 wt% of a crosslinker that bound to the PVA to improve mechanical properties. This process minimizes the additions of synthetic materials. The resultant starch paper provides a remarkable mechanical strength and stability under repeated movements. Robustness tests using various chemical solvents are conducted by immersing the starch paper for 6 h. Excellent nonpolar solvent stabilities are observed. They are important for the manufacture of organic electronics that use nonpolar solution processes. The applicability of the starch paper as a flexible substrate is tested by fabricating flexible organic transistors using pentacene, dinaphtho[2,3‐b:2′,3′‐f]thieno[3,2‐b]thiophene, and poly(dimethyl‐triarylamine) using both vacuum and solution processes. Electrically well‐behaved device performances are identified. Finally, the eco‐friendly biodegradability is verified by subjecting the starch paper to complete degradation by fungi in fishbowl water over 24 d. These developments illuminate new research areas in the field of biodegradable green electronics, enabling the development of extremely low‐cost electronics.     

Gaussian distribution model for gate-to-channel capacitance for carbon nanotube field-effect transistor

ABSTRACT

In this paper, a carbon nanotube (CNT) field-effect transistor gate-to-channel capacitance Gaussian distribution model is proposed. The proposed model is based on the assumption of random placement of CNTs within the channel region, in lieu of the traditional uniform distribution exhibited in the literature. The proposed model is inspired from the fact that the nanotubes in the central region along the channel that are more closely packed together yield a lower capacitance value over those that are widely spaced towards the edges. The Gaussian model as presented in this paper offers more accuracy to simulation results, where simulation results reveal that this model provides more practical answers for gate-to-channel capacitance, with higher percentages of improvement regarding energy consumption by the transistor. Moreover, the effects of several parameters such as type of material, tube diameter and the tube–gate distance have been evaluated using the proposed model.     

Synthesis of a versatile pentacyclic building block for organic electronics

A new pentacyclic building block, benzodibenzofuranquinone (BDBFQ), is synthesized in a single step from the inexpensive and readily available feedstocks chloranil and 3‐bromophenol. This versatile repeat unit is incorporated into a series of conjugated materials as either the redox active quinone form or as an electron‐rich dialkylated benzodibenzofuran (BDBF) unit. To illustrate the performance that can be obtained from these systems, optical and electrochemical properties were studied via UV–vis–NIR spectroscopy and cyclic voltammetry. Thin‐film morphology was characterized via grazing incidence wide‐angle X‐ray scattering with thin‐film field‐effect transistor measurements further demonstrating the utility of this system. © 2017 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2017 , 55, 2618–2628     

Electrical–thermal aging characteristic research of polymer materials by infrared spectroscopy,

Traditional insulation paper (pressboard) used in power transformers has weaknesses such as poor thermostability, low breakdown voltage, and high permittivity, which leads to its degradation or even breakdown over time. For this paper, in order to judge if they could be used as new insulation materials for transformers, polycarbonate and polyester films were selected for electrical–thermal aging tests in temperatures of 110°C and 130°C in comparison with the insulation paper. Several infrared spectral tests were carried out on the three materials under a scanning electron microscope to analyze their electrical–thermal aging characteristics, mechanical behaviors, and degrees of polymerization. The functional group whose absorption peak intensity decreased drastically with aging was referred to as the characteristic functional group, and its peak absorption intensity was used to reflect its aging level. This paper found that the polycarbonate had a better aging resistance than both the insulation paper and PET. Copyright © 2014 John Wiley & Sons, Ltd.