Asymmetric Rolling of Interstitial-Free Steel Using Differential Roll Diameters. Part II: Microstructure and Annealing Effects

The effects of annealing on the microstructure, texture, tensile properties, and R value evolution of an IF steel sheet after room-temperature symmetric and asymmetric rolling were examined. Simulations were carried out to obtain R values from the experimental textures using the viscoplastic self-consistent polycrystal plasticity model. The investigation revealed the variations in the textures due to annealing and symmetric/asymmetric rolling and showed that the R values correlate strongly with the evolution of the texture. An optimum heat treatment for the balance of strength, ductility, and deep drawability was found to be at 873 K (600 °C) for 30 minutes.     

A High‐Capacitance Salt‐Free Dielectric for Self‐Healable,Printable, and Flexible Organic Field Effect Transistors and Chemical Sensor

Printable and flexible electronics attract sustained attention for their low cost, easy scale up, and potential application in wearable and implantable sensors. However, they are susceptible to scratching, rupture, or other damage from bending or stretching due to their “soft” nature compared to their rigid counterparts (Si‐based electronics), leading to loss of functionality. Self‐healing capability is highly desirable for these “soft” electronic devices. Here, a versatile self‐healing polymer blend dielectric is developed with no added salts and it is integrated into organic field transistors (OFETs) as a gate insulator material. This polymer blend exhibits an unusually high thin film capacitance (1400 nF cm^?2 at 120 nm thickness and 20–100 Hz). Furthermore, it shows pronounced electrical and mechanical self‐healing behavior, can serve as the gate dielectric for organic semiconductors, and can even induce healing of the conductivity of a layer coated above it together with the process of healing itself. Based on these attractive properties, we developed a self‐healable, low‐voltage operable, printed, and flexible OFET for the first time, showing promise for vapor sensing as well as conventional OFET applications.     

Emerging Scanning Probe–Based Setups for Advanced Nanoelectronic Research

Scanning probe microscopy (SPM) refers to a family of techniques that have become essential to study many different properties of materials and devices at the nanoscale. All of them have in common that they use an ultrasharp probe tip to scan the surface of a sample. However, although many of these techniques are interrelated, some of them have become very sophisticated and require specific and deep study. While there are plenty of review articles available for most of these techniques, newer developments need to be carefully analyzed in a critical manner in order to promote their development. In this progress report, some of the newest SPM‐based developments that are expected to generate a larger impact in the field of nanoelectronics are discussed, and critical advice on how to improve each of them is provided. In particular, the combination of wear and electrical tests; scanning gate microscopy; the integration of conductive atomic force microscopy into scanning electron microscopy; and the integration of a scanning probe into transmission electron microscopy, multiprobe scanning tunneling microscopy, multiprobe atomic force microscopy, and fountain‐pen nanolithography are focused on.     

Electronic Transport Properties of Ensembles of Perylene‐Substituted Poly‐isocyanopeptide Arrays

The electronic transport properties of stacks of perylene‐bis(dicarboximide) (PDI) chromophores, covalently fixed to the side arms of rigid, helical polyisocyanopeptides, are studied using thin‐film transistors. In device architectures where the transistor channel lengths are somewhat greater than the average polymer chain length, carrier mobilities of order 10^?3 cm² V^?1 s^?1 at 350 K are found, which are limited by inter‐chain transport processes. The influence of π–π interactions on the material properties is studied by using PDIs with and without bulky substituents in the bay area. In order to attain a deeper understanding of both the electronic and the electronic‐transport properties of these systems, studies of self‐assembly on surfaces are combined with electronic characterization using Kelvin probe force microscopy, and also a theoretical study of electronic coupling. The use of a rigid polymer backbone as a scaffold to achieve a full control over the position and orientation of functional groups is of general applicability and interest in the design of building blocks for technologically important functional materials, as well as in more fundamental studies of chromophoric interactions.     

Luminescent Tags on Fullerenes: Eu3+ Complexes with Pendant Fullerenes

Novel fullerene‐containing Eu (III) complexes are obtained by mixing a fullerene derivative bearing chelating pyridinyl groups with an Eu (III) complex possessing three coordinated 4,4,4,‐trifluoro‐1‐(2‐naphtyl)‐1,3‐butanedione residues and two water molecules. One of the complexes designed is formed in water using a water‐soluble fullerene derivative as a precursor material. We investigate the photophysical properties of this new type of highly soluble self‐assembled fullerene‐derivative Eu³⁺ coordination compounds. A strong emission line of the Eu³⁺ 4f–4f transition is recorded under excitation with UV irradiation. The behaviour of the complexes in organic matrices and water is studied as the first steps towards luminescence tagged fullerene derivatives for use in biomedicine and optoelectronics.     

In vivo quantitative MRI: T1 and T2 measurements of the human brain at 0.064 T

Objective

To measure healthy brain \({T}_{1}\) and \({T}_{2}\) relaxation times at 0.064 T.

Materials and methods

\({T}_{1}\) and \({T}_{2}\) relaxation times were measured in vivo for 10 healthy volunteers using a 0.064 T magnetic resonance imaging (MRI) system and for 10 test samples on both the MRI and a separate 0.064 T nuclear magnetic resonance (NMR) system. In vivo \({T}_{1}\) and \({T}_{2}\) values are reported for white matter (WM), gray matter (GM), and cerebrospinal fluid (CSF) for automatic segmentation regions and manual regions of interest (ROIs).

Results

\({T}_{1}\) sample measurements on the MRI system were within 10% of the NMR measurement for 9 samples, and one sample was within 11%. Eight \({T}_{2}\) sample MRI measurements were within 25% of the NMR measurement, and the two longest \({T}_{2}\) samples had more than 25% variation. Automatic segmentations generally resulted in larger \({T}_{1}\) and \({T}_{2}\) estimates than manual ROIs.

Discussion

\({T}_{1}\) and \({T}_{2}\) times for brain tissue were measured at 0.064 T. Test samples demonstrated accuracy in WM and GM ranges of values but underestimated long \({T}_{2}\) in the CSF range. This work contributes to measuring quantitative MRI properties of the human body at a range of field strengths.