The quality of the polymer raw material used in plastic processing methods is an important characteristic because it is one of the main factors in producing quality products. Therefore, the characterization of polymeric pellets in the polymer processing industry is very important to avoid using inferior materials. In general, differences in the interiors of polymeric pellets reflect differences in their densities. In this study, a high-sensitivity magnetic levitation method was used to characterize the polymeric pellets in four different occasions. The device used has a high sensitivity that can distinguish minute differences as small as of 0.0041 g/cm3 in density between different samples. In addition, the method can obtain a sample's density without knowing the weight and volume of the sample. This method can be used to characterize materials by testing only a single pellet, which is very useful for polymeric pellet characterization.

We examined a working hypothesis of sticky thermoelectric (TE) materials, which is inversely designed to mass-produce flexible TE sheets with lamination or roll-to-roll processes without electric conductive adhesives. Herein, we prepared p-type and n-type sticky TE materials via mixing antimony and bismuth powders with low-volatilizable organic solvents to achieve a low thermal conductivity. Since the sticky TE materials are additionally injected into punched polymer sheets to contact with the upper and bottom electrodes in the fabrication process, the sticky TE modules of ca. 2.4 mm in thickness maintained temperature differences of ca. 10°C and 40°C on a hot plate of 40 °C and 120°C under a natural-air cooling condition with a fin. In the single-cell resistance analysis, we found that 75∼150-µm bismuth powder shows lower resistance than the smaller-sized one due to the fewer number of particle-particle interfaces in the electric pass between the upper and bottom electrodes. After adjusting the printed wiring pattern for the upper and bottom electrodes, we achieved 42 mV on a hot plate (120°C) with the 6 x 6 module having 212 Ω in the total resistance. In addition to the possibility of mass production at a reasonable cost, the sticky TE materials provide a low thermal conductivity for flexible TE modules to capture low-temperature waste heat under natural-air cooling conditions with fins for the purpose of energy harvesting.

Pneumonia has contributed greatly to child mortality, especially among children under the ages of five in sub-Saharan Africa, killing more children than the number of children dying from HIV/AIDS. The current methods of diagnosing pneumonia involved physical examination and chest x-ray which are limited by low accuracy, high error margins, higher cost, and stands the risks of inducing cancer. In this work, a low-cost, non-invasive biomedical device was designed and developed to improve accuracy in diagnosing pneumonia. The device functions to detect fluid in a lung consolidated by pneumonia. Dry grouting sponge was used as a phantom for a healthy lung, while a wet sponge was used to mimic a pneumonia-consolidated lung. Surface exciter was used to produce sound waves which travelled through one side of the phantom and are detected on the other end using an electronic stethoscope. The signals detected were digitally analyzed using MATLAB and AUDACITY software. The differences in resonant frequencies from the power spectrum analysis of sound waves as they travelled through the sponges were used to distinguish between a pneumonia-consolidated lung and a healthy lung.

The majority of highly efficient perovskite light-emitting diodes (PeLED) contain PEDOT:PSS (poly(3,4-ethylenedioxythiophene):polystyrenesulfonate) as hole transport layer (HTL). However, the hygroscopic and acidic nature of PEDOT:PSS may lead to deterioration of PeLED performance. Moreover, due to its inferior electron-blocking properties, an additional electron-blocking layer (EBL) is required to establish charge balance and consequently obtain superior emission characteristics in typically electron-rich PeLED structures. In this work, PTAA (poly(bis(4-phenyl)(2,4,6-trimethylphenyl)amine)) serving both as HTL and EBL is employed to substitute PEDOT:PSS in PeLED. The perovskite CsPbBr3 is chosen as emissive layer (EML) material due to its high color purity and photoluminescence (PL) quantum yield. Dense CsPbBr3 films are fabricated on PTAA-coated ITO substrates by employing a one-step spin-coating approach based on nonstoichiometric perovskite precursor solutions. To suppress non-radiative recombination, a small amount of methylammonium bromide (MABr) is incorporated in the CsPbBr3 lattice. The resulting films exhibit excellent coverage and PL intensity. PeLED containing pure CsPbBr3 films as EML show a green emission with a peak at 520 nm, maximum luminance of 11,000 cd/m2, an external quantum efficiency (EQE) of 3.3 % and a current efficiency (CE) of 10.3 cd/A. Further enhancement to 21,000 cd/m2, 7.5 % and 27.0 cd/A is demonstrated by PeLED with MABr-doped CsPbBr3 layers.

X-ray imaging is a valuable technique used for medical imaging and non-destructive inspection of industrial products. However, the radiation may put humans at risk of developing cancer. Consequently, highly sensitive X-ray detectors, which enable X-ray imaging at a low dose rate, are required. Metal halide perovskite materials have demonstrated excellent X-ray detection performance including a high sensitivity owing to their high absorption coefficient, high carrier mobility, and long carrier lifetime. However, perovskite thick films with a large area, which is essential to realize the application of such materials to X-ray imaging devices have not been extensively investigated. To this end, in this study, a polymer is employed as a buffer layer to avoid film exfoliation, which makes it difficult to fabricate perovskite thick films, and a 110-μm-thick CsPbBr3 film is successfully obtained using a scalable solution method. In addition, an X-ray detector based on the CsPbBr3 thick film is fabricated, which demonstrates a sensitivity of 11,840 μC Gyair–1 cm–2. This sensitivity is approximately 600 times higher than that of the existing commercial a-Se X-ray detectors.

Betavoltaics (BV) cells (or nuclear batteries) have long-lasting power and high volumetric energy densities that open a broad range of applications that are not currently available, especially in low-power electronics for the internet-of-things, internal medical devices, and harsh environments. The introduction of very low-power electronics has opened up a market for the wide and accepted use of BV cells. As BVs have potentially decades-long useful lifetimes and are anticipated to be used in harsh environments, a method to describe accelerated contact aging has been developed. Monte Carlo radiation simulations show that energy can be deposited in the interface 10-50 times faster than real-world applications. The models can be used to design contact aging experiments for BV cell deployments.

Nanocomposite hydrogels of poly-n-isopropyl were prepared by incorporating gold and magnetite nanoparticles. The nanocomposite-based hydrogels formed were geometrical, ∼7.3 mm in diameter and 5 mm thick (in the swollen state). Morphological analysis was characterized by a scanning electron microscope. Drug-loaded hydrogels were subjected to laser heating at 1 W, 1.5 W and 2 W for 20 min in each laser cycle. The metabolic activities of the cells were analysed. The photothermal conversion efficiency of the nanocomposite hydrogels was also evaluated for P(NIPA)-AuNP-PG and P(NIPA)-MNP-PG to be 36.93 and 32.57 %, respectively. The result was then discussed for potential applications whereby metal-based hydrogels can be employed in microfluidic devices for targeted cancer drug delivery.

A multilevel nonvolatile memory based on an amorphous indium–gallium–zinc oxide thin-film transistor is successfully demonstrated by using an atomic layer–deposited ZnO film as a charge trapping layer. The memory device shows a much higher erasing efficiency at a negative bias, i.e., after erasing at −13 V for 1 μs, the threshold voltage shift is as large as −7.4 V. In the case of 13 V/1 μs programming (P) and −12 V/1 μs erasing (E), the device demonstrates an ON/OFF readout drain current (IDS) ratio of ∼103 after 105 s, and a large and stable ON/OFF IDS ratio of ∼106 till 104 of P/E cycles. Furthermore, multilevel memory characteristics are also demonstrated on the device, showing an IDS ratio of >102 for 4 different states. Additionally, the device also successfully demonstrates typical synaptic behaviors, such as excitatory and inhibitory postsynaptic current with different memory times at different memory states.

Paper transistors are indispensable devices for paper-based electronic biosensing systems. Existing paper transistors mainly use paper as a mechanical support in a passive fashion. By taking advantage of the cellulose fibers in paper, here we report a transistor-in-paper where paper is employed as an essential part to allow for low-voltage operation, which addresses the long-standing challenge of high-voltage operation with existing paper transistors. Such a low-threshold voltage is because of the ion gel/cellulose fiber composite dielectric formed by modifying the paper with ion gels. We further developed paper-based inverters as examples of logic gates and an integrated tactile sensing mat based on a transistor array–enabled multiplexing device. The results collectively indicate that the ion gel–modified paper leads to a class of flexible, low-voltage transistors and integrated electronic devices, which hold promise in many applications.

High-current switching performance of ovonic threshold switching (OTS) selectors have successfully enabled the commercialization of high-density three-dimensional (3D) stackable phase-change memory in Intel’s 3D Xpoint technology. This bridges the huge performance gap between dynamic random access memory (DRAM) and Flash. Similar to phase-change memory, OTS uses chalcogenide-based materials, but whereas phase-change memory reversibly switches between a high-resistance amorphous phase and a low-resistance crystalline phase, OTS freezes in the amorphous phase. In this article, we review recent developments in OTS materials and their performance in devices, especially current density and selectivity. Advantages and challenges of OTS devices in the integration with the phase-change memory are discussed. We introduce the evolution of theoretical models for explaining the OTS behavior, including thermal runaway, field-induced nucleation, and generation/recombination of charge carriers.

With growing demand for better fuel economy for automobiles, multimaterial solutions are increasingly being utilized in the automotive industry for reducing weight in the vehicle body structure. This poses challenges in terms of joining dissimilar metals, especially those with vastly different properties such as aluminum to steel joining. General Motors has developed a new resistance spot-welding technique for dissimilar materials using a multi-ring domed (MRD) electrode and multiple solidification weld schedules to address this challenge. Originally developed for aluminum to aluminum resistance spot welding, this technology is being deployed as the mainstream aluminum joining solution to leverage existing infrastructure and workforce competency in resistance spot welding. With the recent expansion of MRD technology to aluminum to steel resistance spot welding, there is an ever-greater need to experimentally verify the quality of each aluminum to steel resistance spot-weld application with limited time and resources. Nondestructive evaluation (NDE) would enable the transfer of resistance spot-welding technology to dissimilar aluminum to steel joints. This article describes the current state of the art of aluminum to steel resistance spot welding and the challenges in developing a robust NDE process for this technology.

Conventional silicon-based electronics have faced challenges in the realization of soft bioelectronics, such as wearable and implantable integrated devices, which necessitate electrically and mechanically interactive biotic–abiotic interfacing without disturbing the daily life of the user or posing biocompatibility issues. Recently, much effort has been directed at overcoming the mechanical limitations of conventional rigid electronics by replacement of bulky, thick, and rigid electronic materials with biocompatible, soft, and nanoscale electronic materials, which exhibit intrinsic mechanical deformability as well as superior electrical properties. Recent advances in the synthesis of unconventional nanomaterials, surface functionalization methods, and integrated device fabrication techniques have resulted in further improvements in the performance of nanomaterials-based soft bioelectronics. Numerous studies have focused on the biological, electrical, and mechanical analyses of heterogeneous nanomaterial–biosystem interfaces as well as the development of efficient integration processes of soft nanomaterials into devices. In this article, we summarize the latest advances and future prospects in nanomaterials synthesis, processing, and integration strategies for flexible and stretchable bioelectronics, and their application to wearable and implantable devices.

A fundamental design rule that nature has developed for biological machines is the intimate correlation between motion and function. One class of biological machines is molecular motors in living cells, which directly convert chemical energy into mechanical work. They coexist in every eukaryotic cell, but differ in their types of motion, the filaments they bind to, the cargos they carry, as well as the work they perform. Such natural structures offer inspiration and blueprints for constructing DNA-assembled artificial systems, which mimic their functionality. In this article, we describe two groups of cytoskeletal motors, linear and rotary motors. We discuss how their artificial analogues can be built using DNA nanotechnology. Finally, we summarize ongoing research directions and conclude that DNA origami has a bright future ahead.

Increasing the number of quantum bits while preserving precise control of their quantum electronic properties is a significant challenge in materials design for the development of semiconductor quantum computing devices. Semiconductor heterostructures can host multiple quantum dots that are electrostatically defined by voltages applied to an array of metallic nanoelectrodes. The structural distortion of multiple-quantum-dot devices due to elastic stress associated with the electrodes has been difficult to predict because of the large micrometer-scale overall sizes of the devices, the complex spatial arrangement of the electrodes, and the sensitive dependence of the magnitude and spatial variation of the stress on processing conditions. Synchrotron X-ray nanobeam Bragg diffraction studies of a GaAs/AlGaAs heterostructure reveal the magnitude and nanoscale variation of these distortions. Investigations of individual linear electrodes reveal lattice tilts consistent with a 28-MPa compressive residual stress in the electrodes. The angular magnitude of the tilts varies by up to 20% over distances of less than 200 nm along the length of the electrodes, consistent with heterogeneity in the metal residual stress. A similar variation of the crystal tilt is observed in multiple-quantum-dot devices, due to a combination of the variation of the stress and the complex electrode arrangement. The heterogeneity in particular can lead to significant challenges in the scaling of multiple-quantum-dot devices due to differences between the charging energies of dots and uncertainty in the potential energy landscape. Alternatively, if incorporated in design, stress presents a new degree of freedom in device fabrication.

Scanning tunneling microscopy and spectroscopy (STM/STS) are used to electronically switch atomically-thin memristors, referred to as “atomristors”, based on a graphene/molybdenum disulfide (MoS2)/Au heterostructure. A gold-assisted exfoliation method was used to produce near-millimeter (mm) scale MoS2 on Au thin-film substrates, followed by transfer of a separately exfoliated graphene top layer. Our results reveal that it is possible to switch the conductivity of a graphene/MoS2/Au memristor stack using an STM tip. These results provide a path to further studies of atomically-thin memristors fabricated from heterostructures of two-dimensional materials such as graphene and transition metal dichalcogenides (TMDs).