Photo-patternable and transparent films using cellulose nanofibers for stretchable origami electronics

Substantial progress in flexible or stretchable electronics over the past decade has extensively impacted various technologies such as wearable devices, displays and automotive electronics for smart cars. An important challenge is the reliability of these deformable devices under thermal stress. Different coefficients of thermal expansion (CTE) between plastic substrates and the device components, which include multiple inorganic layers of metals or ceramics, induce thermal stress in the devices during fabrication processes or long-term operations with repetitions of thermal cyclic loading-unloading, leading to device failure and reliability degradation. Here, we report an unconventional approach to form photo-patternable, transparent cellulose nanofiber (CNF) hybrid films as flexible and stretchable substrates to improve device reliability using simultaneous electrospinning and spraying. The electrospun polymeric backbones and sprayed CNF fillers enable the resulting hybrid structure to be photolithographically patternable as a negative photoresist and thermally and mechanically stable, presenting outstanding optical transparency and low CTE. We also formed stretchable origami substrates using the CNF hybrid that are composed of rigid support fixtures and elastomeric joints, exploiting the photo-patternability. A demonstration of transparent organic light-emitting diodes and touchscreen panels on the hybrid film suggests its potential for use in next-generation electronics.ope

Stretchable and transparent electrodes based on in-plane structures

Stretchable electronics has attracted great interest with compelling potential applications that require reliable operation under mechanical deformation. Achieving stretchability in devices, however, requires a deeper understanding of nanoscale materials and mechanics beyond the success of flexible electronics. In this regard, tremendous research efforts have been dedicated toward developing stretchable electrodes, which are one of the most important building blocks for stretchable electronics. Stretchable transparent thin-film electrodes, which retain their electrical conductivity and optical transparency under mechanical deformation, are particularly important for the favourable application of stretchable devices. This minireview summarizes recent advances in stretchable transparent thin-film electrodes, especially employing strategies based on in-plane structures. Various approaches using metal nanomaterials, carbon nanomaterials, and their hybrids are described in terms of preparation processes and their optoelectronic/mechanical properties. Some challenges and perspectives for further advances in stretchable transparent electrodes are also discussed. © 2015 The Royal Society of Chemistry.open0

High Performance Pd catalysts Modified with MoOx for LOHC

Liquid organic hydrogen carrier systems (LOHCs) are an efficient approach for storing hydrogen in organic molecules. Catalytic hydrogenation makes it possible to safely store and efficiently store and transport hydrogen. By dehydrogenation, hydrogen can be released. However, high temperatures are required for the dehydrogenation reaction, which reduces process efficiency and decomposes organic substances as a side reaction, limiting reuse. In this study, a low-temperature dehydrogenation reaction was performed using 1-methylindole (NMID)/Octahydro-1-methylindole (8H-NMID) as a heterocyclic LOHC compound containing a nitrogen atom in a ring structure. As a strategy to enhance the Pd-catalyzed dehydrogenation performance, MoOx was added to control the electronic structure of Pd. The addition of a small amount of MoOx to the Pd/Al2O3catalyst improved the Pd dispersion due to hydrogen spillover, resulting in a 1.52-fold increase in dehydrogenation activity compared to the original Pd/Al2O3

Photo-Patternable and Transparent Films Using Cellulose Nanofibers for Stretchable, Origami Electronics

Substantial progress in flexible or stretchable electronics over the past decade has extensively impacted on various technologies such as wearable devices, displays, or automotive electronics for smart cars. An important challenge here is reliability of these deformable devices against thermal stress. Different coefficients of thermal expansion (CTE) between plastic substrates and the device components which include multiple inorganic layers of metals or ceramics induce thermal stress to the devices during fabrication processes or long-term operations with repetitions of thermal cyclic loading-unloading, lead to device failure and degrade their reliability. Here we report an unconventional approach to form photo-patternable, transparent cellulose nanofiber (CNF) hybrid films as flexible and stretchable substrates toward reliable devices, using simultaneous electrospinning and spraying. The electrospun polymeric backbones and sprayed cellulose nanofiber fillers enable the resulting hybrid structure to be patternable photolithographically as a negative photoresist, and stable thermally and mechanically, with presenting outstanding optical transparency (~ 89 %) and low CTE (< 10 ppm/K). We also formed stretchable, origami substrates using the CNF hybrid, which are composed of rigid support fixtures and elastomeric joints, exploiting the photo-patternability. Demonstrations of transparent organic light-emitting diodes and touch-screen panels on the hybrid film suggest a promise for next generation electronics

Recent Advances in Transparent Electronics with Stretchable Forms

Advances in materials science and the desire for next-generation electronics have driven the development of stretchable and transparent electronics in the past decade. Novel applications, such as smart contact lenses and wearable sensors, have been introduced with stretchable and transparent form factors, requiring a deeper and wider exploration of materials and fabrication processes. In this regard, many research efforts have been dedicated to the development of mechanically stretchable, optically transparent materials and devices. Recent advances in stretchable and transparent electronics are discussed herein, with special emphasis on the development of stretchable and transparent materials, including substrates and electrodes. Several representative examples of applications enabled by stretchable and transparent electronics are presented, including sensors, smart contact lenses, heaters, and neural interfaces. The current challenges and opportunities for each type of stretchable and transparent electronics are also discussed

A Novel Vital-Sign Sensing Algorithm for Multiple Subjects Based on 24-GHz FMCW Doppler Radar

A novel non-contact vital-sign sensing algorithm for use in cases of multiple subjects is proposed. The approach uses a 24 GHz frequency-modulated continuous-wave Doppler radar with the parametric spectral estimation method. Doppler processing and spectral estimation are concurrently implemented to detect vital signs from more than one subject, revealing excellent results. The parametric spectral estimation method is utilized to clearly identify multiple targets, making it possible to distinguish multiple targets located less than 40 cm apart, which is beyond the limit of the theoretical range resolution. Fourier transformation is used to extract phase information, and the result is combined with the spectral estimation result. To eliminate mutual interference, the range integration is performed when combining the range and phase information. By considering breathing and heartbeat periodicity, the proposed algorithm can accurately extract vital signs in real time by applying an auto-regressive algorithm. The capability of a contactless and unobtrusive vital sign measurement with a millimeter wave radar system has innumerable applications, such as remote patient monitoring, emergency surveillance, and personal health care