The frontier of tungsten oxide nanostructures in electronic applications

Electrochromic (EC) glazing has garnered significant attention recently as a crucial solution for enhancing energy efficiency in future construction and automotive sectors. EC glazing could significantly reduce the energy usage of buildings compared to traditional blinds and glazing. Despite their commercial availability, several challenges remain, including issues with switching time, leakage of electrolytes, production costs, etc. Consequently, these areas demand more attention and further studies. Among inorganic-based EC materials, tungsten oxide nanostructures are essential due to its outstanding advantages such as low voltage demand, high coloration coefficient, large optical modulation range, and stability. This review will summarize the principal design and mechanism of EC device fabrication. It will highlight the current gaps in understanding the mechanism of EC theory, discuss the progress in material development for EC glazing, including various solutions for improving EC materials, and finally, introduce the latest advancements in photo-EC devices that integrate photovoltaic and EC technologies.

Topology optimization for near-junction thermal spreading of electronics in ballistic-diffusive regime

Hotspots in electronic devices can cause overheating and reduce performance. Enhancing the thermal spreading ability is critical for reducing device temperature to improve the reliability. However, as devices shrink, phonon ballistic effects can increase thermal resistance, making conventional optimization methods less effective. This paper presents a topology optimization method that combines the phonon Boltzmann transport equation with solid isotropic material with penalization method to optimize high thermal conductivity (HTC) material distributions for thermal spreading problems. Results show that the contraction-expansion structure can effectively reduce thermal resistance. Optimal distributions differ from that based on Fourier's heat conduction law, and only the trunk structure appears in optimized layouts due to the size effect. Additionally, HTC material with longer mean free paths tends to be filled around the heat source with a gap in a ballistic-diffusive regime. This work deepens understanding of thermal spreading and aids in thermal optimization of microelectronic chips.

Flexible organic optoelectronic devices on paper

Paper substrate has many advantages, such as low cost, bendable, foldable, printable, and environmentally friendly recycling. Nowadays, paper has been further extended as a flexible platform to deliver electronic information with the integration of organic optoelectronic devices, such as organic thin-film transistor, organic solar cell, organic electrochromic device, and organic light-emitting device. It has great potential to become the new generation of flexible substrate. Given rough surface and porous of paper, many efforts have been underway in recent years to enable the compatibility between optoelectronics and paper substrate. In this review, we present the development history of paper and its physicochemical properties, and summarize the current development of paper-based organic optoelectronic devices. We also discuss the challenges that need to be addressed before practical uses of paper-based organic optoelectronic devices.

Improved electrical ideality and photoresponse in near-infrared phototransistors realized by bulk heterojunction channels

The factors that affect the electrical ideality and photoresponse in near-infrared (NIR) organic phototransistors (OPTs) are still nebulous. Here, simultaneous increase in electrical ideality and NIR response in the OPTs is realized by applying a bulk heterojunction (BHJ) channel. The acceptor in the channel helps to trap the undesirable injected electrons, avoiding the accumulation of the electrons at the active channel/dielectric interface, and thereby improving the hole transporting. Use of a BHJ channel also helps reducing the contact resistance in the OPTs. The electrical stability is then improved with mitigated dependence of charge mobility on gate voltage in the saturation region. The BHJ channel also offers an improved photoresponse through enhanced exciton dissociation, leading to more than one order of magnitude increase in responsivity than that in a control OPT. The results are encouraging, which pave the way for the development of high-performing NIR OPTs.

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The use of BHJ channel in NIR OPTs improves the electrical ideality and photoresponse

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The acceptor traps injected electrons to maintain the efficient hole transport

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The contact resistance in OPTs with BHJ channel is reduced

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The better exciton dissociation in BHJ channel offers improved photoresponse

Recent advances in liquid-metal-based wearable electronics and materials

Soft wearable electronics are rapidly developing through exploration of new materials, fabrication approaches, and design concepts. Although there have been many efforts for decades, a resurgence of interest in liquid metals (LMs) for sensing and wiring functional properties of materials in soft wearable electronics has brought great advances in wearable electronics and materials. Various forms of LMs enable many routes to fabricate flexible and stretchable sensors, circuits, and functional wearables with many desirable properties. This review article presents a systematic overview of recent progresses in LM-enabled wearable electronics that have been achieved through material innovations and the discovery of new fabrication approaches and design architectures. We also present applications of wearable LM technologies for physiological sensing, activity tracking, and energy harvesting. Finally, we discuss a perspective on future opportunities and challenges for wearable LM electronics as this field continues to grow.

Paper-based wearable electronics

Skin-interfaced wearable electronics can find a broad spectrum of applications in healthcare, human-machine interface, robotics, and others. The state-of-the-art wearable electronics usually suffer from costly and complex fabrication procedures and nonbiodegradable polymer substrates. Paper, comprising entangled micro- or nano-scale cellulose fibers, is compatible with scalable fabrication techniques and emerges as a sustainable, inexpensive, disposable, and biocompatible substrate for wearable electronics. Given various attractive properties (e.g., breathability, flexibility, biocompatibility, and biodegradability) and rich tunability of surface chemistry and porous structures, paper offers many exciting opportunities for wearable electronics. In this review, we first introduce the intriguing properties of paper-based wearable electronics and strategies for cellulose modifications to satisfy specific demands. We then overview the applications of paper-based devices in biosensing, energy storage and generation, optoelectronics, soft actuators, and several others. Finally, we discuss some challenges that need to be addressed before practical uses and wide implementation of paper-based wearable electronics.

Electronic fibers and textiles: Recent progress and perspective

Wearable electronics are receiving increasing attention with the advances of human society and technologies. Among various types of wearable electronics, electronic fibers/textiles, which integrate the comfort and appearance of conventional fibers/textiles with the functions of electronic devices, are expected to play important roles in remote health monitoring, disease diagnosis/treatment, and human-machine interface. This article aims to review the recent advances in electronic fibers/textiles, thus providing a comprehensive guiding reference for future work. First, we review the selection of functional materials and fabrication strategies of fiber-shaped electronic devices with emphasis on the newly developed functional materials and technologies. Their applications in sensing, light emitting, energy harvest, and energy storage are discussed. Then, the fabrication strategies and applications of electronic textiles are summarized. Furthermore, the integration of multifunctional electronic textiles and their applications are summarized. Finally, we discuss the existing challenges and propose the future development of electronic fibers/textiles.

Recent advances in wearable sensors and portable electronics for sleep monitoring

Despite the increasing awareness of the importance of sleep, the number of people suffering from insufficient sleep has increased every year. The gold-standard sleep assessment uses polysomnography (PSG) with various sensors to identify sleep patterns and disorders. However, due to the high cost of PSG and limited availability, many people with sleep disorders are left undiagnosed. Recent wearable sensors and electronics enable portable, continuous monitoring of sleep at home, overcoming the limitations of PSG. This report reviews the advances in wearable sensors, miniaturized electronics, and system packaging for home sleep monitoring. New devices available in the market and systems are collectively summarized based on their overall structure, form factor, materials, and sleep assessment method. It is expected that this review provides a comprehensive view of newly developed technologies and broad insights on wearable sensors and portable electronics toward advanced sleep monitoring as well as at-home sleep assessment.

DFT study of structural and electronic properties of 1,4-diarylcyclopenta[d] pyridazines and oxazines for non-linear optical applications

Polymer and molecular-based electronic materials incorporating heterocycles like thiophenes and pyrroles are attractive possibilities as substitutes for semimetal materials. Heterocyclic materials are heavily studied in this regard due to the large variations in possible substrates. Herein we evaluated four different 5,6-fused ring heterocycles to gain a better understanding of any favorable optical and electronic properties that were due to incorporation of certain moieties. The molecules chosen would highlight the effects that the central ring (pyridazine versus oxazine), aromatic substituent, and heterocyclic side group may have on electronic and optical properties. Computational analysis of these four molecules was done using density functional theory (B3LYP and PBEPBE) with 6-31G(d,p), 6-311 ++G(d,p), and cc-pVTZ basis sets. The constituent molecules were optimized, and calculations were done for the dipole moment, polarizability, first-order hyperpolarizability (β), HOMO and LUMO orbitals, and a natural bonding order (NBO) analysis. These calculations allow for the study of charge density via electrostatic potential mapping and bonding orbitals. The results indicated that the pyridazine molecules presented here are more favorable than the oxazines for non-linear optical (NLO) applications. It is also noted that side ring substituents (thienyl and furyl) in the two pyridazines studied showed very little calculated differences. Finally, heterocyclic rings showed more favorable properties when incorporated as substituents for NLO applications over hydrocarbon aromatics. Graphical abstract.

Peptides as Bio-inspired Molecular Electronic Materials

Understanding the electronic properties of single peptides is not only of fundamental importance to biology, but it is also pivotal to the realization of bio-inspired molecular electronic materials. Natural proteins have evolved to promote electron transfer in many crucial biological processes. However, their complex conformational nature inhibits a thorough investigation, so in order to study electron transfer in proteins, simple peptide models containing redox active moieties present as ideal candidates. Here we highlight the importance of secondary structure characteristic to proteins/peptides, and its relevance to electron transfer. The proposed mechanisms responsible for such transfer are discussed, as are details of the electrochemical techniques used to investigate their electronic properties. Several factors that have been shown to influence electron transfer in peptides are also considered. Finally, a comprehensive experimental and theoretical study demonstrates that the electron transfer kinetics of peptides can be successfully fine tuned through manipulation of chemical composition and backbone rigidity. The methods used to characterize the conformation of all peptides synthesized throughout the study are outlined, along with the various approaches used to further constrain the peptides into their geometric conformations. The aforementioned sheds light on the potential of peptides to one day play an important role in the fledgling field of molecular electronics.