Stretchable electronic devices with intrinsically stretchable components have significant inherent advantages, including simple fabrication processes, a high integrity of the stacked layers, and low ...cost in comparison with stretchable electronic devices based on non‐stretchable components. The research in this field has focused on developing new intrinsically stretchable components for conductors, semiconductors, and insulators. New methodologies and fabrication processes have been developed to fabricate stretchable devices with intrinsically stretchable components. The latest successful examples of stretchable conductors for applications in interconnections, electrodes, and piezoresistive devices are reviewed here. Stretchable conductors can be used for electrode or sensor applications depending on the electrical properties of the stretchable conductors under mechanical strain. A detailed overview of the recent progress in stretchable semiconductors, stretchable insulators, and other novel stretchable materials is also given, along with a discussion of the associated technological innovations and challenges. Stretchable electronic devices with intrinsically stretchable components such as field‐effect transistors (FETs), photodetectors, light‐emitting diodes (LEDs), electronic skins, and energy harvesters are also described and a new strategy for development of stretchable electronic devices is discussed. Conclusions and future prospects for the development of stretchable electronic devices with intrinsically stretchable components are discussed.
Stretchable electronic devices based on stretchable components with intrinsic stretchability have significant advantages over other strategies including a simple fabrication process, high integrity of stacked layers, and low cost. Recent developments in methodologies and fabrication processes to fabricate stretchable devices with intrinsically stretchable components, which are of interest in many exciting next‐generation applications, such as e‐skin, personal healthcare, robotics, and human–machine interfaces, are reviewed.
Stretchable and conformal humidity sensors that can be attached to the human body for continuously monitoring the humidity of the environment around the human body or the moisture level of the human ...skin can play an important role in electronic skin and personal healthcare applications. However, most stretchable humidity sensors are based on the geometric engineering of non-stretchable components and only a few detailed studies are available on stretchable humidity sensors under applied mechanical deformations. In this paper, we propose a transparent, stretchable humidity sensor with a simple fabrication process, having intrinsically stretchable components that provide high stretchability, sensitivity, and stability along with fast response and relaxation time. Composed of reduced graphene oxide-polyurethane composites and an elastomeric conductive electrode, this device exhibits impressive response and relaxation time as fast as 3.5 and 7 s, respectively. The responsivity and the response and relaxation time of the device in the presence of humidity remain almost unchanged under stretching up to a strain of 60% and after 10,000 stretching cycles at a 40% strain. Further, these stretchable humidity sensors can be easily and conformally attached to a finger for monitoring the humidity levels of the environment around the human body, wet objects, or human skin.
Although the corporate governance model of Asian family firms has recently gained increased attention, it remains unclear how these firms’ corporate governance mechanisms (and their effectiveness) ...differ from those of family firms in the western world. Drawing upon a comparative institutional perspective, this paper systematically reviews 148 published articles in peer‐reviewed journals from 1980 to 2015. The aim of this paper is to contribute to the understanding of institutional complementarities that constitute informal governance mechanisms adopted by Asian family firms by considering a wider set of institutional factors (i.e. political environment, cultural values and social norms) embedded in the Asian context. The main findings suggest that: (i) given the lack of market‐supporting institutions and the presence of strong political control over Asian economies, family firms tend to cultivate political connections to respond to the failure of legal systems; (ii) Asian family firms still rely heavily on personal networks (e.g. guanxi) to reduce uncertainty, strengthen business ties, and gain access to external resources; and (iii) cultural values and social norms (e.g. ‘face’ saving, reputational concerns and adult child adoption) lead to functionally equivalent corporate governance mechanisms in Asian family firms. The downstream effects of such mechanisms are also discussed, and future research avenues are identified.
Imbuing bio-inspired sensory devices with intelligent functions of human sensory organs has been limited by challenges in emulating the preprocessing abilities of sensory organs such as reception, ...filtering, adaptation, and sensory memory at the device level itself. Merkel cells, which is a part of tactile sensory organs, form synapse-like connections with afferent neuron terminals referred to as Merkel cell-neurite complexes. Here, inspired by structure and intelligent functions of Merkel cell-neurite complexes, we report a flexible, artificial, intrinsic-synaptic tactile sensory organ that mimics synapse-like connections using an organic synaptic transistor with ferroelectric nanocomposite gate dielectric of barium titanate nanoparticles and poly(vinylidene fluoride-trifluoroethylene). Modulation of the post-synaptic current of the device induced by ferroelectric dipole switching due to triboelectric-capacitive coupling under finger touch allowed reception and slow adaptation. Modulation of synaptic weight by varying the nanocomposite composition of gate dielectric layer enabled tuning of filtering and sensory memory functions.
Electronic skin (e-skin) is designed to mimic the comprehensive nature of human skin. Various advances in e-skin continue to drive the development of the multimodal tactile sensor technology on ...flexible and stretchable platforms. e-skin incorporates pressure, temperature, texture, photographic imaging, and other sensors as well as data acquisition and signal processing units formed on a soft substrate for humanoid robots, wearable devices, and health monitoring electronics that are the most critical applications of soft electronics. This artificial skin has developed very rapidly toward becoming real technology. However, the complex nature of e-skin technology presents significant challenges in terms of materials, devices, sophisticated integration methods, and interference-free data acquisition. These challenges range from functional materials, device architecture, pixel design, array structure, and data acquisition method to multimodal sensing performance with negligible interference. In this article, we present recent research trends and approaches in the field of flexible and stretchable multimodal sensors for e-skin focusing on the following aspects: 1) flexible and stretchable platforms; 2) operating principles and materials suitable for pressure, temperature, strain, photograph, and hairy sensor devices; 3) device and integration architectures, including multimodal single cells, three-axis tactile sensors, vertical-stacked sensor arrays, active matrix sensor arrays, and integration electronics; 4) reliable acquisition methods for various texture sensing and machine-learning algorithms for processing tactile sensing data; and 5) future outlook.
The rapid growth of research in the areas of chemical and biochemical sensors, lab-on-a-chip, mobile technology, and wearable electronics offers an unprecedented opportunity in the development of ...mobile and wearable point-of-care testing (POCT) systems for self-testing. Successful implementation of such POCT technologies leads to minimal user intervention during operation to reduce user errors; user-friendly, easy-to-use and simple detection platforms; high diagnostic sensitivity and specificity; immediate clinical assessment; and low manufacturing and consumables costs. In this review, we discuss recent developments in the field of highly integrated mobile and wearable POCT systems. In particular, aspects of sample handling platforms, recognition elements and sensing methods, and new materials for signal transducers and powering devices for integration into mobile or wearable POCT systems will be highlighted. We also summarize current challenges and future prospects for providing personal healthcare with sample-in result-out mobile and wearable POCT.
POCT systems have been developed toward new form factors as wearable and mobile POCT. New advancements in these POCT systems may provide self-testing capability for on-the-spot diagnosis and monitoring to facilitate rapid treatment decisions.
Starting from simple graphite flakes, an electrochemical sensor for sunset yellow monitoring is developed by using a very simple and effective strategy. The direct electrochemical reduction of a ...suspension of exfoliated graphene oxide (GO) onto a glassy carbon electrode (GCE) surface leads to the electrodeposition of electrochemically reduced oxide at the surface, obtaining GCE/ERGO-modified electrodes. They are characterized by cyclic voltammetry (CV) measurements and field emission scanning electron spectroscopy (FE-SEM). The GCE/ERGO electrode has a high electrochemically active surface allowing efficient adsorption of SY. Using differential pulse voltammetry (DPV) technique with only 2 min accumulation, the GCE/ERGO sensor exhibits good performance to SY detection with a good linear calibration for concentration range varying 50–1000 nM (
R
2
= 0.996) and limit of detection (LOD) estimated to 19.2 nM (equivalent to 8.9 μg L
−1
). The developed sensor possesses a very high sensitivity of 9 μA/μM while fabricated with only one component. This electrochemical sensor also displays a good reliability with RSD value of 2.13% (
n
= 7) and excellent reusability (signal response change < 3.5% after 6 measuring/cleaning cycles). The GCE/ERGO demonstrates a successful practical application for determination of sunset yellow in commercial soft drinks.
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•AuNSs@Ag@AAO substrates were prepared for microplastic detection in water.•Nanosized Raman substrates sensitively detected submicrometer-sized particles.•Numerical analysis supported ...strong electromagnetic enhancements of AuNSs@Ag.•A 0.4 μm polystyrene sample could be quantified with a detection limit of ∼0.005 %.•Enhanced Raman spectroscopy provided a fast detection of nanosized plastics.
We prepared novel Raman substrates for the sensitive detection of submicron-sized plastic spheres in water. Anisotropic nanostar dimer-embedded nanopore substrates were prepared for the efficient identification of submicron-sized plastic spheres by providing internal hot spots of electromagnetic field enhancements at the tips of nanoparticles. Silver-coated gold nanostars (AuNSs@Ag) were inserted into anodized aluminum oxide (AAO) nanopores for enhanced microplastic (MP) detection. We found that surface-enhanced Raman scattering (SERS) substrates of AuNSs@Ag@AAO yielded stronger signals at the same weight percentages for polystyrene MP particles with diameters as small as 0.4 μm, whereas such behaviors could not be observed for larger MPs (diameters of 0.8 μm, 2.3 μm, and 4.8 μm). The detection limit of the submicrometer-sized 0.4 μm in our Raman measurements were estimated to be 0.005% (∼0.05 mg/g =50 ppm) along with a fast detection time of only a few min without any sample pretreatments. Our nano-sized dimensional matching substrates may provide a useful tool for the application of SERS substrates for submicrometer MP pollutants in water.
•CAP was conducted for real fMRI data and a stationary null model.•The results of CAP analysis were similar for the real and simulated data.•Similar results for real and simulated data in both ROI- ...and voxel-based analyses.•Results of CAP analysis may not reflect non-stationarity of resting brain activity.
The non-stationarity of resting-state brain activity has received increasing attention in recent years. Functional connectivity (FC) analysis with short sliding windows and coactivation pattern (CAP) analysis are two widely used methods for assessing the dynamic characteristics of brain activity observed with functional magnetic resonance imaging (fMRI). However, the statistical nature of the dynamics captured by these techniques needs to be verified. In this study, we found that the results of CAP analysis were similar for real fMRI data and simulated stationary data with matching covariance structures and spectral contents. We also found that, for both the real and simulated data, CAPs were clustered into spatially heterogeneous modules. Moreover, for each of the modules in the real data, a spatially similar module was found in the simulated data. The present results suggest that care needs to be taken when interpreting observations drawn from CAP analysis as it does not necessarily reflect non-stationarity or a mixture of states in resting brain activity.
Network slicing has emerged as a key concept in 5G systems, allowing Mobile Network Operators (MNOs) to build isolated logical networks (slices) on top of shared infrastructure networks managed by ...Infrastructure Providers (InP). Network slicing requires the assignment of infrastructure network resources to virtual network components at slice activation time and the adjustment of resources for slices under operation. Performing these operations just-in-time, on a best-effort basis, comes with no guarantee on the availability of enough infrastructure resources to meet slice requirements. This paper proposes a prioritized admission control mechanism for concurrent slices based on an infrastructure resource reservation approach. The reservation accounts for the dynamic nature of slice requests while being robust to uncertainties in slice resource demands. Adopting the perspective of an InP, reservation schemes are proposed that maximize the number of slices for which infrastructure resources can be granted while minimizing the costs charged to the MNOs. This requires the solution of a max-min optimization problem with a non-linear cost function and non-linear constraints induced by the robustness to uncertainties of demands and the limitation of the impact of reservation on background services. The cost and the constraints are linearized and several reduced-complexity strategies are proposed to solve the slice admission control and resource reservation problem. Simulations show that the proportion of admitted slices of different priority levels can be adjusted by a differentiated selection of the delay between the reception and the processing instants of a slice resource request.
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