In recent years, tremendous research effort has been aimed at increasing the energy density of supercapacitors without sacrificing high power capability so that they reach the levels achieved in batteries and at lowering fabrication costs For this purpose, two important problems have to be solved: first, it is critical to develop ways to design high performance electrode materials for supercapacitors; second, it is necessary to achieve controllably assembled supercapacitor types (such as symmetric capacitors including double-layer and pseudo-capacitors, asymmetric capacitors, and Li-ion capacitors) The explosive growth of research in this field makes this review timely Recent progress in the research and development of high performance electrode materials and high-energy supercapacitors is summarized Several key issues for improving the energy densities of supercapacitors and some mutual relationships among various effecting parameters are reviewed, and challenges and perspectives in this exciting field are also discussed This provides fundamental insight into supercapacitors and offers an important guideline for future design of advanced next-generation supercapacitors for industrial and consumer applications

Recent Advances in Design and Fabrication of Electrochemical Supercapacitors with High Energy Densities

BACKGROUND Hydrogels are formed through the cross-linking of hydrophilic polymer chains within an aqueous microenvironment. The gelation can be achieved through a variety of mechanisms, spanning physical entanglement of polymer chains, electrostatic interactions, and covalent chemical cross-linking. The water-rich nature of hydrogels makes them broadly applicable to many areas, including tissue engineering, drug delivery, soft electronics, and actuators. Conventional hydrogels usually possess limited mechanical strength and are prone to permanent breakage. The lack of desired dynamic cues and structural complexity within the hydrogels has further limited their functions. Broadened applications of hydrogels, however, require advanced engineering of parameters such as mechanics and spatiotemporal presentation of active or bioactive moieties, as well as manipulation of multiscale shape, structure, and architecture. ADVANCES Hydrogels with substantially improved physicochemical properties have been enabled by rational design at the molecular level and control over multiscale architecture. For example, formulations that combine permanent polymer networks with reversibly bonding chains for energy dissipation show strong toughness and stretchability. Similar strategies may also substantially enhance the bonding affinity of hydrogels at interfaces with solids by covalently anchoring the polymer networks of tough hydrogels onto solid surfaces. Shear-thinning hydrogels that feature reversible bonds impart a fluidic nature upon application of shear forces and return back to their gel states once the forces are released. Self-healing hydrogels based on nanomaterial hybridization, electrostatic interactions, and slide-ring configurations exhibit excellent abilities in spontaneously healing themselves after damages. Additionally, harnessing techniques that can dynamically and precisely configure hydrogels have resulted in flexibility to regulate their architecture, activity, and functionality. Dynamic modulations of polymer chain physics and chemistry can lead to temporal alteration of hydrogel structures in a programmed manner. Three-dimensional printing enables architectural control of hydrogels at high precision, with a potential to further integrate elements that enable change of hydrogel configurations along prescribed paths. OUTLOOK We envision the continuation of innovation in new bioorthogonal chemistries for making hydrogels, enabling their fabrication in the presence of biological species without impairing cellular or biomolecule functions. We also foresee opportunities in the further development of more sophisticated fabrication methods that allow better-controlled hydrogel architecture across multiple length scales. In addition, technologies that precisely regulate the physicochemical properties of hydrogels in spatiotemporally controlled manners are crucial in controlling their dynamics, such as degradation and dynamic presentation of biomolecules. We believe that the fabrication of hydrogels should be coupled with end applications in a feedback loop in order to achieve optimal designs through iterations. In the end, it is the combination of multiscale constituents and complementary strategies that will enable new applications of this important class of materials.

/pdf/advances-in-engineering-hydrogels-1gju2afbgf.pdf

Advances in engineering hydrogels

Wearable biosensors are garnering substantial interest due to their potential to provide continuous, real-time physiological information via dynamic, noninvasive measurements of biochemical markers in biofluids, such as sweat, tears, saliva and interstitial fluid. Recent developments have focused on electrochemical and optical biosensors, together with advances in the noninvasive monitoring of biomarkers including metabolites, bacteria and hormones. A combination of multiplexed biosensing, microfluidic sampling and transport systems have been integrated, miniaturized and combined with flexible materials for improved wearability and ease of operation. Although wearable biosensors hold promise, a better understanding of the correlations between analyte concentrations in the blood and noninvasive biofluids is needed to improve reliability. An expanded set of on-body bioaffinity assays and more sensing strategies are needed to make more biomarkers accessible to monitoring. Large-cohort validation studies of wearable biosensor performance will be needed to underpin clinical acceptance. Accurate and reliable real-time sensing of physiological information using wearable biosensor technologies would have a broad impact on our daily lives.

Wearable biosensors for healthcare monitoring.

Skin-like electronics that can adhere seamlessly to human skin or within the body are highly desirable for applications such as health monitoring, medical treatment, medical implants and biological studies, and for technologies that include human-machine interfaces, soft robotics and augmented reality. Rendering such electronics soft and stretchable-like human skin-would make them more comfortable to wear, and, through increased contact area, would greatly enhance the fidelity of signals acquired from the skin. Structural engineering of rigid inorganic and organic devices has enabled circuit-level stretchability, but this requires sophisticated fabrication techniques and usually suffers from reduced densities of devices within an array. We reasoned that the desired parameters, such as higher mechanical deformability and robustness, improved skin compatibility and higher device density, could be provided by using intrinsically stretchable polymer materials instead. However, the production of intrinsically stretchable materials and devices is still largely in its infancy: such materials have been reported, but functional, intrinsically stretchable electronics have yet to be demonstrated owing to the lack of a scalable fabrication technology. Here we describe a fabrication process that enables high yield and uniformity from a variety of intrinsically stretchable electronic polymers. We demonstrate an intrinsically stretchable polymer transistor array with an unprecedented device density of 347 transistors per square centimetre. The transistors have an average charge-carrier mobility comparable to that of amorphous silicon, varying only slightly (within one order of magnitude) when subjected to 100 per cent strain for 1,000 cycles, without current-voltage hysteresis. Our transistor arrays thus constitute intrinsically stretchable skin electronics, and include an active matrix for sensory arrays, as well as analogue and digital circuit elements. Our process offers a general platform for incorporating other intrinsically stretchable polymer materials, enabling the fabrication of next-generation stretchable skin electronic devices.

Skin electronics from scalable fabrication of an intrinsically stretchable transistor array.

Plastic bioelectronics is a research field that takes advantage of the inherent properties of polymers and soft organic electronics for applications at the interface of biology and electronics. The resulting electronic materials and devices are soft, stretchable and mechanically conformable, which are important qualities for interacting with biological systems in both wearable and implantable devices. Work is currently aimed at improving these devices with a view to making the electronic-biological interface as seamless as possible.

The rise of plastic bioelectronics

Background: The purpose of this study was to compare the physical activity and caloric intake trends of lipid-lowering drug users with those of non-users among Korean adults with dyslipidemia. Methods: This study was a repeated cross-sectional study with a nationally representative sample of 2,635 Korean adults with dyslipidemia based on the 2010–2013 Korea National Health and Nutrition Examination Survey. Physical activity was assessed using the International Physical Activity Questionnaire, and caloric intake was estimated through 24-hour dietary recall. All statistical analyses were conducted using IBM SPSS ver. 21.0 (IBM Co., Armonk, NY, USA). The changes in physical activity and caloric intake were investigated for lipid-lowering drug users and non-users using generalized linear models. Results: The proportion of lipid-lowering drug users in the 2010–2013 survey population increased from 3.5% to 5.0% (P<0.001). Among adults of dyslipidemia, total of 1,562 participants (56.6%) reported taking lipid-lowering drugs, and 1,073 (43.4%) reported not taking lipid-lowering drugs. Drug users were more likely to be older and less educated and to have a diagnosis of diabetes, higher body mass index, and lower low density lipoprotein cholesterol level. Physical activity trends were tested separately for the lipid-lowering drug users and non-users, and a significant decrease was found among the drug users during the study period. Physical activity among the drug users in 2013 was 38% lower (1,357.3±382.7 metabolic equivalent [MET]; P for trend=0.002) than in 2010 (2,201.4±442.6 MET). In contrast, there was no statistically significant difference between drug users and non-users in the trend of caloric intake during the same period. Conclusion: Physical activity significantly decreased among lipid-lowering drug users between 2010 and 2013, which was not observed among non-users. The importance of physical activity may need to be re-emphasized for lipid-lowering drug users.

/pdf/comparing-the-trend-of-physical-activity-and-caloric-intake-28lnaagxhn.pdf

Comparing the Trend of Physical Activity and Caloric Intake between Lipid-Lowering Drug Users and Nonusers among Adults with Dyslipidemia: Korean National Health and Nutrition Examination Surveys (2010–2013)

Neuromorphic skin is an emerging electronic skin that demonstrates sensory, memory, learning, and motor responses in a neuromorphic way by using advanced artificial synaptic devices that emulate the biological nervous system and its neural plasticity. Many types of artificial synapses that emulate brain‐inspired computing have been developed and are being integrated in electronic skin to demonstrate artificial sensory and motor nervous systems. The neuromorphic skin, which operates using voltage spikes thereof, precisely mimics the energy‐efficient information processing of biological nervous system in the brain and body and enables the implementation of power‐ and time‐efficient cognitive sensors and computing, biomimetic robotics and electronics, and biocompatible neuroprosthetics. Here, biological synapses and emerging artificial synapses are introduced, and recent research is reviewed on neuromorphic skins that use artificial synapses for sensing, memory, learning, and motor systems. Finally, the outlook and challenges to be addressed are provided for future advanced neuromorphic skin in which all neuromorphic parts are integrated with brain‐inspired computing and bioinspired robotics.

Neuromorphic Skin Based on Emerging Artificial Synapses

Developing facile methods for inducing phase transformation between metallic and semiconducting 2D transition metal dichalcogenide (TMDC) materials is crucial toward leveraging their use in cutting-edge energy devices. Herein, 2H-to-1T' phase transformations in chemically exfoliated Tungsten Disulfide (WS2 ) nanosheet films, triggered by antioxidants toward highly conductive 2D TMDC electrode materials, are introduced. It is found that antioxidants cause residual LiOx compounds to reduce to Li metal, subsequently inducing 1T' phase transformations in layered WS2 nanosheets, resulting in significantly enhanced conductivity across the overall films. Both thermoelectric devices and supercapacitors are fabricated utilizing the highly conductive 1T' phase WS2 nanosheet films as a working electrode, allowing for outstanding performance due to the increased conductivity of the WS2 nanosheet films. The method constitutes a facile approach toward the use of chemically exfoliated 1T' TMDC nanosheets for highly efficient energy device applications.

Antioxidant Triggered Metallic 1T' Phase Transformations of Chemically Exfoliated Tungsten Disulfide (WS2 ) Nanosheets.

Background: In this study, we investigated the relation of serum 25-hydroxyvitamin D (25(OH)D) and parathyroid hormone (PTH) concentrations with the risk of dyslipidemia in Korean adults aged 50 years and older, by using the most recent available Korean National Health and Nutrition Examination Surveys data. Methods: The sample of this population-based cross-sectional study consisted of 467 Korean adults who participated in the fifth Korean National Health and Nutrition Examination Surveys conducted in 2011. Participants who were taking lipid medications were excluded. Serum 25(OH)D concentrations were measured with radioimmunoassay, and serum PTH concentrations were measured with chemiluminescence assay. Results: The median concentrations of serum 25(OH)D and PTH for the entire group were 17.25 ng/mL and 65.07 pg/mL, respectively. In logistic regression analyses, the serum 25(OH)D and PTH concentrations were not significantly associated with the risk of dyslipidemia after adjustment for age, region, income, education level, smoking status, alcohol intake, and physical activity (p > 0.05). Conclusion: Serum 25(OH)D and PTH concentrations are not independently associated with serum lipid levels or an increased risk of dyslipidemia in the Korean population ≥ 50 years.

Relation of serum 25-hydroxyvitamin D and parathyroid hormone with dyslipidemia in Korean adults aged 50 years and older: Based on the Korea National Health and Nutrition Examination Survey, 2011

A polymer includes a first repeating unit and a second repeating unit forming a main chain, the first repeating unit including at least one first conjugated system, and the second repeating unit including at least one second conjugated system and a multiple hydrogen bonding moiety represented by Chemical Formula 1.

Jin Young Oh

Papers

Comparing the Trend of Physical Activity and Caloric Intake between Lipid-Lowering Drug Users and Nonusers among Adults with Dyslipidemia: Korean National Health and Nutrition Examination Surveys (2010–2013)

Neuromorphic Skin Based on Emerging Artificial Synapses

Antioxidant Triggered Metallic 1T' Phase Transformations of Chemically Exfoliated Tungsten Disulfide (WS2 ) Nanosheets.

Relation of serum 25-hydroxyvitamin D and parathyroid hormone with dyslipidemia in Korean adults aged 50 years and older: Based on the Korea National Health and Nutrition Examination Survey, 2011

Polymer and electronic device and organic thin film transistor including the same