Wearable activity trackers offer the opportunity to increase physical activity through continuous monitoring. Viewing tracker use as a beneficial health behavior, we explored the factors that ...facilitate and hinder long-term activity tracker use, applying the transtheoretical model of behavior change with the focus on the maintenance stage and relapse.
The aim of this study was to investigate older adults' perceptions and uses of activity trackers at different points of use: from nonuse and short-term use to long-term use and abandoned use to determine the factors to maintain tracker use and prevent users from discontinuing tracker usage.
Data for the research come from 10 focus groups. Of them, 4 focus groups included participants who had never used activity trackers (n=17). These focus groups included an activity tracker trial. The other 6 focus groups (without the activity tracker trial) were conducted with short-term (n=9), long-term (n=11), and former tracker users (n=11; 2 focus groups per user type).
The results revealed that older adults in different tracker use stages liked and wished for different tracker features, with long-term users (users in the maintenance stage) being the most diverse and sophisticated users of the technology. Long-term users had developed a habit of tracker use whereas other participants made an effort to employ various encouragement strategies to ensure behavior maintenance. Social support through collaboration was the primary motivator for long-term users to maintain activity tracker use. Short-term and former users focused on competition, and nonusers engaged in vicarious tracker use experiences. Former users, or those who relapsed by abandoning their trackers, indicated that activity tracker use was fueled by curiosity in quantifying daily physical activity rather than the desire to increase physical activity. Long-term users saw a greater range of pros in activity tracker use whereas others focused on the cons of this behavior.
The results suggest that activity trackers may be an effective technology to encourage physical activity among older adults, especially those who have never tried it. However, initial positive response to tracker use does not guarantee tracker use maintenance. Maintenance depends on recognizing the long-term benefits of tracker use, social support, and internal motivation. Nonadoption and relapse may occur because of technology's limitations and gaining awareness of one's physical activity without changing the physical activity level itself.
There is currently enormous and growing demand for flexible electronics for personalized mobile equipment, human–machine interface units, wearable medical‐healthcare systems, and bionic intelligent ...robots. Cellulose is a well‐known natural biopolymer that has multiple advantages including low cost, renewability, easy processability, and biodegradability, as well as appealing mechanical performance, dielectricity, piezoelectricity, and convertibility. Because of its multiple merits, cellulose is frequently used as a substrate, binder, dielectric layer, gel electrolyte, and derived carbon material for flexible electronic devices. Leveraging the advantages of cellulose to design advanced functional materials will have a significant impact on portable intelligent electronics. Herein, the unique molecular structure and nanostructures (nanocrystals, nanofibers, nanosheets, etc.) of cellulose are briefly introduced, the structure–property–application relationships of cellulosic materials summarized, and the processing technologies for fabricating cellulose‐based flexible electronics considered. The focus then turns to the recent advances of cellulose‐based functional materials toward emerging intelligent electronic devices including flexible sensors, optoelectronic devices, field‐effect transistors, nanogenerators, electrochemical energy storage devices, biomimetic electronic skins, and biological detection devices. Finally, an outlook of the potential challenges and future prospects for developing cellulose‐based wearable devices and bioelectronic systems is presented.
The recent research in the field of cellulose‐based materials for flexible electronic applications is reviewed, including flexible sensors, biomimetic electronic skin, portable electrochemical energy storage devices, flexible nanogenerators, flexible organic thin‐film transistors, printed radio‐frequency identification devices, thin‐film photovoltaic devices, and miniaturized bioelectronic devices. An outlook of future perspectives for this field is also presented.
Skin-like intrinsically stretchable soft electronic devices are essential to realize next-generation remote and preventative medicine for advanced personal healthcare
. The recent development of ...intrinsically stretchable conductors and semiconductors has enabled highly mechanically robust and skin-conformable electronic circuits or optoelectronic devices
. However, their operating frequencies have been limited to less than 100 hertz, which is much lower than that required for many applications. Here we report intrinsically stretchable diodes-based on stretchable organic and nanomaterials-capable of operating at a frequency as high as 13.56 megahertz. This operating frequency is high enough for the wireless operation of soft sensors and electrochromic display pixels using radiofrequency identification in which the base-carrier frequency is 6.78 megahertz or 13.56 megahertz. This was achieved through a combination of rational material design and device engineering. Specifically, we developed a stretchable anode, cathode, semiconductor and current collector that can satisfy the strict requirements for high-frequency operation. Finally, we show the operational feasibility of our diode by integrating it with a stretchable sensor, electrochromic display pixel and antenna to realize a stretchable wireless tag. This work is an important step towards enabling enhanced functionalities and capabilities for skin-like wearable electronics.
Rapid advances in soft electronics, microfabrication technologies, miniaturization and electronic skins are facilitating the development of wearable sensor devices that are highly conformable and ...intimately associated with human skin. These devices-referred to as 'smart skins'-offer new opportunities in the research study of human biology, in physiological tracking for fitness and wellness applications, and in the examination and treatment of medical conditions. Over the past 12 months, electronic skins have been developed that are self-healing, intrinsically stretchable, designed into an artificial afferent nerve, and even self-powered. Greater collaboration between engineers, biologists, informaticians and clinicians will be required for smart skins to realize their full potential and attain wide adoption in a diverse range of real-world settings.
With the rapid development of optoelectronic fields, electrochromic (EC) materials and devices have received remarkable attention and have shown attractive potential for use in emerging wearable and ...portable electronics, electronic papers/billboards, see-through displays, and other new-generation displays, due to the advantages of low power consumption, easy viewing, flexibility, stretchability, etc. Despite continuous progress in related fields, determining how to make electrochromics truly meet the requirements of mature displays (e.g., ideal overall performance) has been a long-term problem. Therefore, the commercialization of relevant high-quality products is still in its infancy. In this review, we will focus on the progress in emerging EC materials and devices for potential displays, including two mainstream EC display prototypes (segmented displays and pixel displays) and their commercial applications. Among these topics, the related materials/devices, EC performance, construction approaches, and processing techniques are comprehensively disscussed and reviewed. We also outline the current barriers with possible solutions and discuss the future of this field.
Alkoxy side chain engineering on the β-position of the thienothiophene units of Y6 derivatives plays a vital role in improving photovoltaic performances with simultaneously increasing open-circuit ...voltage (V oc) and fill factor (FF). In this work, we prepared a series of asymmetric non-fullerene acceptors (NFAs) by introducing alkoxy side chains and phenoxy groups on the state-of-the-art Y6-derivative BTP-BO-4F. For the comparison, 2O-BO-4F with a symmetric alkoxy side chain on the outer thiophene units and BTP-PBO-4F with an asymmetric N-attached phenoxy alkyl chain on the pyrrole ring are synthesized from BTP-BO-4F. Thereafter, we construct four asymmetric NFAs by introducing different lengths of linear/branched alkoxy chains on the β-position of the thienothiophene units of BTP-PBO-4F. The resulting NFAs, named L10-PBO, L12-PBO, B12-PBO, and B16-PBO (L = linear and B = branched alkoxy side chains), are collectively called OR-PBO-series. Unexpectedly, all OR-PBO NFAs exhibit strong edge-on molecular packing and weaker π–π interactions in the film state, which diminish the charge transfer in organic solar cell (OSC) devices. As a consequence, the optimal devices of OR-PBO-based binary blends show poor photovoltaic performances power conversion efficiency (PCE) = 6.52–9.62% in comparison with 2O-BO-4F (PCE = 12.42%) and BTP-PBO-4F (PCE = 15.30%) reference blends. Nevertheless, the OR-PBO-based binary devices show a higher V oc and smaller V loss. Especially, B12-PBO- and B16-PBO-based devices achieve V oc over 1.00 V, which is the highest value of Y-series OSC devices to the best of our knowledge. Therefore, by utilizing higher V oc of OR-PBO binary blends, B12-PBO and B16-PBO are incorporated into the PM6:BTP-PBO-4F-based binary blend and fabricated ternary devices. As a result, the PM6:BTP-PBO-4F:B12-PBO ternary device delivers the best PCE of 15.60% with an increasing V oc and FF concurrently.
Organic solar cells (OSCs) have been a popular topic of research for a long time. As a well-known electron transport layer (ETL) material for inverted device architecture, sol-gel-derived zinc oxide ...(ZnO) displays certain defective surfaces that cause excessive charge recombination and lower device performance. While ultraviolet (UV)-light soaking is sometimes necessary for the ZnO layer to function properly, the latter can also cause the photodegradation of conjugated organic semiconductors. The photostability of OSCs has always been a hot research topic, as the radiation of UV light may cause changes in the material’s properties, and that, in turn, may cause rapid attenuation of the devices. Herein, ZnO is modified by inserting the commonly used sunscreen ingredient benzophenone-3 (BP-3) between the photoactive layer, consisting of a PM6:Y6 blend, and ZnO to reduce the impact of UV radiation on the photosensitive layer. The addition of BP-3 successfully enhances the photovoltaic parameters, and a remarkable open-circuit voltage (V oc) value of 0.887 V is obtained for PM6:Y6-based inverted solar cells, corresponding to a V oc loss as small as 0.547 V. Finally, the application of this strategy increases the device’s power conversion efficiency from 12.44 to 13.71% and provides improved UV stability.
In this paper, planar chiral helicenes based on 2.2paracyclophane PCPH5 acted as both chiral inducers and energy donors to construct the circularly polarized luminescence (CPL)-active ternary ...cholesteric liquid crystals (T-N*-LCs) in a commercial nematic liquid crystal (SLC1717, N-LCs) medium. Induced red CPL emission based on the energy acceptor of the achiral polymer DTBTF8 could be successfully promoted by the intermolecular Förster resonance energy transfer mechanism. The resulting T-N*-LCs can generate intensive CPL signals with g lum up to +0.70/–0.67. Interestingly, this kind of “on–off” CPL switching of T-N*-LCs can be manipulated by the applied direct current electric field.
The primary developing trends in flexible and stretchable electronics involve the innovation of material synthesis, mechanical design, and fabrication strategies that employ soft substrates. The ...biggest challenge is that the entire electronic system must allow not only bending but also stretching. Therefore, stretchable conductors become a crucial construction unit for the connection of working circuits of various stretchable devices. Owing to the success of stretchable conductors, various stretchable electronic devices are fabricated with the help of multiple manufacturing strategies, including stretchable heaters, stretchable energy conversion and storage devices, stretchable transistors, sensors and artificial skin. The continuous development of stretchable electronics has led to the new functionality of transparency, and the fabrication of transparent stretchable electronic devices has gained a lot of interest due to the potential of wearable electronic systems. This review presents technology developments in the preparation of related materials, fabrication strategies and various applications of stretchable electronics. It focuses on the fundamental structural design, mechanisms, and tactics, as well as on challenges and opportunities in the manufacture of stretchable electronic devices and their various applications.
The van der Waals heterojunctions of 2D materials offer tremendous opportunities in designing and investigating multifunctional and high‐performance electronic and optoelectronic devices. In this ...study, a vertical p–n diode is constructed by vertically stacking p‐type few‐layer black phosphorus (BP) on n‐type few‐layer indium selenide (InSe). The photodetector based on the heterojunction displays a broadband and gate‐modulated photoresponse under illumination. More importantly, by taking advantage of the strong linear dichroism of BP, the device demonstrates a highly polarization‐sensitive photocurrent with an anisotropy ratio as high as 0.83. Additionally, the device can function in a zero‐bias photovoltaic mode, enabling a fast photoresponse and low dark current. The external quantum efficiency can reach ≈3%, which is impressive for BP‐based devices. The results pave the way for the implementation of p‐BP/n‐InSe heterostructure as a promising candidate for future multifunctional optoelectronics and, especially, polarization‐sensitive applications.
A vertical van der Waals heterojunction between few‐layer p‐black phosphorus (BP) and n‐InSe is constructed. The photocurrent anisotropy ratio of the device can reach 0.83, substantially higher than those of reported BP‐based photodetectors. Moreover, this device features a wide‐range, fast, self‐powered, and gate‐modulated photoresponse. These results demonstrate the heterojunction as a promising candidate for multifunctional optoelectronics, especially, highly polarization‐sensitive applications.
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