Biodegradable food packaging gains a lot of significance for the sake of environment, and increased prohibition of using plastic package. Further, the functionality of sensing food status is in great importance because of health and environmental issues. Here, we report laser-induced graphene based on paper for smart food decay sensor. Direct irradiation of continuous-wave laser converts any type of commercially available papers into effective laser-induced graphene (LIG). Paper-based LIG electrodes have enough conductivity to be applicated as the electrical circuit with the sensibility on certain aspects. LIG electrode could detect either temperature alteration or gaseous chemical compounds that ejects from spoiling food. As a proof-of-concept, we developed the smart food decay sensor based on LIG-on-paper with detecting temperature of food and food decaying gas, which information is able to directly sent to users' mobile devices through Wi-Fi network. Herein, we believe that the smart food decay sensor could contribute on environment as green electronics, and food safety with preservation of food.
Abstract As environmental issues have become the dominant agenda worldwide, the necessity for more environmentally friendly electronics has recently emerged. Accordingly, biodegradable or nature‐derived materials for green electronics have attracted increased interest. Initially, metal‐green hybrid electronics are extensively studied. Although these materials are partially biodegradable, they have high utility owing to their metallic components. Subsequently, carbon‐framed materials (such as graphite, cylindrical carbon nanomaterials, graphene, graphene oxide, laser‐induced graphene) have been investigated. This has led to the adoption of various strategies for carbon‐based materials, such as blending them with biodegradable materials. Moreover, various conductive polymers have been developed and researchers have studied their potential use in green electronics. Researchers have attempted to fabricate conductive polymer composites with high biodegradability by shortening the polymer chains. Furthermore, various physical, chemical, and biological sensors that are essential to modern society have been studied using biodegradable compounds. These recent advances in green electronics have paved the way toward their application in real life, providing a brighter future for society.
Abstract Along with visual and tactile sensations, thermal sensation by temperature feeling on the skin can provide rich physical information on the environment and objects. With a simple touch of objects, relative temperature can be sensed and even objects can be differentiated with different thermal properties without any visual cue. Thus, artificially reproducing accurate/controllable thermal sensation haptic signals on human epidermis will certainly be a major research area to reconstruct a more realistic virtual reality (VR) environment. In this study, for the first time, a skin‐like, highly soft and stretchable and bi‐functional (both cold and hot sensation) thermo‐haptic device is reported for wearable VR applications with a single device structure (not separate heater and cooler). The skin‐like thermo‐haptic (STH) device can actively cool down and heat up deformable skin surfaces with instantaneous and accurate adjustment of temperature based upon a feedback control algorithm to mimic desirable thermal sensation with 230% stretchability. As a proof‐of‐concept, the STH device is integrated with a finger‐motion tracking glove to provide artificial thermal sensation information to the skin in various situations such as touching cold beer bottles and hot coffee cups in virtual space. This new type of STH device can offer potential implications for next‐generation haptic devices to provide unique thermal information for a more realistic virtual‐world field and medical thermal treatment.
Abstract This study proposes a Janus structure‐based stretchable and breathable thermoelectric skin with radiative cooling (RC) and solar heating (SH) functionalities for sustainable energy harvesting. The challenge of the wearable thermoelectric generator arises from the small temperature difference. Thus, this dual‐sided structure maximizes the thermal gradient between the body and the surrounding environment, unlike the previous works that rather concentrate on the efficiency of the thermoelectric generator itself. The Janus structure allows the device to switch to the other mode, optimizing electricity generation from a given weather condition. For these functionalities, for the first time, boron nitride‐polydimethylsiloxane (BP) and graphene nanoplatelet‐polydimethylsiloxane (GP) nanofiber (NF) are developed as substrates. The BP NF generates the RC capability of Δ T cooling = 4 °C, and the high solar absorbance of the GP NF enables it to be photothermally heated. The flip‐overable thermoelectric skin (FoTES) achieves a maximum power output ( P max ) of 5.73 µW cm −2 in RC mode, surpassing SH mode by 5.55 µW cm −2 in the morning. In the afternoon, it generates a P max of 18.59 µW cm −2 in SH mode, outperforming RC mode by 15.56 µW cm −2 . This work contributes to the advancement of wearable electronics, offering a sustainable power source in a wearable form.
Abstract In spite of its excellent electrical, mechanical, and low‐cost characteristics, copper nanowire has fatal issues in the oxidation problem and the lack of biological compatibility, which occasionally outweighs its advantages and limits its usage as electronics or biodevice applications. In this study, a novel wet chemical synthesis method is developed for the oxidation‐free Cu–Au core–shell nanowire based on the prepared Cu nanowire with alkylamine‐mediated synthesis and ligand exchange. The synthesized Cu–Au core–shell nanowire exhibits improved electrical stability against thermal oxidation under the harsh environment of 80 °C and 80% relative humidity. Additionally, to substantiate suitability for the biomedical application, the enhanced chemical stability and biocompatibility are investigated by utilizing the artificial perspiration and the cell culture. As a proof‐of‐concept demonstration, high performance wearable electromyogram (EMG), electrocardiogram (ECG) sensors for electrophysiological monitoring with the Cu–Au core–shell nanowire electrode are demonstrated with superior oxidation‐resistance and biocompatibility even after the harsh environment test. The Cu–Au core–shell nanowire can provide promising, cost‐effective electrode materials for various wearable electronics applications.
Abstract The decline in muscular strength and control due to age or stroke-related side-effect has afflicted many individuals with neuromotor disorders because it affects essential motor functions to perform everyday activities and restrains their functional independence. In this regard, a myriad of wearable exoskeletons and functional components have been developed to deliver mechanical force for assisting the movements of different human body parts. However, many of the reported wearable exoskeletons suffer from several critical drawbacks that limit functional usage and practicality despite the significant technological advance of general wearable exoskeletons. Here, this review offers a comprehensive summary of the recent advances of wearable exoskeletons and their constituting functional components. In addition, we discuss the essential challenges that need to be tackled to enhance the functional practicality of the next-generation wearable exoskeletons in assisting the strength and control of individuals with neuromotor disorders.
Controlling the surface morphology of the electrode on the nanoscale has been studied extensively because the surface morphology of a material directly leads to the functionalization in various fields of studies. In this study, we designed a simple and cost-effective method to fine-tune the surface morphology and create controlled nanopores on the silver electrode by utilizing 2-ethoxyethanol and two successive heat treatments. High electrical conductivity and mechanical robustness of nanoporous silver corroborate its prospect to be employed in various applications requiring a certain degree of flexibility. As a proof-of-concept, a high-performance supercapacitor was fabricated by electrodepositing MnO2. This method is expected to be useful in various electronic applications as well as energy storage devices.
Animal locomotion offers valuable references as it is a critical component of survival as animals adapting to a specific environment. Especially, underwater locomotion poses a challenge because water exerts a high antagonistic drag force against the direction of progress. However, marine vertebrates usually use much lower aerobic energy for locomotion than aerial or terrestrial vertebrates due to their unique intermittent gliding locomotion. None of the prior works demonstrate the locomotive strategies of marine vertebrates. Herein, an untethered soft robotic fish capable of reconstructing the marine vertebrates’ effective locomotion and traveling underwater by controlling localized buoyancy with thermoelectric pneumatic actuators is introduced. The actuators enable both heating and cooling to control a localized buoyancy while providing a substantial driving force to the system. Besides mimicking the locomotion, the bidirectional communication system enables the untethered delivery of commands to the underwater subject and real‐time acquisition of the robotic fish's physical information. Underwater imaging validates the fish's practical use as a drone, allowing for inspecting the aquatic environment that is not easily accessible to humans. Future work studies the operation of the robotic fish as a collective swarm to examine a broader range of the underwater area and conduct various strategic missions.
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