The advance of fiber-shaped lithium ion batteries

With the development of wearable devices, much attention has been paid to the energy supply for these devices. Traditional batteries are not suitable for wearable devices due to their rigidity and high-density. Meanwhile, flexible and lightweight planar batteries cannot be fitted to the fabric well and have poor permeability, which lower the degree of the wearing comfort of the fabric. Therefore, the fiber-shaped lithium ion battery (LIB) becomes one of the best energy storage devices which can solve all the problems mentioned above because of its light-weight, flexibility, weavability and stretchability. However, the capacity of fiber-shaped LIBs is always lower than the capacity of planar batteries because of the low loading of active materials, and the circuit connection will be very complicated in further weaving. In this review article, we introduce the development of the fiber-shaped LIB, summarize the main challenges and finally point out the future direction of this field.     

银-氯化银柔性脑电电极的制备及其评价

本文采用丝网印刷技术制备了一种基于聚酰亚胺(PI)柔性塑料基片的Ag/AgCl脑电电极,并建立了一套系统评价柔性脑电电极性能的方法。评价方法主要包括扫描电镜(SEM)表征、电极电位/时间响应和稳定性测试、电化学阻抗测试、附着性测试。结果表明,该柔性电极表面为多孔结构,且与基底粘附性好;该电极呈现Ag/AgCl的电化学界面性质,其平衡电位为0.97±0.20mV,与Ag/AgCl粉末电极接近;且电极电位一致性和稳定性良好,最大极差电位不超过0.7mV,4h后电位漂移值在10μV/4min以内;经磨砂导电膏GT5处理后,电极-皮肤阻抗在5kΩ以内,满足脑电记录要求;相对于人体皮肤的高阻抗值,柔性电极-导电膏(GT20)的界面阻抗仅为166Ω·cm2。该评价方法系统、实用,可为制定相应国家标准提供技术参考。     

Wearable electrochemical sensors for noninvasive monitoring of health—a perspective

Global problems today such as aging society and rising health costs have made preventive care and health monitoring increasingly important, so research on wearable electrochemical sensors for noninvasive monitoring of health has become very popular during the past several years. But the new technologies cannot be some dues ex machine who wrought changes overnight. Problems about fundamentals of electrochemistry under wearable conditions, software algorithms to treat signal artifacts in the real wearable detection, reliable sensors for prolonged wearable sensing in body fluid, platforms for tests of newly developed sensors, validation of test results, reproducible and standardized sampling methods, as well as clinical significance of wearable testing data still require to be addressed. The short review is not to include all important works recently published or reach any conclusion but to focus on the challenges as well as some of the promising approaches that help to overcome these challenges.     

Wearable Electrochemical Sensors Based on Nanomaterials for Healthcare Applications

Wearable electrochemical sensors have attracted great interest in health care applications because of their flexibility, biocompatibility, low cost and light weight. This review briefly focuses on the main concepts and methods that are related to the application of nanoparticles (NPs) in wearable electrochemical sensors. Moreover, attempts to bring together different perspectives and terms that are commonly used in NPs-based wearable electrochemical sensors along with the introduction and discussion of common manufacturing methods and recent achievements. In the end, future challenges and prospects are also discussed on the development of wearable electrochemical sensors based on nanoparticles.     

柔性印刷可穿戴电化学传感器

实现对人体的健康监测和慢性病监测是包括材料科学、信息技术、电子技术、分析化学等科学领域在内的世界前沿课题。通过连续获取温度、压力、应力等物理信号来实现对人体活动情况和心率、血压、脑电图、心电图等实时监测的可穿戴设备已实现商业化,但连续监测人体体液、呼出气中的各类化学物质的可穿戴传感器仍面临许多问题,比如传感器的柔韧性、灵敏度、准确性以及与人体皮肤的贴合性等。针对这些问题,本文以柔性印刷技术为出发点,综述了各类柔性基底在电化学传感器/生物传感器领域的应用,同时对可穿戴传感器的发展方向提出了建议。     

Efficacy of a wideband flexible antenna on a multilayer polymeric nanocomposites Fe3O4-PDMS substrate for wearable applications

The recently introduced polymeric nanocomposites substrate layer technology is used in the design of a flexible antenna array for wearable applications. This new technology allows a considerable widening of the bandwidth of classical microstrip topologies. This means that a relatively wide band can be combined with a full ground plane in a very simple structure, which is an ideal combination in wearable applications. The wideband and flexible features enabled the antenna to mitigate body-detuning effects. The proposed antenna prototype consists of a 2 × 2 array of rectangular patch elements with dimensions of 70 × 70 × 4.2 mm³. The measurements are performed in free space, and on-body under bent conditions. The antenna working within the frequency band of 5 GHz–8.2 GHz, with a fractional impedance (FBW) bandwidth of 50.34%. The antenna demonstrates a maximum radiation efficiency of 60%, and 9.8 dB of realized gain. Since this antenna is intended for on body-centric wireless communication application, the specific absorption rate is evaluated when the antenna is placed on the right arm of a realistic human phantom. The performances and features of the proposed antenna paved the way for off-body connections in a WBAN and wearable applications including WiFi, telemedicine and Vehicle-to-Everything (V2X).     

Interface-Anchored Covalent Organic Frameworks@Amino-Modified Ti3C2Tx MXene on Nylon 6 Film for High-Performance Deformable Supercapacitors

Designing deformable supercapacitors (D-SCs) that have robust skeleton and smoothly active channels for charges kinetic migration and faradic storage are highly crucial for wearable systems. Here, we develop the high-performance D-SCs made of the covalent organic frameworks(COF)@amino-modified Ti₃C₂T_x deposited on decorated nylon 6 (DPA) film (COF@N-Ti₃C₂T_x/DPA) via layer-by-layer fabrication. The hierarchical COF@N-Ti₃C₂T_x/DPA exhibits admirable specific capacitance, rate performance and cycling stability in three-electrode system due to the superior H⁺ storage property and large interfacial charge transfer clarified by density functional theory calculations. Additionally, the solid-state D-SCs deliver favourable energy density and practical energy-supply applications. Particularly, the solid-state D-SCs present high deformable stabilities, with regard to 80.7, 80.6 and 83.4 % capacitance retention after 5000 bending cycles, 2000 stretching cycles and 5000 folding cycles, separately.     

Noninvasive monitoring of diabetes and hypoxia by wearable flow-through biosensors

Noninvasively collected sweat via clinically relevant procedure can be used for assessing the human condition, particularly for monitoring of diabetes and hypoxia. Positive correlations in variation rates, claimed as su?cient requirements for diagnostics, between glucose and lactate concentrations in sweat and the corresponding values in blood are shown. Continuous monitoring of human condition is possible only with the use of flow-through wearable devices providing a delivery of sweat to the biosensor almost immediately after excretion. Owing to both low sweat glucose content and inactivation of platinum by sweat components, the use of Prussian blue–based biosensors for wearable devices is preferable. Operation of the latter in power generation mode allows significant noise reduction and clear readout of the signal. Evaluating blood glucose through sweat analysis upon glucose tolerance test, we clearly show that humans can actually be monitored reliably via noninvasive approach.     

Biohydrogel from unsaturated polyesteramide: Synthesis,properties and utilization as electrolytic medium for electrochemical supercapacitors

The utilization of hydrogels derived from biopolymers as solid electrolyte (SE) of electrochemical supercapacitors (ESCs) is a topic of increasing interest because of their promising applications in biomedicine (e.g. for energy storage in autonomous implantable devices). In this work an unsaturated polyesteramide that contains phenylalanine, butenediol and fumarate as building blocks has been photo-crosslinked to obtain a hydrogel (UPEA-h). The structure of UPEA-h, which is characterized by a network of open interconnected pores surrounded by regions with compact morphology, favors ion transport, while the biodegradability and biocompatibility conferred by the α-amino acid unit and the ester group are appropriated for its usage in the biomedical field. Voltammetric and galvanostatic assays have been conducted to evaluate the behavior of UPEA-h when used as SE in ESCs with poly(3,4-ethylenedioxythiophene) (PEDOT) electrodes. Hence, PEDOT/UPEA-h devices displayed supercapacitor response of up 179 F/g and capacitance retention higher than 90%. Moreover, the long-term stability, leakage-current, and self-discharging response of PEDOT/UPEA-h ESCs reflect the great potential of UPEA-h as ion-conductive electrolyte. Indeed, the performance of PEDOT/UPEA-h is higher than found in analogous devices constructed using other biohydrogels as SE (e.g. κ-carrageenan, poly-γ-glutamic acid and cellulose hydrogels).     

Ion-selective potentiometric sensors with silicone sensing membranes: A review

Ion-selective electrodes (ISEs) are used widely in mainframe analyzers for clinical chemistry, but there is also an increasing interest in the development of paper-based devices, wearable and implantable sensors, and other miniaturized ISEs. This trend is spurring much research in developing solid contact materials that enable miniaturization. The development of suitable polymeric matrixes for such sensors has only received less attention. In particular, in spite of lifetime limitations and toxicity concerns, polymeric matrixes comprising plasticizers are still commonly used. To that end, we note the benefits of silicone materials as alternative polymeric matrixes and, in particular, their promise for enhanced biocompatibility. While there has been steady progress in the development of ISEs with silicone membranes, this topic has not been reviewed for many years. This review critically discusses key fundamental characteristics of ISEs with silicone sensing and reference membranes, including their biocompatibility, adhesion to device substrates, water uptake, polarity, common impurities, and commercial availabilities. This is followed by a discussion of specific types of silicones and their use in ISEs, with the goal to inform and stimulate future research efforts into such devices.