Chemresistor Smart Sensors from Silk Fibroin-Graphene Composites for Touch-free Wearables.

With the rapid development of wearable electronics, low-cost, multifunctional, ultrasensitive touch-free wearables for human-machine interaction and human/plant healthcare management have attracted great attention. The experience of fighting the COVID-19 epidemic has also confirmed the great significance of contactless sensation. Herein, a wearable smart-sensing platform using silk fibroin-reduced graphene oxide (SF-rGO) as bifunctional sensing active layers has been fabricated and integrated with a noncontact moisture/thermo sensor and Joule heater. As a result, the as-prepared smart sensor operated at 0.1 V exhibits good stability and sensitivity (sensor response of 60 for 97% RH) under a wide linear range of 6-97% RH, fast response/recover speed (real test: 21.51 s/85.62 s) toward touch-free humidity/temperature sensing for wearables, and thermal readings that can be accurately corrected by Joule heater. Impressively, it can achieve breath monitoring, mental state prediction, or elevator switching by identifying fingertip humidity variation. Prospectively, this all-in-one wearable smart sensor would set an example for improving sensing performance from structure-function relationship points of view and building a noncontact sensing system for daily life.

Monoclinic Bimetallic Prussian Blue Analog Cathode with High Capacity and Long Life for Advanced Sodium Storage.

Prussian blue analogs (PBAs) are regarded as promising cathode materials for sodium-ion batteries (SIBs), but most of them suffer from an incompatibility between capacity and structural stability. Herein, an innovative disodium ethylenediaminetetraacetate (Na2EDTA)-assisted hydrothermal method is proposed to synthesize monoclinic Fe-substituted Ni-rich PBA (H-PBA) cathodes for Na-ion storage. The as-designed H-PBA cathode combines the merits of the low strain of a Ni-based PBA framework and the enhanced capacity of N-Fe3+/Fe2+ redox sites. It can achieve superior sodium-storage performance in terms of capacity, rate capability, and cycle stability. Moreover, ex situ measurements reveal that solid solution (2.0-3.0 V) and phase-transition (3.0-4.0 V) reactions occur during the charge/discharge process to allow almost 1.5 Na+ storage in the H-PBA lattice. Meanwhile, the H-PBA//NaTi2(PO4)3@C full cell also delivers remarkable electrochemical properties. Prospectively, this work would promote the practical application of SIBs in grid-scale electric energy storage.

Wearable Self-Powered Smart Sensors for Portable Nutrition Monitoring.

Self-powered sensors have attracted great attention in the field of analysis owing to the necessity of power resources for the routine use of sensor devices. However, it is still challenging to construct wearable self-powered sensors in a simple and efficient way. Herein, wearable self-powered textile smart sensors based on advanced bifunctional polyaniline/reduced graphene oxide (PANI/RGO) films have been successfully developed for remote real-time detection of vitamin C. Specifically, a pH-assisted oil/water (O/W) self-assembly strategy was proposed to boost the O/W self-assembled PANI/RGO films via proton regulation. The as-obtained PANI/RGO films could be directly loaded on the textile substrate, with good capacitive and biosensing performance due to the multifunctionality of PANI and RGO, respectively. Moreover, both wearable power supply devices and wearable biosensors based on PANI/RGO films possess good electrochemical performance, which paves the way for the actual application of self-powered nutrition monitoring. Significantly, obvious signals have been obtained in the detection of vitamin C beverages, exhibiting promising application values in daily nutrition track necessities. Prospectively, this study would provide an effective and simple strategy for integrating wearable self-powered sensors, and the developed smart sensing system is an ideal choice for the portable detection of nutrition.

Wearable healthcare smart electrochemical biosensors based on co-assembled prussian blue-graphene film for glucose sensing.

Wearable film-based smart biosensors have been developed for real-time biomolecules detection. Particularly, interfacial co-assembly of reduced graphene oxide-prussian blue (PB-RGO) film through electrostatic interaction has been systematically studied by controllable pH values, achieving optimal PB-RGO nanofilms at oil/water (O/W) phase interface driven by minimization of interfacial free energy for wearable biosensors. As a result, as-prepared wearable biosensors of PB-RGO film could be easily woven into fabrics, exhibiting excellent glucose sensing performance in amperometric detection with a sensitivity of 27.78 µA mM-1 cm-2 and a detection limit of 7.94 µM, as well as impressive mechanical robustness of continuously undergoing thousands of bending or twist. Moreover, integrated wearable smartsensing system could realize remotely real-time detection of biomarkers in actual samples of beverages or human sweat via cellphones. Prospectively, interfacial co-assembly engineering driven by pH-induced electrostatic interaction would provide a simple and efficient approach for acquiring functional graphene composites films, and further fabricate wearable smartsensing devices in health monitoring fields.

Wearable Motion Smartsensors Self-Powered by Core-Shell Au@Pt Methanol Fuel Cells.

A wearable self-powered sensor is a promising frontier in recent flexible electronic devices. In this work, a wearable fuel cell (FC)-type self-powering motion smartsensor has been fabricated, particularly in choosing methanol vapor as a target fuel for the first time. The core-shell structure of Pt@Au/N-rGO and the porous carbon network act as methanol oxidation and oxygen reduction reaction catalysts, with a highly conductive alkaline hydrogel as a solid-state electrolyte. As a result, a wearable FC for a self-powered sensing system demonstrates excellent sensing performance toward 2-20% (v/v) methanol vapor with a maximum power density of 2.26 µW cm-1 and good mechanical behaviors during the bending or twisting process. Significantly, this wearable FC device could power strain sensors of human motion, and real-time signals can be easily remotely detected via a cellphone. With attractive biocompatibility and self-powering performance, wearable FCs for a self-powering system would provide new opportunities for next-generation flexible smartsensing electronics and initiate a developed self-powering platform in future practical application of wearable smart monitoring.

Wearable Helical Molybdenum Nitride Supercapacitors for Self-Powered Healthcare Smartsensors.

To meet the increasing demand for wearable sensing devices, flexible supercapacitors (SCs) as energy storage devices play significant roles in powering sensors/biosensors for healthcare monitoring. Because of its high conductivity and remarkable specific capacitance in SCs, molybdenum nitride (MoN) has been widely used. Herein, a flexible helical structure of MoN modified on nitrogen-doped carbon cloth (CC@CN@MoN) has been prepared by a simple nitride process, delivering an ultralong cycle life of 10,000 cycles and high areal capacitance of 467.6 mF cm-2 as SCs. Moreover, the as-fabricated flexible all-solid-state asymmetrical SCs (ASCs) of CC@CN@MoN//CC@NiCo2O4 demonstrated outstanding electrochemical behavior after 10,000 cycles and over 90% retention, and the value of areal capacitance could reach 90.8 mF cm-2 at 10 mA cm-2. Integrated with solar energy, ASCs could be used as a self-powered energy system for strain sensors in detecting human movement, and finger movements could be further real-time monitored remotely via a smartphone. Prospectively, wearable helical MoN solid-state SCs for self-powered strain smartsensors would inspire the development of structured materials in the application of energy storage, portable self-powering, and strain or chemical/biochemical smartsensors.

Wearable Porous Au Smartsensors for On-Site Detection of Multiple Metal Ions.

Owing to advantages of miniaturization, convenient integration, flexibility, and real-time monitoring, wearable smartsensors have received numerous attention and greatly developed in various fields. However, there usually appears a contradiction between sensing behaviors and simple fabricated methods, seriously limiting on-site detection of actual samples. In this work, a porous Au-based smartsensor has been in situ prepared by combining screen printing technology and sacrificial template electrodeposition. Thanks to abundant active adsorption sites, multiple metal ions (Pb, Cu, and Hg) can be easily achieved on-site detection by this smart platform with a low limit of detection as well as high sensitivity, excellent selectivity, good stability, repeatability, and bending performance. Significantly, it also exhibits a reliable detective capability in actual liquid cosmetic samples with a portable cellphone, which identically corresponds to standard inductively coupled plasma-mass spectrometry (ICP--MS) evaluation. Therefore, this wearable smartsensor provides a promising platform for artificial intelligence application in future daily life.

Wearable Textile Supercapacitors for Self-Powered Enzyme-Free Smartsensors.

Wearable energy storage and flexible body biomolecule detection are two key factors for real-time monitoring of human health in a practical environment. It would be rather exciting if one wearable system could be used for carrying out both energy storage and biomolecule detection. Herein, carbon fiber-based NiCoO2 nanosheets coated with nitrogen-doped carbon (CF@NiCoO2@N-C) have been prepared via a simple electrochemical deposition method. Interestingly, being a dual-functional active material, CF@NiCoO2@N-C exhibits excellent behaviors as a supercapacitor and prominent electrocatalytic properties, which can be applied for enzyme-free biosensor. It exhibits outstanding energy storage, high capacitive stability (94% capacitive retention after 10,000 cycles), and pre-eminent flexible ability (95% capacitive retention after 10,000 bending cycles), as well as high sensitivity for enzyme-free glucose detection (592  µA mM-1). Moreover, the CF@NiCoO2@N-C-based wearable supercapacitors would be used as self-powered energy systems for enzyme-free biosensors. Integrating with bluetooth, we have successfully developed a wearable self-powered enzyme-free smartsensor, remotely controlled using a smartphone for health monitoring in a practical environment. From this prospective study, it was found that the design of wearable self-powered smartsensors, demonstrating energy storage and enzyme-free biosensing in one system, provides a promising device for detecting body biomolecules, which has the potential to be implemented in the artificial intelligent fields.

Wearable biomolecule smartsensors based on one-step fabricated berlin green printed arrays.

The wearable smart detection of body biomolecules and biomarkers is being of significance in the practical fields. Hydrogen peroxide (H2O2) is a product of some enzyme-catalyzed biomolecular reactions. The detection of H2O2 could reflect the concentration information of the enzyme reaction biomolecule substrate such as glucose. A high-performance berlin green (BG) carbon ink for monitoring H2O2 was prepared in this work. And we have successfully developed the wearable smartsensors for detecting H2O2 and glucose based on one-step fabricated BG arrays by screen-printing technology. Comparing with other detection methods, these sensors are wearable, movable, flexible and biocompatible for monitoring biomolecules. As a result, the sensors exhibited good sensitivity, specificity, stability and reproductivity towards H2O2 and glucose. Additionally, there also received stable response after near one hundred times stretching and thousands of bending. Moreover, the wearable sensors could be easily remotely controlled by a smart phone, when integrated with wireless into the device. In prospective studies, the one-step fabricated wearable smartsensors is of great significance in developing a straightforward, highly-efficient and low-cost method for actual detection of biomolecules reflecting body health status, and would potentially be applied in the artificial intelligence (AI) fields.

Flexible electrochromic supercapacitor hybrid electrodes based on tungsten oxide films and silver nanowires.

We successfully fabricate flexible electrochromic supercapacitor (SC) electrodes employing novel flexible transparent conducting substrates. The as-synthesized flexible electrochromic SC electrodes exhibit great electrochemical performances (13.6 mF cm(-2), 138.2 F g(-1)) and high coloration efficiency (80.2 cm(2) C(-1)), which demonstrate their potential applications in flexible smart windows combining energy storage and electrochromism.