Stretchable multifunctional sensor based on porous silver nanowire/silicone rubber conductive film

As one of the promising human–machine interfaces,wearable sensors play an important role in modern society,which advances the development of wearable fields,especially in the promising applications of electronic skin(e-skin),robotics,prosthetics,healthcare.In the last decades,wearable sensors tend to be capable of attractive capabilities such as miniaturization,multifunction,smart integration,wearable properties such as lightweight,flexibility,stretchability,conformability for wider applications.In this work,we developed a stretchable multifunctional sensor based on porous silver nanowire/silicone rubber conductive film(P-AgNW/SR).Its unique structural configuration,i.e.,an assembly of the P-AgNW/SR with good conductivity,stability,resistance response,the insulated silicone rubber layer,provided the feasibility for realizing multiple sensing capabilities.Specifically,porous microstructures of the P-AgNW/SR made the device to be used for pressure sensing,exhibiting outstanding dynamic and static resistive responsive behaviors and having a maximum sensitivity of 9.062%∙N^(−1) in a continuous compressive force range of~16 N.With the merit of the good piezoresistive property of AgNW/SR networks embedded into the surface of micropores of the P-AgNW/SR,the device was verified to be a temperature sensor for detecting temperature changes in the human body and environment.The temperature sensor had good sensitivity of 0.844%∙℃^(−1),high linearity of 0.999 in the range of 25–125℃,remarkable dynamic stability.Besides,the developed sensor was demonstrated to be a single electrode-triboelectric sensor for active sensing,owing to the unique assembly of the conductive PAgNW/SR electrode and the silicone rubber friction layer.Based on the coupling effect of the triboelectrification and electrostatic induction,the generated electrical signals could be used to sense the human motions,according to the quantitative correlation between the human motions and the features in amplitude and waveform of the output signals.Thus,the developed stretchable sensor successfully achieved the integration of two types of passive sensing capabilities,i.e.,pressure and temperature sensing,and one type of active sensing capability,i.e.,triboelectric sensing,demonstrating the feasibility of monitoring multiple variables of the human body and environment.

High-performance hybrid nanogenerator for selfpowered wireless multi-sensing microsystems

Wireless sensor network nodes are widely used in wearable devices,consumer electronics,and industrial electronics and are a crucial component of the Internet of Things(IoT).Recently,advanced power technology with sustainable energy supply and pollution-free characteristics has become a popular research focus.Herein,to realize an unattended and reliable power supply unit suitable for distributed IoT systems,we develop a high-performance triboelectricelectromagnetic hybrid nanogenerator(TEHNG)to harvest mechanical energy.The TEHNG achieves a high load power of 21.8 mW by implementing improvements of material optimization,configuration optimization and pyramid microstructure design.To realize a self-powered integrated microsystem,a power management module,energy storage module,sensing signal processing module,and microcontroller unit are integrated into the TEHNG.Furthermore,an all-in-one wireless multisensing microsystem comprising the TEHNG,the abovementioned integrated functional circuit and three sensors(temperature,pressure,and ultraviolet)is built.The milliwatt microsystem operates continuously with the TEHNG as the only power supply,achieving self-powered operations of sensing environmental variables and transmitting wireless data to a terminal in real time.This shows tremendous application potential in the IoT field.

连续退化和随机冲击下基于状态的结构维修策略优化（英文）

目的:结构在使用过程中,其性能往往发生劣化而导致其安全性能(可靠度)不断降低。本文旨在探讨结构在连续退化和冲击荷载共同作用下,其可靠度随时间的变化情况。此外,研究结构的最佳维修策略,使其在满足可靠度约束条件的同时,将平均费用降到最低。创新点:1.在连续退化和冲击荷载的共同影响下,建立结构时变可靠度计算模型。2.在前述可靠度分析的基础上,建立基于状态维修的非周期检测模型;基于剩余使用寿命检测策略,确定检测时间,并确定系统的最优维护策略,旨在将平均维护成本率降至最低。3.针对无限时间域和有限时间域,分别确定对应的最佳维修策略。方法:1.通过理论推导,构建结构时变可靠度计算公式(公式(13)),分析各参数与可靠度之间的变化关系(图4)。2.通过仿真模拟,运用蒙特卡洛法确定结构在使用过程中的最佳维修策略(图5和6)。结论:1.与仅考虑连续退化的情况相比,随机冲击荷载的存在,使得系统的可靠度降低,更容易发生失效。2.冲击载荷的存在,对最佳维修策略具有显著影响。3.有限时间域的最优解与无限时间域的最优解之间存在很大的不同,因此,有必要对这两种情况分别进行研究。

Recent progress in silk fibroin-based flexible electronics

With the rapid development of the Internet of Things(loT)and the emergence of 5G,traditional silicon-based electronics no Ion ger fully meet market dema nds such as nonplanar application scenarios due to mechanical mismatch.This provides unprecedented opportunities for flexible electronics that bypass the physical rigidity through the introduction of flexible materials.In recent decades,biological materials with outstanding biocompatibility and biodegradability,which are considered some of the most promising candidates for next-generation flexible electronics,have received increasing attention,e.g.,silk fibroin,cellulose,pectin,chitosan,and melanin.Among them,silk fibroin presents greater superiorities in biocompatibility and biodegradability,and moreover,it also possesses a variety of attractive properties,such as adjustable water solubility,remarkable optical transmittance,high mechanical robustness,light weight,and ease of processing,which are partially or even completely lacking in other biological materials.Therefore,silk fibroin has been widely used as fundamental components for the construction of biocompatible flexible electronics,particularly for wearable and implantable devices.Furthermore,in recent years,more attention has been paid to the investigation of the functional characteristics of silk fibroin;such as the dielectric properties,piezoelectric properties,strong ability to lose electrons,and sensitivity to environmental variables.Here,this paper not only reviews the preparation technologies for various forms of silk fibroin and the recent progress in the use of silk fibroin as a fundamental material but also focuses on the recent advaneed works in which silk fibroin serves as functional components.Additi on ally,the challenges and future development of silk fibroin-based flexible electronics are summarized.

Wearable multi-sensing double-chain thermoelectric generator

Wearable electronics play a crucial role in advancing the rapid development of artificial intelligence,and as an attractive future vision,all-in-one wearable microsystems integrating powering,sensing,actuating and other functional components on a single chip have become an appealing tendency.Herein,we propose a wearable thermoelectric generator(ThEG)with a novel double-chain configuration to simultaneously realize sustainable energy harvesting and multi-functional sensing.In contrast to traditional single-chain ThEGs with the sole function of thermal energy harvesting,each individual chain of the developed double-chain thermoelectric generator(DC-ThEG)can be utilized to scavenge heat energy,and moreover,the combination of the two chains can be employed as functional sensing electrodes at the same time.The mature mass-fabrication technology of screen printing was successfully introduced to print n-type and p-type thermoelectric inks atop a polymeric substrate to form thermocouples to construct two independent chains,which makes this DC-ThEG flexible,high-performance and cost-efficient.The emerging material of silk fibroin was employed to cover the gap of the fabricated two chains to serve as a functional layer for sensing the existence of liquid water molecules in the air and the temperature.The powering and sensing functions of the developed DC-ThEG and their interactions were systematically studied via experimental measurements,which proved the DC-ThEG to be a robust multi-functional power source with a 151 mV open-circuit voltage.In addition,it was successfully demonstrated that this DC-ThEG can convert heat energy to achieve a 3.3 V output,matching common power demands of wearable electronics,and harvest biothermal energy to drive commercial electronics(i.e.,a calculator).The integration approach of powering and multi-functional sensing based on this new double-chain configuration might open a new chapter in advanced thermoelectric generators,especially in the applications of all-in-one self-powered microsystems.

Integrated hybrid sensing and microenergy for compact active microsystems

Wearable electronics,as essential components of the Internet of Things(IoT),have attracted widespread attention,and the trend is to configure attractive wearable smart microsystems by integrating sensing,powering,and other,functions.Herein,we developed an elastic hybrid triboelectric-electromagnetic microenergy harvester(named EHTE)to realize hybrid sensing and microenergy simultaneously.This EHTE is a highly integrated triboelectric nanogenerator(TENG)and electromagnetic nanogenerator(EMG).Based on the triboelectric-electromagnetic hybrid mechanism,an enhanced electrical output of the EHTE was achieved successfully,which demonstrates the feasibility of the EHTE for microelectronics powering.Moreover,with the merits of the EMG,the developed hybrid microenergy harvester integrated both active frequency sensing and passive inductive sensing capabilities.Specifically,the almost linear correlation of the electromagnetic outputs to the frequencies of the external stimulus endowed the proposed EHTE with an outstanding active frequency sensing ability.in addition,due to the unique structural configuration of the EMG(i.e,a conductive permanent magnet(PM),hybrid deformation layer,and flexible printed circuit board(FPCB)coil),an opportunity was provided for the developed EHTE to serve as a passive inductive sensor based on the eddy current effect(ie.,a form of electromagnetic induction).Therefore,the developed EHTE successfully achieved the integration of hybrid sensing(i.e,active frequency sensing and passive inductive sensing)and microenergy(ie,the combination of electromagnetic effect and triboelectric effect)within a single device,which demonstrates the potential of this newly developed EHTE for wearable electronic applications,especially in applications of compact active microsystems.

Electron-Ion Coupling Mechanism to Construct Stable Output Performance Nanogenerator

Recently,triboelectric nanogenerators(TENGs)have been promoted as an effective technique for ambient energy harvesting,given their large power density and high energy conversion efficiency.However,traditional TENGs based on the combination of triboelectrification effect and electrostatic induction have proven susceptible to environmental influence,which intensively restricts their application range.Herein,a new coupling mechanism based on electrostatic induction and ion conduction is proposed to construct flexible stable output performance TENGs(SOP-TENGs).The calcium chloride doped-cellulose nanofibril(CaCl_(2)-CNF)film made of natural carrots was successfully introduced to realize this coupling,resulting from its intrinsic properties as natural nanofibril hydrogel serving as both triboelectric layer and electrode.The coupling of two conductive mechanisms of SOP-TENG was comprehensively investigated through electrical measurements,including the effects of moisture content,relative humidity,and electrode size.In contrast to the conventional hydrogel ionotronic TENGs that require moisture as the carrier for ion transfer and use a hydrogel layer as the electrode,the use of a CaCl_(2)-CNF film(i.e.,ion-doped natural hydrogel layer)as a friction layer in the proposed SOP-TENG effectively realizes a superstable electrical output under varying moisture contents and relative humidity due to the compound transfer mechanism of ions and electrons.This new working principle based on the coupling of electrostatic induction and ion conduction opens a wider range of applications for the hydrogel ionotronic TENGs,as the superstable electrical output enables them to be more widely applied in various complex environments to supply energy for low-power electronic devices.

Electron-Ion Coupling Mechanism to Construct Stable Output Performance Nanogenerator

Recently,triboelectric nanogenerators(TENGs)have been promoted as an effective technique for ambient energy harvesting,given their large power density and high energy conversion efficiency.However,traditional TENGs based on the combination of triboelectrification effect and electrostatic induction have proven susceptible to environmental influence,which intensively restricts their application range.Herein,a new coupling mechanism based on electrostatic induction and ion conduction is proposed to construct flexible stable output performance TENGs(SOP-TENGs).The calcium chloride doped-cellulose nanofibril(CaCl_(2)-CNF)film made of natural carrots was successfully introduced to realize this coupling,resulting from its intrinsic properties as natural nanofibril hydrogel serving as both triboelectric layer and electrode.The coupling of two conductive mechanisms of SOP-TENG was comprehensively investigated through electrical measurements,including the effects of moisture content,relative humidity,and electrode size.In contrast to the conventional hydrogel ionotronic TENGs that require moisture as the carrier for ion transfer and use a hydrogel layer as the electrode,the use of a CaCl_(2)-CNF film(i.e.,ion-doped natural hydrogel layer)as a friction layer in the proposed SOP-TENG effectively realizes a superstable electrical output under varying moisture contents and relative humidity due to the compound transfer mechanism of ions and electrons.This new working principle based on the coupling of electrostatic induction and ion conduction opens a wider range of applications for the hydrogel ionotronic TENGs,as the superstable electrical output enables them to be more widely applied in various complex environments to supply energy for low-power electronic devices.

Transparent micropatterned conductive films based on highlyordered nanowire network

Transparent conductive films that are based on nanowire networks are essential to construct flexible,wearable,and even stretchable electronics.However,large-scale precise micropatterning,especially with regard to the controllability of the organizing orientation of nanowires,is a critical challenge.Herein,we proposed a liquid film rupture self-assembly approach for manufacturing transparent conductive films with microstructure arrays based on a highly ordered nanowire network.The large-scale microstructure conductive films were fabricated through air-liquid interface self-assembly and liquid film rupture self-assembly.Six typical micropattern morphologies,including square,hexagon,circle,serpentine,etc.,were prepared to reveal the universal applicability of the proposed approach.The homogeneity and controllability of this approach were verified for multiple assemblies.With the assembly cycles increasing,the optical transmittance decreases slightly.In addition,theoretical model analysis is carried out,and the analytical formula of the speed of the film moving with the surface tension and the density of the liquid film is presented.Finally,the feasibility of this approach for piezoresistive strain sensors is verified.This fabrication approach demonstrated a cost-effective and efficient method for precisely arranging nanowires,which is useful in transparent and wearable applications.