Energy Autonomous Wearable Sensors for Smart Healthcare: A Review

Energy Autonomous Wearable Sensors (EAWS) have attracted a large interest due to their potential to provide reliable measurements and continuous bioelectric signals, which help to reduce health risk factors early on, ongoing assessment for disease prevention, and maintaining optimum, lifelong health quality. This review paper presents recent developments and state-of-the-art research related to three critical elements that enable an EAWS. The first element is wearable sensors, which monitor human body physiological signals and activities. Emphasis is given on explaining different types of transduction mechanisms presented, and emerging materials and fabrication techniques. The second element is the flexible and wearable energy storage device to drive low-power electronics and the software needed for automatic detection of unstable physiological parameters. The third is the flexible and stretchable energy harvesting module to recharge batteries for continuous operation of wearable sensors. We conclude by discussing some of the technical challenges in realizing energy-autonomous wearable sensing technologies and possible solutions for overcoming them.

[1]  Yucheng Ding,et al.  Self-powered flexible pressure sensors with vertically well-aligned piezoelectric nanowire arrays for monitoring vital signs , 2015 .

[2]  Qiuyun Ouyang,et al.  Three-dimensional hierarchical MoS2 nanoflake array/carbon cloth as high-performance flexible lithium-ion battery anodes , 2014 .

[3]  Zengmei Wang,et al.  PVDF/BCT-BZT Nanocomposite Film for a Piezo-Driven Self-Charging Power Cell , 2018 .

[4]  Myeong-Lok Seol,et al.  High-performance nanopattern triboelectric generator by block copolymer lithography , 2015 .

[5]  Hongwei Zhu,et al.  Recent advances in wearable tactile sensors: Materials, sensing mechanisms, and device performance , 2017 .

[6]  John A Rogers,et al.  Imprintable, Bendable, and Shape‐Conformable Polymer Electrolytes for Versatile‐Shaped Lithium‐Ion Batteries , 2013, Advanced materials.

[7]  John A Rogers,et al.  Skin sensors are the future of health care , 2019, Nature.

[8]  Peiyi Song,et al.  Self-adaptive Bioinspired Hummingbird-wing Stimulated Triboelectric Nanogenerators , 2017, Scientific Reports.

[9]  Sheng Xu,et al.  Soft, stretchable, high power density electronic skin-based biofuel cells for scavenging energy from human sweat , 2017 .

[10]  Deqing Mei,et al.  Wearable thermoelectric generator to harvest body heat for powering a miniaturized accelerometer , 2018 .

[11]  Chiyul Yoon,et al.  Ferroelectret film-based patch-type sensor for continuous blood pressure monitoring , 2014 .

[12]  K. Razeeb,et al.  Fabrication of micro-thermoelectric devices for power generation and the thermal management of photonic devices , 2019, Journal of Micromechanics and Microengineering.

[13]  Daniel A. Steingart,et al.  Review—Power Sources for the Internet of Things , 2018 .

[14]  Byeong-Su Kim,et al.  Flexible Textile Strain Wireless Sensor Functionalized with Hybrid Carbon Nanomaterials Supported ZnO Nanowires with Controlled Aspect Ratio , 2016 .

[15]  Fan Yang,et al.  In Vivo Self-Powered Wireless Cardiac Monitoring via Implantable Triboelectric Nanogenerator. , 2016, ACS nano.

[16]  Transparent, Stretchable and Direct Skin-Touchable Multi-Functional Electronic Skin Sensors , 2018 .

[17]  Haihua Xu,et al.  An ultra-stretchable, highly sensitive and biocompatible capacitive strain sensor from an ionic nanocomposite for on-skin monitoring. , 2019, Nanoscale.

[18]  M. Kaltenbrunner,et al.  An ultra-lightweight design for imperceptible plastic electronics , 2013, Nature.

[19]  Franklin Bien,et al.  Soft, smart contact lenses with integrations of wireless circuits, glucose sensors, and displays , 2018, Science Advances.

[20]  Benjamin C. K. Tee,et al.  Flexible polymer transistors with high pressure sensitivity for application in electronic skin and health monitoring , 2013, Nature Communications.

[21]  Xuemei Sun,et al.  Weaving Sensing Fibers into Electrochemical Fabric for Real‐Time Health Monitoring , 2018, Advanced Functional Materials.

[22]  Haiyang Zou,et al.  A Highly Stretchable and Washable All-Yarn-Based Self-Charging Knitting Power Textile Composed of Fiber Triboelectric Nanogenerators and Supercapacitors. , 2017, ACS nano.

[23]  Andrea Facchinetti,et al.  Head-to-head comparison of the accuracy of Abbott FreeStyle Libre and Dexcom G5 mobile. , 2018, Nutrition, metabolism, and cardiovascular diseases : NMCD.

[24]  J. Lewis,et al.  3D Printing of Interdigitated Li‐Ion Microbattery Architectures , 2013, Advanced materials.

[25]  Ali Javey,et al.  Wearable sweat sensors , 2018 .

[26]  Zhong Lin Wang,et al.  Self-powered textile for wearable electronics by hybridizing fiber-shaped nanogenerators, solar cells, and supercapacitors , 2016, Science Advances.

[27]  Itthipon Jeerapan.  Wearable Skin-Worn Enzyme-Based Electrochemical Devices: Biosensing, Energy Harvesting, and Self-Powered Sensing , 2019, Wearable Devices - the Big Wave of Innovation.

[28]  Chuan Wang,et al.  Physical and Chemical Sensing With Electronic Skin , 2019, Proceedings of the IEEE.

[29]  Yi Cui,et al.  Thin, flexible secondary Li-ion paper batteries. , 2010, ACS nano.

[30]  Manoj Kumar Gupta,et al.  Unidirectional High‐Power Generation via Stress‐Induced Dipole Alignment from ZnSnO3 Nanocubes/Polymer Hybrid Piezoelectric Nanogenerator , 2014 .

[31]  Sungjoon Lim,et al.  Recent advances in noninvasive flexible and wearable wireless biosensors. , 2019, Biosensors & bioelectronics.

[32]  Benjamin C. K. Tee,et al.  Skin-like pressure and strain sensors based on transparent elastic films of carbon nanotubes. , 2011, Nature nanotechnology.

[33]  Jun Wang,et al.  A highly sensitive and flexible pressure sensor with electrodes and elastomeric interlayer containing silver nanowires. , 2015, Nanoscale.

[34]  Daniel Alquier,et al.  Organic/Inorganic Hybrid Stretchable Piezoelectric Nanogenerators for Self‐Powered Wearable Electronics , 2018 .

[35]  Hua Zhang,et al.  Electrochemical energy storage devices for wearable technology: a rationale for materials selection and cell design. , 2018, Chemical Society reviews.

[36]  Wendong Zhang,et al.  Highly Sensitive, Stretchable Strain Sensor Based on Ag@COOH‐Functionalized CNTs for Stroke and Pronunciation Recognition , 2019, Advanced Electronic Materials.

[37]  Zhuo Liu,et al.  Wearable and Implantable Triboelectric Nanogenerators , 2019, Advanced Functional Materials.

[38]  Yang Liu,et al.  Sensitive, high-strain, high-rate bodily motion sensors based on graphene-rubber composites. , 2014, ACS nano.

[39]  Hyung Joon Shim,et al.  Wearable Electrocardiogram Monitor Using Carbon Nanotube Electronics and Color-Tunable Organic Light-Emitting Diodes. , 2017, ACS nano.

[40]  Hao Sun,et al.  Integrating photovoltaic conversion and lithium ion storage into a flexible fiber , 2016 .

[41]  Kuniharu Takei,et al.  Multifunctional Skin‐Inspired Flexible Sensor Systems for Wearable Electronics , 2019, Advanced Materials Technologies.

[42]  Sam Emaminejad,et al.  Autonomous sweat extraction and analysis applied to cystic fibrosis and glucose monitoring using a fully integrated wearable platform , 2017, Proceedings of the National Academy of Sciences.

[43]  Carlos Manuel Ferreira Carvalho,et al.  On the Feasibility of Indoor Light Energy Harvesting for Wireless Sensor Networks , 2014 .

[44]  J. Bahk,et al.  Flexible thermoelectric materials and device optimization for wearable energy harvesting , 2015 .

[45]  Jin-Woo Park,et al.  Wearable and Transparent Capacitive Strain Sensor with High Sensitivity Based on Patterned Ag Nanowire Networks. , 2017, ACS applied materials & interfaces.

[46]  Saleh A. Al-Sayari,et al.  Highly Sensitive Pressure Sensor Based on Bioinspired Porous Structure for Real‐Time Tactile Sensing , 2016 .

[47]  Prem C. Pandey,et al.  Current Advancements in Transdermal Biosensing and Targeted Drug Delivery , 2019, Sensors.

[48]  P. Clarys,et al.  Evaluation and review of body fluids saliva, sweat and tear compared to biochemical hydration assessment markers within blood and urine , 2017, European Journal of Clinical Nutrition.

[49]  Yonggang Huang,et al.  Conformable amplified lead zirconate titanate sensors with enhanced piezoelectric response for cutaneous pressure monitoring , 2014, Nature Communications.

[50]  Wenzhao Jia,et al.  Tattoo-based potentiometric ion-selective sensors for epidermal pH monitoring. , 2013, The Analyst.

[51]  K. Lee,et al.  Self-adhesive epidermal carbon nanotube electronics for tether-free long-term continuous recording of biosignals , 2014, Scientific Reports.

[52]  Minbaek Lee,et al.  Flexible Nanocomposite Generator Made of BaTiO3 Nanoparticles and Graphitic Carbons , 2012, Advanced materials.

[53]  Chwee Teck Lim,et al.  Emerging flexible and wearable physical sensing platforms for healthcare and biomedical applications , 2016, Microsystems & Nanoengineering.

[54]  Taeghwan Hyeon,et al.  Enzyme‐Based Glucose Sensor: From Invasive to Wearable Device , 2018, Advanced healthcare materials.

[55]  Jonathan Rossiter,et al.  Stretchable Piezoelectric Sensing Systems for Self‐Powered and Wireless Health Monitoring , 2019, Advanced Materials Technologies.

[56]  Aydogan Ozcan,et al.  Wearable and Implantable Sensors for Biomedical Applications. , 2018, Annual review of analytical chemistry.

[57]  M. Armand,et al.  Building better batteries , 2008, Nature.

[58]  S. Mukhopadhyay,et al.  Strain induced graphite/PDMS sensors for biomedical applications , 2018 .

[59]  Xuewen Wang,et al.  Silk‐Molded Flexible, Ultrasensitive, and Highly Stable Electronic Skin for Monitoring Human Physiological Signals , 2014, Advanced materials.

[60]  Yonggang Huang,et al.  Conformal piezoelectric systems for clinical and experimental characterization of soft tissue biomechanics. , 2015, Nature materials.

[61]  Qiongfeng Shi,et al.  Self-powered liquid triboelectric microfluidic sensor for pressure sensing and finger motion monitoring applications , 2016 .

[62]  Jie Wang,et al.  Stretchable and Waterproof Self-Charging Power System for Harvesting Energy from Diverse Deformation and Powering Wearable Electronics. , 2016, ACS nano.

[63]  Seung Hwan Ko,et al.  Highly Sensitive and Stretchable Multidimensional Strain Sensor with Prestrained Anisotropic Metal Nanowire Percolation Networks. , 2015, Nano letters.

[64]  Iztok Fister,et al.  Sensors and Functionalities of Non-Invasive Wrist-Wearable Devices: A Review , 2018, Sensors.

[65]  Hao Sun,et al.  Energy harvesting and storage in 1D devices , 2017 .

[66]  Zhong Lin Wang,et al.  A Triboelectric Nanogenerator‐Based Smart Insole for Multifunctional Gait Monitoring , 2018, Advanced Materials Technologies.

[67]  Chiung-Chih Chang,et al.  Perceived Occupational Stress is associated with Decreased Cortical Activity of the Prefrontal Cortex: A Multichannel Near-infrared Spectroscopy Study , 2016, Scientific Reports.

[68]  Chunya Wang,et al.  Carbonized Silk Nanofiber Membrane for Transparent and Sensitive Electronic Skin , 2017 .

[69]  H. Bottner,et al.  New thermoelectric components using microsystem technologies , 2004, Journal of Microelectromechanical Systems.

[70]  Huanyu Cheng,et al.  Graphene Reinforced Carbon Nanotube Networks for Wearable Strain Sensors , 2016 .

[71]  Seung Hwan Ko,et al.  A Hyper‐Stretchable Elastic‐Composite Energy Harvester , 2015, Advanced materials.

[72]  Cheng Lv,et al.  Kirigami-based stretchable lithium-ion batteries , 2015, Scientific Reports.

[73]  Jiantong Li,et al.  All-solid-state micro-supercapacitors based on inkjet printed graphene electrodes , 2016 .

[74]  Guofa Cai,et al.  Extremely Stretchable Strain Sensors Based on Conductive Self‐Healing Dynamic Cross‐Links Hydrogels for Human‐Motion Detection , 2016, Advanced science.

[75]  Petra Pötschke,et al.  Piezoresistive natural rubber-multiwall carbon nanotube nanocomposite for sensor applications , 2016 .

[76]  John A Rogers,et al.  Conformal piezoelectric energy harvesting and storage from motions of the heart, lung, and diaphragm , 2014, Proceedings of the National Academy of Sciences.

[77]  Carmen C. Y. Poon,et al.  Flexible Piezoresistive Sensor Patch Enabling Ultralow Power Cuffless Blood Pressure Measurement , 2016 .

[78]  Taemin Lee,et al.  Crack-based strain sensor with diverse metal films by inserting an inter-layer , 2017 .

[79]  Dong-Hwa Seo,et al.  Flexible energy storage devices based on graphene paper , 2011 .

[80]  Haider Butt,et al.  Wearable Contact Lens Biosensors for Continuous Glucose Monitoring Using Smartphones , 2018, ACS nano.

[81]  G. Jabbour,et al.  Inkjet Printing—Process and Its Applications , 2010, Advanced materials.

[82]  B. Lu,et al.  High-Performance Piezoelectric Nanogenerators with Imprinted P(VDF-TrFE)/BaTiO3 Nanocomposite Micropillars for Self-Powered Flexible Sensors. , 2017, Small.

[83]  Jing Zhang,et al.  Laminated Cross‐Linked Nanocellulose/Graphene Oxide Electrolyte for Flexible Rechargeable Zinc–Air Batteries , 2016 .

[84]  Sung Youb Kim,et al.  Giant tunneling piezoresistance of composite elastomers with interlocked microdome arrays for ultrasensitive and multimodal electronic skins. , 2014, ACS nano.

[85]  Zhiyong Fan,et al.  A Fully Integrated and Self-Powered Smartwatch for Continuous Sweat Glucose Monitoring. , 2019, ACS sensors.

[86]  Kin Fong Lei,et al.  The Structure Design of Piezoelectric Poly(vinylidene Fluoride) (PVDF) Polymer-Based Sensor Patch for the Respiration Monitoring under Dynamic Walking Conditions , 2015, Sensors.

[87]  M. Pumera,et al.  Self‐Contained Polymer/Metal 3D Printed Electrochemical Platform for Tailored Water Splitting , 2018 .

[88]  L Tian,et al.  Wearable sensors: modalities, challenges, and prospects. , 2018, Lab on a chip.

[89]  Huisheng Peng,et al.  The Recent Advance in Fiber‐Shaped Energy Storage Devices , 2018, Advanced Electronic Materials.

[90]  Wenlong Cheng,et al.  Resistive electronic skin , 2017 .

[91]  Hai-Long Jiang,et al.  A Stretchable Electronic Fabric Artificial Skin with Pressure‐, Lateral Strain‐, and Flexion‐Sensitive Properties , 2016, Advanced materials.

[92]  Gustave Savourey,et al.  Physiological stress monitoring using sodium ion potentiometric microsensors for sweat analysis , 2016 .

[93]  Long Lin,et al.  Replacing a Battery by a Nanogenerator with 20 V Output , 2012, Advanced materials.

[94]  Jonghwa Park,et al.  Fingertip skin–inspired microstructured ferroelectric skins discriminate static/dynamic pressure and temperature stimuli , 2015, Science Advances.

[95]  Ravinder Dahiya,et al.  Energy autonomous electronic skin , 2019, npj Flexible Electronics.

[96]  Yan Qiao,et al.  Fully Printed Ultraflexible Supercapacitor Supported by a Single-Textile Substrate. , 2016, ACS applied materials & interfaces.

[97]  Tatsuo Nakagawa,et al.  Wearable Wireless Tyrosinase Bandage and Microneedle Sensors: Toward Melanoma Screening , 2018, Advanced healthcare materials.

[98]  Chang Kyu Jeong,et al.  Highly‐Efficient, Flexible Piezoelectric PZT Thin Film Nanogenerator on Plastic Substrates , 2014, Advanced materials.

[99]  Chanseok Lee,et al.  Ultrasensitive mechanical crack-based sensor inspired by the spider sensory system , 2014, Nature.

[100]  Mohammed Ismail,et al.  Characterization of Human Body-Based Thermal and Vibration Energy Harvesting for Wearable Devices , 2014, IEEE Journal on Emerging and Selected Topics in Circuits and Systems.

[101]  Hyung Jin Sung,et al.  Highly Stretchable, Hysteresis-Free Ionic Liquid-Based Strain Sensor for Precise Human Motion Monitoring. , 2017, ACS applied materials & interfaces.

[102]  Dipankar Mandal,et al.  Origin of piezoelectricity in an electrospun poly(vinylidene fluoride-trifluoroethylene) nanofiber web-based nanogenerator and nano-pressure sensor. , 2011, Macromolecular rapid communications.

[103]  Wenzan Zhang,et al.  Wearable carbon nanotubes-based polymer electrodes for ambulatory electrocardiographic measurements , 2017 .

[104]  Huihua Xu,et al.  Multiscale nanowire-microfluidic hybrid strain sensors with high sensitivity and stretchability , 2018, npj Flexible Electronics.

[105]  Zhong Lin Wang,et al.  Flexible triboelectric generator , 2012 .

[106]  Eduardo Rocon,et al.  Smartwatch for the analysis of rest tremor in patients with Parkinson's disease , 2019, Journal of the Neurological Sciences.

[107]  G.Y. Yang,et al.  Mechanically robust micro-fabricated strain gauges for use on bones , 2005, 2005 3rd IEEE/EMBS Special Topic Conference on Microtechnology in Medicine and Biology.

[108]  J. F. Randall,et al.  Is AM1.5 applicable in practice? Modelling eight photovoltaic materials with respect to light intensity and two spectra , 2003 .

[109]  Xin Cai,et al.  Fiber Supercapacitors Utilizing Pen Ink for Flexible/Wearable Energy Storage , 2012, Advanced materials.

[110]  Shalini Prasad,et al.  Flexible nanoporous tunable electrical double layer biosensors for sweat diagnostics , 2015, Scientific Reports.

[111]  Alan S Campbell,et al.  Wearable non-invasive epidermal glucose sensors: A review. , 2018, Talanta.

[112]  Long Lin,et al.  Stretchable‐Rubber‐Based Triboelectric Nanogenerator and Its Application as Self‐Powered Body Motion Sensors , 2015 .

[113]  Hossam Haick,et al.  Autonomous Flexible Sensors for Health Monitoring , 2018, Advanced materials.

[114]  Wei Wu,et al.  Recent progress in printed flexible solid-state supercapacitors for portable and wearable energy storage , 2019 .

[115]  N. Camara,et al.  Measurement of Spurious Voltages in ZnO Piezoelectric Nanogenerators , 2016, Journal of Microelectromechanical Systems.

[116]  Sylvie Grugeon,et al.  Highly Loaded Graphite–Polylactic Acid Composite-Based Filaments for Lithium-Ion Battery Three-Dimensional Printing , 2018, Chemistry of Materials.

[117]  O. Kanoun,et al.  Highly sensitive capacitive pressure sensors for robotic applications based on carbon nanotubes and PDMS polymer nanocomposite , 2019, Journal of Sensors and Sensor Systems.

[118]  Nam-In Kim,et al.  A half millimeter thick coplanar flexible battery with wireless recharging capability. , 2015, Nano letters.

[119]  Eric Pop,et al.  Microstructural origin of resistance–strain hysteresis in carbon nanotube thin film conductors , 2018, Proceedings of the National Academy of Sciences.

[120]  Simiao Niu,et al.  Topographically-designed triboelectric nanogenerator via block copolymer self-assembly. , 2014, Nano letters.

[121]  B. Shirinzadeh,et al.  A wearable and highly sensitive pressure sensor with ultrathin gold nanowires , 2014, Nature Communications.

[122]  Huisheng Peng,et al.  Novel Electric Double‐Layer Capacitor with a Coaxial Fiber Structure , 2013, Advanced materials.

[123]  Wenbin Hu,et al.  Atomically Thin Mesoporous Co3O4 Layers Strongly Coupled with N‐rGO Nanosheets as High‐Performance Bifunctional Catalysts for 1D Knittable Zinc–Air Batteries , 2018, Advanced materials.

[124]  Vladimir Leonov,et al.  Wearable electronics self-powered by using human body heat: The state of the art and the perspective , 2009 .

[125]  Bill J. Van Heyst,et al.  A review of the state of the science on wearable thermoelectric power generators (TEGs) and their existing challenges , 2017 .

[126]  Chih-Ming Chen,et al.  The Study of Blocking Effect of Nb2O5in Dye-Sensitized Solar Cells under Low Power Lighting , 2018 .

[127]  Jonghwa Park,et al.  Bioinspired Interlocked and Hierarchical Design of ZnO Nanowire Arrays for Static and Dynamic Pressure‐Sensitive Electronic Skins , 2015 .

[128]  Xue Wang,et al.  Rotation sensing and gesture control of a robot joint via triboelectric quantization sensor , 2018, Nano Energy.

[129]  Geng Yang,et al.  Non-Invasive Flexible and Stretchable Wearable Sensors With Nano-Based Enhancement for Chronic Disease Care , 2019, IEEE Reviews in Biomedical Engineering.

[130]  Yang Zou,et al.  Self‐Powered Pulse Sensor for Antidiastole of Cardiovascular Disease , 2017, Advanced materials.

[131]  Wei Liu,et al.  Flexible and Stretchable Energy Storage: Recent Advances and Future Perspectives , 2017, Advanced materials.

[132]  Sungjoo Hwang,et al.  Wristband-type wearable health devices to measure construction workers' physical demands , 2017 .

[133]  Abdullah Khan,et al.  Silica Nanoparticle-Induced Structural Reorganizations in Pulmonary Surfactant Films: What Monolayer Compression Isotherms Do Not Say , 2018, ACS Applied Nano Materials.

[134]  Yang Kuang,et al.  Energy harvesting during human walking to power a wireless sensor node , 2017 .

[135]  Wei Xiang,et al.  Internet of Things for Smart Healthcare: Technologies, Challenges, and Opportunities , 2017, IEEE Access.

[136]  Sung-Bock Kim,et al.  Wearable Respiratory Rate Monitoring using Piezo-resistive Fabric Sensor , 2009 .

[137]  Shalini Prasad,et al.  A new paradigm in sweat based wearable diagnostics biosensors using Room Temperature Ionic Liquids (RTILs) , 2017, Scientific Reports.

[138]  F. Angelis,et al.  Next-generation textiles: from embedded supercapacitors to lithium ion batteries , 2016 .

[139]  S. Yao,et al.  Wearable multifunctional sensors using printed stretchable conductors made of silver nanowires. , 2014, Nanoscale.

[140]  Alan S. Go,et al.  Incidence and timing of potentially high-risk arrhythmias detected through long term continuous ambulatory electrocardiographic monitoring , 2016, BMC Cardiovascular Disorders.

[141]  Tao Liu,et al.  A Review: Carbon Nanotube-Based Piezoresistive Strain Sensors , 2012, J. Sensors.

[142]  Changsoon Choi,et al.  Flexible Supercapacitor Made of Carbon Nanotube Yarn with Internal Pores , 2014, Advanced materials.

[143]  Ja Hoon Koo,et al.  Conductive Fiber‐Based Ultrasensitive Textile Pressure Sensor for Wearable Electronics , 2015, Advanced materials.

[144]  Guang-Zhong Yang,et al.  A wearable multisensing patch for continuous sweat monitoring. , 2017, Biosensors & bioelectronics.

[145]  Qifa Zhou,et al.  Monitoring of the central blood pressure waveform via a conformal ultrasonic device , 2018, Nature Biomedical Engineering.

[146]  Zhaona Wang,et al.  Eardrum‐Inspired Active Sensors for Self‐Powered Cardiovascular System Characterization and Throat‐Attached Anti‐Interference Voice Recognition , 2015, Advanced materials.

[147]  Yan Zhang,et al.  3D Printed Graphene Based Energy Storage Devices , 2017, Scientific Reports.

[148]  Cheng Yang,et al.  Flexible asymmetric supercapacitors based on ultrathin two-dimensional nanosheets with outstanding electrochemical performance and aesthetic property , 2013, Scientific Reports.

[149]  Benji Maruyama,et al.  3D Printable Ceramic–Polymer Electrolytes for Flexible High‐Performance Li‐Ion Batteries with Enhanced Thermal Stability , 2017 .

[150]  Yong Wang,et al.  All‐Solid‐State, Foldable, and Rechargeable Zn‐Air Batteries Based on Manganese Oxide Grown on Graphene‐Coated Carbon Cloth Air Cathode , 2017 .

[151]  Daniel M. Vogt,et al.  Embedded 3D Printing of Strain Sensors within Highly Stretchable Elastomers , 2014, Advanced materials.

[152]  S. Asher,et al.  Photonic crystal glucose-sensing material for noninvasive monitoring of glucose in tear fluid. , 2004, Clinical chemistry.

[153]  Yang Zou,et al.  Self-Powered, One-Stop, and Multifunctional Implantable Triboelectric Active Sensor for Real-Time Biomedical Monitoring. , 2016, Nano letters.

[154]  J. Windmiller,et al.  A potentiometric tattoo sensor for monitoring ammonium in sweat. , 2013, The Analyst.

[155]  Giovanni Sparacino,et al.  Calibration of Minimally Invasive Continuous Glucose Monitoring Sensors: State-of-The-Art and Current Perspectives , 2018, Biosensors.

[156]  Chongwu Zhou,et al.  Hierarchical three-dimensional ZnCo₂O₄ nanowire arrays/carbon cloth anodes for a novel class of high-performance flexible lithium-ion batteries. , 2012, Nano letters.

[157]  Zhiping Xu,et al.  Carbonized Silk Fabric for Ultrastretchable, Highly Sensitive, and Wearable Strain Sensors , 2016, Advanced materials.

[158]  Mark G. Allen,et al.  Deformable Strain Sensors Based on Patterned MWCNTs/ Polydimethylsiloxane Composites , 2013 .

[159]  G. J. Snyder,et al.  The Thermoelectric Properties of Bismuth Telluride , 2019, Advanced Electronic Materials.

[160]  F. G. Benedict,et al.  A Biometric Study of Human Basal Metabolism. , 1918, Proceedings of the National Academy of Sciences of the United States of America.

[161]  Elena Nicolescu Veety,et al.  Wearable thermoelectric generators for human body heat harvesting , 2016 .

[162]  Xuewen Wang,et al.  Flexible Capacitive Tactile Sensor Based on Micropatterned Dielectric Layer. , 2016, Small.

[163]  M. Kishi,et al.  Micro thermoelectric modules and their application to wristwatches as an energy source , 1999, Eighteenth International Conference on Thermoelectrics. Proceedings, ICT'99 (Cat. No.99TH8407).

[164]  Huisheng Peng,et al.  Super-stretchy lithium-ion battery based on carbon nanotube fiber , 2014 .

[165]  Jie Liu,et al.  Integrated Flexible Conversion Circuit between a Flexible Photovoltaic and Supercapacitors for Powering Wearable Sensors , 2018 .

[166]  Jie Chen,et al.  A highly sensitive, self-powered triboelectric auditory sensor for social robotics and hearing aids , 2018, Science Robotics.

[167]  S. Prasad,et al.  A Four-Channel Electrical Impedance Spectroscopy Module for Cortisol Biosensing in Sweat-Based Wearable Applications , 2018, SLAS technology.

[168]  Lim Wei Yap,et al.  Highly Stretchy Black Gold E‐Skin Nanopatches as Highly Sensitive Wearable Biomedical Sensors , 2015 .

[169]  Jin-Woo Choi,et al.  Strain-Dependent Resistance of PDMS and Carbon Nanotubes Composite Microstructures , 2010, IEEE Transactions on Nanotechnology.

[170]  T. Trung,et al.  Flexible and Stretchable Physical Sensor Integrated Platforms for Wearable Human‐Activity Monitoringand Personal Healthcare , 2016, Advanced materials.

[171]  Eric McAdams,et al.  The Challenges Facing Wearable Sensor Systems , 2012, pHealth.

[172]  B. Liu,et al.  Flexible Energy‐Storage Devices: Design Consideration and Recent Progress , 2014, Advanced materials.

[173]  S. Haigh,et al.  3D Printing of Freestanding MXene Architectures for Current‐Collector‐Free Supercapacitors , 2019, Advanced materials.

[174]  M. Asheghi,et al.  Experimental Characterization of Microfabricated Thermoelectric Energy Harvesters for Smart Sensor and Wearable Applications , 2018 .

[175]  Yang Zou,et al.  Symbiotic cardiac pacemaker , 2019, Nature Communications.

[176]  Zhong Lin Wang,et al.  Microfibre–nanowire hybrid structure for energy scavenging , 2008, Nature.

[177]  Bin Liu,et al.  Hierarchical silicon nanowires-carbon textiles matrix as a binder-free anode for high-performance advanced lithium-ion batteries , 2013, Scientific Reports.

[178]  K. Hata,et al.  A stretchable carbon nanotube strain sensor for human-motion detection. , 2011, Nature nanotechnology.

[179]  Benji Maruyama,et al.  Composite batteries: a simple yet universal approach to 3D printable lithium-ion battery electrodes , 2016 .

[180]  Chee Kai Chua,et al.  Layer-by-layer printing of laminated graphene-based interdigitated microelectrodes for flexible planar micro-supercapacitors , 2015 .

[181]  S. Bhansali,et al.  Carbon fiber based electrochemical sensor for sweat cortisol measurement , 2019, Scientific Reports.

[182]  N. Lee,et al.  Flexible and Stretchable Piezoelectric Sensor with Thickness-Tunable Configuration of Electrospun Nanofiber Mat and Elastomeric Substrates. , 2016, ACS applied materials & interfaces.

[183]  Jie Yu,et al.  Weavable, Conductive Yarn-Based NiCo//Zn Textile Battery with High Energy Density and Rate Capability. , 2017, ACS nano.

[184]  Kevin Barraclough,et al.  I and i , 2001, BMJ : British Medical Journal.

[185]  W. March,et al.  Fluorescent measurement in the non-invasive contact lens glucose sensor. , 2006, Diabetes technology & therapeutics.

[186]  G. Alici,et al.  Ultra-stretchable MWCNT–Ecoflex piezoresistive sensors for human motion detection applications , 2019, Composites Science and Technology.

[187]  Hiroyuki Matsui,et al.  Noninvasive Sweat-Lactate Biosensor Emplsoying a Hydrogel-Based Touch Pad , 2019, Scientific Reports.

[188]  Joseph Wang,et al.  A wearable chemical–electrophysiological hybrid biosensing system for real-time health and fitness monitoring , 2016, Nature Communications.

[189]  Zhongwei Chen,et al.  Flexible Rechargeable Zinc‐Air Batteries through Morphological Emulation of Human Hair Array , 2016, Advanced materials.

[190]  Jeong Sook Ha,et al.  Highly Stretchable and Sensitive Strain Sensors Using Fragmentized Graphene Foam , 2015 .

[191]  Caizhi Liao,et al.  Highly sensitive glucose sensors based on enzyme-modified whole-graphene solution-gated transistors , 2015, Scientific Reports.

[192]  Huisheng Peng,et al.  Elastic and wearable wire-shaped lithium-ion battery with high electrochemical performance. , 2014, Angewandte Chemie.

[193]  K. Razeeb,et al.  Optimization of annealing conditions to enhance thermoelectric performance of electrodeposited p-type BiSbTe thin films , 2019, APL Materials.

[194]  Huisheng Peng,et al.  Wearable solar cells by stacking textile electrodes. , 2014, Angewandte Chemie.

[195]  Benjamin C. K. Tee,et al.  Tunable Flexible Pressure Sensors using Microstructured Elastomer Geometries for Intuitive Electronics , 2014 .

[196]  Vladimir Leonov,et al.  Thermoelectric Energy Harvesting of Human Body Heat for Wearable Sensors , 2013, IEEE Sensors Journal.

[197]  A. Westover,et al.  Carbon Nanotube Reinforced Structural Composite Supercapacitor , 2018, Scientific Reports.

[198]  SeongHwan Cho,et al.  Self-Powered Wearable Electrocardiography Using a Wearable Thermoelectric Power Generator , 2018 .

[199]  Jonathan A. Fan,et al.  Stretchable batteries with self-similar serpentine interconnects and integrated wireless recharging systems , 2013, Nature Communications.

[200]  B. Gray,et al.  Editors' Choice—Development of Screen-Printed Flexible Multi-Level Microfluidic Devices with Integrated Conductive Nanocomposite Polymer Electrodes on Textiles , 2019, Journal of The Electrochemical Society.

[201]  Dong-Weon Lee,et al.  Piezoresistive sensor-integrated PDMS cantilever: A new class of device for measuring the drug-induced changes in the mechanical activity of cardiomyocytes , 2017 .

[202]  Ying-Chih Lai,et al.  Electric Eel‐Skin‐Inspired Mechanically Durable and Super‐Stretchable Nanogenerator for Deformable Power Source and Fully Autonomous Conformable Electronic‐Skin Applications , 2016, Advanced materials.

[203]  N. Sohoni,et al.  Passive Detection of Atrial Fibrillation Using a Commercially Available Smartwatch , 2018, JAMA cardiology.

[204]  C. Zhi,et al.  Recent Advances in Electrode Fabrication for Flexible Energy‐Storage Devices , 2019, Advanced Materials Technologies.

[205]  Huisheng Peng,et al.  Winding aligned carbon nanotube composite yarns into coaxial fiber full batteries with high performances. , 2014, Nano letters.

[206]  Zhong Lin Wang,et al.  Self-powered nanowire devices. , 2010, Nature nanotechnology.

[207]  Joseph Wang,et al.  Noninvasive Alcohol Monitoring Using a Wearable Tattoo-Based Iontophoretic-Biosensing System , 2016 .

[208]  Yonggang Huang,et al.  High performance piezoelectric devices based on aligned arrays of nanofibers of poly(vinylidenefluoride-co-trifluoroethylene) , 2013, Nature Communications.

[209]  Ji-Sik Kim,et al.  Hysteresis Compensation of Piezoresistive Carbon Nanotube/Polydimethylsiloxane Composite-Based Force Sensors , 2017, Sensors.

[210]  C. Zhang,et al.  Graphene based piezoresistive pressure sensor , 2013 .

[211]  Dimos Poulikakos,et al.  Highly flexible, all solid-state micro-supercapacitors from vertically aligned carbon nanotubes , 2014, Nanotechnology.

[212]  Wan-Young Chung,et al.  Wireless sensor network based wearable smart shirt for ubiquitous health and activity monitoring , 2009 .

[213]  Qing Jiang,et al.  Decorating Waste Cloth via Industrial Wastewater for Tube‐Type Flexible and Wearable Sodium‐Ion Batteries , 2017, Advanced materials.

[214]  Shekhar Bhansali,et al.  Electrochemical Sensing of Cortisol: A Recent Update , 2014, Applied Biochemistry and Biotechnology.

[215]  L. Piwek,et al.  The Rise of Consumer Health Wearables: Promises and Barriers , 2016, PLoS medicine.

[216]  Tuan Sang Tran,et al.  Graphene-Based Inks for Printing of Planar Micro-Supercapacitors: A Review , 2019, Materials.

[217]  Luca Benini,et al.  Human body heat for powering wearable devices: From thermal energy to application , 2017 .

[218]  Babak A. Parviz,et al.  A contact lens with an integrated lactate sensor , 2012 .

[219]  Jayoung Kim,et al.  Wearable biosensors for healthcare monitoring , 2019, Nature Biotechnology.

[220]  Liwei Lin,et al.  High quality Mn-doped (Na,K)NbO3 nanofibers for flexible piezoelectric nanogenerators. , 2014, ACS applied materials & interfaces.

[221]  Suresh Neethirajan,et al.  Noninvasive Label-Free Detection of Cortisol and Lactate Using Graphene Embedded Screen-Printed Electrode , 2018, Nano-micro letters.

[222]  Zhong Lin Wang,et al.  Functional electrical stimulation by nanogenerator with 58 V output voltage. , 2012, Nano letters.

[223]  Benjamin A. Katchman,et al.  Accessing analytes in biofluids for peripheral biochemical monitoring , 2019, Nature Biotechnology.

[224]  Meng Wang,et al.  Air-Flow-Driven Triboelectric Nanogenerators for Self-Powered Real-Time Respiratory Monitoring. , 2018, ACS nano.

[225]  Dermot Diamond,et al.  Glucose Sensing for Diabetes Monitoring: Recent Developments , 2017, Sensors.

[226]  Shalini Prasad,et al.  Portable biosensor for monitoring cortisol in low-volume perspired human sweat , 2017, Scientific Reports.

[227]  Mehmet C. Öztürk,et al.  Designing thermoelectric generators for self-powered wearable electronics , 2016 .

[228]  M. Vosgueritchian,et al.  Stretchable Energy‐Harvesting Tactile Electronic Skin Capable of Differentiating Multiple Mechanical Stimuli Modes , 2014, Advanced materials.

[229]  I. Park,et al.  Highly stretchable and sensitive strain sensor based on silver nanowire-elastomer nanocomposite. , 2014, ACS nano.

[230]  F. Fan,et al.  Flexible Nanogenerators for Energy Harvesting and Self‐Powered Electronics , 2016, Advanced materials.

[231]  I. Park,et al.  Stretchable, Skin‐Mountable, and Wearable Strain Sensors and Their Potential Applications: A Review , 2016 .

[232]  E. O. Polat,et al.  Energy‐Autonomous, Flexible, and Transparent Tactile Skin , 2017 .

[233]  Laura Ortega,et al.  Self-powered smart patch for sweat conductivity monitoring , 2019, Microsystems & Nanoengineering.

[234]  A. Khosla,et al.  Synthesis and Characterization of an Efficient Hole-Conductor Free Halide Perovskite CH3NH3PbI3 Semiconductor Absorber Based Photovoltaic Device for IOT , 2018 .

[235]  N. Lee,et al.  Stretchable, Transparent, Ultrasensitive, and Patchable Strain Sensor for Human-Machine Interfaces Comprising a Nanohybrid of Carbon Nanotubes and Conductive Elastomers. , 2015, ACS nano.

[236]  Yang Lu,et al.  Recent developments in bio-monitoring via advanced polymer nanocomposite-based wearable strain sensors. , 2019, Biosensors & bioelectronics.

[237]  Hao Sun,et al.  A twisted wire-shaped dual-function energy device for photoelectric conversion and electrochemical storage. , 2014, Angewandte Chemie.