Review

. 2023 Mar 28;17(6):5211-5295.

doi: 10.1021/acsnano.2c12606. Epub 2023 Mar 9.

Technology Roadmap for Flexible Sensors

Yifei Luo^{1

2}, Mohammad Reza Abidian³, Jong-Hyun Ahn⁴, Deji Akinwande^{5

6}, Anne M Andrews⁷, Markus Antonietti⁸, Zhenan Bao⁹, Magnus Berggren^{10

11}, Christopher A Berkey¹², Christopher John Bettinger¹³, Jun Chen¹⁴, Peng Chen¹⁵, Wenlong Cheng^{16

17}, Xu Cheng¹⁸, Seon-Jin Choi¹⁹, Alex Chortos²⁰, Canan Dagdeviren²¹, Reinhold H Dauskardt¹², Chong-An Di²², Michael D Dickey²³, Xiangfeng Duan²⁴, Antonio Facchetti²⁵, Zhiyong Fan²⁶, Yin Fang¹⁵, Jianyou Feng²⁷, Xue Feng²⁸, Huajian Gao^{29

30}, Wei Gao³¹, Xiwen Gong³², Chuan Fei Guo³³, Xiaojun Guo³⁴, Martin C Hartel¹⁴, Zihan He²², John S Ho^{35

36

37}, Youfan Hu³⁸, Qiyao Huang³⁹, Yu Huang⁴⁰, Fengwei Huo⁴¹, Muhammad M Hussain⁴², Ali Javey^{43

44}, Unyong Jeong⁴⁵, Chen Jiang⁴⁶, Xingyu Jiang⁴⁷, Jiheong Kang⁴⁸, Daniil Karnaushenko⁴⁹, Ali Khademhosseini⁵⁰, Dae-Hyeong Kim⁵¹, Il-Doo Kim⁵², Dmitry Kireev^{5

6}, Lingxuan Kong¹⁵, Chengkuo Lee^{36

53

54

55}, Nae-Eung Lee⁵⁶, Pooi See Lee^{57

58}, Tae-Woo Lee^{59

60

61

62}, Fengyu Li⁶³, Jinxing Li⁶⁴, Cuiyuan Liang⁶⁵, Chwee Teck Lim^{66

67

68}, Yuanjing Lin⁶⁹, Darren J Lipomi⁷⁰, Jia Liu⁷¹, Kai Liu⁷², Nan Liu⁷³, Ren Liu⁷¹, Yuxin Liu^{1

74}, Yuxuan Liu⁷⁵, Zhiyuan Liu⁷⁶, Zhuangjian Liu³⁰, Xian Jun Loh¹, Nanshu Lu⁷⁷, Zhisheng Lv¹, Shlomo Magdassi⁷⁸, George G Malliaras⁷⁹, Naoji Matsuhisa⁸⁰, Arokia Nathan⁸¹, Simiao Niu⁸², Jieming Pan³⁶, Changhyun Pang⁸³, Qibing Pei⁸⁴, Huisheng Peng²⁷, Dianpeng Qi⁶⁵, Huaying Ren⁸⁵, John A Rogers^{86

87}, Aaron Rowe^{88

89}, Oliver G Schmidt^{49

90

91}, Tsuyoshi Sekitani⁹², Dae-Gyo Seo⁵⁹, Guozhen Shen⁹³, Xing Sheng⁹⁴, Qiongfeng Shi^{36

53

54}, Takao Someya⁹⁵, Yanlin Song⁹⁶, Eleni Stavrinidou⁹⁷, Meng Su⁹⁶, Xuemei Sun²⁷, Kuniharu Takei⁹⁸, Xiao-Ming Tao⁹⁹, Benjamin C K Tee^{100

101}, Aaron Voon-Yew Thean^{36

102}, Tran Quang Trung⁵⁶, Changjin Wan¹⁰³, Huiliang Wang¹⁰⁴, Joseph Wang¹⁰⁵, Ming Wang^{106

107}, Sihong Wang¹⁰⁸, Ting Wang¹⁰⁹, Zhong Lin Wang^{110

111}, Paul S Weiss¹¹², Hanqi Wen^{15

113}, Sheng Xu¹¹⁴, Tailin Xu¹¹⁵, Hongping Yan⁹, Xuzhou Yan⁷², Hui Yang¹¹⁶, Le Yang^{1

117}, Shuaijian Yang¹¹⁸, Lan Yin¹¹⁹, Cunjiang Yu¹²⁰, Guihua Yu¹²¹, Jing Yu⁵⁷, Shu-Hong Yu¹²², Xinge Yu¹²³, Evgeny Zamburg^{36

102}, Haixia Zhang¹²⁴, Xiangyu Zhang^{36

102}, Xiaosheng Zhang¹²⁵, Xueji Zhang¹²⁶, Yihui Zhang¹²⁷, Yu Zhang^{36

102}, Siyuan Zhao⁷¹, Xuanhe Zhao¹²⁸, Yuanjin Zheng¹²⁹, Yu-Qing Zheng¹³⁰, Zijian Zheng¹³¹, Tao Zhou¹³², Bowen Zhu¹³³, Ming Zhu¹³⁴, Rong Zhu¹³⁵, Yangzhi Zhu¹³⁶, Yong Zhu¹³⁷, Guijin Zou³⁰, Xiaodong Chen^{1

138}

Affiliations

¹ Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Republic of Singapore.
² Innovative Centre for Flexible Devices (iFLEX), School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
³ Department of Biomedical Engineering, University of Houston, Houston, Texas 77024, United States.
⁴ School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea.
⁵ Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, United States.
⁶ Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States.
⁷ Department of Chemistry and Biochemistry, California NanoSystems Institute, and Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, and Hatos Center for Neuropharmacology, University of California, Los Angeles, Los Angeles, California 90095, United States.
⁸ Colloid Chemistry Department, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany.
⁹ Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States.
¹⁰ Laboratory of Organic Electronics, Department of Science and Technology, Campus Norrköping, Linköping University, 83 Linköping, Sweden.
¹¹ Wallenberg Initiative Materials Science for Sustainability (WISE) and Wallenberg Wood Science Center (WWSC), SE-100 44 Stockholm, Sweden.
¹² Department of Materials Science and Engineering, Stanford University, Stanford, California 94301, United States.
¹³ Department of Biomedical Engineering and Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
¹⁴ Department of Bioengineering, University of California, Los Angeles, Los Angeles, California 90095, United States.
¹⁵ School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, Singapore 637457, Singapore.
¹⁶ Nanobionics Group, Department of Chemical and Biological Engineering, Monash University, Clayton, Australia, 3800.
¹⁷ Monash Institute of Medical Engineering, Monash University, Clayton, Australia3800.
¹⁸ Applied Mechanics Laboratory, Department of Engineering Mechanics, Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing 100084, PR China.
¹⁹ Division of Materials of Science and Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea.
²⁰ School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47906, United States.
²¹ Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
²² Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
²³ Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27606, United States.
²⁴ Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States.
²⁵ Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
²⁶ Department of Electronic and Computer Engineering and Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China.
²⁷ State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, and Laboratory of Advanced Materials, Fudan University, Shanghai 200438, PR China.
²⁸ Laboratory of Flexible Electronics Technology, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
²⁹ School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore.
³⁰ Institute of High Performance Computing (IHPC), Agency for Science, Technology and Research (A*STAR), 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Republic of Singapore.
³¹ Andrew and Peggy Cherng Department of Medical Engineering, California Institute of Technology, Pasadena, California, 91125, United States.
³² Department of Chemical Engineering, Department of Materials Science and Engineering, Department of Electrical Engineering and Computer Science, Applied Physics Program, and Macromolecular Science and Engineering Program, University of Michigan, Ann Arbor, Michigan, 48109 United States.
³³ Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
³⁴ National Key Laboratory of Science and Technology on Micro/Nano Fabrication, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
³⁵ Institute for Health Innovation and Technology, National University of Singapore, Singapore 117599, Singapore.
³⁶ Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore.
³⁷ The N.1 Institute for Health, National University of Singapore, Singapore 117456, Singapore.
³⁸ School of Electronics and Center for Carbon-Based Electronics, Peking University, Beijing 100871, China.
³⁹ School of Fashion and Textiles, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
⁴⁰ Department of Materials Science and Engineering, California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States.
⁴¹ Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing 211816, PR China.
⁴² mmh Labs, Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47906, United States.
⁴³ Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, United States.
⁴⁴ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
⁴⁵ Department of Materials Science and Engineering, Pohang University of Science and Engineering (POSTECH), Pohang, Gyeong-buk 37673, Korea.
⁴⁶ Department of Electronic Engineering, Tsinghua University, Beijing 100084, China.
⁴⁷ Department of Biomedical Engineering, Southern University of Science and Technology, No 1088, Xueyuan Road, Xili, Nanshan District, Shenzhen, Guangdong 518055, PR China.
⁴⁸ Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
⁴⁹ Research Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, Chemnitz 09126, Germany.
⁵⁰ Terasaki Institute for Biomedical Innovation, Los Angeles, CA, USA.
⁵¹ Center for Nanoparticle Research, Institute for Basic Science (IBS), School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea.
⁵² Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.
⁵³ Center for Intelligent Sensors and MEMS (CISM), National University of Singapore, Singapore 117608, Singapore.
⁵⁴ National University of Singapore Suzhou Research Institute (NUSRI), Suzhou Industrial Park, Suzhou 215123, China.
⁵⁵ NUS Graduate School-Integrative Sciences and Engineering Programme (ISEP), National University of Singapore, Singapore 119077, Singapore.
⁵⁶ School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Kyunggi-do 16419, Republic of Korea.
⁵⁷ School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
⁵⁸ Singapore-HUJ Alliance for Research and Enterprise (SHARE), Campus for Research Excellence and Technological Enterprise (CREATE), Singapore 138602, Singapore.
⁵⁹ Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.
⁶⁰ School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea.
⁶¹ Institute of Engineering Research, Research Institute of Advanced Materials, Seoul National University, Soft Foundry, Seoul 08826, Republic of Korea.
⁶² Interdisciplinary Program in Bioengineering, Seoul National University, Seoul 08826, Republic of Korea.
⁶³ College of Chemistry and Materials Science, Jinan University, Guangzhou, Guangdong 510632, China.
⁶⁴ Department of Biomedical Engineering, Department of Electrical and Computer Engineering, Neuroscience Program, BioMolecular Science Program, and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan 48823, United States.
⁶⁵ School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China.
⁶⁶ Department of Biomedical Engineering, National University of Singapore, Singapore 117583, Singapore.
⁶⁷ Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.
⁶⁸ Institute for Health Innovation and Technology, National University of Singapore, Singapore 119276, Singapore.
⁶⁹ School of Microelectronics, Southern University of Science and Technology, Shenzhen 518055, China.
⁷⁰ Department of Nano and Chemical Engineering, University of California, San Diego, La Jolla, California 92093-0448, United States.
⁷¹ John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts, 02134, United States.
⁷² School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Jiao Tong University, Shanghai 200240, PR China.
⁷³ Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, PR China.
⁷⁴ Department of Biomedical Engineering, N.1 Institute for Health, Institute for Health Innovation and Technology (iHealthtech), National University of Singapore, Singapore 119077, Singapore.
⁷⁵ Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States.
⁷⁶ Neural Engineering Centre, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China 518055.
⁷⁷ Department of Aerospace Engineering and Engineering Mechanics, Department of Electrical and Computer Engineering, Department of Mechanical Engineering, Department of Biomedical Engineering, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States.
⁷⁸ Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
⁷⁹ Electrical Engineering Division, Department of Engineering, University of Cambridge CB3 0FA, Cambridge United Kingdom.
⁸⁰ Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
⁸¹ Darwin College, University of Cambridge, Cambridge CB3 9EU, United Kingdom.
⁸² Department of Biomedical Engineering, Rutgers University, Piscataway, New Jersey 08854, United States.
⁸³ School of Chemical Engineering and Samsung Advanced Institute for Health Science and Technology, Sungkyunkwan University, Suwon 16419, Republic of Korea.
⁸⁴ Department of Materials Science and Engineering, Department of Mechanical and Aerospace Engineering, California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States.
⁸⁵ Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California, 90095, United States.
⁸⁶ Querrey Simpson Institute for Bioelectronics, Northwestern University, Evanston, Illinois 60208, United States.
⁸⁷ Department of Materials Science and Engineering, Department of Mechanical Engineering, Department of Biomedical Engineering, Departments of Electrical and Computer Engineering and Chemistry, and Department of Neurological Surgery, Northwestern University, Evanston, Illinois 60208, United States.
⁸⁸ Becton, Dickinson and Company, 1268 N. Lakeview Avenue, Anaheim, California 92807, United States.
⁸⁹ Ready, Set, Food! 15821 Ventura Blvd #450, Encino, California 91436, United States.
⁹⁰ Material Systems for Nanoelectronics, Chemnitz University of Technology, Chemnitz 09107, Germany.
⁹¹ Nanophysics, Faculty of Physics, TU Dresden, Dresden 01062, Germany.
⁹² The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Osaka, Japan 5670047.
⁹³ School of Integrated Circuits and Electronics, Beijing Institute of Technology, Beijing 100081, China.
⁹⁴ Department of Electronic Engineering, Beijing National Research Center for Information Science and Technology, Institute for Precision Medicine, Center for Flexible Electronics Technology, and IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, 100084, China.
⁹⁵ Department of Electrical Engineering and Information Systems, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
⁹⁶ Key Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences, Beijing, Beijing 100190, China.
⁹⁷ Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, SE-601 74 Norrkoping, Sweden.
⁹⁸ Department of Physics and Electronics, Osaka Metropolitan University, Sakai, Osaka 599-8531, Japan.
⁹⁹ Research Institute for Intelligent Wearable Systems, School of Fashion and Textiles, Hong Kong Polytechnic University, Hong Kong, China.
¹⁰⁰ Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore.
¹⁰¹ iHealthtech, National University of Singapore, Singapore 119276, Singapore.
¹⁰² Singapore Hybrid-Integrated Next-Generation μ-Electronics Centre (SHINE), Singapore 117583, Singapore.
¹⁰³ School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China.
¹⁰⁴ Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas 78712, United States.
¹⁰⁵ Department of Nanoengineering, University of California, San Diego, California 92093, United States.
¹⁰⁶ Frontier Institute of Chip and System, State Key Laboratory of Integrated Chip and Systems, Zhangjiang Fudan International Innovation Center, Fudan University, Shanghai, 200433, China.
¹⁰⁷ the Shanghai Qi Zhi Institute, 41th Floor, AI Tower, No.701 Yunjin Road, Xuhui District, Shanghai 200232, China.
¹⁰⁸ Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois, 60637, United States.
¹⁰⁹ State Key Laboratory of Organic Electronics and Information Displays and Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.
¹¹⁰ Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, China.
¹¹¹ Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States.
¹¹² California NanoSystems Institute, Department of Chemistry and Biochemistry, Department of Bioengineering, and Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States.
¹¹³ Institute of Flexible Electronics Technology of THU, Jiaxing, Zhejiang, China 314000.
¹¹⁴ Department of Nanoengineering, Department of Electrical and Computer Engineering, Materials Science and Engineering Program, and Department of Bioengineering, University of California San Diego, La Jolla, California, 92093, United States.
¹¹⁵ School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen, Guangdong, 518060, PR China.
¹¹⁶ Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University, Tianjin, China, 300072.
¹¹⁷ Department of Materials Science and Engineering, National University of Singapore (NUS), 9 Engineering Drive 1, #03-09 EA, Singapore 117575, Singapore.
¹¹⁸ School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom.
¹¹⁹ School of Materials Science and Engineering, The Key Laboratory of Advanced Materials of Ministry of Education, State Key Laboratory of New Ceramics and Fine Processing, and Center for Flexible Electronics Technology, Tsinghua University, Beijing, 100084, China.
¹²⁰ Department of Engineering Science and Mechanics, Department of Biomedical Engineering, Department of Material Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania, 16802, United States.
¹²¹ Materials Science and Engineering Program and Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas, 78712, United States.
¹²² Department of Chemistry, Institute of Biomimetic Materials and Chemistry, Hefei National Research Center for Physical Science at the Microscale, University of Science and Technology of China, Hefei 230026, China.
¹²³ Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China.
¹²⁴ National Key Laboratory of Science and Technology on Micro/Nano Fabrication; Beijing Advanced Innovation Center for Integrated Circuits, School of Integrated Circuits, Peking University, Beijing 100871, China.
¹²⁵ School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China.
¹²⁶ School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen, Guangdong 518060, PR China.
¹²⁷ Applied Mechanics Laboratory, Department of Engineering Mechanics; Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing 100084, PR China.
¹²⁸ Department of Mechanical Engineering, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States.
¹²⁹ Center for Integrated Circuits and Systems, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
¹³⁰ National Key Laboratory of Science and Technology on Micro/Nano Fabrication; School of Integrated Circuits, Peking University, Beijing 100871, China.
¹³¹ Department of Applied Biology and Chemical Technology, Faculty of Science, Research Institute for Intelligent Wearable Systems, Research Institute for Smart Energy, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
¹³² Center for Neural Engineering, Department of Engineering Science and Mechanics, The Huck Institutes of the Life Sciences, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
¹³³ Key Laboratory of 3D Micro/Nano Fabrication and Characterization of Zhejiang Province, School of Engineering, Westlake University, Hangzhou 310024, China.
¹³⁴ Institute for Digital Molecular Analytics and Science (IDMxS), Nanyang Technological University, 59 Nanyang Drive, Singapore 636921, Singapore.
¹³⁵ Department of Precision Instrument, Tsinghua University, Beijing 100084, China.
¹³⁶ Terasaki Institute for Biomedical Innovation, Los Angeles, California, 90064, United States.
¹³⁷ Department of Mechanical and Aerospace Engineering, Department of Materials Science and Engineering, and Department of Biomedical Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States.
¹³⁸ Innovative Center for Flexible Devices (iFLEX), Max Planck-NTU Joint Laboratory for Artificial Senses, School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.

PMID: 36892156
PMCID: PMC11223676
DOI: 10.1021/acsnano.2c12606

Review

Technology Roadmap for Flexible Sensors

Yifei Luo et al. ACS Nano. 2023.

. 2023 Mar 28;17(6):5211-5295.

doi: 10.1021/acsnano.2c12606. Epub 2023 Mar 9.

Authors

Affiliations

¹ Institute of Materials Research and Engineering (IMRE), Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, #08-03 Innovis, Singapore 138634, Republic of Singapore.
² Innovative Centre for Flexible Devices (iFLEX), School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
³ Department of Biomedical Engineering, University of Houston, Houston, Texas 77024, United States.
⁴ School of Electrical and Electronic Engineering, Yonsei University, Seoul 03722, Republic of Korea.
⁵ Department of Electrical and Computer Engineering, The University of Texas at Austin, Austin, Texas 78712, United States.
⁶ Microelectronics Research Center, The University of Texas at Austin, Austin, Texas 78758, United States.
⁷ Department of Chemistry and Biochemistry, California NanoSystems Institute, and Department of Psychiatry and Biobehavioral Sciences, Semel Institute for Neuroscience and Human Behavior, and Hatos Center for Neuropharmacology, University of California, Los Angeles, Los Angeles, California 90095, United States.
⁸ Colloid Chemistry Department, Max Planck Institute of Colloids and Interfaces, 14476 Potsdam, Germany.
⁹ Department of Chemical Engineering, Stanford University, Stanford, California 94305, United States.
¹⁰ Laboratory of Organic Electronics, Department of Science and Technology, Campus Norrköping, Linköping University, 83 Linköping, Sweden.
¹¹ Wallenberg Initiative Materials Science for Sustainability (WISE) and Wallenberg Wood Science Center (WWSC), SE-100 44 Stockholm, Sweden.
¹² Department of Materials Science and Engineering, Stanford University, Stanford, California 94301, United States.
¹³ Department of Biomedical Engineering and Department of Materials Science and Engineering, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213, United States.
¹⁴ Department of Bioengineering, University of California, Los Angeles, Los Angeles, California 90095, United States.
¹⁵ School of Chemistry, Chemical Engineering and Biotechnology, Nanyang Technological University, Singapore 637457, Singapore.
¹⁶ Nanobionics Group, Department of Chemical and Biological Engineering, Monash University, Clayton, Australia, 3800.
¹⁷ Monash Institute of Medical Engineering, Monash University, Clayton, Australia3800.
¹⁸ Applied Mechanics Laboratory, Department of Engineering Mechanics, Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing 100084, PR China.
¹⁹ Division of Materials of Science and Engineering, Hanyang University, 222 Wangsimni-ro, Seongdong-gu, Seoul 04763, Republic of Korea.
²⁰ School of Mechanical Engineering, Purdue University, West Lafayette, Indiana 47906, United States.
²¹ Media Lab, Massachusetts Institute of Technology, Cambridge, Massachusetts 02139, United States.
²² Beijing National Laboratory for Molecular Sciences, CAS Key Laboratory of Organic Solids, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
²³ Department of Chemical and Biomolecular Engineering, North Carolina State University, Raleigh, North Carolina 27606, United States.
²⁴ Department of Chemistry and Biochemistry, California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States.
²⁵ Department of Chemistry and the Materials Research Center, Northwestern University, Evanston, Illinois 60208, United States.
²⁶ Department of Electronic and Computer Engineering and Department of Chemical and Biological Engineering, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong SAR, China.
²⁷ State Key Laboratory of Molecular Engineering of Polymers, Department of Macromolecular Science, and Laboratory of Advanced Materials, Fudan University, Shanghai 200438, PR China.
²⁸ Laboratory of Flexible Electronics Technology, Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China.
²⁹ School of Mechanical and Aerospace Engineering, Nanyang Technological University, Singapore 639798, Singapore.
³⁰ Institute of High Performance Computing (IHPC), Agency for Science, Technology and Research (A*STAR), 1 Fusionopolis Way, #16-16 Connexis, Singapore 138632, Republic of Singapore.
³¹ Andrew and Peggy Cherng Department of Medical Engineering, California Institute of Technology, Pasadena, California, 91125, United States.
³² Department of Chemical Engineering, Department of Materials Science and Engineering, Department of Electrical Engineering and Computer Science, Applied Physics Program, and Macromolecular Science and Engineering Program, University of Michigan, Ann Arbor, Michigan, 48109 United States.
³³ Department of Materials Science and Engineering, Southern University of Science and Technology, Shenzhen 518055, China.
³⁴ National Key Laboratory of Science and Technology on Micro/Nano Fabrication, School of Electronic Information and Electrical Engineering, Shanghai Jiao Tong University, Shanghai 200240, China.
³⁵ Institute for Health Innovation and Technology, National University of Singapore, Singapore 117599, Singapore.
³⁶ Department of Electrical and Computer Engineering, National University of Singapore, Singapore 117583, Singapore.
³⁷ The N.1 Institute for Health, National University of Singapore, Singapore 117456, Singapore.
³⁸ School of Electronics and Center for Carbon-Based Electronics, Peking University, Beijing 100871, China.
³⁹ School of Fashion and Textiles, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
⁴⁰ Department of Materials Science and Engineering, California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States.
⁴¹ Key Laboratory of Flexible Electronics (KLOFE) and Institute of Advanced Materials (IAM), Nanjing Tech University (NanjingTech), 30 South Puzhu Road, Nanjing 211816, PR China.
⁴² mmh Labs, Elmore Family School of Electrical and Computer Engineering, Purdue University, West Lafayette, Indiana 47906, United States.
⁴³ Electrical Engineering and Computer Sciences, University of California, Berkeley, California 94720, United States.
⁴⁴ Materials Sciences Division, Lawrence Berkeley National Laboratory, Berkeley, California 94720, United States.
⁴⁵ Department of Materials Science and Engineering, Pohang University of Science and Engineering (POSTECH), Pohang, Gyeong-buk 37673, Korea.
⁴⁶ Department of Electronic Engineering, Tsinghua University, Beijing 100084, China.
⁴⁷ Department of Biomedical Engineering, Southern University of Science and Technology, No 1088, Xueyuan Road, Xili, Nanshan District, Shenzhen, Guangdong 518055, PR China.
⁴⁸ Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), Daejeon 34141, Republic of Korea.
⁴⁹ Research Center for Materials, Architectures and Integration of Nanomembranes (MAIN), Chemnitz University of Technology, Chemnitz 09126, Germany.
⁵⁰ Terasaki Institute for Biomedical Innovation, Los Angeles, CA, USA.
⁵¹ Center for Nanoparticle Research, Institute for Basic Science (IBS), School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea.
⁵² Department of Materials Science and Engineering, Korea Advanced Institute of Science and Technology (KAIST), 291 Daehak-ro, Yuseong-gu, Daejeon 34141, Republic of Korea.
⁵³ Center for Intelligent Sensors and MEMS (CISM), National University of Singapore, Singapore 117608, Singapore.
⁵⁴ National University of Singapore Suzhou Research Institute (NUSRI), Suzhou Industrial Park, Suzhou 215123, China.
⁵⁵ NUS Graduate School-Integrative Sciences and Engineering Programme (ISEP), National University of Singapore, Singapore 119077, Singapore.
⁵⁶ School of Advanced Materials Science and Engineering, Sungkyunkwan University, Suwon, Kyunggi-do 16419, Republic of Korea.
⁵⁷ School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.
⁵⁸ Singapore-HUJ Alliance for Research and Enterprise (SHARE), Campus for Research Excellence and Technological Enterprise (CREATE), Singapore 138602, Singapore.
⁵⁹ Department of Materials Science and Engineering, Seoul National University, Seoul 08826, Republic of Korea.
⁶⁰ School of Chemical and Biological Engineering, Seoul National University, Seoul 08826, Republic of Korea.
⁶¹ Institute of Engineering Research, Research Institute of Advanced Materials, Seoul National University, Soft Foundry, Seoul 08826, Republic of Korea.
⁶² Interdisciplinary Program in Bioengineering, Seoul National University, Seoul 08826, Republic of Korea.
⁶³ College of Chemistry and Materials Science, Jinan University, Guangzhou, Guangdong 510632, China.
⁶⁴ Department of Biomedical Engineering, Department of Electrical and Computer Engineering, Neuroscience Program, BioMolecular Science Program, and Institute for Quantitative Health Science and Engineering, Michigan State University, East Lansing, Michigan 48823, United States.
⁶⁵ School of Chemistry and Chemical Engineering, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China.
⁶⁶ Department of Biomedical Engineering, National University of Singapore, Singapore 117583, Singapore.
⁶⁷ Mechanobiology Institute, National University of Singapore, Singapore 117411, Singapore.
⁶⁸ Institute for Health Innovation and Technology, National University of Singapore, Singapore 119276, Singapore.
⁶⁹ School of Microelectronics, Southern University of Science and Technology, Shenzhen 518055, China.
⁷⁰ Department of Nano and Chemical Engineering, University of California, San Diego, La Jolla, California 92093-0448, United States.
⁷¹ John A. Paulson School of Engineering and Applied Sciences, Harvard University, Boston, Massachusetts, 02134, United States.
⁷² School of Chemistry and Chemical Engineering, Frontiers Science Center for Transformative Molecules, Shanghai Jiao Tong University, Shanghai 200240, PR China.
⁷³ Beijing Key Laboratory of Energy Conversion and Storage Materials, College of Chemistry, Beijing Normal University, Beijing 100875, PR China.
⁷⁴ Department of Biomedical Engineering, N.1 Institute for Health, Institute for Health Innovation and Technology (iHealthtech), National University of Singapore, Singapore 119077, Singapore.
⁷⁵ Department of Mechanical and Aerospace Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States.
⁷⁶ Neural Engineering Centre, Shenzhen Institute of Advanced Technology, Chinese Academy of Sciences, Shenzhen, China 518055.
⁷⁷ Department of Aerospace Engineering and Engineering Mechanics, Department of Electrical and Computer Engineering, Department of Mechanical Engineering, Department of Biomedical Engineering, Texas Materials Institute, The University of Texas at Austin, Austin, Texas 78712, United States.
⁷⁸ Institute of Chemistry and the Center for Nanoscience and Nanotechnology, The Hebrew University of Jerusalem, Jerusalem 9190401, Israel.
⁷⁹ Electrical Engineering Division, Department of Engineering, University of Cambridge CB3 0FA, Cambridge United Kingdom.
⁸⁰ Institute of Industrial Science, The University of Tokyo, 4-6-1 Komaba, Meguro-ku, Tokyo 153-8505, Japan.
⁸¹ Darwin College, University of Cambridge, Cambridge CB3 9EU, United Kingdom.
⁸² Department of Biomedical Engineering, Rutgers University, Piscataway, New Jersey 08854, United States.
⁸³ School of Chemical Engineering and Samsung Advanced Institute for Health Science and Technology, Sungkyunkwan University, Suwon 16419, Republic of Korea.
⁸⁴ Department of Materials Science and Engineering, Department of Mechanical and Aerospace Engineering, California NanoSystems Institute, University of California, Los Angeles, Los Angeles, California 90095, United States.
⁸⁵ Department of Chemistry and Biochemistry, University of California, Los Angeles, Los Angeles, California, 90095, United States.
⁸⁶ Querrey Simpson Institute for Bioelectronics, Northwestern University, Evanston, Illinois 60208, United States.
⁸⁷ Department of Materials Science and Engineering, Department of Mechanical Engineering, Department of Biomedical Engineering, Departments of Electrical and Computer Engineering and Chemistry, and Department of Neurological Surgery, Northwestern University, Evanston, Illinois 60208, United States.
⁸⁸ Becton, Dickinson and Company, 1268 N. Lakeview Avenue, Anaheim, California 92807, United States.
⁸⁹ Ready, Set, Food! 15821 Ventura Blvd #450, Encino, California 91436, United States.
⁹⁰ Material Systems for Nanoelectronics, Chemnitz University of Technology, Chemnitz 09107, Germany.
⁹¹ Nanophysics, Faculty of Physics, TU Dresden, Dresden 01062, Germany.
⁹² The Institute of Scientific and Industrial Research (SANKEN), Osaka University, Osaka, Japan 5670047.
⁹³ School of Integrated Circuits and Electronics, Beijing Institute of Technology, Beijing 100081, China.
⁹⁴ Department of Electronic Engineering, Beijing National Research Center for Information Science and Technology, Institute for Precision Medicine, Center for Flexible Electronics Technology, and IDG/McGovern Institute for Brain Research, Tsinghua University, Beijing, 100084, China.
⁹⁵ Department of Electrical Engineering and Information Systems, Graduate School of Engineering, The University of Tokyo, Tokyo 113-8656, Japan.
⁹⁶ Key Laboratory of Green Printing, Institute of Chemistry, Chinese Academy of Sciences, Beijing, Beijing 100190, China.
⁹⁷ Laboratory of Organic Electronics, Department of Science and Technology, Linköping University, SE-601 74 Norrkoping, Sweden.
⁹⁸ Department of Physics and Electronics, Osaka Metropolitan University, Sakai, Osaka 599-8531, Japan.
⁹⁹ Research Institute for Intelligent Wearable Systems, School of Fashion and Textiles, Hong Kong Polytechnic University, Hong Kong, China.
¹⁰⁰ Materials Science and Engineering, National University of Singapore, Singapore 117575, Singapore.
¹⁰¹ iHealthtech, National University of Singapore, Singapore 119276, Singapore.
¹⁰² Singapore Hybrid-Integrated Next-Generation μ-Electronics Centre (SHINE), Singapore 117583, Singapore.
¹⁰³ School of Electronic Science and Engineering, Nanjing University, Nanjing 210023, China.
¹⁰⁴ Department of Biomedical Engineering, University of Texas at Austin, Austin, Texas 78712, United States.
¹⁰⁵ Department of Nanoengineering, University of California, San Diego, California 92093, United States.
¹⁰⁶ Frontier Institute of Chip and System, State Key Laboratory of Integrated Chip and Systems, Zhangjiang Fudan International Innovation Center, Fudan University, Shanghai, 200433, China.
¹⁰⁷ the Shanghai Qi Zhi Institute, 41th Floor, AI Tower, No.701 Yunjin Road, Xuhui District, Shanghai 200232, China.
¹⁰⁸ Pritzker School of Molecular Engineering, The University of Chicago, Chicago, Illinois, 60637, United States.
¹⁰⁹ State Key Laboratory of Organic Electronics and Information Displays and Jiangsu Key Laboratory for Biosensors, Institute of Advanced Materials (IAM), Nanjing University of Posts and Telecommunications, 9 Wenyuan Road, Nanjing 210023, China.
¹¹⁰ Beijing Institute of Nanoenergy and Nanosystems, Chinese Academy of Sciences, Beijing 100083, China.
¹¹¹ Georgia Institute of Technology, Atlanta, Georgia 30332-0245, United States.
¹¹² California NanoSystems Institute, Department of Chemistry and Biochemistry, Department of Bioengineering, and Department of Materials Science and Engineering, University of California, Los Angeles, Los Angeles, California 90095, United States.
¹¹³ Institute of Flexible Electronics Technology of THU, Jiaxing, Zhejiang, China 314000.
¹¹⁴ Department of Nanoengineering, Department of Electrical and Computer Engineering, Materials Science and Engineering Program, and Department of Bioengineering, University of California San Diego, La Jolla, California, 92093, United States.
¹¹⁵ School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen, Guangdong, 518060, PR China.
¹¹⁶ Tianjin Key Laboratory of Molecular Optoelectronic Sciences, Department of Chemistry, School of Science, Tianjin University, Tianjin, China, 300072.
¹¹⁷ Department of Materials Science and Engineering, National University of Singapore (NUS), 9 Engineering Drive 1, #03-09 EA, Singapore 117575, Singapore.
¹¹⁸ School of Biomedical Sciences, Faculty of Biological Sciences, University of Leeds, Leeds, LS2 9JT, United Kingdom.
¹¹⁹ School of Materials Science and Engineering, The Key Laboratory of Advanced Materials of Ministry of Education, State Key Laboratory of New Ceramics and Fine Processing, and Center for Flexible Electronics Technology, Tsinghua University, Beijing, 100084, China.
¹²⁰ Department of Engineering Science and Mechanics, Department of Biomedical Engineering, Department of Material Science and Engineering, Materials Research Institute, Pennsylvania State University, University Park, Pennsylvania, 16802, United States.
¹²¹ Materials Science and Engineering Program and Walker Department of Mechanical Engineering, The University of Texas at Austin, Austin, Texas, 78712, United States.
¹²² Department of Chemistry, Institute of Biomimetic Materials and Chemistry, Hefei National Research Center for Physical Science at the Microscale, University of Science and Technology of China, Hefei 230026, China.
¹²³ Department of Biomedical Engineering, City University of Hong Kong, Hong Kong, China.
¹²⁴ National Key Laboratory of Science and Technology on Micro/Nano Fabrication; Beijing Advanced Innovation Center for Integrated Circuits, School of Integrated Circuits, Peking University, Beijing 100871, China.
¹²⁵ School of Electronic Science and Engineering, University of Electronic Science and Technology of China, Chengdu 611731, China.
¹²⁶ School of Biomedical Engineering, Health Science Center, Shenzhen University, Shenzhen, Guangdong 518060, PR China.
¹²⁷ Applied Mechanics Laboratory, Department of Engineering Mechanics; Laboratory of Flexible Electronics Technology, Tsinghua University, Beijing 100084, PR China.
¹²⁸ Department of Mechanical Engineering, Department of Civil and Environmental Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts, 02139, United States.
¹²⁹ Center for Integrated Circuits and Systems, School of Electrical and Electronic Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore 639798, Singapore.
¹³⁰ National Key Laboratory of Science and Technology on Micro/Nano Fabrication; School of Integrated Circuits, Peking University, Beijing 100871, China.
¹³¹ Department of Applied Biology and Chemical Technology, Faculty of Science, Research Institute for Intelligent Wearable Systems, Research Institute for Smart Energy, The Hong Kong Polytechnic University, Hung Hom, Kowloon, Hong Kong SAR, China.
¹³² Center for Neural Engineering, Department of Engineering Science and Mechanics, The Huck Institutes of the Life Sciences, Materials Research Institute, The Pennsylvania State University, University Park, Pennsylvania 16802, United States.
¹³³ Key Laboratory of 3D Micro/Nano Fabrication and Characterization of Zhejiang Province, School of Engineering, Westlake University, Hangzhou 310024, China.
¹³⁴ Institute for Digital Molecular Analytics and Science (IDMxS), Nanyang Technological University, 59 Nanyang Drive, Singapore 636921, Singapore.
¹³⁵ Department of Precision Instrument, Tsinghua University, Beijing 100084, China.
¹³⁶ Terasaki Institute for Biomedical Innovation, Los Angeles, California, 90064, United States.
¹³⁷ Department of Mechanical and Aerospace Engineering, Department of Materials Science and Engineering, and Department of Biomedical Engineering, North Carolina State University, Raleigh, North Carolina 27695, United States.
¹³⁸ Innovative Center for Flexible Devices (iFLEX), Max Planck-NTU Joint Laboratory for Artificial Senses, School of Materials Science and Engineering, Nanyang Technological University, Singapore 639798, Singapore.

PMID: 36892156
PMCID: PMC11223676
DOI: 10.1021/acsnano.2c12606

Abstract

Humans rely increasingly on sensors to address grand challenges and to improve quality of life in the era of digitalization and big data. For ubiquitous sensing, flexible sensors are developed to overcome the limitations of conventional rigid counterparts. Despite rapid advancement in bench-side research over the last decade, the market adoption of flexible sensors remains limited. To ease and to expedite their deployment, here, we identify bottlenecks hindering the maturation of flexible sensors and propose promising solutions. We first analyze challenges in achieving satisfactory sensing performance for real-world applications and then summarize issues in compatible sensor-biology interfaces, followed by brief discussions on powering and connecting sensor networks. Issues en route to commercialization and for sustainable growth of the sector are also analyzed, highlighting environmental concerns and emphasizing nontechnical issues such as business, regulatory, and ethical considerations. Additionally, we look at future intelligent flexible sensors. In proposing a comprehensive roadmap, we hope to steer research efforts towards common goals and to guide coordinated development strategies from disparate communities. Through such collaborative efforts, scientific breakthroughs can be made sooner and capitalized for the betterment of humanity.

Keywords: bioelectronics; body area sensor networks; conformable sensors; flexible electronics; human-machine interfaces; mechanics engineering; soft materials; sustainable electronics; technology translation.

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Figures

**Figure 1.**
Evolution of sensor technology. Sensors 1.0 only served the function of detection. Sensors 2.0 had the hallmark of electrical feedback. The first transistors achieved sensing as well as the amplification of current.^, Sensors 3.0 are characterized by miniaturization and integration. A smartphone is equipped with pressure sensors, light sensors, sound sensors, temperature sensors, image sensors, motion sensors, location sensors, among many others; smartwatches are likewise equipped with an increasing cohort of diverse sensors. Budding Sensors 4.0 technologies involve sensor networks and advanced algorithms to achieve enhanced perception capabilities and intimate cooperation between humans and machines.

**Figure 2.**
An overview of issues covered in this Review, including challenges for flexible sensors in the near future (left) and issues to address in the long run (right). The five aspects of challenges are interrelated, reflected by the tan lines in the background.

**Figure 3.**
Overview of key issues in the sensing performance of flexible sensors.

**Figure 4.**
Barrier properties against (a) water and (b) oxygen of common materials used in flexible sensors, plotted versus elastic modulus. Softer materials are more flexible and usually more stretchable but suffer from poorer barrier properties. Soft barrier materials with moduli comparable to elastomers and hydrogels, as well as permeabilities comparable to inorganics are highly desirable for effective encapsulation (red arrows). Adapted with permission from ref . Copyright 2018 American Chemical Society.

**Figure 5.**
Selective gas sensors. (a) Overview of the strategies to achieve selective gas sensing, including specific sensing materials and selective sensing arrays. Flexible gas sensors target applications in health monitoring and point-of-care diagnostics. AI, artificial intelligence. (b) Examples of metal–organic framework-based nanomaterials with high sensing specificity to gas molecules. Cu₃-(HHTP)₂ (HHTP=2,3,6,7,10,11-hexahydroxytriphenylene) thin film for room-temperature NH₃ detection. Adapted with permission from ref . Copyright 2017 Wiley-VCH Verlag GmbH &Co. KGaA, Weinheim. Bimetallic nanoparticles (PtRu) confined in two-dimensional Cu₃-(HHTP)₂ for NO₂ detection. Adapted with permission from ref . Copyright 2021 Wiley-VCH GmbH. Zn-based zeolite imidazole framework (ZIF-8) as molecular sieving layer for selective H₂ filtration on Pd nanowires. Adapted with permission from ref . Copyright 2017 American Chemical Society. (c) An example of nanomaterial-based selective sensing array for volatile organic compound (VOC) identification. A graphene-based stretchable chemiresistive sensor array for identification of 13 plant VOCs. Reproduced with permission from ref . Copyright 2021 Elsevier.

**Figure 6.**
Current interconnection approaches for flexible sensors and arrays. (a) Extended flexible sensor system layout contains flexible cable and pins suitable for a flat flexible cable (FFC) connector. (b) External FFC is bonded to the flexible sensor system *via* an anisotropic conductive film (ACF). (c) Printed conductors connect flexible sensor system with external electronics directly.

**Figure 7.**
Performance of intrinsically stretchable (a) conductors and (b) semiconductors. (a) Intrinsically stretchable conductors are realized in three materials categories: nanocomposites, conducting polymers, and liquid metals; ionic conductors are not included. Conductivities of stretched liquid metals are calculated from resistance changes under unidirectional strain, based on the assumption of incompressible solid undergoing uniform deformation. Non-stretchable bulk metals are plotted in the gray band for comparison. Values extracted from refs , , -. (b) Stretchable semiconductors are based on semiconducting CNTs or conjugated polymers. Mobility measurement was done in either stretched materials transferred to non-stretchable substrates (channel only) or fully stretchable transistors and transistor arrays (full transistor). Values for stretch directions both parallel and perpendicular to the channel length are included. Typical mobilities of common non-stretchable semiconductors are plotted in bands for comparison. Red arrow indicates area for improvement. Values extracted from refs , , -.

**Figure 8.**
Conventional time division multiple access (blue panel) and emerging event-driven spike generation (red panel) as array data collection strategies. (a,b) Passive-matrix and active-matrix designs are the most commonly used array readout strategies. (c) Biological somatosensory system uses spike trains to encode tactile information with high spatiotemporal resolution and energy efficiency. (d) Artificial sensory systems can mimic the structure and function of the biological somatosensory system. Each sensing pixel generates potential spikes and is thus called an artificial receptor. (e) Two reported methods of generating spikes in individual artificial receptors include integrating an analog-to-digital converter (ADC) at each pixel and using sensing materials that can self-generate potential spikes. Circuit and photograph of one sensing pixel incorporating ADC adapted with permission from ref . Copyright 2019 American Association for the Advancement of Science. Schematics of self-spiking ion-electron conductor adapted with permission from ref . Copyright 2022 American Association for the Advancement of Science.

**Figure 9.**
Subthreshold Schottky-barrier thin-film transistors (SB-TFTs). (a) Schematic of a metal oxide-based inorganic SB-TFT. IGZO, indium-gallium-zinc-oxide; LC, less compensated; MC, more compensated. (b,c) Measured input characteristics in linear scale (b), indicating V_T (the threshold voltage), and in logarithmic scale (c), indicating V_ref (the reference voltage), respectively. I_G, gate leakage current. (d) Conceptual color bar of output power consumption (P_out) for a 1 V supply, normalized with W (channel width), clearly indicating each operational regime. Frames a–d adapted with permission from ref . Copyright 2016 American Association for the Advancement of Science. (e) Schematic of an organic SB-TFT. CYTOP, a commercial fluoropolymer; C8-BTBT, 2,7-dioctyl[1] benzothieno[3,2-b][1]benzothiophene; PS, polystyrene; PVC, polyvinyl cinnamate; PEN, polyethylene naphthalate. (f,g) Comparison of intrinsic gain (f) and transconductance efficiency (g) of different transistors. Organic SB-TFTs have the best performance. MOSFET, metal-oxide-semiconductor field-effect transistor. Frames e–g adapted with permission from ref . Copyright 2019 American Association for the Advancement of Science.

**Figure 10.**
Challenges in achieving compatible sensor-biology interfaces. Arrows indicate the influence of one property (open dots) on another (solid dots). The issues stemming from different features of biological tissues are stated at the sensor-tissue interface and indicated by thick gray arrows.

**Figure 11.**
Major innovations in materials and form factors, respectively, towards seamless sensor-biology interfaces. Materials innovations images (from left to right, top to bottom): Adapted with permission from ref . Copyright 2018 Springer Nature. Adapted under the terms of the Creative Commons CC BY license from ref ; published 2022 Springer Nature. Adapted under the terms of the Creative Commons CC BY license from ref ; published 2021 Springer Nature. Adapted with permission from ref . Copyright 2018 Springer Nature. Adapted with permission from ref . Copyright 2016 Springer Nature. Form factor images (from left to right, top to bottom): Adapted with permission from ref . Copyright 2013 Springer Nature. Adapted with permission from ref . Copyright 2015 Springer Nature. Adapted with permission from ref . Copyright 2017 American Chemical Society. Adapted with permission from ref . Copyright 2016 Springer Nature. Adapted with permission from ref . Copyright 2021 Springer Nature. Adapted with permission from ref . Copyright 2018 Springer Nature. PAA, polyacrylic acid; SBS, poly(styrene-butadiene-styrene).

**Figure 12.**
An energy-efficient sensing system incorporating multiple strategies for power management: reliable and high-power ambient energy harvesting (representative devices for light, mechanical, and chemical energy harvesting are shown; full list of devices is provided in Table 4), large-capacity energy storage in flexible form factors, reliable and efficient wireless power transfer, and systemic power management. TENG, triboelectric nanogenerator; PTE, power transfer efficiency.

**Figure 13.**
Outlook for flexible sensor networks. Black arrows denote connectivity. A group of sensor nodes can communicate within themselves and may be accessed by more than one cloud server. Due to dense connection, the two networks merge into one. Ultimately, numerous sensor nodes may be connected in a ‘meganetwork’ involving more gateways and servers (dot-outlined shapes). Cloud computing and fog computing will be instrumental in the realization of extensive sensor connectivity. Images for “imperceptible form factors”: Adapted with permission from ref . Copyright 2019 Springer Nature. Adapted with permission from ref . Copyright 2021 Springer Nature. Adapted with permission from ref . Copyright 2021 Springer Nature.

**Figure 14.**
Key issues to address during the translation of flexible sensors from labs to end-users. Images under “Customers and competitors” designed by Freepik. Images under “Design” adapted with permission from ref . Copyright 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Adapted with permission from ref . Copyright 2022 Wiley-VCH GmbH. Images under “Fabrication” adapted with permission from ref . Copyright 2020 Springer Nature. Adapted with permission from ref . Copyright 2021 American Association for the Advancement of Science. Images under “Modular system” adapted with permission from ref . Copyright 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim. Adapted with permission from ref . Copyright 2016 Springer Nature. Images under “Printing” adapted with permission from ref . Copyright 2018 American Chemical Society. Adapted with permission from ref . Copyright 2021 American Chemical Society. Images under “Polymers & nanomaterials” adapted with permission from ref . Copyright 2021 American Association for the Advancement of Science. Adapted with permission from ref . Copyright 2021 Springer Nature. Images under “System integration” adapted with permission from ref . Copyright 2022 American Association for the Advancement of Science. Adapted with permission from ref . Copyright 2018 Springer Nature. Images under “Data security & privacy” and “Quality, safety & sustainability” designed by Freepik.

**Figure 15.**
A vision for intelligent sensing systems with advantages listed on the left. Edge computing (including near-sensor and in-sensor computing) and neuromorphic computing are plausible ways of achieving sensor intelligence. They are not mutually exclusive and may be implemented in a single system. AI algorithms will be implemented in both central and edge processors. A feedback mechanism not only informs the user but also completes closed-loop operation. Integration with biological tissues permits two-way communication in various forms (details in Figure 16). Dashed black arrows indicate the direction of data flow. Images of non-neural network ML (machine learning) adapted with permission from ref . Copyright 2018 American Chemical Society. Neural network schematic adapted with permission from ref . Copyright 2020 Springer Nature. Deep learning schematic reproduced with permission from ref . Copyright 2015 Nature Publishing Group. Haptics image adapted with permission from ref . Copyright 2022 Springer Nature. Display image adapted with permission from ref . Copyright 2021 Springer Nature.

**Figure 16.**
Evolution of flexible artificial sensory devices and systems for bio-integration. Memristor schematic adapted with permission from ref . Copyright 2010 American Chemical Society. Transistor schematic adapted with permission from ref . Copyright 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Electronic neural interface schematics adapted with permission from ref . Copyright 2020 Springer Nature. Pressure sensory artificial neuron and bio-integration images adapted with permission from ref . Copyright 2018 American Association for the Advancement of Science. Chemical sensory artificial neuron and bio-integration schematics adapted with permission from ref . Copyright 2022 Springer Nature.

**Figure 17.**
A technology roadmap for flexible sensors and systems. Evolution with time is not drawn to scale. Images from left to right: Adapted with permission from ref . Copyright 2021 American Chemical Society. Adapted with permission from ref . Copyright 2021 Wiley-VCH GmbH. Adapted with permission from ref . Copyright 2019 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Adapted with permission from ref . Copyright 2020 Springer Nature. Adapted with permission from ref . Copyright 2016 Nature Publishing Group.

**Scheme 1.. A Holistic Approach to Sensor Accuracy Assurance during the Design, Manufacture, Validation, and Deployment of a Sensor Technology^a**
^aFactors to consider are highlighted in red boxes.

See this image and copyright information in PMC

References

1. Huddleston C. What Are Intelligent Sensors, and Why Should I Care About Them? In Intelligent Sensor Design Using the Microchip Dspic, Huddleston C. Ed.; Elsevier, 2006; pp 1–19.
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1. Heng Zhang Seismoscope. https://www.atlasobscura.com/places/zhang-heng-seismoscope (accessed 2021-10-15).
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Technology Roadmap for Flexible Sensors

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