title: Epidermal devices for noninvasive, precise, and continuous mapping of macrovascular and microvascular blood flow.
abstract: Continuous monitoring of variations in blood flow is vital in assessing the status of microvascular and macrovascular beds for a wide range of clinical and research scenarios. Although a variety of techniques exist, most require complete immobilization of the subject, thereby limiting their utility to hospital or clinical settings. Those that can be rendered in wearable formats suffer from limited accuracy, motion artifacts, and other shortcomings that follow from an inability to achieve intimate, noninvasive mechanical linkage of sensors with the surface of the skin. We introduce an ultrathin, soft, skin-conforming sensor technology that offers advanced capabilities in continuous and precise blood flow mapping. Systematic work establishes a set of experimental procedures and theoretical models for quantitative measurements and guidelines in design and operation. Experimental studies on human subjects, including validation with measurements performed using state-of-the-art clinical techniques, demonstrate sensitive and accurate assessment of both macrovascular and microvascular flow under a range of physiological conditions. Refined operational modes eliminate long-term drifts and reduce power consumption, thereby providing steps toward the use of this technology for continuous monitoring during daily activities.
authors.affiliation: Department of Materials Science and Engineering, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: R Chad
authors.initials: RC
authors.lastname: Webb
authors.affiliation: Departments of Civil and Environmental Engineering, and Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, IL 60208, USA. ; Department of Engineering Mechanics, Center for Mechanics and Materials, Tsinghua University, Beijing 100084, China.
authors.forename: Yinji
authors.initials: Y
authors.lastname: Ma
authors.affiliation: Department of Materials Science and Engineering, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Siddharth
authors.initials: S
authors.lastname: Krishnan
authors.affiliation: Departments of Civil and Environmental Engineering, and Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, IL 60208, USA. ; Institute of Solid Mechanics, Beihang University (BUAA), Beijing 100191, China.
authors.forename: Yuhang
authors.initials: Y
authors.lastname: Li
authors.affiliation: National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Stephen
authors.initials: S
authors.lastname: Yoon
authors.affiliation: Departments of Civil and Environmental Engineering, and Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, IL 60208, USA. ; College of Aerospace and Civil Engineering, Harbin Engineering University, Harbin 150001, China.
authors.forename: Xiaogang
authors.initials: X
authors.lastname: Guo
authors.affiliation: Department of Engineering Mechanics, Center for Mechanics and Materials, Tsinghua University, Beijing 100084, China.
authors.forename: Xue
authors.initials: X
authors.lastname: Feng
authors.affiliation: Departments of Civil and Environmental Engineering, and Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, IL 60208, USA. ; State Key Laboratory of Mechanics and Control of Mechanical Structures, Nanjing University of Aeronautics and Astronautics, Nanjing 210016, China.
authors.forename: Yan
authors.initials: Y
authors.lastname: Shi
authors.affiliation: National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Miles
authors.initials: M
authors.lastname: Seidel
authors.affiliation: Department of Materials Science and Engineering, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Nam Heon
authors.initials: NH
authors.lastname: Cho
authors.affiliation: Department of Materials Science and Engineering, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Jonas
authors.initials: J
authors.lastname: Kurniawan
authors.affiliation: National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: James
authors.initials: J
authors.lastname: Ahad
authors.affiliation: National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Niral
authors.initials: N
authors.lastname: Sheth
authors.affiliation: National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Joseph
authors.initials: J
authors.lastname: Kim
authors.affiliation: Genomic Medicine Section, Hematology Branch, National Heart, Lung, and Blood Institute, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: James G
authors.initials: JG
authors.lastname: Taylor
authors.affiliation: National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Tom
authors.initials: T
authors.lastname: Darlington
authors.affiliation: National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Ken
authors.initials: K
authors.lastname: Chang
authors.affiliation: Department of Electrical and Computer Engineering, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Weizhong
authors.initials: W
authors.lastname: Huang
authors.affiliation: Department of Materials Science and Engineering, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Joshua
authors.initials: J
authors.lastname: Ayers
authors.affiliation: Department of Materials Science and Engineering, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: Alexander
authors.initials: A
authors.lastname: Gruebele
authors.affiliation: L'Oréal California Research Center, 953 Indiana Street, San Francisco, CA 94107, USA.
authors.forename: Rafal M
authors.initials: RM
authors.lastname: Pielak
authors.affiliation: Department of Medicine, Sarver Heart Center, and Department of Biomedical Engineering, The University of Arizona, Tucson, AZ 85724, USA.
authors.forename: Marvin J
authors.initials: MJ
authors.lastname: Slepian
authors.affiliation: Departments of Civil and Environmental Engineering, and Mechanical Engineering, Center for Engineering and Health, and Skin Disease Research Center, Northwestern University, Evanston, IL 60208, USA.
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Huang
authors.affiliation: National Institute of Biomedical Imaging and Bioengineering, National Institutes of Health, Bethesda, MD 20892, USA.
authors.forename: Alexander M
authors.initials: AM
authors.lastname: Gorbach
authors.affiliation: Department of Materials Science and Engineering, and Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL 61801, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Rogers
keywords: Flexible electronics; Sensor; blood flow; circulation; skin; stretchable; thermal transport; wearable electronics