Epidermal devices for noninvasive, precise, and continuous mapping of macrovascular and microvascular blood flow

  1. R. Chad Webb1,*
  2. Yinji Ma2,3,*
  3. Siddharth Krishnan1,*
  4. Yuhang Li2,4
  5. Stephen Yoon5
  6. Xiaogang Guo2,6,
  7. Xue Feng3
  8. Yan Shi2,7
  9. Miles Seidel5
  10. Nam Heon Cho1
  11. Jonas Kurniawan1
  12. James Ahad5
  13. Niral Sheth5,
  14. Joseph Kim5
  15. James G. Taylor VI8
  16. Tom Darlington5
  17. Ken Chang5
  18. Weizhong Huang9
  19. Joshua Ayers1,
  20. Alexander Gruebele1
  21. Rafal M. Pielak10
  22. Marvin J. Slepian11
  23. Yonggang Huang2
  24. Alexander M. Gorbach5and 
  25. John A. Rogers1,

  26. 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.