title: Theoretical and Experimental Studies of Epidermal Heat Flux Sensors for Measurements of Core Body Temperature.
abstract: Long-term, continuous measurement of core body temperature is of high interest, due to the widespread use of this parameter as a key biomedical signal for clinical judgment and patient management. Traditional approaches rely on devices or instruments in rigid and planar forms, not readily amenable to intimate or conformable integration with soft, curvilinear, time-dynamic, surfaces of the skin. Here, materials and mechanics designs for differential temperature sensors are presented which can attach softly and reversibly onto the skin surface, and also sustain high levels of deformation (e.g., bending, twisting, and stretching). A theoretical approach, together with a modeling algorithm, yields core body temperature from multiple differential measurements from temperature sensors separated by different effective distances from the skin. The sensitivity, accuracy, and response time are analyzed by finite element analyses (FEA) to provide guidelines for relationships between sensor design and performance. Four sets of experiments on multiple devices with different dimensions and under different convection conditions illustrate the key features of the technology and the analysis approach. Finally, results indicate that thermally insulating materials with cellular structures offer advantages in reducing the response time and increasing the accuracy, while improving the mechanics and breathability.
authors.affiliation: Departments of Civil and Environmental Engineeringand Mechanical Engineering, Center for Engineering and Healthand Skin Disease Research Center, Northwestern University, Evanston, IL, 60208, USA.|Center for Mechanics and Materials, Tsinghua University, Beijing, 100084, China.
authors.forename: Yihui
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Department of Materials Science and Engineering, Frederick Seitz Materials Research Laboratory, University of Illinois at Urbana-Champaign, Urbana, IL, 61801, USA.
authors.forename: Richard Chad
authors.initials: RC
authors.lastname: Webb
authors.affiliation: Departments of Civil and Environmental Engineeringand Mechanical Engineering, Center for Engineering and Healthand Skin Disease Research Center, Northwestern University, Evanston, IL, 60208, USA.|School of Aerospace Engineering and Applied Mechanics, Tongji University, Shanghai, 200092, China.
authors.forename: Hongying
authors.initials: H
authors.lastname: Luo
authors.affiliation: Departments of Civil and Environmental Engineeringand Mechanical Engineering, Center for Engineering and Healthand Skin Disease Research Center, Northwestern University, Evanston, IL, 60208, USA.
authors.forename: Yeguang
authors.initials: Y
authors.lastname: Xue
authors.affiliation: Department of Materials Science and Engineering, 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: Department of Materials Science and Engineering, 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, 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 Engineeringand Mechanical Engineering, Center for Engineering and Healthand Skin Disease Research Center, Northwestern University, Evanston, IL, 60208, USA.|Institute of Solid Mechanics, Beihang University, Beijing, 100191, China.
authors.forename: Yuhang
authors.initials: Y
authors.lastname: Li
authors.affiliation: Departments of Civil and Environmental Engineeringand Mechanical Engineering, Center for Engineering and Healthand Skin Disease Research Center, Northwestern University, Evanston, IL, 60208, USA.
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Department of Materials Science and Engineering Chemistry, Mechanical Science and Engineering, Electrical and Computer Engineering, Beckman Institute for Advanced Science and Technology 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
mesh_terms: D000465:Algorithms; D001831:Body Temperature; D004817:Epidermis / Q000502:physiology*; D004867:Equipment Design; D006358:Hot Temperature; D006801:Humans; D008962:Models, Theoretical; D015203:Reproducibility of Results; D013814:Thermal Conductivity; D062125:Thermometry / Q000295:instrumentation* / Q000379:methods*
keywords: core body temperature; flexible electronics; heat flux; modeling; stretchable electronics