title: Epidermal photonic devices for quantitative imaging of temperature and thermal transport characteristics of the skin.
abstract: Characterization of temperature and thermal transport properties of the skin can yield important information of relevance to both clinical medicine and basic research in skin physiology. Here we introduce an ultrathin, compliant skin-like, or 'epidermal', photonic device that combines colorimetric temperature indicators with wireless stretchable electronics for thermal measurements when softly laminated on the skin surface. The sensors exploit thermochromic liquid crystals patterned into large-scale, pixelated arrays on thin elastomeric substrates; the electronics provide means for controlled, local heating by radio frequency signals. Algorithms for extracting patterns of colour recorded from these devices with a digital camera and computational tools for relating the results to underlying thermal processes near the skin surface lend quantitative value to the resulting data. Application examples include non-invasive spatial mapping of skin temperature with milli-Kelvin precision (±50 mK) and sub-millimetre spatial resolution. Demonstrations in reactive hyperaemia assessments of blood flow and hydration analysis establish relevance to cardiovascular health and skin care, respectively.
authors.affiliation: Frederick Seitz Materials Research Laboratory, Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Li
authors.initials: L
authors.lastname: Gao
authors.affiliation: 1] Center for Engineering and Health, Skin Disease Research Center, Departments of Civil and Environmental Engineering and Mechanical Engineering, Northwestern University, Evanston, Illinois 60208, USA [2] Center for Mechanics and Materials, Tsinghua University, Beijing 100084, China.
authors.forename: Yihui
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Frederick Seitz Materials Research Laboratory, Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Viktor
authors.initials: V
authors.lastname: Malyarchuk
authors.affiliation: Frederick Seitz Materials Research Laboratory, Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Lin
authors.initials: L
authors.lastname: Jia
authors.affiliation: Frederick Seitz Materials Research Laboratory, Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Kyung-In
authors.initials: KI
authors.lastname: Jang
authors.affiliation: Frederick Seitz Materials Research Laboratory, Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: R Chad
authors.initials: RC
authors.lastname: Webb
authors.affiliation: 1] Center for Engineering and Health, Skin Disease Research Center, Departments of Civil and Environmental Engineering and Mechanical Engineering, Northwestern University, Evanston, Illinois 60208, USA [2] Department of Civil Engineering and Architecture, Zhejiang University, Hangzhou 310058, China.
authors.forename: Haoran
authors.initials: H
authors.lastname: Fu
authors.affiliation: 1] Center for Engineering and Health, Skin Disease Research Center, Departments of Civil and Environmental Engineering and Mechanical Engineering, Northwestern University, Evanston, Illinois 60208, USA [2] 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: 1] Center for Engineering and Health, Skin Disease Research Center, Departments of Civil and Environmental Engineering and Mechanical Engineering, Northwestern University, Evanston, Illinois 60208, USA [2] Key Laboratory of Pressure Systems and Safety (MOE), School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, China.
authors.forename: Guoyan
authors.initials: G
authors.lastname: Zhou
authors.affiliation: Frederick Seitz Materials Research Laboratory, Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Luke
authors.initials: L
authors.lastname: Shi
authors.affiliation: Frederick Seitz Materials Research Laboratory, Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Deesha
authors.initials: D
authors.lastname: Shah
authors.affiliation: Frederick Seitz Materials Research Laboratory, Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Xian
authors.initials: X
authors.lastname: Huang
authors.affiliation: Frederick Seitz Materials Research Laboratory, Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: Baoxing
authors.initials: B
authors.lastname: Xu
authors.affiliation: 1] Department of Mechanical Engineering, University of Houston, Houston, Texas 77204, USA [2] Department of Electrical and Computer Engineering, University of Houston, Houston, Texas 77204, USA.
authors.forename: Cunjiang
authors.initials: C
authors.lastname: Yu
authors.affiliation: Center for Engineering and Health, Skin Disease Research Center, Departments of Civil and Environmental Engineering and Mechanical Engineering, Northwestern University, Evanston, Illinois 60208, USA.
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Huang
authors.affiliation: Frederick Seitz Materials Research Laboratory, Department of Materials Science and Engineering, Beckman Institute, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
authors.forename: John A
authors.initials: JA
authors.lastname: Rogers
mesh_terms: D000465:Algorithms; D002138:Calibration; D003952:Diagnostic Imaging; D004058:Diffusion; D020724:Elastomers; D004817:Epidermis / Q000502:physiology*; D006801:Humans; D036103:Nanotechnology; D017785:Photons; D015203:Reproducibility of Results; D012867:Skin / Q000473:pathology*; D012881:Skin Temperature
chemical_list: D020724:Elastomers