Thermal transport characteristics of human skin measured in vivo using ultrathin conformal arrays of thermal sensors and actuators

PLoS One. 2015 Feb 6;10(2):e0118131. doi: 10.1371/journal.pone.0118131. eCollection 2015.

Abstract

Measurements of the thermal transport properties of the skin can reveal changes in physical and chemical states of relevance to dermatological health, skin structure and activity, thermoregulation and other aspects of human physiology. Existing methods for in vivo evaluations demand complex systems for laser heating and infrared thermography, or they require rigid, invasive probes; neither can apply to arbitrary regions of the body, offers modes for rapid spatial mapping, or enables continuous monitoring outside of laboratory settings. Here we describe human clinical studies using mechanically soft arrays of thermal actuators and sensors that laminate onto the skin to provide rapid, quantitative in vivo determination of both the thermal conductivity and thermal diffusivity, in a completely non-invasive manner. Comprehensive analysis of measurements on six different body locations of each of twenty-five human subjects reveal systematic variations and directional anisotropies in the characteristics, with correlations to the thicknesses of the epidermis (EP) and stratum corneum (SC) determined by optical coherence tomography, and to the water content assessed by electrical impedance based measurements. Multivariate statistical analysis establishes four distinct locations across the body that exhibit different physical properties: heel, cheek, palm, and wrist/volar forearm/dorsal forearm. The data also demonstrate that thermal transport correlates negatively with SC and EP thickness and positively with water content, with a strength of correlation that varies from region to region, e.g., stronger in the palmar than in the follicular regions.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Algorithms
  • Humans
  • Models, Theoretical
  • Regional Blood Flow
  • Skin Physiological Phenomena*
  • Temperature
  • Thermal Conductivity*
  • Thermosensing*

Grant support

RCW acknowledges support from the National Science Foundation under grant no. DGE-1144245 (http://www.nsf.gov/). JN acknowledges support from Tekes grant no: 40150/12 (http://www.tekes.fi/). The above funding sources had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. Materials, instrumentation and human study costs were supported by L’Oréal Research & Innovation. RMP PB MM and GB are employed by L’Oréal and contributed to study design, data analysis and writing of the paper.