An Analytic Orthotropic Heat Conduction Model for the Stretchable Network Heaters

Abstract

Compared with other physiotherapy devices, epidermal electronic systems (EES) used in medical applications such as hyperthermia have obvious advantages of conformal attachment, lightness and high efficiency. The stretchable flexible electrode is an indispensable component. The structurally designed flexible inorganic stretchable electrode has the advantage of stable electrical properties under tensile deformation and has received enough attention. However, the space between the patterned electrodes introduced to ensure the tensile properties will inevitably lead to the uneven temperature distribution of the thermotherapy electrodes and degrade the effect of thermotherapy. It is of great practical value to study the temperature uniformity of the stretchable patterned electrode. In order to improve the uniformity of temperature distribution in the heat transfer system with stretchable electrodes, a temperature distribution manipulation strategy for orthotropic substrates is proposed in this paper. A theoretical model of the orthotropic heat transfer system based on the horseshoe-shaped mesh electrode is established. Combined with finite element analysis, the effect of the orthotropic substrate on the uniformity of temperature distribution in three types of heat source heat transfer systems is studied based on this model. The influence of the thermal conductivity ratio in different directions on the temperature distribution is studied parametrically, which will help to guide the design and fabrication of the stretchable electrode that can produce a uniform temperature distribution.

Editorial for the Special Issue on Structural Analyses and Designs for Flexible/Stretchable Electronics

“…Twelve articles are by authors from China and one paper each was contributed by authors from Germany, Italy, Poland, and Russia. A comprehensive range of aspects related to the structural analyses, designs, and fabrication of flexible/stretchable devices and smart materials are covered, including mechanical analyses of flexible/stretchable devices [ 1 , 2 , 3 , 4 ], thermal analyses of flexible heaters [ 5 , 6 , 7 , 8 , 9 ], mechanical–conductive analyses of island-type structures in flexible/stretchable devices [ 10 ], thermo-mechanical analyses and designs of morphing aircraft structures [ 11 ], adhesive bonding technology for flexible substrates [ 12 ], electrohydrodynamic jet printing technology for flexible substrates [ 13 ], process parameters’ influence on the resistance of 3D-printed electrically conductive structures [ 14 ], and recent advances in flexible radio frequency microelectromechanical systems (RE MEMS) [ 15 ] and triboelectric nanogenerators (TENGs) [ 16 ].…”

“…Li et al [ 4 ] employed the shooting method to analyze the finite-deformation-theory-based mechanical behaviors of origami-inspired horseshoe-shaped solar arrays, followed by their counterparts with the FEM for comparison. He et al [ 5 , 6 ] conducted a study on analytic models for the orthotropic transient heat conduction of stretchable rectangular and network heat sources to investigate the heat flux manipulation mechanism and the temperature distribution homogenization effect in epidermal electronic systems. Zhao et al [ 7 ] developed a Fourier-cosine-transform-based analytic orthotropic heat conduction model with a complex serpentine heat source, which was validated using the FEM, and investigated the effects of geometric spacing and orthotropic thermal conductivity on the thermal properties.…”