Functional Soft Composites As Thermal Protecting Substrates for Wearable Electronics

Abstract

Thermal management of wearable electronics integrated with biological tissues remains one of the critical challenges for their practical applications. The undesired heating can cause thermal discomfort or even thermal damage to biological tissues. Here, a novel thermal protecting substrate design is proposed for wearable electronics with abilities to manipulate the heat flow and efficiently absorb the excessive heat energy without the compromise of substrate flexibility. The thermal protecting substrate features a functional soft composite, which incorporates the embedded phase change material with a thin metal film on the top in a soft polymer. Compared with conventional substrate, the proposed thermal protecting substrate can reduce the peak temperature increase by over 85% with appropriate parameters. Experimental and numerical studies reveal the fundamental aspects of the design and operation of functional soft composite to effectively avoid excessive heating of biological tissues. Influences of geometrical parameters on temperature reduction are investigated. Device demonstration of thermal protecting substrate in a wearable heater on pig skin illustrates the unusual capability to reduce the maximum skin temperature, thereby enabling practical applications of wearable electronics and creating engineering opportunities in biointegrated applications requiring thermal protection of biological tissues.

Conformal Devices for Thermal Sensing and Heating in Biomedical and Human–Machine Interaction Applications

“…The boundary conditions were set to be constant heat flux at the interface between the heater and liver, whereas other boundary conditions were set to be undergone natural convection with coefficient h = 0.5 W m −2 K −1 . In practical situation, perfusion of blood will induce temperature drop in the tissue during thermal ablation . The effect of perfuison is similar to the water flow experiment discussed in Figure S4, Supporting Information.…”

“…In the current work, we present Archimedean spiral gold wire which can be used as a conformal heater as well as temperature sensor on different organs and epidermis. Several mechanics designs have been reported such as serpentine and circular and demonstrate promising results . Nevertheless, Archimedean spiral exhibits higher stretchability (200%) compared with serpentine design (98–112%) under the same areal coverage and contour length .…”

Recent Advances on Thermal Management of Flexible Inorganic Electronics

“…In practical applications of FIEDs integrated with biological tissues, it is important to prevent the undesired heating induced by FIEDs to dissipate to biological tissues through the substrate of FIEDs. Several active thermal designs [82][83][84][85][86] have been reported to help thermal management of the FIED/skin system. This section will briefly review the recently developed orthotropic substrate design [83] and the functional soft composite design [85].…”

Graphene Modified Montmorillonite Based Phase Change Material for Thermal Energy Storage with Enhanced Interfacial Thermal Transfer

“…Among a variety of PCM, organic phase change materials, such as fatty acid, paraffin wax, alkane and polyethylene glycol demonstrate great advantages due to nontoxicity [5], reusability [6], high thermal storage capacity [7], small temperature and volume change during energy storage and release processes [8]. However, the efficient energy storage and release applications of organic phase change materials are restricted by their poor mechanical stability and low thermal conductivity, which could lead to potential leakage risk and low energy storage rate during phase change process.…”