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.
The first EAST (Experimental Advanced Superconducting Tokamak) plasma ignited in 2006 with non-actively cooled steel plates as the plasma-facing materials and components (PFMCs) which were then upgraded into full graphite tiles bolted onto water-cooled copper heat sinks in 2008. The first wall was changed further into molybdenum alloy in 2012, while keeping the graphite for both the upper and lower divertors. With the rapid increase in heating and current driving power in EAST, the W/Cu divertor project was launched around the end of 2012, aiming at achieving actively cooled full W/Cu-PFCs for the upper divertor, with heat removal capability up to 10 MW m−2. The W/Cu upper divertor was finished in the spring of 2014, consisting of 80 cassette bodies toroidally assembled. Commissioning of the EAST upper W/Cu divertor in 2014 was unsatisfactory and then several practical measures were implemented to improve the design, welding quality and reliability, which helped us achieve successful commissioning in the 2015 Spring Campaign. In collaboration with the IO and CEA teams, we have demonstrated our technological capability to remove heat loads of 5000 cycles at 10 MW m−2 and 1000 cycles at 20 MW m−2 for the small scale monoblock mockups, and surprisingly over 300 cycles at 20 MW m−2 for the flat-tile ones. The experience and lessons we learned from batch production and commissioning are undoubtedly valuable for ITER (International Thermonuclear Experimental Reactor) engineering validation and tungsten-related plasma physics.
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