Soft, ultrathin photonic material
Researchers from City University of Hong Kong develop a groundbreaking, ultrathin material that significantly enhances heat dissipation in wearable electronics, reducing temperatures by over 56°C, preventing skin burns, and improving device performance.
Skin-like electronics are a burgeoning field in wearable devices, with applications in healthcare monitoring, virtual and augmented reality (VR/AR), and more. However, effective thermal management is crucial for maintaining sensing stability and user comfort. Existing technologies primarily rely on non-radiative means to dissipate heat, which can be bulky, rigid, and hinder the flexibility of wireless wearable devices.
The CityU team developed a multifunctional composite polymer coating that provides both radiative and non-radiative cooling without using electricity. It also improves wearability and stretchability. The less than one-millimeter-thick, lightweight cooling interface is composed of hollow silicon dioxide (SiO2) microspheres, titanium dioxide (TiO2) nanoparticles, and fluorescent pigments.
When heat is generated in an electronic device, it flows to the cooling interface layer and dissipates to the ambient environment through thermal radiation and air convection. The interface also exhibits excellent resistance to environmental heat sources, which could otherwise affect the cooling effect and device performance.
The team tested the cooling capacity of their invention by coating a metallic resistance wire, a common component causing temperature rise in electronics. With a 75 μm-thick coating, the temperature of the wire dropped from 140.5°C to 101.3°C. With a 600 μm-thick coating, the temperature dropped to 84.2°C, achieving a temperature drop of more than 56°C.
Dr Yu Xinge of the Department of Biomedical Engineering, emphasised the importance of keeping device temperatures below 44°C to avoid skin burns. He noted that their cooling interface could reduce the resistance wire's temperature from 64.1°C to 42.1°C with a 150 μm-thick coating.
The cooling interface positively impacted the performance of several skin electronic devices developed by the team, including wireless power transfer efficiency to light emitting diodes (LEDs) and the signal stability of a skin-interfaced wireless sensor under environmental obstructions.
Dr Lei Dangyuan of the Department of Materials Science and Engineering, highlighted the intrinsically flexible nature of the cooling interface, which allows for stable cooling even under extreme deformation.
The team's cooling-interface-integrated stretchable wireless-based epidermal lighting system demonstrated higher illumination intensity and stable performance, even upon stretching from 5% to 50% 1,000 times.
The researchers have submitted a US patent application for their invention and won a Gold Medal at the 48th International Exhibition of Inventions Geneva. The findings were published in the journal Science Advances under the title "Ultrathin, soft, radiative cooling interfaces for advanced thermal management in skin electronics". To see a copy of the publication click here.