Self‐Cooling Gallium‐Based Transformative Electronics with a Radiative Cooler for Reliable Stiffness Tuning in Outdoor Use

Abstract

Reconfigurability of a device that allows tuning of its shape and stiffness is utilized for personal electronics to provide an optimal mechanical interface for an intended purpose. Recent approaches in developing such transformative electronic systems (TES) involved the use of gallium liquid metal, which can change its liquid-solid phase by temperature to facilitate stiffness control of the device. However, the current design cannot withstand excessive heat during outdoor applications, leading to undesired softening of the device when the rigid mode of operation is favored. Here, a gallium-based TES integrated with a flexible and stretchable radiative cooler is presented, which offers zero-power thermal management for reliable rigid mode operation in the hot outdoors. The radiative cooler can both effectively reflect the heat transfer from the sun and emit thermal energy. It, therefore, allows a TES-in-the-air to maintain its temperature below the melting point of gallium (29.8 °C) under hot weather with strong sun exposure, thus preventing unwanted softening of the device. Comprehensive studies on optical, thermal, and mechanical characteristics of radiative-cooler-integrated TES, along with a proof-of-concept demonstration in the hot outdoors verify the reliability of this design approach, suggesting the possibility of expanding the use of TES in various environments.

Effects of a Graphene Heating Device on Fatigue Recovery of Biceps Brachii

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“…[3,22,28,29] Moreover, the promising attempt of the combination between radiative cooling and wearable devices also endows great application potential of this technology. The recent reports by Xu et al [24] and Song group [25,26] have made great progress.…”

“…[9,10] With the joint efforts, RSC technology has achieved striking advances in building cooling, [4,11] photovoltaic cooling, [12][13][14] cryogenic cooling, [15,16] RSC driving thermoelectricity, [17][18][19] atmospheric water harvesting, [20,21] personal thermal management [3,22,23] and wearable devices. [24][25][26] For building cooling, the pioneering reports by Goldstein et al and Zhao et al have demonstrated that building-integrated RSC modules can provide continuous day-and-night cooling and can potentially save 32%-45% of the electricity consumption for cooling in summer. [4,11] For photovoltaic cooling, selective photonic cooler can lower the temperature of solar panels by over 5.7 K and afford the greater cooling…”

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“…6,7 Effective PRC material designs such as micro/ nanophotonic structures, 8−10 thin films, 11−13 coatings, 14−16 textiles, 17−19 and biomimetic materials 20−22 have been widely investigated and even realize subambient cooling performance. Among them, the micro-and nanopore structures exhibit remarkable optical properties derived from optimizable size and density for a wide range of applications in personal thermal comfort, energy-efficient green buildings, and wearable devices, 23,24 which can be found in the latest review papers. 25,26 In addition, the promising applications of color radiative cooling 27,28 and dynamic radiative cooling 29,30 have also received a lot of attention.…”

“…Passive radiative cooling (PRC) can spontaneously cool terrestrial objects without external energy source under direct sunlight, offering an innovative path toward outdoor thermal management. , It simultaneously exhibits ultrahigh reflectance in the solar wavelengths (0.3–2.5 μm) and radiate excessive heat through an atmospheric transparency window (ATW, 8–13 μm) to outer cold space (4K) in the form of thermal radiation. , Effective PRC material designs such as micro/nanophotonic structures, − thin films, − coatings, − textiles, − and biomimetic materials − have been widely investigated and even realize subambient cooling performance. Among them, the micro- and nanopore structures exhibit remarkable optical properties derived from optimizable size and density for a wide range of applications in personal thermal comfort, energy-efficient green buildings, and wearable devices, , which can be found in the latest review papers. , In addition, the promising applications of color radiative cooling , and dynamic radiative cooling , have also received a lot of attention.…”