Outdoor Worker Stress Monitoring Electronics with Nanofabric Radiative Cooler-Based Thermal Management.

Severe stress endangers outdoor workers who are in an exceedingly hot workplace. Although recent studies quantify stress levels on the human skin, they still rely on rigid, bulky sensor modules, causing data loss from motion artifacts and limited field-deployability for continuous health monitoring. Moreover, no prior work shows a wearable device that can endure heat exposure while showing continuous monitoring of a subject's stress under realistic working environments. Herein, a soft, field-deployable, wearable bioelectronic system is introduced for detecting outdoor workers' stress levels with negligible motion artifacts and controllable thermal management. A nanofabric radiative cooler (NFRC) and miniaturized sensors with a nanomembrane soft electronic platform are integrated to measure stable electrodermal activities and temperature in hot outdoor conditions. The NFRC exhibits outstanding cooling performance in sub-ambient air with high solar reflectivity and high thermal emissivity. The integrated wearable device with all embedded electronic components and the NFRC shows a lower temperature (41.1%) in sub-ambient air than the NFRC-less device while capturing improved operation time (18.2%). In vivo human study of the bioelectronics with agricultural activities demonstrates the device's capability for portable, continuous, real-time health monitoring of outdoor workers with field deployability.

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

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 â„ƒ) 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.

NFC-Based Wearable Optoelectronics Working with Smartphone Application for Untact Healthcare.

With growing interest in healthcare, wearable healthcare devices have been developed and researched. In particular, near-field communication (NFC) based wearable devices have been actively studied for device miniaturization. Herein, this article proposes a low-cost and convenient healthcare system, which can monitor heart rate and temperature using a wireless/battery-free sensor and the customized smartphone application. The authors designed and fabricated a customized healthcare device based on the NFC system, and developed a smartphone application for real-time data acquisition and processing. In order to achieve compact size without performance degradation, a dual-layered layout is applied to the device. The authors demonstrate that the device can operate as attached on various body sites such as wrist, fingertip, temple, and neck due to outstanding flexibility of device and adhesive strength between the device and the skin. In addition, the data processing flow and processing result are presented for offering heart rate and skin temperature. Therefore, this work provides an affordable and practical pathway for the popularization of wireless wearable healthcare system. Moreover, the proposed platform can easily delivery the measured health information to experts for contactless/personal health consultation.