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Batteryless wearables use energy harvested from the environment, eliminating the burden of charging or replacing batteries. This makes them convenient and environmentally friendly. However, these benefits come at a price. Batteryless wearables operate intermittently (based on energy availability), which adds complexity to their design and introduces usability limitations not present in their battery-powered counterparts. In this paper, we conduct a scenario-based study with 400 wearable users to explore how users perceive the inherent trade-offs of batteryless wearable devices. Our results reveal users’ concerns, expectations, and preferences when transitioning from battery-powered to batteryless wearable use. We discuss how the findings of this study can inform the design of usable batteryless wearables. 

Communication presents a critical challenge for emerging intermittently powered batteryless sensors. Batteryless devices that operate entirely on harvested energy often experience frequent, unpredictable power outages and have trouble keeping time accurately. Consequently, effective communication using today’s low-power wireless network standards and protocols becomes difficult, particularly because existing standards are usually designed to support reliably powered devices with predictable node availability and accurate timekeeping capabilities for connection and congestion management. In this article, we present Greentooth, a robust and energy-efficient wireless communication protocol for intermittently powered sensor networks. It enables reliable communication between a receiver and multiple batteryless sensors using Time Division Multiple Access–style scheduling and low-power wake-up radios for synchronization. Greentooth employs lightweight and energy-efficient connections that are resilient to transient power outages, while significantly improving network reliability, throughput, and energy efficiency of both the battery-free sensor nodes and the receiver—which could be untethered and energy constrained. We evaluate Greentooth using a custom-built batteryless sensor prototype on synthetic and real-world energy traces recorded from different locations in a garden across different times of the day. Results show that Greentooth achieves 73% and 283% more throughput compared to Asynchronous Wake-up on Demand MAC and Receiver-Initiated Consecutive Packet Transmission Wake-up Radios, respectively, under intermittent ambient solar energy and over 2× longer receiver lifetime. 

Batteryless, energy-harvesting systems could reshape the Internet of Things into a more sustainable societal infrastructure. 

Poor eating habits in children and teenagers can lead to obesity, eating disorders, or life-threatening health problems. Although researchers have studied children’s eating behavior for decades, the research community has had limited technology to support the observation and measurement of fine-grained details of a child’s eating behavior. In this paper, we present the feasibility of adapting the Auracle, an existing research-grade earpiece designed to automatically and unobtrusively recognize eating behavior in adults, for measuring children’s eating behavior. We identified and addressed several challenges pertaining to monitoring eating behavior in children, paying particular attention to device fit and comfort. We also improved the accuracy and robustness of the eating-activity detection algorithms. We used this improved prototype in a lab study with a sample of 10 children for 60 total sessions and collected 22.3 hours of data in both meal and snack scenarios. Overall, we achieved an accuracy exceeding 85.0% and an F1 score exceeding 84.2% for eating detection with a 3-second resolution, and a 95.5% accuracy and a 95.7% F1 score for eating detection with a 1-minute resolution. 

Abstract Horizontal convective rolls (HCRs) and cellular convection (cells) are frequently observed within the planetary boundary layer. Yet understanding of the evolution, seasonal variation, and characteristics of such boundary layer phenomena is limited as previous studies used observations from field experiments or satellites. As a result, little is known about the mean climatology and monthly variation of HCRs and cells. Polarimetric WSR-88D radar observations are used to develop a 10-yr April–September climatology in central Oklahoma including HCR and cell occurrence, duration, and aspect ratios as well as HCR orientation angles and wavelengths. Results indicate that HCRs or cells occur on over 92% of days without precipitation during the warm season. HCRs or cells typically form in midmorning and may persist throughout the day or transition between modes before dissipating around sunset. HCRs generally persist for 1–6 h with typical wavelengths of 2–10 km and most aspect ratios between 1 and 7. Rolls are often oriented within 10° of the mean boundary layer wind but can be as much as 30° off this direction. Mean HCR aspect ratios in this study remain constant during the afternoon, but decrease early in the day and increase late in the day, diverging from previous overland HCR studies. Cells generally persist for 2–6 h with aspect ratios of 1–6. These results should facilitate future studies on convection initiation, formation mechanisms of boundary layer organization, and model parameterization.