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As the military adopts wearable devices, soldiers use them to check their own health and perform operations. Under these conditions, measurement errors in military smartwatches can significantly affect soldier safety and survival. Photoplethysmogram (PPG) measurement errors may arise from various factors including the physical condition of the user, contact point, and environmental conditions. In particular, soldiers may experience rapid changes in their heart rates owing to intense training and operational activities. In such situations, errors in PPG measurements may pose challenges in accurately assessing the health status of soldiers. Therefore, enhancing PPG measurement functionality using wearable devices is important to accurately assess the health status, improve survivability, and enhance the operational performance of soldiers on the battlefield. Consequently, research and development in this area are necessary. Thus, our study examined the factors contributing to potential PPG measurement errors in smartwatches, assessed the extent of these errors, and discussed approaches to improve and mitigate them.

Abstract The growing demand for soft intelligent systems, which have the potential to be used in a variety of fields such as wearable technology and human‐robot interaction systems, has spurred the development of advanced soft transducers. Among soft systems, sensor–actuator hybrid systems are considered the most promising due to their effective and efficient performance, resulting from the synergistic and complementary interaction between their sensor and actuator components. Recent research on integrated sensor and actuator systems has resulted in a range of conceptual and practical soft systems. This review article provides a comprehensive analysis of recent advances in sensor and actuator integrated systems, which are grouped into three categories based on their primary functions: i) actuator–assisted sensors for intelligent detection, ii) sensor‐assisted actuators for intelligent movement, and iii) sensor‐actuator interactive devices for a hybrid of intelligent detection and movement. In addition, several bottlenecks in current studies are discussed, and prospective outlooks, including potential applications, are presented. This categorization and analysis will pave the way for the advancement and commercialization of sensor and actuator‐integrated systems.

Abstract Individuals who are unable to walk independently spend most of the day in a wheelchair. This population is at high risk for developing pressure injuries caused by sitting. However, early diagnosis and prevention of these injuries still remain challenging. Herein, we introduce battery-free, wireless, multimodal sensors and a movable system for continuous measurement of pressure, temperature, and hydration at skin interfaces. The device design includes a crack-activated pressure sensor with nanoscale encapsulations for enhanced sensitivity, a temperature sensor for measuring skin temperature, and a galvanic skin response sensor for measuring skin hydration levels. The movable system enables power harvesting, and data communication to multiple wireless devices mounted at skin-cushion interfaces of wheelchair users over full body coverage. Experimental evaluations and numerical simulations of the devices, together with clinical trials for wheelchair patients, demonstrate the feasibility and stability of the sensor system for preventing pressure injuries caused by sitting.

A basketball was dropped into puddles with depths of water ranging from zero to 4 mm from a height of 1.1 m to investigate the relationship between the depth of water in a puddle and the coefficient of restitution with measurements of the drop height and bounce height. It is shown that the coefficient of restitution has a square root relationship with the depth of the puddle. A “puddle constant” is defined and found for this drop height and this ball to be 830 kgm/s2.

The article presents a study which offered a fabrication method of three-dimensional electronics (3DE) based on predistorted pattern generation and thermoforming process (PG3DE). Topics discussed include overview of PG3DE featuring high customizability, 3D conformability, and stretchability, fabrication process of PGT3DE, and thermoforming simulation.