As a natural material, leather has been widely used in daily life due to its high biocompatibility, wearing comfort, and excellent mechanical strength. However, with the increasing demand for a better life among people, the single function of leather has difficulty in meeting the requirements, which limits its application prospects. It is particularly important to develop multifunctional leather composites with diverse characteristics. Therefore, leather can be modified and functionally designed through physical and chemical methods towards intelligent wearable devices. From this perspective, we review the research progress of intelligent leather-based wearable composites, mainly focusing on the preparation methods and application directions in recent years. Finally, we emphasize the challenges that leather composites will face in practical applications and propose future research directions.
Recent advancements in materials and mechanics have paved the way for transforming rigid circuits into flexible electronics. Their ability to laminate onto the skin has led to the development of skin-interfaced electronics, including mechano-acoustic sensors and haptic systems. However, the challenges of the coupled mechanics between the skin and skin-interfaced electronics call for further understanding of biomechanics, bioelectronics, and their interactions. This perspective article highlights the emerging trend of employing computer vision methods to optimize the next generation of skin-interfaced electronics by characterizing associated biomechanics and vice versa. The cyclic research process involves the development of soft electronics, the identification of coupled mechanics, and their quantification using computer vision methods. The article describes state-of-the-art computer vision techniques in the context of skin-interfaced electronics and their potential applications in other forms of soft electronics.
In recent years, the development of worm-like robots has increased significantly. These robots use peristaltic motion comprised of radial expansion and axial elongation to move leglessly through their environments. Soft worm-like robots have the advantage of conforming to their environment, making them ideal for confined spaces such as pipelines which are essential to societal infrastructure. Pipeline contamination and corrosion can be detrimental and costly and thus regular checking is vital. Some pipes are difficult to access due to size, access restrictions and harmful waste contamination (such as in nuclear power plants). This has led to an increase of research into soft worm-like robots for pipe inspection. This review will analyse the recent progress in this area to assess current robotic capabilities and where work may be further needed to ensure they are applicable to real-world applications.
Soft robotics has emerged as a transformative field, leveraging bio-inspired novel actuation mechanisms to enable more adaptable, compliant, and sophisticated robotic systems. However, the portability of soft pneumatic actuators is typically constrained by the tethering to bulky power sources. This review offers a thorough analysis of autonomous power alternatives facilitated by chemical reactions for gas generation and absorption, a concept analogous to biological energy conversion processes. These bio-inspired strategies propel soft pneumatic actuators towards new horizons of autonomy and portability, essential for real-world applications. This comprehensive review explores the critical intersection of gas evolution reactions (GERs) and gas consumption reactions (GCRs) as a power source for pneumatic actuation in soft robotics. We here emphasize the importance and impact of bio-inspired design, control, efficiency, safety, and sustainability within soft robotics to not only mimic biological motions but to enhance them. This review explores the fundamentals of both pneumatic and chemically powered actuation, highlighting the need for careful consideration of reaction kinetics. Additionally, this work highlights key aspects of smart materials that draw from biological structures and response mechanisms, along with state-of-the-art techniques for precise pressure modulation. Finally, we chart prospective development pathways and provide a future outlook for bio-inspired soft robotics, emphasizing the transformative impact of integrating chemical actuation methods. This exploration underlines the quest for further autonomy in soft robotic systems and points towards the future opportunities in this exciting and fast-developing field.
This comprehensive review underscores the pivotal role wearable electrochemical sensors play in the proactive management and prevention of diabetes mellitus (DM) and its associated complications. Acknowledging the substantial impact of DM on individuals and the urgency for effective monitoring strategies, wearable sensors have emerged as a pragmatic solution. These sensors can detect analytical signals from biofluids, including sweat, tears, saliva, and interstitial fluid (ISF), employing minimally invasive techniques facilitated by technological advancements. The seamless integration of these sensors with computational platforms such as smartphones enhances their practicality for routine use. The review systematically explores diverse methodologies, encompassing both enzymatic and non-enzymatic principles, employed for the surveillance of analytes within biofluids. These foundational principles are meticulously applied to wearable devices, affording point-of-care solutions catering to the detection of individual analytes or simultaneous multiplexed analyte detection. The integration of wireless systems and the incorporation of machine learning algorithms introduce a layer of sophistication, elevating the capability of these sensors for the nuanced monitoring of DM and its complications. Through an in-depth analysis of these advancements, this review describes the significant potential of wearable electrochemical sensors as an essential tool for real-time monitoring and managing DM. The diverse approaches presented underscore the adaptability, versatility, and inherent efficacy of these sensors in addressing the multifaceted challenges intrinsic to DM and its associated complications within academic discourse.
The skin, a vital medium for human-environment communication, stands as an indispensable and pivotal element in the realms of both production and daily life. As the landscape of science and technology undergoes gradual evolution and the demand for seamless human-machine interfaces continues to surge, an escalating need emerges for a counterpart to our biological skin - electronic skins (e-skins). Achieving high-performance sensing capabilities comparable to our skin has consistently posed a formidable challenge. In this article, we systematically outline fundamental strategies enabling e-skins with capabilities including strain sensing, pressure sensing, shear sensing, temperature sensing, humidity sensing, and self-healing. Subsequently, complex e-skin systems and current major applications were briefly introduced. We conclude by envisioning the future trajectory, anticipating continued advancements and transformative innovations shaping the dynamic landscape of e-skin technology. This article provides a profound insight into the current state of e-skins, potentially inspiring scholars to explore new possibilities.
Sweat contains diverse types of biomarkers that can mirror an individual’s health condition. The forefront research of sweat monitoring primarily focuses on sensing basic parameters, i.e., sweat rate and single electrolyte imbalances in controlled laboratory settings. However, recent works show the potential of sweat for the rich biomarkers in aspects of comprehensive health status display, timely safety alarming, and energy harvesting. The advances in wearable flexible electronics enable continuous, real-time, noninvasive detection of multiple sweat components, providing molecular-level insights into human physiology and psychology information; additionally, the efficient sweat extraction technologies of flexible electronics promote its application in energy harvesting, contributing to advancing a flexible sweat platform. This review comprehensively explores flexible sweat-based electronics, encompassing four key aspects: sweat sampling methods, sweat-based sensors, sweat-based energy harvesters, and sweat data display methods. Firstly, the traditional sweat-based platform is discussed in sweat sampling, sensing, and data analysis. Then, the development of wearable sweat sampling methods is discussed with a comparison of the traditional sweat collection methods. After that, the recent advances in sweat-based biosensors for monitoring diverse sweat analytes, such as the perspiration volume, glucose, lactate, and uric acid levels, are summarized. Subsequently, this review also highlights the recent progress and potential value of sweat-based energy harvesters in sweat-activated batteries and bio-fuel cells. Furthermore, multiple data display methods are proposed to achieve accurate feedback on health status, such as colorimetric techniques, light-emitting diodes, actuators, etc. Finally, this review concludes the main current challenges faced in practical applications of sweat-based bioelectronic systems and proposes a vision for the future evolution of this promising field.
Recently, flexible/stretchable micro-scale light-emitting diodes (LEDs), with dimensions significantly smaller than conventional diodes used for illuminations, have emerged for promising applications in areas such as deformable displays, wearable devices for healthcare, etc. For such applications, these devices must have some unusual features that common inorganic LEDs do not intrinsically own, including conformability, biocompatibility, mechanical flexibility, etc. This Perspective focuses on summarizing the most recent progress in developing such flexible emitters based on inorganic semiconductors, followed by reviewing their potential applications. Finally, major challenges and future research directions of deformable micro-scale LEDs are presented.
The rapid development of point-of-care testing has made prompt diagnosis, monitoring and treatment possible for many patients suffering from chronic respiratory diseases. Currently, the biggest challenge is further optimizing testing devices to facilitate more functionalities with higher efficiency and performance, along with specificity toward patient needs. By understanding that patients with chronic respiratory diseases may have difficulty breathing within a normal range, a respiration sensor is developed focusing on sensitivities in the lower air pressure range. In contrast to the simpler airflow data, the sensor can provide respiratory air pressure as an output using a magnetic-based pressure sensor. This unconventional but highly reliable approach, combined with the rest of the simple 3D-printed design of the sensor, offers a wide range of tunability and functionalities. Due to the detachable components of the respiration sensor, the device can be easily transformed into other respiratory uses such as an inspiratory muscle training device or modified to cater for higher-ranged deep breathing. Therefore, not only does it reach very low air pressure measurement (0.1 cmH2O) for normal, tidal breathing, but the sensor can also be manipulated to detect high levels of air pressure (up to 35 cmH2O for exhalation and 45 cmH2O for inhalation). With its excellent sensitivities (0.0456 mV/cmH2O for inhalation, -0.0940 mV/cmH2O for exhalation), impressive distinction between inhalation and exhalation, and fully reproducible and convenient design, we believe that this respiration sensor will pave the way for developing multimodal and multifunctional respiration sensors within the biomedical field.
Soft electronics have achieved significant development, attracting substantial interest due to their promising potential as a dominant form of future electronics. In this rapidly evolving field, the fully soft Schottky diode plays a critical role as a fundamental building block for electronic circuitry systems. These systems, constructed entirely from soft materials, can tolerate various mechanical deformations when interfaced with human skin, making them ideal for use in health monitoring systems and interactive human-machine interfaces. In this study, we introduce a Schottky diode fabricated entirely from soft materials using a facile solution process, further enabling all-printing fabrication systems. Utilizing the mechanical softness of poly(3,4-ethylenedioxythiophene) polystyrene sulfonate-based soft electrode, poly(3-hexylthiophene) nanofibril composite soft semiconductor, and liquid metal, we successfully fabricated a fully soft Schottky diode. This diode exhibits exceptional electrical characteristics even under various mechanical deformations, showcasing the high durability of the device. We have further developed fully soft rectifiers and logic gates, highlighting the versatility of our study. By incorporating these devices with a piezoelectric nanogenerator in a skin-interfaced energy harvesting system, they exhibit sufficient capability for rectification, ensuring a stable power supply as part of a power supply management system. This approach offers substantial potential for future skin-interfaced electronics, paving the way for advanced wearable technology.