glasses, watches, wristbands, or belts, are either fully or partially composed of planar and rigid materials, which require the use of obtrusive, hard supports or additional bendable strips to be mounted on the human body. Therefore, clinical devices that use the existing wearables cause discomfort and limit monitoring of human physiological data in the laboratory. This is the big limitation factor to overcome despite the ever-growing market for wearables in broader screenings outside of the clinic. By this account, it is necessary to replace the bulky and rigid plastics and metal components in the sensors and electronics with skin-like materials for enhanced wearability and functionality.The concept of WFHE poses a possible solution to address the aforementioned difficulties by providing user comfort, compliant mechanics, soft integration, multifunctionality, and smart diagnostics with embedded machine learning algorithms. Specifically, such electronics would provide stable and intimate contact to the soft human skin without adding any mechanical and thermal loadings or causing skin breakdown. Current development strategies and approaches for advanced WFHE focus on soft, flexible form factors, nonirritating and nontoxic characteristics, fully autonomous energy components, seamless wireless communications, Recent advances in soft materials and system integration technologies have provided a unique opportunity to design various types of wearable flexible hybrid electronics (WFHE) for advanced human healthcare and humanmachine interfaces. The hybrid integration of soft and biocompatible materials with miniaturized wireless wearable systems is undoubtedly an attractiveprospect in the sense that the successful device performance requires high degrees of mechanical flexibility, sensing capability, and user-friendly simplicity. Here, the most up-to-date materials, sensors, and system-packaging technologies to develop advanced WFHE are provided. Details of mechanical, electrical, physicochemical, and biocompatible properties are discussed with integrated sensor applications in healthcare, energy, and environment. In addition, limitations of the current materials are discussed, as well as key challenges and the future direction of WFHE. Collectively, an all-inclusive review of the newly developed WFHE along with a summary of imperative requirements of material properties, sensor capabilities, electronics performance, and skin integrations is provided. Wearable Flexible Hybrid ElectronicsThe ORCID identification number(s) for the author(s) of this article can be found under https://doi.

Researchers report advances in materials and designs for skin-integrated devices capable of measuring acoustic signatures.

Combination of optogenetics and pharmacology represents a unique approach to dissect neural circuitry with high specificity and versatility. However, conventional tools available to perform these experiments, such as optical fibers and metal cannula, are limited due to their tethered operation and lack of biomechanical compatibility. To address these issues, a miniaturized, battery-free, soft optofluidic system that can provide wireless drug delivery and optical stimulation for spatiotemporal control of the targeted neural circuit in freely behaving animals is reported. The device integrates microscale inorganic light-emitting diodes and microfluidic drug delivery systems with a tiny stretchable multichannel radiofrequency antenna, which not only eliminates the need for bulky batteries but also offers fully wireless, independent control of light and fluid delivery. This design enables a miniature (125 mm ), lightweight (220 mg), soft, and flexible platform, thus facilitating seamless implantation and operation in the body without causing disturbance of naturalistic behavior. The proof-of-principle experiments and analytical studies validate the feasibility and reliability of the fully implantable optofluidic systems for use in freely moving animals, demonstrating its potential for wireless in vivo pharmacology and optogenetics.

Traditionally, electronics have been designed with static form factors to serve designated purposes. This approach has been an optimal direction for maintaining the overall device performance and reliability for targeted applications. However, electronics capable of changing their shape, flexibility, and stretchability will enable versatile and accommodating systems for more diverse applications. Here, we report design concepts, materials, physics, and manufacturing strategies that enable these reconfigurable electronic systems based on temperature-triggered tuning of mechanical characteristics of device platforms. We applied this technology to create personal electronics with variable stiffness and stretchability, a pressure sensor with tunable bandwidth and sensitivity, and a neural probe that softens upon integration with brain tissue. Together, these types of transformative electronics will substantially broaden the use of electronics for wearable and implantable applications.