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.

Recent advances in nanomaterials and nano-microfabrication have enabled the development of flexible wearable electronics. However, existing manufacturing methods still rely on a multi-step, error-prone complex process that requires a costly cleanroom facility. Here, we report a new class of additive nanomanufacturing of functional materials that enables a wireless, multilayered, seamlessly interconnected, and flexible hybrid electronic system. All-printed electronics, incorporating machine learning, offers multi-class and versatile human-machine interfaces. One of the key technological advancements is the use of a functionalized conductive graphene with enhanced biocompatibility, anti-oxidation, and solderability, which allows a wireless flexible circuit. The high-aspect ratio graphene offers gel-free, high-fidelity recording of muscle activities. The performance of the printed electronics is demonstrated by using real-time control of external systems via electromyograms. Anatomical study with deep learning-embedded electrophysiology mapping allows for an optimal selection of three channels to capture all finger motions with an accuracy of about 99% for seven classes.

The continuous monitoring of hemodynamics attainable with wireless implantable devices would improve the treatment of vascular diseases. However, demanding requirements of size, wireless operation, and compatibility with endovascular procedures have limited the development of vascular electronics. Here, we report an implantable, wireless vascular electronic system, consisting of a multimaterial inductive stent and printed soft sensors capable of real-time monitoring of arterial pressure, pulse rate, and flow without batteries or circuits. Developments in stent design achieve an enhanced wireless platform while matching conventional stent mechanics. The fully printed pressure sensors demonstrate fast response times, high durability, and sensing at small bending radii. The device is monitored via inductive coupling at communication distances notably larger than prior vascular sensors. The wireless electronic system is validated in artery models, while minimally invasive catheter implantation is demonstrated in an in vivo rabbit study. Overall, the vascular system offers an adaptable framework for comprehensive monitoring of hemodynamics.

Soft strain sensors that are mechanically flexible or stretchable are of significant interest in the fields of structural health monitoring, human physiology, and human–machine interfaces. However, existing deformable strain sensors still suffer from complex fabrication processes, poor reusability, limited adhesion strength, or structural rigidity. In this work, we introduce a versatile, high-throughput fabrication method of nanostructured, soft material-enabled, miniaturized strain sensors for both structural health monitoring and human physiology detection. Aerosol jet printing of polyimide and silver nanowires enables multifunctional strain sensors with tunable resistance and gauge factor. Experimental study of soft material compositions and multilayered structures of the strain sensor demonstrates the capabilities of strong adhesion and conformal lamination on different surfaces without the use of conventional fixtures and/or tapes. A two-axis, printed strain gauge enables the detection of force-induced strain changes on a curved stem valve for structural health management while offering reusability over 10 times without losing the sensing performance. Direct comparison with a commercial film sensor captures the advantages of the printed soft sensor in enhanced gauge factor and sensitivity. Another type of a stretchable strain sensor in skin-wearable applications demonstrates a highly sensitive monitoring of a subject’s motion, pulse, and breathing, validated by comparing it with a clinical-grade system. Overall, the presented comprehensive study of materials, mechanics, printing-based fabrication, and interfacial adhesion shows a great potential of the printed soft strain sensor for applications in continuous structural health monitoring, human health detection, machine-interfacing systems, and environmental condition monitoring.

This study introduces a high‐throughput, large‐scale manufacturing method that uses aerosol jet 3D printing for a fully printed stretchable, wireless electronics. A comprehensive study of nanoink preparation and parameter optimization enables a low‐profile, multilayer printing of a high‐performance, capacitance flow sensor. The core printing process involves direct, microstructured patterning of biocompatible silver nanoparticles and polyimide. The optimized fabrication approach allows for transfer of highly conductive, patterned silver nanoparticle films to a soft elastomeric substrate. Stretchable mechanics modeling and seamless integration with an implantable stent display a highly stretchable and flexible sensor, deployable by a catheter for extremely low‐profile, conformal insertion in a blood vessel. Optimization of a transient, wireless inductive coupling method allows for wireless detection of biomimetic cerebral aneurysm hemodynamics with the maximum readout distance of 6 cm through meat. In vitro demonstrations include wireless monitoring of flow rates (0.05–1 m s−1) in highly contoured and narrow human neurovascular models. Collectively, this work shows the potential of the printed biosystem to offer a high throughput, additive manufacturing of stretchable electronics with advances toward batteryless, real‐time wireless monitoring of cerebral aneurysm hemodynamics.