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Myocardial infarction (MI) is one of the leading causes of death and disability. Recently developed cardiac patches provide mechanical support and additional conductive paths to promote electrical signal propagation in the MI area to synchronize cardiac excitation and contraction. Cardiac patches based on conductive polymers offer attractive features; however, the modest levels of elasticity and high impedance interfaces limit their mechanical and electrical performance. These structures also operate as permanent implants, even in cases where their utility is limited to the healing period of tissue damaged by the MI. The work presented here introduces a highly conductive cardiac patch that combines bioresorbable metals and polymers together in a hybrid material structure configured in a thin serpentine geometry that yields elastic mechanical properties. Finite element analysis guides optimized choices of layouts in these systems. Regular and synchronous contraction of human induced pluripotent stem cell‐derived cardiomyocytes on the cardiac patch and ex vivo studies offer insights into the essential properties and the bio‐interface. These results provide additional options in the design of cardiac patches to treat MI and other cardiac disorders. [ABSTRACT FROM AUTHOR]

With the high flexibility, good conformability and lightweight, the next‐generation energy harvesters could exist in the format of epidermal electronics. They are able to convert the mechanical energy from daily body motions into electrical signals for energy harvesting and human‐machine interfaces. Triboelectric nanogenerators (TENGs) have proven to be excellent candidates for wearable energy harvesters, however, the reported TENGs commonly face the hurdles of poor adhesion to skin and relative thick in geometry up to several cm. Herein, a series of ultrathin, soft, tattoo‐like triboelectric nanogenerators (TL‐TENGs) with well‐designed aesthetic patterns are introduced. With the ultrathin materials applied and state of art processing techniques in epidermal electronics, the TL‐TENGs present an outstanding mechanical property of high robustness and thickness of tens of μm. Besides, TL‐TENGs own remarkable electrical characteristics, the open‐circuit voltage and short circuit current can reach up to ≈180 V and ≈2.2 μA under constant tapping (≈16 kPa), respectively. With the well structural mechanics designs, the TL‐TENGs can be customized into various tattoo patterns, such as twelve Chinese zodiac signs. Demonstrations of TL‐TENGs in energy harvesting and the human‐machine interface indicate great potential in next generation wearable nanogenerators and internet of things. [ABSTRACT FROM AUTHOR]

Injured peripheral nerves typically exhibit unsatisfactory and incomplete functional outcomes, and there are no clinically approved therapies for improving regeneration. Post‐operative electrical stimulation (ES) increases axon regrowth, but practical challenges, from the cost of extended operating room time to the risks and pitfalls associated with transcutaneous wire placement, have prevented broad clinical adoption. This study presents a possible solution in the form of advanced bioresorbable materials for a type of thin, flexible, wireless implant that provides precisely controlled ES of the injured nerve for a brief time in the immediate post‐operative period. Afterward, rapid, complete, and safe modes of bioresorption naturally and quickly eliminate all of the constituent materials in their entirety, without the need for surgical extraction. The unusually high rate of bioresorption follows from the use of a unique, bilayer enclosure that combines two distinct formulations of a biocompatible form of polyanhydride as an encapsulating structure, to accelerate the resorption of active components and confine fragments until complete resorption. Results from mouse models of tibial nerve transection with re‐anastomosis indicate that this system offers levels of performance and efficacy that match those of conventional wired stimulators, but without the need to extend the operative period or to extract the device hardware. [ABSTRACT FROM AUTHOR]

In nature, animals or plants often use soft organs to move and hunt. Research works on bioinspired materials and devices have attracted more and more interest as which show the potential for future intelligent robots. As key components of soft robots, biomimetic soft actuators are adapted to greater requirements for convenient, accurate, and programmable controlling robots. Here, a class of materials and processing routes of ultrathin actuators are reported for bioinspired piecewise controllable soft robots, where the actuators associate with thermal‐responsible soft silicone thin film with thickness as thin as 45 µm and electrically driven by well mechanical designed metallic thin film electrodes. Multiple electrodes in the robots in charge of individual segments control allow the soft robots exhibiting similar functionalities of animals or plants (for example, imitating the tongue of a reptile, such as chameleon to hunt moving preys, and mimicking vines to tightly wind around objects). These bionic results in the soft robots demonstrate their advantages in precise and flexible operation, which provides a good reference for the future research of intelligent soft actuators and robots. [ABSTRACT FROM AUTHOR]

Abstract: The work presented here introduces a materials strategy that involves physically transferred, ultrathin layers of silicon dioxide (SiO2) thermally grown on silicon wafers and then coated with hafnium oxide (HfO2) by atomic layer deposition, as barriers that satisfy requirements for even the most challenging flexible electronic devices. Materials and physics aspects of hydrolysis and ionic transport associated with such bilayers define their performance and reliability characteristics. Systematic experimental studies and reactive diffusion modeling suggest that the HfO2 film, even with some density of pinholes, slows dissolution of the underlying SiO2 by orders of magnitude, independent of the concentration of ions in the surrounding biofluids. Accelerated tests that involve immersion in phosphate‐buffered saline solution at a pH of 7.4 and under a constant electrical bias demonstrate that this bilayer barrier can also obstruct the transport of ions that would otherwise cause drifts in the operation of the electronics. Theoretical drift–diffusion modeling defines the coupling of dissolution and ion diffusion, including their effects on device lifetime. Demonstrations of such barriers with passive and active components in thin, flexible electronic test structures highlight the potential advantages for wide applications in chronic biointegrated devices. [ABSTRACT FROM AUTHOR]

Development of unconventional technologies for wireless collection and analysis of quantitative, clinically relevant information on physiological status is of growing interest. Soft, biocompatible systems are widely regarded as important because they facilitate mounting on external (e.g., skin) and internal (e.g., heart and brain) surfaces of the body. Ultraminiaturized, lightweight, and battery-free devices have the potential to establish complementary options in biointegration, where chronic interfaces (i.e., months) are possible on hard surfaces such as the fingernails and the teeth, with negligible risk for irritation or discomfort. Here, the authors report materials and device concepts for flexible platforms that incorporate advanced optoelectronic functionality for applications in wireless capture and transmission of photoplethysmograms, including quantitative information on blood oxygenation, heart rate, and heart rate variability. Specifically, reflectance pulse oximetry in conjunction with near-field communication capabilities enables operation in thin, miniaturized flexible devices. Studies of the material aspects associated with the body interface, together with investigations of the radio frequency characteristics, the optoelectronic data acquisition approaches, and the analysis methods capture all of the relevant engineering considerations. Demonstrations of operation on various locations of the body and quantitative comparisons to clinical gold standards establish the versatility and the measurement accuracy of these systems, respectively. [ABSTRACT FROM AUTHOR]

A class of thin, lightweight, flexible, near-field communication (NFC) devices with ultraminiaturized format is introduced, and systematic investigations of the mechanics, radio frequency characteristics, and materials aspects associated with their optimized construction are presented. These systems allow advantages in mechanical strength, placement versatility, and minimized interfacial stresses compared to other NFC technologies and wearable electronics. Detailed experimental studies and theoretical modeling of the mechanical and electromagnetic properties of these systems establish understanding of the key design considerations. These concepts can apply to many other types of wireless communication systems including biosensors and electronic implants. [ABSTRACT FROM AUTHOR]

Recent advances in thin, soft skin‐integrated electronics have brought many opportunities in the wearable technics. A simple platform with the functionality of self‐powering for epidermal electronics is reported. These electronics can generate electricity from external mechanical stresses that associates with triboelectric effect, and therefore afford excellent performance in tactile sensing and energy harvesting. Combined advances in materials and mechanics of the skin‐integrated electronics with high efficiency energy harvesting techniques, triboelectric nanogenerators (TENGs) in an epidermal format is realized for the first time. The dots‐distributed electrode pattern allows these electronics exhibiting excellent flexibility and stretchability, distinguishing a broad range of pressures that are relevant to normal body motions. The electricity output of the epidermal device from simple finger tapping modes can achieve >60 V of voltage and >1 µA of current, which is sufficient to light up 15 small light‐emitting diodes. Furthermore, the authors also report a 4 × 4 sensor array based on these TENGs, and demonstrate a skin‐like electronics for real‐time motion monitoring and tactile mapping. [ABSTRACT FROM AUTHOR]

Thin, soft, skin‐like electronics capable of transforming body mechanical motions to electrical signals have broad potential applications in biosensing and energy harvesting. Forming piezoelectric materials into flexible and stretchable formats and integrating with soft substrate would be a considerable strategy for this aspect. Here, a skin‐integrated rubbery electronic device that associates with a simple low‐cost fabrication method for a ternary piezoelectric rubber composite of graphene, lead zirconate tinanate (PZT), and polydimethylsiloxane (PDMS) is introduced. Comparing to the binary composite that blend with PZT and PDMS, the graphene‐embedded ternary composite exhibits a significant enhancement of self‐powered behavior, with a maximum power density of 972.43 µW cm−3 under human walking. Combined experimental and theoretical studies of the graphene‐embedded PZT rubber allow the skin‐integrated electronic device to exhibit excellent mechanical tolerance to bending, stretching, and twisting for thousands of cycles. Customized device geometries guided by optimized mechanical design enable a more comprehensive integration of the rubbery electronics with the human body. For instance, annulus‐shape devices can perfectly mount on the joints and ensure great power output and stability under continuous and large deformations. This work demonstrates the potential of large‐area, skin‐integrated, self‐powered electronics for energy harvesting as well as human health related mechanical sensing. [ABSTRACT FROM AUTHOR]

Bioresorbable electronic technologies form the basis for classes of biomedical devices that undergo complete physical and chemical dissolution after a predefined operational period, thereby eliminating the costs and risks associated with secondary surgical extraction. A continuing area of opportunity is in the development of strategies for power supply for these systems, where previous studies demonstrate some utility for biodegradable batteries, radio frequency harvesters, solar cells, and others. This paper introduces a type of bioresorbable system for wireless power transfer, in which a rotating magnet serves as the transmitter and a bioresorbable antenna as the remote receiver, with capabilities for operation at low frequencies (<200 Hz). Systematic experimental and numerical studies demonstrate several unique advantages of this system, most significantly the elimination of impedance matching and electromagnetic radiation exposure presented with the types of radio frequency energy harvesters explored previously. These results add to the portfolio of power supply options in bioresorbable electronic implants. [ABSTRACT FROM AUTHOR]

Recent progress in stretchable forms of inorganic electronic systems has established a route to new classes of devices, with particularly unique capabilities in functional biointerfaces, because of their mechanical and geometrical compatibility with human tissues and organs. A reliable approach to physically and chemically protect the electronic components and interconnects is indispensable for practical applications. Although recent reports describe various options in soft, solid encapsulation, the development of approaches that do not significantly reduce the stretchability remains an area of continued focus. Herein, a generic, soft encapsulation strategy is reported, which is applicable to a wide range of stretchable interconnect designs, including those based on two‐dimensional (2D) serpentine configurations, 2D fractal‐inspired patterns, and 3D helical configurations. This strategy forms the encapsulation while the system is in a prestrained state, in contrast to the traditional approach that involves the strain‐free configuration. A systematic comparison reveals that substantial enhancements (e.g., ≈6.0 times for 2D serpentine, ≈4.0 times for 2D fractal, and ≈2.6 times for 3D helical) in the stretchability can be achieved through use of the proposed strategy. Demonstrated applications in highly stretchable light‐emitting diodes systems that can be mounted onto complex curvilinear surfaces illustrate the general capabilities in functional device systems. A generic soft encapsulation strategy is reported, applicable to a wide range of stretchable interconnected designs, including those based on 2D serpentine configurations, 2D fractal‐inspired patterns, and 3D helical configurations. Systematic studies demonstrate that the proposed method enables substantial enhancements in the stretchability as compared to traditional strategies, according to results of experiments and finite‐element analyses. [ABSTRACT FROM AUTHOR]

In article number 1803149, Yonggang Huang, Yihui Zhang, John A. Rogers, and co‐workers present deterministic assembly processes for transforming conventional, planar devices based on flexible printed circuit board (FPCB) platforms into those with 3D architectures in a manner that is fully compatible with off‐the‐shelf packaged or unpackaged component parts. The strategy to 3D FPCB technologies creates immediate opportunities for designs in multifunctional systems that leverage state‐of‐the‐art components. [ABSTRACT FROM AUTHOR]

This paper describes deterministic assembly processes for transforming conventional, planar devices based on flexible printed circuit board (FPCB) platforms into those with 3D architectures in a manner that is fully compatible with off‐the‐shelf packaged or unpackaged component parts. The strategy involves mechanically guided geometry transformation by out‐of‐plane buckling motions that follow from controlled forces imposed at precise locations across the FPCB substrate by a prestretched elastomer platform. The geometries and positions of cuts, slits, and openings defined into the FPCB provide additional design parameters to control the final 3D layouts. The mechanical tunability of the resulting 3D FPCB platforms, afforded by elastic deformations of the substrate, allows these electronic systems to operate in an adaptable manner, as demonstrated in simple examples of an optoelectronic sensor that offers adjustable detecting angle/area and a near‐field communication antenna that can be tuned to accommodate changes in the electromagnetic properties of its surroundings. These approaches to 3D FPCB technologies create immediate opportunities for designs in multifunctional systems that leverage state‐of‐the‐art components. Buckling‐induced processes for geometry transformation provide routes to 3D flexible printed circuit board (FPCB) technologies as device platforms with electrically and mechanically adaptable properties. These schemes, taken together with accurate simulation tools, provide simple and versatile means to access 3D designs in FPCB platforms, in ways that are fully compatible with off‐the‐shelf device components. [ABSTRACT FROM AUTHOR]

A concept for millimeter‐scale, battery‐free sensors for measuring heart rate and blood oxygenation in presented by J. A. Rogers and co‐workers on page 1604373. Reflectance pulse oximetry data is devoid of motion artifacts when obtained by wireless near‐field communication from various body locations. The concept bears excellent potential for be employed in flexible devices. Image taken by Philipp Gutruf. [ABSTRACT FROM AUTHOR]

U. Paik, J. A. Rogers, and co‐workers present miniaturized flexible electronic systems with wireless power and near‐field communication capabilities on page 4761. The key features are thin, lightweight, flexible construction and minimized interfacial stresses for bio‐integration. These concepts provide new opportunities in biosensors and electronic implants with wireless communication, for use on the fingernails and other regions of the body. [ABSTRACT FROM AUTHOR]