Skin-inspired wearable electronic/biomedical systems based on functional nanomaterials with exceptional electrical and mechanical properties have revolutionized wearable applications, such as ...portable Internet of Things, personalized healthcare monitors, human–machine interfaces, and even always-connected precise medicine systems. Despite these advancements, including the ability to predict and to control nanolevel phenomena of functional nanomaterials precisely and strategies for integrating nanomaterials onto desired substrates without performance losses, skin-inspired electronic nanosystems are not yet feasible beyond proof-of-concept devices. In this Perspective, we provide an outlook on skin-like electronics through the review of several recent reports on various materials strategies and integration methodologies of stretchable conducting and semiconducting nanomaterials, which are used as electrodes and active layers in stretchable sensors, transistors, multiplexed arrays, and integrated circuits. To overcome the challenge of realizing robust electronic nanosystems, we discuss using nanomaterials in dynamically cross-linked polymer matrices, focusing on the latest innovations in stretchable self-healing electronics, which could change the paradigm of wearable electronics.
Stretchable conductors are essential building blocks for stretchable electronic devices used in next-generation wearables and soft robotics. Over 10 years of research in stretchable electronics has ...produced stretchable sensors, circuits, displays, and energy harvesters, mostly enabled by unique stretchable conductors. This review covers recent advances in stretchable conductors, which have been achieved by engineering their structures, materials, or both. Advantages, mechanisms, and limitations of the different classes of stretchable conductors are discussed to provide insight into which class of stretchable conductor is suitable for fabrication of various stretchable electronic devices. The significantly improved electronic performance and wide variety of stretchable conductors are creating a new paradigm in stretchable electronics.
Stretchable conductors developed through structural and materials engineering are contributing to the realization of next-generation soft electronic devices for healthcare and soft-robotics.
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Stretchable electronics have increasingly gained interest both in the academic and industrial communities owing to its potential to enable a wide variety of applications, especially ...wearable and implantable devices for biomedical applications. As the key component for electronic devices, the design of a suitable semiconductor is essential, while the solution processability and structural tunability of polymer semiconductor make it a promising candidate. Along this line, it is important to consider the mechanical properties of polymer semiconductors in the design of flexible and stretchable devices placed on soft and curved surfaces to accommodate the constant movement of the human body. However, achieving high mechanical deformability and high charge transport properties simultaneously in polymer semiconductors remains a major challenge. In this trend article, we survey various approaches in designing intrinsically stretchable conjugated polymers, focusing on structure-property relationships from a molecular perspective, such as molecular weight, regioregularity, backbone and side chain modifications. Understanding the influence of these molecular structure parameters on thin film morphology may provide general guidelines for achieving desired microstructures that allow mechanical deformation without interrupting charge transport. Beyond highlighting recent key work in this field, we will discuss future prospects of stretchable conjugated polymers.
Stretchable and ultraflexible electronic devices have a broad range of potential uses, from robust devices for energy storage and conversion to biomedical devices that make conformal interfaces with ...the skin and internal organs. Organics have long been associated with mechanical compliance, which enables inexpensive manufacturing via roll-to-roll printing. This article provides an overview of the use of organic electronic materials, including π-conjugated polymers and small molecules, in highly deformable devices. It begins with a comparison of devices based on organic devices to those based on inorganic composites. The thin-film nature of organic semiconductor devices has also led to the development of several techniques for metrology that can be applied specifically to brittle organic thin films. The article concludes with a brief discussion of the applications of stretchable and ultraflexible organic electronic devices and a prescriptive outlook for successful collaborative work in this exciting, interdisciplinary field.
Electronic second skin is touted as the next interface to expand applications of electronics for natural and seamless interactions with humans to enable smart health care, the Internet of Things, and ...even to amplify human sensory abilities. Thus, electronic materials are now being actively investigated to construct “second skin.” Accordingly, electronic devices are desirable to have skin‐like properties such as stretchability, self‐healing ability, biocompatibility, and biodegradability. This work reviews recent major progress in the development of both electronic materials and devices toward the second skin. It is concluded with comments on future research directions of the field.
Second skin enabled by advanced electronics is emerging as a next interface of electronics to expand applications of electronics from smart health care to even amplification of human's sensing abilities. Recent progress in fields of materials and devices with noble capabilities for the second skin are highlighted and its perspectives are also suggested.
Flexible electronics offer a wide-variety of applications such as flexible circuits, flexible displays, flexible solar cells, skin-like pressure sensors, and conformable RFID tags. Carbon nanotubes ...(CNTs) are a promising material for flexible electronics, both as the channel material in field-effect transistors (FETs) and as transparent electrodes, due to their high intrinsic carrier mobility, conductivity, and mechanical flexibility. In this feature article, we review the recent progress of CNTs in flexible electronics by describing both the processing and the applications of CNT-based flexible devices. To employ CNTs as the channel material in FETs, single-walled carbon nanotubes (SWNTs) are used. There are generally two methods of depositing SWNTs on flexible substrates-transferring CVD-grown SWNTs or solution-depositing SWNTs. Since CVD-grown SWNTs can be highly aligned, they often outperform solution-processed SWNT films that are typically in the form of random network. However, solution-based SWNTs can be printed at a large-scale and at low-cost, rendering them more appropriate for manufacturing. In either case, the removal of metallic SWNTs in an effective and a scalable manner is critical, which must still be developed and optimized. Nevertheless, promising results demonstrating SWNT-based flexible circuits, displays, RF-devices, and biochemical sensors have been reported by various research groups, proving insight into the exciting possibilities of SWNT-based FETs. In using carbon nanotubes as transparent electrodes (TEs), two main strategies have been implemented to fabricate highly conductive, transparent, and mechanically compliant films-superaligned films of CNTs drawn from vertically grown CNT forests using the "dry-drawing" technique and the deposition or embedding of CNTs onto flexible or stretchable substrates. The main challenge for CNT based TEs is to fabricate films that are both highly conductive and transparent. These CNT based TEs have been used in stretchable and flexible pressure, strain, and chemical and biological sensors. In addition, they have also been used as the anode and cathode in flexible light emitting diodes, solar cells, and supercapacitors. In summary, there are a number of challenges yet to overcome to optimize the processing and performance of CNT-based flexible electronics; nonetheless, CNTs remain a highly suitable candidate for various flexible electronic applications in the near future.
This article comprehensively reviews the recent progress and outlook of carbon nanotube film-based flexible electronics.
Electrochemical energy storage devices are becoming increasingly important to our global society, and polymer materials are key components of these devices. As the demand for high-energy density ...devices increases, innovative new materials that build on the fundamental understanding of physical phenomena and structure–property relationships will be required to enable high-capacity next-generation battery chemistries. In this Review, we discuss core polymer science principles that are used to facilitate progress in battery materials development. Specifically, we discuss the design of polymeric materials for desired mechanical properties, increased ionic and electronic conductivity and specific chemical interactions. We also discuss how polymer materials have been designed to create stable artificial interfaces and improve battery safety. The focus is on these design principles applied to advanced silicon, lithium-metal and sulfur battery chemistries.Polymers are ubiquitous in batteries as binders, separators, electrolytes and electrode coatings. In this Review, we discuss the principles underlying the design of polymers with advanced functionalities to enable progress in battery engineering, with a specific focus on silicon, lithium-metal and sulfur battery chemistries.
The distributed network of receptors, neurons, and synapses in the somatosensory system efficiently processes complex tactile information. We used flexible organic electronics to mimic the functions ...of a sensory nerve. Our artificial afferent nerve collects pressure information (1 to 80 kilopascals) from clusters of pressure sensors, converts the pressure information into action potentials (0 to 100 hertz) by using ring oscillators, and integrates the action potentials from multiple ring oscillators with a synaptic transistor. Biomimetic hierarchical structures can detect movement of an object, combine simultaneous pressure inputs, and distinguish braille characters. Furthermore, we connected our artificial afferent nerve to motor nerves to construct a hybrid bioelectronic reflex arc to actuate muscles. Our system has potential applications in neurorobotics and neuroprosthetics.
Deformable energy storage devices are needed to power next‐generation wearable electronics that interface intimately with human skin. Currently, deformable energy storage devices demonstrate poor ...performance compared to their rigid lithium‐ion counterparts, forcing wearable manufacturers to design their devices around bulky battery compartments. However, technological advances to create deformable batteries at the component and device level have yielded continuous improvement in stretchable batteries over the last five years. In this Essay, the major strategies at the component and device level that have been successfully employed to create stretchable batteries are reviewed. The outstanding challenges facing deformable energy storage are also discussed, namely, energy density, packaging, delamination, device integration, and manufacturing. This Essay will give researchers who are interested in contributing to the development of deformable batteries a cursory understanding of the most successful strategies to date, and provide insights into the most important directions to pursue in the future.
Deformable batteries are needed to enable the next generation of skin‐conformable electronics. This Essay describes past strategies to enable stretchable batteries at the device and component level. These strategies demonstrate significant advances in stretchable battery technology; however, there are still limitations that must be overcome. This Essay also describes the five main challenges that the development of deformable batteries encounters.
Conductive and stretchable materials that match the elastic moduli of biological tissue (0.5-500 kPa) are desired for enhanced interfacial and mechanical stability. Compared with inorganic and dry ...polymeric conductors, hydrogels made with conducting polymers are promising soft electrode materials due to their high water content. Nevertheless, most conducting polymer-based hydrogels sacrifice electronic performance to obtain useful mechanical properties. Here we report a method that overcomes this limitation using two interpenetrating hydrogel networks, one of which is formed by the gelation of the conducting polymer PEDOT:PSS. Due to the connectivity of the PEDOT:PSS network, conductivities up to 23 S m
are achieved, a record for stretchable PEDOT:PSS-based hydrogels. Meanwhile, the low concentration of PEDOT:PSS enables orthogonal control over the composite mechanical properties using a secondary polymer network. We demonstrate tunability of the elastic modulus over three biologically relevant orders of magnitude without compromising stretchability ( > 100%) or conductivity ( > 10 S m
).
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