Inkjet printing (IJP) technology, adapted from home and office printing, has proven to be an essential research tool and industrial manufacturing technique in a wide range of printed electronic technologies, including optoelectronics. Its primary advantage over other deposition methods is the low-cost and maskless on-demand patterning, which offers unmatched freedom-of-design. Additional benefits include the efficient use of materials, contactless high-resolution deposition, and scalability, enabling rapid translation of learning from small-scale, laboratory-based research into large-scale industrial roll-to-roll manufacturing. In the development of organic solar cells (OSCs), IJP has enabled the printing of many of the multiple functional layers which comprise the complete cell as part of an additive printing scheme. Although IJP is only recently employed in perovskite solar cell (PeSC) fabrication, it is already showing great promise and is anticipated to find broader application with this class of materials. As OSCs and PeSCs share many common functional materials and device architectures, this review presents a progress report on the IJP of OSCs and PeSCs in order to facilitate knowledge transfer between the two technologies, with critical analyses of the challenges and opportunities also presented.

With the rapid development of wearable electronics, it is desirable to design and develop flexible power supplies, especially rechargeable lithium ion batteries, with high performance and superior flexibility and durability for integration into electronics. Structures and materials are two key factors in achieving the flexibility of batteries. Therefore, it becomes important to understand the fundamental mechanics in order to better guide us in the design of flexible batteries to meet the requirements of wearable electronics. In this work, we review recent research progress on batteries for wearable electronics based on structures and materials, covering the fundamental mechanics underlying the structural design mechanism and intrinsically deformable materials as building blocks for flexible batteries. In addition, we review and discuss emerging new materials and structures that could potentially revolutionize the design concepts of flexible batteries for wearable electronics. Therefore, these flexible and wearable materials and structures are not limited to batteries. We can envision that the mechanics and design concepts can also be extended to other electronics for wearable applications.

Assembly of lightweight engineering and functional materials with superb mechanical performance, such as high stiffness, super resilience, and stability, is highly demanded to pave ways for their practical applications. [1] However, how to simultaneously achieve both stiffness and resilience in a man-made material at low-density remains a challenging scientific and engineering issue. Biological materials have found their way to achieve outstanding mechanical properties at low density by assembling sophisticate hierarchical structures from microscopic to macroscopic scales, and thus provide inspirations for designing and manufacturing advanced biomimetic materials. [2] Plant materials, such as plant stem [3] and wood, [4] represent an important class of lightweight natural materials with superb mechanical properties. The slender grass stems of Elytrigia repens is a representative natural material with high mechanical performance and lightweight features owing to a specially evolved hierarchical architecture with a macroscopically hollow and microscopically cellular structure. The macroscopically hollow structure combined with the cellular microstructure serves as an excellent force-bearing structure that is conducive to the dispersion of strain and stress, and thus efficiently enhances the stiffness, and resilience and reduce the density, simultaneously. [5] In recent years, the constructions of biomimetic structures have attracted extensive attention because of their potential ability to achieve high mechanical properties and lightweight artificial engineering and functional materials. [6] Despite progresses in the construction of biomimetic structures, the poor mechanical properties at low density remain as a major bottleneck in artificial biomimetic materials, which are mainly due to the lack of appropriate structures at both macro-and microlevels at the same time.The ink-based 3D printing, as a powerful additive manufacturing technique for producing 3D structures both in microscopic and macroscopic scales, [6b,7] shows great potential to assembly materials into 3D hierarchical structures. Additionally, 3D printing displays distinct advantages of high degree of freedom in structure design, which enable the ability to design and construct versatile structures for realizing the Biological materials with hierarchical architectures (e.g., a macroscopic hollow structure and a microscopic cellular structure) offer unique inspiration for designing and manufacturing advanced biomimetic materials with outstanding mechanical performance and low density. Most conventional biomimetic materials only benefit from bioinspired architecture at a single length scale (e.g., microscopic material structure), which largely limits the mechanical performance of the resulting materials. There exists great potential to maxime the mechanical performance of biomimetic materials by leveraging a bioinspired hierarchical structure. An ink-based three-dimensional (3D) printing strategy to manufacture an ultralight biomimetic hierarchical g...

Anisotropic cellular materials with direction-dependent structure and durable mechanical properties enable various applications (e.g., nanofluidics, biomedical devices, tissue engineering, and water purification), but their widespread use is often hindered by complex and scale-limited fabrication and unsatisfactory mechanical performance. Here, inspired by the anisotropic and hierarchical material structure of tendons, we demonstrate a facile, scalable top-down approach for fabricating a highly elastic, ionically conductive, anisotropic cellulosic material (named elastic wood) directly from natural wood via chemical treatment. The resulting elastic wood demonstrates good elasticity and durable compressibility, showing no sign of fatigue after 10 000 compression cycles. The chemical treatment not only softens the wood cell walls by partially removing lignin and hemicellulose but introduces an interconnected cellulose fibril network into the wood channels. Atomistic and continuum modeling further reveals that the absorbed water can freely and reversibly move inside the elastic wood and therefore helps the elastic wood accommodate large compressive deformation and recover to its original shape upon compression release. In addition, the elastic wood showed a high ionic conductivity of up to 0.5 mS cm −1 at a low KCl concentration of 10 −4 M, which can be tuned by changing the compression ratio of the material. The demonstrated elastic, mechanically robust, and ionically conductive cellulosic material combining inherited anisotropic cellular structure from natural wood and a self-formed internal gel may find a variety of potential applications in ionic nanofluidics, sensors, soft robots, artificial muscle, environmental remediation, and energy storage.

Red phosphorus offers a high theoretical sodium capacity and has been considered as a candidate anode for sodium-ion batteries. Similar to silicon anodes for lithium-ion batteries, the electrochemical performance of red phosphorus is plagued by the large volume variation upon sodiation. Here we perform in situ transmission electron microscopy analysis of the synthesized red-phosphorus-impregnated carbon nanofibers with the corresponding chemo-mechanical simulation, revealing that, the sodiated red phosphorus becomes softened with a “liquid-like” mechanical behaviour and gains superior malleability and deformability against pulverization. The encapsulation strategy of the synthesized red-phosphorus-impregnated carbon nanofibers has been proven to be an effective method to minimize the side reactions of red phosphorus in sodium-ion batteries, demonstrating stable electrochemical cycling. Our study provides a valid guide towards high-performance red-phosphorus-based anodes for sodium-ion batteries.