Polysaccharide-based functional materials for flexible electronics: A comprehensive review of synthesis strategies, functionalization, and applications

Skin-mountable electronic materials are being intensively evaluated for use in bio-integrated devices that can mutually interact with the human body. Over the past decade, functional electronic materials inspired by the skin are developed with new functionalities to address the limitations of traditional electronic materials for bio-integrated devices. Herein, the recent progress in skin-mountable functional electronic materials for skin-like electronics is introduced with a focus on five perspectives that entail essential functionalities: stretchability, self-healing ability, biocompatibility, breathability, and biodegradability. All functionalities are advanced with each strategy through rational material designs. The skin-mountable functional materials enable the fabrication of bio-integrated electronic devices, which can lead to new paradigms of electronics combining with the human body.

Direct ink writing (DIW) presents a flexible and resource-efficient approach towards the prototyping of functional materials and devices with complex shapes. Printed functional materials for electronic devices depend on conductive fillers such as graphene nanoplatelets (GNPs), which are increasingly popular in printed electronics and energy materials thanks to their low cost, non-toxicity and high specific surface area. However, non-spherical colloids with large filler-to-nozzle size ratios like GNPs present a challenge for high-resolution DIW due to risk of nozzle clogging. As DIW of platelet-based inks is gaining traction in several fields, the feasibility of high-resolution DIW of platelet-based inks is demonstrated here on the example of GNPs (< 50 μm). A workflow for the combined optimization of ink rheology and printing process parameters was developed to gain a predictive understanding of filament quality and morphology. Using two inks and two nozzle diameters per ink, filaments ranging from <100 – 1200 μm in width and 30 – 300 μm in height were produced, with conductivities suitable for application in sensors or electrodes. The derived predictive models were successfully deployed to predict filament dimensions and to achieve excellent print quality even for fine sub-nozzle size structures with very high filler-to-nozzle size ratios within only one iteration of the workflow. With this study, we advocate for the integrated development of materials for processes and processes for materials. This study will benefit high-resolution rapid prototyping of a large class of functional materials for wearable electronics, sensors, RF passives, energy materials and tissue engineering.

Flexible electronics and intelligent wearable technology are one of the core driving forces for future intelligent living, and their combination is reshaping the hardware form of industries such as consumer electronics, medical health, and industrial testing. Flexible electronics breaks through the physical limitations of traditional rigid devices by integrating electronic components on flexible substrates, endowing devices with excellent flexibility, extensibility, and biocompatibility, thereby promoting the development of wearable devices towards thinner, more comfortable, and multifunctional directions. This article is based on various research findings in flexible electronics and smart wearables, and introduces the characteristics, preparation methods, and processing techniques of functional materials applied in this technology. At the same time, research on practical industrial production applications is collected. In the future development, flexible electronics still need considerable improvement in mechanical and electrical properties, and the preparation process needs to be developed towards low-cost, large-scale manufacturing, etc. Based on the current research status, flexible electronics will continue to expand its application scenarios and intelligent trends, becoming an important development direction and application tool in multiple disciplines and fields.

Glycosaminoglycans have quietly transitioned from biomaterials to advanced functional materials for energy devices and flexible electronics. Gathered here are 45 years of research highlighting both fundamental studies and recent advances and trends.

Flexible electronics technology has emerged as a transformative technology and is developing rapidly. However, traditional metals and inorganic semiconductors face limitations in flexible devices due to poor stretchability and adaptability. Polymers, with their lightweight, flexible, and multifunctional properties, are considered key materials for the fabrication of flexible electronic devices. Additionally, functional polymer materials offer tunable chemical structures, low cost, and compatibility with solution processing techniques, playing a significant role in enabling lightweight, stretchable, and wearable devices. This paper reviews recent advances in the design, synthesis, and integration of conductive, dielectric, piezoelectric, self-healing, biodegradable, and two-dimensional material-enhanced polymers. Additionally, the applications of functional polymer materials in flexible electronics are discussed. Finally, the challenges faced by functional polymer materials in flexible electronics are analyzed, and feasible future development directions are explored.

Bacterial cellulose (BC) is produced via the fermentation of various microorganisms. It has an interconnected 3D porous network structure, strong water-locking ability, high mechanical strength, chemical stability, anti-shrinkage properties, renewability, biodegradability, and a low cost. BC-based materials and their derivatives have been utilized to fabricate advanced functional materials for electrochemical energy storage devices and flexible electronics. This review summarizes recent progress in the development of BC-related functional materials for electrochemical energy storage devices. The origin, components, and microstructure of BC are discussed, followed by the advantages of using BC in energy storage applications. Then, BC-related material design strategies in terms of solid electrolytes, binders, and separators, as well as BC-derived carbon nanofibers for electroactive materials are discussed. Finally, a short conclusion and outlook regarding current challenges and future research opportunities related to BC-based advanced functional materials for next-generation energy storage devices suggestions are proposed.

PARC has been a leading innovator in printed electronics with over a decade of experience in large area electronics, application of novel and current printing technology to industrial applications and the printing of electronic circuits and devices. We are currently applying this knowledge to the concept of printing multi-material 3 dimensional objects with electronic and/or mechanical functionality. The concept is to develop capability and provide means of manufacturing functional objects which may be difficult to manufacture or even not be manufacturable by other means.In this paper, we will outline the creation of a rapid digital manufacturing system and considerations for building such a &#x201C;printer&#x201D; with the ability to integrate a structural material with functional electronic materials. The printer incorporates inkjet and extrusion techniques on the same platform, along with an in-line UV-curing lamp. This platform enables a wide processing window for structural and electronic materials; i.e., it is capable of patterning inks with viscosity ranging from 1 to 25000 cP The printer has been optimized to yield smooth printed features (down to tens of microns) without implementing pressure-leveling steps.

Flexible electronics technology plays an important role in regulating the properties of semiconducting materials, leading to the breakthrough in traditional strain engineering that is limited by the rigid and brittle inorganic materials and the fixed strain values. Thereby, the relevant research not only provides a new clue for strain regulation of semiconductor materials or other functional materials, but also lays a theoretical foundation for the performance evaluation of stretchable and flexible electronic devices based on inorganic functional materials in large-deformation environments. In this paper, the research progress of flexible inorganic electronics and strain effects on band structures, especially the property regulation of semiconducting materials in flexible electronics, is reviewed. Firstly, the nano-diamond particles based thinning process and the transfer printing are emphatically expounded with their influence on the properties of semiconducting electronics explored. In addition, the development and application of strain effect on band structure in recent years are introduced. In particular, the strain control based on buckling GaAs nanoribbon and buckling quantum well structure are studied to demonstrate the superior advantage of flexible electronics technology in the property regulation of semiconducting materials. The application and developing trend of strain engineering in the future are prospected finally.

Over the past several years, a new surge of interest in paper electronics has arisen due to the numerous merits of simple micro/nanostructured substrates. Herein, the latest advances and principal issues in the design and fabrication of paper-based flexible electronics are highlighted. Following an introduction of the fascinating properties of paper matrixes, the construction of paper substrates from diverse functional materials for flexible electronics and their underlying principles are described. Then, notable progress related to the development of versatile electronic devices is discussed. Finally, future opportunities and the remaining challenges are examined. It is envisioned that more design concepts, working principles, and advanced papermaking techniques will be developed in the near future for the advanced functionalization of paper, paving the way for the mass production and commercial applications of flexible paper-based electronic devices.

Next generation active electronic materials used in devices are undergoing continual improvements to generate devices that are high performance, lighter, flexible, stretchable, and more energy efficient with lower cost. Carbon based novel solution processable π-functional conjugated materials are the focus of intense academic and industrial research since they are important class of soft materials for large area electronics including transistors, displays, sensors and light harvesting devices. The active organic semiconducting materials are emerging due to their tunable light absorption/emission, interesting charge transport properties, relatively adequate HOMO-LUMO energies and ink formulation capability.In my talk, I will explain the various classes of conjugated carbon-based materials either as polymers, small molecules or quantum dots prepared via chemically and electrochemically using various novel aromatic conjugated building blocks. In this presentation, the design, synthesis, optoelectronic properties, and device performance of novel advanced materials for field effect/electrochemical transistors, perovskite solar cells, light emitting diodes, optical sensors and various sensing devices will be discussed. Such materials and devices have great potential in future electronics, energy, health, and environmental monitoring. Figure 1

Influences of metal, non-metal precursors, and substrates on atomic layer deposition processes for the growth of selected functional electronic materials

Although MXene sheets are highly conductive, it is still challenging to prepare MXene complex functional materials for flexible electronics by simple and effective methods. In 3D printing, especially direct ink writing (DIW), different materials are used to create complex 3D shapes by formulating inks with controlled rheological properties. Herein, a printable MXene ink is developed, exhibiting good rheological properties, to print different complex shapes, and potentially manufacture electronic devices such as sensors. Then, we fabricated a highly sensitive hierarchical structure MXene composite materials composed of two layers of bionic micro-spine microstructure and network structure, formed by 3D printing and freeze casting. The obtained MXene composite materials exhibit good pressuring sensing properties with a sensitivity of 17.5 kPa−1, a fast response time (<100 ms), and excellent cycle stability exceeding 10,000 cycles. The sensing mechanism suggesting that the hierarchical structure can effectively improve the sensitivity and response time. It also has good potential application in the monitoring of human health activities, including the detection of human joint activities, walking, pressure distribution, and other sports.

ABSTRACTCurrent technological advances and prolific endeavors have entrenched two‐dimensional conducting polymers as the rapidly emerging interface across a diversity of functional materials for flexible electronics, sensors, ion‐exchange membranes, biotechnology, catalysis, energy storage, and conversion. Rational design and fabrication of polymeric nanostructures enriched with well‐ordered geometry are appealing and endorse significant impact on their in‐built electrical, optical, and mechanical properties. In particular, recent interest in controlled hierarchical assembly of monomers/oligomers proved the free‐standing sheet‐like structures with exotic features of high conductivity and flexibility. Yet, the ongoing research to make nanometer‐thick polymers suffers from limitations to access large‐area, mechanical stability, and high‐range internal ordering. In this perspective, we focus on the radical approaches that highlight confinement‐entitled features of two‐dimensional polymeric materials correlating to their interface or template‐assisted synthesis, structure–property relationship, charge transport properties, and future scopes for relevant practical enactments. © 2019 Wiley Periodicals, Inc. J. Polym. Sci., Part B: Polym. Phys. 2019, 57, 1169–1176

Porous conductive elastomeric composites with carbon nanotubes suspended in the narrow pores from Co-continuous polymer blend nanocomposites

Organic synthesis plays a pivotal role in the development of innovative organic functional materials for optoelectronic applications such as organic light emitting diodes (OLEDs), photovoltaics (OPVs), non‐linear optics (NLOs), field effect transistors (OFETs) and sensors. Chemical functionalization methods available for polyaromatic hydrocarbons (PAHs) are particularly attractive as they provide opportunities to fine‐tune the physicochemical, charge transporting and device parameters. Among the PAHs containing heteroatoms, carbazole is recognized as one of the most promising building blocks for assembling the functional materials for organic electronics, particularly for OLED and OPVs due to its unique features such as good hole transporting ability, excellent thermal and morphological stability, amorphous nature, low cost, high triplet energy and flexibility for functionalization. Until 2011, carbazole‐based functional materials were limited to use as a donor in donor–acceptor molecular configurations and as difunctionalized (C3,C6‐ or C2,C7‐ or N‐) derivatives capable of hole transporting/emitting characteristics. Recently, polyfunctionalization on carbazole at various positions has drawn significant attention as a result of their promising structure–function relationships. Although some reviews have focused on structure–property relationships within difunctionalized carbazoles, recent synthetic advances in the field of polyfunctionalized carbazoles and their resultant structure–property relationships remain unreviewed. To bridge this gap, in this article we review newly emerged synthetic approaches for polyfunctionalization of carbazole and discuss the effects of substitution pattern, chromophore nature and its density on the photophysical and device properties.