Polymer nanocomposite meshes for flexible electronic devices
Graphical abstract
Polymer nanocomposite mesh-based electronic devices, featuring high flexibility, well-controlled compositions, high surface areas, lightweight, and porous structures permeable to air and liquid, are becoming tremendously popular for applications in healthcare monitoring, electronic skin, energy harvesting and storage devices, flexible displays and implantable bioelectronics. The emerging progress in polymer nanocomposite mesh-based flexible electronic devices and in the related mechanisms behind the mesh structure-induced functionalities have been intensively described. The related critical challenges and prospects are provided to offer inspiration for the design of advanced polymer nanocomposite meshes, as well as to promote the utilization and integration of polymer nanocomposite mesh scaffolds into multifunctional flexible electronic devices with outstanding performance and environmental friendliness for various applications.
Introduction
Flexible electronic devices are attracting considerable attention regarding their wearability, flexibility, and compatibility with various applications including touch screens [1,2], healthcare monitoring [[3], [4], [5], [6], [7], [8]], electronic skin [[9], [10], [11], [12], [13], [14], [15], [16]], energy harvesting and storage devices [[17], [18], [19], [20]], and implantable bioelectronics [[21], [22], [23], [24], [25], [26], [27]]. Studies committed to improve the structures, functionalities and performances of flexible electronic devices are rapidly increasing worldwide since these devices will have a profound effect on people’s daily life. The general term “flexible electronic devices” means that the devices can still function well during bending, folding, compression or stretching [28]. Two main strategies have been presented for the construction of electronic devices with excellent flexibility and stretchability: using intrinsically soft materials and devising special geometrical configurations [[29], [30], [31], [32]]. Existing flexible electronic devices are generally based on inorganic/organic composites, such as metals [33], metal oxide semiconductors [[34], [35], [36]], carbon materials [37,38], and polymers [[39], [40], [41], [42], [43]]. Inorganic semiconductors and metals are considered to be a reasonable choice for the fabrication of electronic devices owing to their high conductivity and reproducable performance. However, the relatively high-density and rigidity of these materials oppose their ability to withstand repeated bending or stretching [44]. Abundant advanced structural designs and optimizations are devoted to endowing metal-based materials with enhanced flexibility. The task is generally feasible through the physical or chemical deposition of bendable ultrathin metal films with particular layouts (e.g., wavy structures, buckling, serpentine patterns, coiled springs and others) on flexible polymer substrates [[45], [46], [47], [48]]. To date, polymers have played considerable roles in the development of strategies and materials for high-performance flexible electronics [[49], [50], [51], [52], [53], [54], [55], [56], [57], [58]]. The internal rotations among single bonds facilitate the conformation changes of molecular chains and lead to the inherent high flexibility of polymers [59] which therefore highlight the broad space to readily tune the properties and functionalities of polymers through engineering molecular structures. In general, polymers may serve as supporting substrates for conductive components, protective encapsulants, adhesives, matrix, or active materials. Polydimethylsiloxane (PDMS), poly(ethylene terephthalate) (PET), polyimide (PI) and Ecoflex are among the most intensively used substrates for flexible electronic devices due to their remarkable flexibility. Conductive polymers, particularly those based on unique π-conjugated structures, such as polyaniline (PANI), polypyrrole (PPy), polythiophene (PT), and so on, have attracted great interest by virtue of their tunable electronic properties, solution processability and excellent mechanical compliance for large-area processing [60,61]. Conjugated polymers are still considered to be the ideal candidates for flexible electronics even though inorganic materials exhibit better performance in terms of the conductivity and charge transport characteristics. The Young’s modulus of a semiconducting polymer is comparable to that of human skin (0.34 MPa), which greatly underlines the potential of these materials for implementation in attachable and wearable on-skin electronics [62,63]. In flexible device engineering, the appropriate geometrical designs of high-performance materials constitute another valid strategy for improved flexibility and stretchability. In this respect, polymer materials can be readily processed into various two-dimensional (2D) or three-dimensional (3D) micro/macrostructures, such as porous [64], fibrous [65], woven [66], coiled [67], wavy [68] and other hierarchical and patterned configurations [69], via different fabrication techniques. Compared to conventional polymer thin films with mechanical mismatches and limited permeability, the fibrous mesh scaffolds, assembled from interlacing fibers, filaments or yarns, offer fascinating opportunities for flexible electronic devices with well-controlled compositions, softness, higher surface areas, porous structures permeable to air and liquid, and high tolerance to damage [[70], [71], [72]]. In addition, the mesh structure is expected to play a vital role in devising ultrathin, lightweight, wearable and conformal electronic devices, which are promising for enhancing the properties of existing applications and for extending the range of new applications [73,74]. There are many delicate mesh structures assembled from natural polymer fibers, such as spider webs woven from silk fibers, and paper and textiles processed from cellulose fibers. Additionally, many kinds of meshes based on synthetic polymers are available thanks to the contributions of polymer science and engineering that benefited fiber-forming and weaving technologies [75]. Moreover, nanoscale conductive materials promote flexibility and electrical performance [76,77]. Therefore, the combination of soft polymer materials and active nanomaterials to prepare polymer nanocomposite mesh-based electronic devices with improved performance has sparked interest over the past two decade, preparing a solid foundation for new routes towards mesh-based polymer nanocomposite electronic materials (Fig. 1). Recently, several reviews have summarized the applications of fibers and textiles based on metals, carbon materials, and conductive polymers in energy harvesting and storage systems as well as wearable electronics [72,[78], [79], [80], [81]]. However, a review that highlights the applicability of polymer mesh composites in various kinds of flexible electronics including strain/pressure sensors, electronic skin, transparent conductors, energy harvesting and storage systems, flexible displays and bioelectronics is lacking. In this review, we will first focus on the strategies for preparing polymer nanocomposite meshes, which can be further integrated into flexible electronic devices via natural-resource-based meshes (cellulose paper, cotton fabric, and silk fabric), electrospinning, in situ polymerization with simultaneous deposition and photolithography (Fig. 2). The related mechanisms of the polymer mesh structure-induced functionalities, as well as device performances, will be elaborated. Then, the versatile methods for engineering polymer nanocomposite mesh scaffolds as passive components (such as functional substrates, templates, precursors, etc.) and active components (such as friction layers for nanogenerators, electrolyte separators for energy storage devices, sensing layers for chemical sensors, etc.) for various high-performance flexible electronic devices will be described in details by highlighting the most relevant and recent advances with the most representative examples (Fig. 3). Finally, the future perspectives for developing polymer nanocomposite mesh-based flexible electronic devices will be discussed to provide understanding of the design and synthesis of polymer mesh nanocomposites and of facilitating the design and assembly of polymer nanocomposite mesh-based wearable electronic devices exhibiting excellent performances, flexibility, compatibility, and environmental friendliness [82].
Section snippets
Material design and fabrication strategies for polymer nanocomposite meshes
Mesh structures, assembled from interconnected fibers, can be fabricated from various polymer nanocomposite components [103,104]. Fibers, referring to the materials consisting of continuous or discontinuous filaments, are ubiquitous in plants, animals and minerals in the nature of cellulose, proteins and minerals. Through well-established natural ingenuity, these fibers are further assembled into one-, two- and three-dimensional fiber meshes. For instance, proteinaceous silk fibers have been
Polymeric nanocomposite meshes as passive components for electronic devices
Flexible electronic devices have attracted attention for on-skin electronics, electronic skin, energy harvesting devices, environmental monitoring and implantable bioelectronics. Conventional flexible electronic devices are generally assembled from conductive material layers on supporting flexible substrates, such as PDMS and PET. However, the mechanical mismatch and limited permeability of conventional flexible substrates have restricted the applications of these electronic devices. Compared
Friction layer for nanogenerators
With the concerns regarding fossil fuel exhaustion and environmental pollution, the interest in renewable energy and energy conversion has been increasing [227,228]. Notably, energy harvesting that aims to capture, accumulate and store small amounts of energy resulting from motion, vibration, or heat is highly desirable [229]. It was since 2006 when piezoelectric nanogenerators (PENGs) were successfully demonstrated to convert mechanical energy into electrical energy on the basis of
Conclusions and perspectives
Interdisciplinary research initiatives have led to significant advancements in the field of flexible electronic devices for flexible sensors, electronic skin, energy harvesting and storage devices, flexible displays and bioelectronics. Polymers, featuring inherent flexibility, synthetic viability, and tunable physical and chemical properties, are one of the most promising candidates for the realization of flexible electronics. Versatile methods for polymer processing have been developed to
Declaration of Competing Interest
There is no conflict of interest to be considered.
Acknowledgements
This work was financially supported by the National Key Research and Development Program of China (2017YFB0306905, 2016YFC0801302), the National Natural Science Foundation of China (21404006, 21774012 and 51973008), the Major Program of the National Nature Science and Foundation of China (51790500), the Beijing Natural Science Foundation (2152023 and 2202042), and the Fundamental Research Funds for the Central Universities.
References (376)
- et al.
Stretchable helical architecture inorganic-organic hetero thermoelectric generator
Nano Energy
(2016) - et al.
Active polymer nanofibers for photonics, electronics, energy generation and micromechanics
Prog Polym Sci
(2015) - et al.
Designing π-conjugated polymers for organic electronics
Prog Polym Sci
(2013) - et al.
Stretchable and self-healing polymers and devices for electronic skin
Prog Polym Sci
(2013) - et al.
PDMS with designer functionalities—properties, modifications strategies, and applications
Prog Polym Sci
(2018) - et al.
Electrically conductive hydrogels for flexible energy storage systems
Prog Polym Sci
(2019) - et al.
Functional materials by electrospinning of polymers
Prog Polym Sci
(2013) - et al.
Carbon nanotube–polyaniline composites
Prog Polym Sci
(2014) - et al.
Graphene tribotronics for electronic skin and touch screen applications
Adv Mater
(2017) - et al.
Printable transparent conductive films for flexible electronics
Adv Mater
(2018)
Lab-on-skin: a review of flexible and stretchable electronics for wearable health monitoring
ACS Nano
Flexible electronics toward wearable sensing
Acc Chem Res
Alignment-free liquid-capsule pressure sensor for cardiovascular monitoring
Adv Funct Mater
A real-time wearable UV-radiation monitor based on a high-performance p-CuZnS/n-TiO2 photodetector
Adv Mater
Flexible hybrid electronics: direct interfacing of Soft and hard electronics for wearable health monitoring
Adv Funct Mater
Methylxanthine drug monitoring with wearable sweat sensors
Adv Mater
Chemical and engineering approaches to enable organic field-effect transistors for electronic skin applications
Acc Chem Res
Highly conductive, flexible, and compressible all-graphene passive electronic skin for sensing human touch
Adv Mater
MoS2-based tactile sensor for electronic skin applications
Adv Mater
Silk-molded flexible, ultrasensitive, and highly stable electronic skin for monitoring human physiological signals
Adv Mater
Linearly and highly pressure-sensitive electronic skin based on a bioinspired hierarchical structural array
Adv Mater
Stretchable and multimodal all graphene electronic skin
Adv Mater
Fingertip skin–inspired microstructured ferroelectric skins discriminate static/dynamic pressure and temperature stimuli
Sci Adv
Large-area high-performance flexible pressure sensor with carbon nanotube active matrix for electronic skin
Nano Lett
Towards flexible solid-state supercapacitors for smart and wearable electronics
Chem Soc Rev
Nanocarbon-based materials for flexible all-solid-State supercapacitors
Adv Mater
Bioinspired, spine-like, flexible, rechargeable lithium-ion batteries with high energy density
Adv Mater
Stretchable organic semiconductor devices
Adv Mater
Bioelectronics: soft implants for long-term use
Nat Mater
Materials and techniques for implantable nutrient sensing using flexible sensors integrated with metal-organic frameworks
Adv Mater
Recent advances in materials, devices, and systems for neural interfaces
Adv Mater
Advanced materials and devices for bioresorbable electronics
Acc Chem Res
Programmable nano-bio interfaces for functional biointegrated devices
Adv Mater
Recent advances in flexible and stretchable bio-electronic devices integrated with nanomaterials
Adv Mater
Wearable and implantable devices for cardiovascular healthcare: from monitoring to therapy based on flexible and stretchable electronics
Adv Funct Mater
Recent progress on flexible lithium rechargeable batteries
Energy Environ Sci
Nature-inspired structural materials for flexible electronic devices
Chem Rev
Design considerations for unconventional electrochemical energy storage architectures
Adv Energy Mater
Stretchable, elastic materials and devices for solar energy conversion
Energy Environ Sci
Chemical formation of soft metal electrodes for flexible and wearable electronics
Chem Soc Rev
Flexible photodetectors based on 1D inorganic nanostructures
Adv Sci
Flexible light emission diode arrays made of transferred Si microwires-ZnO nanofilm with piezo-phototronic effect enhanced lighting
ACS Nano
Piezo-phototronic effect enhanced flexible solar cells based on n-ZnO/p-SnS core-shell nanowire array
Adv Sci
Graphene-based materials for flexible supercapacitors
Chem Soc Rev
Carbon-nanomaterial-Based flexible batteries for wearable electronics
Adv Mater
Conjugated polymers for flexible energy harvesting and storage
Adv Mater
Conducting polymer dough for deformable electronics
Adv Mater
Large-Area, Semitransparent, and Flexible All-Polymer Photodetectors
Adv Funct Mater
Flexible electronics
Science
Stretchable, curvilinear electronics based on inorganic materials
Adv Mater
Cited by (123)
Room temperature synthesis and hydrophobic surface protection of silver dendrites for hydrogel stretchable sensors
2024, Sensors and Actuators A: PhysicalTriboelectric nanogenerator based on multi-component crosslinked network hydrogel for intelligent human motion sensing
2024, Chemical Engineering JournalHighly aligned electrospun film with wave-like structure for multidirectional strain and visual sensing
2024, Chemical Engineering JournalCellulose based materials to accelerate the transition towards sustainability
2024, Industrial Crops and ProductsDeveloping curcumin loaded-magnetic montmorillonite nanoparticles/polyvinyl alcohol/hyaluronic acid/chitosan nanofiber mats as a wound dressing
2024, Journal of Drug Delivery Science and Technology