Inkjet-Printed Ultrathin MoS2-Based Electrodes for Flexible In-Plane Microsupercapacitors

MOF-Based Bioelectronic Supercapacitors

Metal-organic frameworks (MOFs) represent a highly promising material class for bioelectronic supercapacitors, characterized by their adjustable structures, extensive surface areas, and superior electrochemical properties. This research explores the synthesis and incorporation of MOF-based materials into bioelectronic devices aimed at energy storage and biosensing applications. The focus is on improving the electrochemical performance of MOFs while preserving their structural integrity through functionalization with biocompatible polymers and conductive materials. The resulting MOF-based bioelectronic supercapacitors exhibit significant improvements in specific capacitance, energy density, and cycling stability. Additionally, the inclusion of bioreceptors allows for the simultaneous detection of biochemical signals alongside energy storage, thus enabling innovative applications in wearable electronics and health monitoring systems. These results suggest that MOF-based supercapacitors have the capacity to fulfill energy storage needs while also advancing bioelectronics by merging energy and sensing capabilities.

A review on electrode materials of supercapacitors used in wearable bioelectronics and implantable biomedical applications

Supercapacitors, a class of electrochemical energy storage devices, offer a promising solution for powering wearable bioelectronics and implantable biomedical devices. Their high-power density, rapid charge-discharge capabilities, and long cycle life make them ideal for applications requiring quick bursts of energy and extended operation. To address the challenges of energy density, self-discharge, miniaturization, integration, and power consumption, researchers are exploring various strategies, including developing novel electrode materials, optimizing device architectures, and integrating advanced fabrication techniques. Metal oxides, carbon-based materials, MXenes, and their composites have emerged as promising electrode materials due to their high specific surface area, excellent conductivity, and biocompatibility. For wearable bioelectronics, supercapacitors can power a wide range of devices, including wearable sensors, smart textiles, and other devices that require intermittent or pulsed energy. In implantable biomedical devices, supercapacitors offer a reliable and safe power source for applications such as pacemakers, neural implants, and drug delivery systems. By addressing the challenges and capitalizing on emerging technologies, supercapacitors have the potential to revolutionize the field of bioelectronics and biomedical engineering, enabling the development of innovative devices that improve healthcare and quality of life.

A critical review on printed electronics and its application

In light of the industry's environmental constraints, sustainable manufacturing technology has emerged as a critical goal for emerging applications. Due to the increased need for electronic production around the world, the requirement for environmentally safe technology is the necessity of this decade as the world government shifts towards sustainability in all manufacturing technology. Henceforth, printed electronics will be one such solution to regulate the electronic device and components production requirement of this decade. The article has discussed about the recent advances in inkjet-printed electronics across a wide range of electronics applications. We have discussed several inkjet printing inks and their formulation methods, which are required for minimizing environmental waste. In addition, we have discussed the future scope of printed electronics production and its impact on the economy as well as the environment.

Solution-Processable and Printable Two-Dimensional Transition Metal Dichalcogenide Inks

Two-dimensional (2D) transition metal dichalcogenides (TMDs) with layered crystal structures have been attracting enormous research interest for their atomic thickness, mechanical flexibility, and excellent electronic/optoelectronic properties for applications in diverse technological areas. Solution-processable 2D TMD inks are promising for large-scale production of functional thin films at an affordable cost, using high-throughput solution-based processing techniques such as printing and roll-to-roll fabrications. This paper provides a comprehensive review of the chemical synthesis of solution-processable and printable 2D TMD ink materials and the subsequent assembly into thin films for diverse applications. We start with the chemical principles and protocols of various synthesis methods for 2D TMD nanosheet crystals in the solution phase. The solution-based techniques for depositing ink materials into solid-state thin films are discussed. Then, we review the applications of these solution-processable thin films in diverse technological areas including electronics, optoelectronics, and others. To conclude, a summary of the key scientific/technical challenges and future research opportunities of solution-processable TMD inks is provided.

Recent Progress and Challenges in Paper-Based Microsupercapacitors for Flexible Electronics: A Comprehensive Review

Recent advances in paper-based microsupercapacitors (p-MSCs) have attracted significant attention due to their potential as substrates for flexible electronics. This review summarizes progress in the field of p-MSCs, discussing their challenges and prospects. It covers various aspects, including the fundamental characteristics of paper, the modification of paper with functional materials, and different methods for device fabrication. The review critically analyzes recent advancements, materials, and fabrication techniques for p-MSCs, exploring their potential applications and benefits, such as flexibility, cost-effectiveness, and sustainability. Additionally, this review highlights gaps in current research, guiding future investigations and innovations in the field. It provides an overview of the current state of p-MSCs and offers valuable insights for researchers and professionals in the field. The critical analysis and discussion presented herein offer a roadmap for the future development of p-MSCs and their potential impact on the domain of flexible electronics.

Multiscale Structural Design of 2D Nanomaterials-based Flexible Electrodes for Wearable Energy Storage Applications

2D nanomaterials play a critical role in realizing high-performance flexible electrodes for wearable energy storge devices, owing to their merits of large surface area, high conductivity and high strength. The electrode is a complex system and the performance is determined by multiple and interrelated factors including the intrinsic properties of materials and the structures at different scales from macroscale to atomic scale. Multiscale design strategies have been developed to engineer the structures to exploit full potential and mitigate drawbacks of 2D materials. Analyzing the design strategies and understanding the working mechanisms are essential to facilitate the integration and harvest the synergistic effects. This review summarizes the multiscale design strategies from macroscale down to micro/nano-scale structures and atomic-scale structures for developing 2D nanomaterials-based flexible electrodes. It starts with brief introduction of 2D nanomaterials, followed by analysis of structural design strategies at different scales focusing on the elucidation of structure-property relationship, and ends with the presentation of challenges and future prospects. This review highlights the importance of integrating multiscale design strategies. Finding from this review may deepen the understanding of electrode performance and provide valuable guidelines for designing 2D nanomaterials-based flexible electrodes.

Layer-by-Layer Inkjet-Printed Manganese Oxide Nanosheets on Graphene for High-Performance Flexible Supercapacitors

The widespread adoption of wearable, movable, and implantable smart devices has sparked the evolution of flexible, miniaturized power supplies. High-resolution inkjet printing of flexible microsupercapacitor (μSC) electrodes is a fast, inexpensive, and waste-free alternative manufacturing technology. In this work, a 2D birnessite-type manganese dioxide (δ-MnO2) water-based ink is used to print 10-25 layers of δ-MnO2 symmetrically on a preprinted interdigitated cell consisting of 10 layers of electrochemically exfoliated graphene (EEG). The cell with 10 printed layers of δ-MnO2 achieved the highest specific capacitance, energy density, and power density of 0.44 mF cm-2, 0.045 μW h cm-2, and 0.0012 mW cm-2, respectively. Since inkjet-printing technology supports μSC manufacturing with parallel/series connectivity, four cells were used to study and improve the potential window and capacitance that can be used to construct μSC arrays as power banks. This work provides the first approach for designing an inkjet-printed interdigitated hybrid cell based on δ-MnO2@EEG that could be a versatile candidate for the large-scale production of flexible and printable electronic devices for energy storage.

Current Trends and Promising Electrode Materials in Micro-Supercapacitor Printing

The development of scientific and technological foundations for the creation of high-performance energy storage devices is becoming increasingly important due to the rapid development of microelectronics, including flexible and wearable microelectronics. Supercapacitors are indispensable devices for the power supply of systems requiring high power, high charging-discharging rates, cyclic stability, and long service life and a wide range of operating temperatures (from -40 to 70 °C). The use of printing technologies gives an opportunity to move the production of such devices to a new level due to the possibility of the automated formation of micro-supercapacitors (including flexible, stretchable, wearable) with the required type of geometric implementation, to reduce time and labour costs for their creation, and to expand the prospects of their commercialization and widespread use. Within the framework of this review, we have focused on the consideration of the key commonly used supercapacitor electrode materials and highlighted examples of their successful printing in the process of assembling miniature energy storage devices.

Recent Advances in Molybdenum Disulfide and Its Nanocomposites for Energy Applications: Challenges and Development

Energy storage and conversion are critical components of modern energy systems, enabling the integration of renewable energy sources and the optimization of energy use. These technologies play a key role in reducing greenhouse gas emissions and promoting sustainable development. Supercapacitors play a vital role in the development of energy storage systems due to their high power density, long life cycles, high stability, low manufacturing cost, fast charging-discharging capability and eco-friendly. Molybdenum disulfide (MoS₂) has emerged as a promising material for supercapacitor electrodes due to its high surface area, excellent electrical conductivity, and good stability. Its unique layered structure also allows for efficient ion transport and storage, making it a potential candidate for high-performance energy storage devices. Additionally, research efforts have focused on improving synthesis methods and developing novel device architectures to enhance the performance of MoS₂-based devices. This review article on MoS₂ and MoS₂-based nanocomposites provides a comprehensive overview of the recent advancements in the synthesis, properties, and applications of MoS₂ and its nanocomposites in the field of supercapacitors. This article also highlights the challenges and future directions in this rapidly growing field.

Recent advances in inkjet-printing technologies for flexible/wearable electronics

The rapid development of flexible/wearable electronics requires novel fabricating strategies. Among the state-of-the-art techniques, inkjet printing has aroused considerable interest due to the possibility of large-scale fabricating flexible electronic devices with good reliability, high time efficiency, a low manufacturing cost, and so on. In this review, based on the working principle, recent advances in the inkjet printing technology in the field of flexible/wearable electronics are summarized, including flexible supercapacitors, transistors, sensors, thermoelectric generators, wearable fabric, and for radio frequency identification. In addition, some current challenges and future opportunities in this area are also addressed. We hope this review article can give positive suggestions to the researchers in the area of flexible electronics.

Printed Electronics Based on 2D Material Inks: Preparation, Properties, and Applications toward Memristors

Printed electronics, which fabricate electrical components and circuits on various substrates by leveraging functional inks and advanced printing technologies, have recently attracted tremendous attention due to their capability of large-scale, high-speed, and cost-effective manufacturing and also their great potential in flexible and wearable devices. To further achieve multifunctional, practical, and commercial applications, various printing technologies toward smarter pattern-design, higher resolution, greater production flexibility, and novel ink formulations toward multi-functionalities and high quality have been insensitively investigated. 2D materials, possessing atomically thin thickness, unique properties and excellent solution-processable ability, hold great potential for high-quality inks. Besides, the great variety of 2D materials ranging from metals, semiconductors to insulators offers great freedom to formulate versatile inks to construct various printed electronics. Here, a detailed review of the progress on 2D material inks formulation and its printed applications has been provided, specifically with an emphasis on emerging printed memristors. Finally, the challenges facing the field and prospects of 2D material inks and printed electronics are discussed.

Inkjet Printing of MnO2 Nanoflowers on Surface-Modified A4 Paper for Flexible All-Solid-State Microsupercapacitors

Printing technologies are gaining growing attention as a sustainable route for the fabrication of high-performance and flexible power sources such as microsupercapacitors (MSCs). Here, the inkjet printing method is utilized for the fabrication of manganese dioxide (MnO₂)-based, flexible all-solid-state MSCs on surface-modified A4 paper substrate. The appropriate rheology of the formulated ethanol-based ink (Fromm number <10) and the proper dimensions of MnO₂ nanoflowers (average size ∼600 nm) ensure a reliable inkjet printing process. Moreover, the underlying graphene/Ag nanowire pattern serves as a primer and highly conductive (R_s < 2 Ω sq^-1) layer on top of the paper to facilitate the anchoring of MnO₂ nanoflowers and rapid electron transportation. The resulting all-solid-state MSCs deliver a maximum areal capacitance of 0.68 mF cm^-2 at a current density of 25 μA cm^-2, reasonable durability (>80% of capacity remained after 3000 cycles), and remarkable foldability. Additionally, the inkjet-printed MSC devices deliver a superior areal energy density of 0.01 μWh cm^-2 and also a power density of 1.19 μW cm^-2. This study demonstrates the power of the inkjet printing method to produce MSCs on flexible substrates, which have great potential for flexible/wearable electronics.

DLP printing of a flexible micropattern Si/PEDOT:PSS/PEG electrode for lithium-ion batteries

We report on a free-standing 3D-printed Si/PEDOT:PSS/PEG electrode based on silicon nanoparticles (Si) as an active material for lithium-ion batteries (LIBs) that are fabricated by 3D printing via digital light processing (DLP). Compared with the Si electrode prepared by the traditional method, the 3D-printed Si/PEDOT:PSS/PEG electrode developed by DLP preserves a specific discharge capacity of 1658.4 mA h g^-1, with a capacity fade of 0.3% per cycle at a current density of 800 mA g^-1 after 125 cycles. This helps in maintaining its structural integrity and enables it to exhibit significantly high flexibility with an enhanced load of 4.2 mg cm^-2. The resulting free-standing electrode shows that 3D printing has significant potential for application to a variety of LIB technologies.

Ink Formulation and Printing Parameters for Inkjet Printing of Two Dimensional Materials: A Mini Review

Inkjet printing of two-dimensional (2D) material has been a center of interest for wearable electronics and has become a promising platform for next-generation technologies. Despite the enormous progress made in printed 2D materials, there are still challenges in finding the optimal printing conditions involving the ink formulation and printing parameters. Adequate ink formulation and printing parameters for target 2D materials rely on empirical studies and repeated trials. Therefore, it is essential to compile promising strategies for ink formulation and printing parameters. In this context, this review discusses the optimal ink formulations to prepare stable ink and steady ink jetting and then explores the critical printing parameters for fabricating printed 2D materials of a high quality. The summary and future prospects for inkjet-printed 2D materials are also addressed.

Sand-Milling Fabrication of Screen-Printable Graphene Composite Inks for High-Performance Planar Micro-Supercapacitors

Rational engineering and simplified production of printable graphene inks are essential for building high-energy and flexible graphene micro-supercapacitors (MSCs). However, few graphene-based MSCs show impressive areal capacitance and energy density, especially based on additive-manufacturing, cost-effective, and printable inks. Herein, a new-style and solution-processable graphene composite ink is ingeniously formulated for scalable screen printing MSCs. More importantly, the as-formulated inks consist of interwoven two-dimensional graphene and activated carbon nanofillers, which are delaminated by one-step sand-milling turbulent flow exfoliation. Notably, embedding the activated carbon nanoplatelets into graphene layers drastically boosts the electrochemical performance of screen-printed micro-supercapacitors (denoted as Gr/AC-MSCs), such as an outstanding areal capacitance of 12.5 mF cm^-2 (about 20 times than pure graphene). The maximum energy density, maximum power density, and exceptional cyclability are 1.07 μW h cm^-2, 0.004 mW cm^-2, and 88.1% after 5000 cycles, respectively. As such, the as-printed MSCs on paper display high resolution and pronounced energy-storage performance. Furthermore, the packaged and optimized Gr/AC-MSCs showcase remarkable mechanical flexibility even under highly folded and excellent water resistance, maintaining 91.8% capacitance retention after being washed for 90 min. The versatile methodology highlights the promise of graphene and analogous 2D nanosheet functional inks for scalable fabrication of flexible energy-storage devices.