Laser photonic-reduction stamping for graphene-based micro-supercapacitors ultrafast fabrication

One-Step Fabrication of Packaged Glass Microheater Using Selective Laser Welding

The increasing demand for miniaturized and versatile microdevices has driven advancements in micropatterning technologies; however, packaging considerations are often overlooked or addressed with basic additions. This study introduces a new selective laser welding process facilitated by a silver (Ag) thin film, enabling simultaneous micropatterning and packaging in a single step. In the proposed method, the Ag thin film serves as a laser absorber in the welded area, where it transitions to a fully insulating state, while in the unwelded areas, the remaining Ag thin film serves as an electrode without transitions. Mathematical modeling and heat transfer simulations were conducted to examine the laser energy transfer mechanism and determine the optimal thickness of the Ag thin film. Laser scan paths were designed for the Joule heating microheater and generated for subsequent selective laser welding. The designed microheater was fabricated and hermetically packaged between the glass substrates. Finally, a reusable cell culture tester was fabricated to demonstrate the practical applicability of the packaged glass microheater. The prototype was directly applicable to cell culture without requiring additional packaging. Moreover, it demonstrated consistent heating performance even after washing for reuse, indicating its feasibility for reusable devices. These results indicate that the proposed selective laser welding process, demonstrating the potential for advancing micropatterning and packaging technologies with diverse applications, is a promising approach for manufacturing packaged microdevices.

Dynamic spectral tailoring of a 10 GHz laser frequency comb for enhanced calibration of astronomical spectrographs

Laser frequency combs (LFCs) are an important component of Doppler radial velocity (RV) spectroscopy that pushes fractional precision to the 10-10 level, as required to identify and characterize Earth-like exoplanets. However, large intensity variations across the LFC spectrum that arise in the nonlinear broadening limit the range of comb modes that can be used for optimal wavelength calibration with sufficient signal-to-noise ratio. Furthermore, temporal spectral-intensity fluctuations of the LFC, that are coupled to flux-dependent detector defects, alter the instrumental point spread function (PSF) and result in spurious RV shifts. To address these issues and improve calibration precision, spectral flattening is crucial for LFCs to maintain a constant photon flux per comb mode. In this work, we demonstrate a dynamic spectral shaping setup using a spatial light modulator (SLM) over the wavelength range of 800-1300 nm. The custom shaping compensates for amplitude fluctuations in real time and can also correct for wavelength-dependent spectrograph transmission, achieving a spectral profile that delivers the constant readout necessary for maximizing precision. Importantly, we characterize the out-of-loop properties of the spectral flattener to verify a twofold improvement in spectral stability. This technique, combined with our approach of pumping the waveguide spectral broadener out-of-band at 1550 nm, reduces the required dynamic range. While this spectral region is tailored for the LFC employed at the Habitable-zone Planet Finder (HPF) spectrograph, the method is broadly applicable to any LFC used for astronomical spectrograph calibration.

One-Step Laser-Guided Fabrication of 3D Self-Assembled Graphene Micro-Rolls

Laser-induced graphene (LIG) has been systematically investigated and employed because of the spartan laser synthesis and functional three dimensional (3D) foam-like structures. However, thermally induced deformation during laser processing is generally undesirable and, therefore, strictly suppressed. This work introduces a novel laser-guided self-assembly approach integrated into the fabrication of LIG to generate multiscale 3D graphene foam structures in a single step. Leveraging the photothermal effects of laser ablation on polyimide films, we achieve concurrent LIG production and self-assembly, enabling the transformation of two dimensional films into 3D micro-rolls. The process is finely tuned through interface modification and optimized laser parameters, allowing precise control over the geometry of the resulting structures. Systematic investigations reveal that varying laser power and line spacing effectively adjust the diameters of the LIG micro-rolls. Characterization indicates that the LIG micro-rolls can be fabricated with very large curvature and limited internal space, enhancing the potential for microscale applications. Furthermore, our laser strategy facilitates the creation of symmetric, asymmetric, and double-tube micro-rolls, underscoring its design flexibility. This work highlights the potential of the laser-guided self-assembly strategy in graphene nanomaterials and miniaturized applications, which has been exemplarily verified through the LIG micro-roll supercapacitors.

In-situ construction of integrated asymmetric micro-supercapacitors achieving monolithic hundred-volt output

Asymmetric micro-supercapacitors (MSCs) exhibit higher energy density while face significant challenges in power density as well as cycling life and large dimensions. The key factors contributing to these dilemmas include the match of electrode materials and electrolytes, poor uniformity of device, and complicated while low-precise fabrication processes. Herein we develop a laser scribing-engraving (LSE) strategy to fabricate MSCs with monolithic high-voltage output and scalable array integration. Utilizing this strategy, we induce the conversion of the majority of Ti3C2Tx-MXene into TiO2 and graphene oxide into laser-scribed graphene (LSG), yielding asymmetric MSCs with laser-induced MXene/graphene oxide as the negative electrode and MXene/graphene oxide as the positive electrode. A single asymmetric micro-supercapacitor exhibits a high voltage window of 1.8 V, delivering an outstanding energy density (240 mWh cm-3) and power density (9503 mW cm-3), coupled with excellent cycling stability. Moreover, the LSE strategy enables monolithically integrated 64 devices to achieve a high-voltage output of 115.2 V. Our approach showcases the potential for integrating micro-energy storage devices into various microsystems, increasing the practicality of asymmetric micro-supercapacitors.

Light-Material Interactions Using Laser and Flash Sources for Energy Conversion and Storage Applications

This review provides a comprehensive overview of the progress in light-material interactions (LMIs), focusing on lasers and flash lights for energy conversion and storage applications. We discuss intricate LMI parameters such as light sources, interaction time, and fluence to elucidate their importance in material processing. In addition, this study covers various light-induced photothermal and photochemical processes ranging from melting, crystallization, and ablation to doping and synthesis, which are essential for developing energy materials and devices. Finally, we present extensive energy conversion and storage applications demonstrated by LMI technologies, including energy harvesters, sensors, capacitors, and batteries. Despite the several challenges associated with LMIs, such as complex mechanisms, and high-degrees of freedom, we believe that substantial contributions and potential for the commercialization of future energy systems can be achieved by advancing optical technologies through comprehensive academic research and multidisciplinary collaborations.

Chitosan Oligosaccharide Laser Lithograph: A Facile Route to Porous Graphene Electrodes for Flexible On-Chip Microsupercapacitors

In this study, a convenient chitosan oligosaccharide laser lithograph (COSLL) technology was developed to fabricate laser-induced graphene (LIG) electrodes and flexible on-chip microsupercapacitors (MSCs). With a simple one-step CO2 laser, the pyrolysis of a chitosan oligosaccharide (COS) and in situ welding of the generated LIGs to engineering plastic substrates are achieved simultaneously. The resulting LIG products display a hierarchical porous architecture, excellent electrical conductivity (6.3 Ω sq-1), and superhydrophilic properties, making them ideal electrode materials for MSCs. The pyrolysis-welding coupled mechanism is deeply discussed through cross-sectional analyses and finite element simulations. The MSCs prepared by COSLL exhibit considerable areal capacitance of over 4 mF cm-2, which is comparable to that of the polyimide-LIG-based counterpart. COSLL is also compatible with complementary metal-oxide-semiconductor (CMOS) and micro-electro-mechanical system (MEMS) processes, enabling the fabrication of LIG/Au MSCs with comparable areal capacitance and lower internal resistance. Furthermore, the as-prepared MSCs demonstrate excellent mechanical robustness, long-cycle capability, and ease of series-parallel integration, benefiting their practical application in various scenarios. With the use of eco-friendly biomass carbon source and convenient process flowchart, the COSLL emerges as an attractive method for the fabrication of flexible LIG on-chip MSCs and various other advanced LIG devices.

Ultra-Stable High-Capacity Polythiophene Derivative for Wide-Potential-Window Supercapacitors

Conducting polymer (CP)-based supercapacitors show great promise for applications in the field of wearable and portable electronics. However, these supercapacitors face persistent challenges, notably low energy density and inadequate stability. In this study, we introduce a polythiophene derivative, designated as poly(EPE), synthesized via the electrochemical polymerization of 8-bis(2,3-dihydrothieno[3,4-b][1,4]dioxin-5-yl)-3,3-dimethyl-3,4-dihydro-2H-thieno[3,4-b][1,4]dioxepine (EPE). The resulting poly(EPE) polymer exhibits an exemplary 3D porous network-like structure, significantly enhancing its capacitance performance. When employed as the electrode material, the symmetric supercapacitor demonstrates an exceptionally high specific capacitance of 1342 F g-1 at a current density of 4.0 A g-1, along with impressive energy and power densities of 119.3 W h kg-1 and 38.83 kW kg-1, respectively. These capacitance values surpass those of previously reported pristine CP-based supercapacitors. Notably, the supercapacitor showcases outstanding stability, maintaining a retention rate of 92.5% even after 50,000 charge-discharge cycles. These findings underscore the substantial potential of poly(EPE) as an electrode material for the advancement of the supercapacitor technology.

The status and challenging perspectives of 3D-printed micro-batteries

In the era of the Internet of Things and wearable electronics, 3D-printed micro-batteries with miniaturization, aesthetic diversity and high aspect ratio, have emerged as a recent innovation that solves the problems of limited design diversity, poor flexibility and low mass loading of materials associated with traditional power sources restricted by the slurry-casting method. Thus, a comprehensive understanding of the rational design of 3D-printed materials, inks, methods, configurations and systems is critical to optimize the electrochemical performance of customizable 3D-printed micro-batteries. In this review, we offer a key overview and systematic discussion on 3D-printed micro-batteries, emphasizing the close relationship between printable materials and printing technology, as well as the reasonable design of inks. Initially, we compare the distinct characteristics of various printing technologies, and subsequently emphatically expound the printable components of micro-batteries and general approaches to prepare printable inks. After that, we focus on the outstanding role played by 3D printing design in the device architecture, battery configuration, performance improvement, and system integration. Finally, the future challenges and perspectives concerning high-performance 3D-printed micro-batteries are adequately highlighted and discussed. This comprehensive discussion aims at providing a blueprint for the design and construction of next-generation 3D-printed micro-batteries.

Spatial Writing of Ultrafast All-Optical Switching

Writing spatial information on ultrafast all-optical switching is essential for constructing ultrafast processing units in photonic applications, such as optical communication and computing networks. However, most methods ignore the fabrication and imaging of controllable switching area, limiting its spatial information and the further design in ultrafast devices. Here, we propose a method to spatially write in ultrafast all-optical switching based on MAPbI3 perovskite with nanocone structure and visualize the switching effect in arbitrary designed area. Due to the light confinement effect of nanocone fabrication using a fs laser, the light is strongly absorbed by perovskite and reach saturable absorption. It leads to ultrafast broadband transmittance change with 25 fs switching time and 10% modulation depth in nanocone perovskite area. Our preparation method offers high efficiency, performance, and flexibility for the spatial writing of ultrafast all-optical switching, which is promising for developing ultrafast all-optical networks and the next generation of communication technology.

Laser-Induced Electron Synchronization Excitation for Photochemical Synthesis and Patterning Graphene-Based Electrode

Micro-supercapacitors (MSCs) represent a pressing requirement for powering the forthcoming generation of micro-electronic devices. The simultaneous realization of high-efficiency synthesis of electrode materials and precision patterning for MSCs in a single step presents an ardent need, yet it poses a formidable challenge. Herein, a unique shaped laser-induced patterned electron synchronization excitation strategy has been put forward to photochemical synthesis RuO2 /reduced graphene oxide (rGO) electrode and simultaneously manufacture the micron-scale high-performance MSCs with ultra-high resolution. Significantly, the technique represents a noteworthy advancement over traditional laser direct writing (LDW) patterning and photoinduced synthetic electrode methods. It not only improves the processing efficiency for MSCs and the controllability of laser-induced electrode material but also enhances electric fields and potentials at the interface for better electrochemical performance. The resultant MSCs exhibit excellent area and volumetric capacitance (516 mF cm-2 and 1720 F cm-3 ), and ultrahigh energy density (0.41 Wh cm-3 ) and well-cycle stability (retaining 95% capacitance after 12000 cycles). This investigation establishes a novel avenue for electrode design and underscores substantial potential in the fabrication of diverse microelectronic devices.

Laser maskless fast patterning for multitype microsupercapacitors

Downsizing electrode architectures have significant potential for microscale energy storage devices. Asymmetric micro-supercapacitors play an essential role in various applications due to their high voltage window and energy density. However, efficient production and sophisticated miniaturization of asymmetric micro-supercapacitors remains challenging. Here, we develop a maskless ultrafast fabrication of multitype micron-sized (10 × 10 μm²) micro-supercapacitors via temporally and spatially shaped femtosecond laser. MXene/1T-MoS₂ can be integrated with laser-induced MXene-derived TiO₂ and 1T-MoS₂-derived MoO₃ to generate over 6,000 symmetric micro-supercapacitors or 3,000 asymmetric micro-supercapacitors with high-resolution (200 nm) per minute. The asymmetric micro-supercapacitors can be integrated with other micro devices, thanks to the ultrahigh specific capacitance (220 mF cm^-2 and 1101 F cm^-3), voltage windows in series (52 V), energy density (0.495 Wh cm^-3) and power density (28 kW cm^-3). Our approach enables the industrial manufacturing of multitype micro-supercapacitors and improves the feasibility and flexibility of micro-supercapacitors in practical applications.

N-Doped Graphene-like Film/Silicon Structures as Micro-Capacitor Electrodes

Currently, the miniaturization of portable and autonomous devices is challenging for modern electronics. Graphene-based materials have recently emerged as one of the ideal candidates for supercapacitor electrodes, while Si is a common platform for direct component-on-chip integration. We have proposed the direct liquid-based CVD of N-doped graphene-like films (N-GLFs) on Si as a promising way to achieve solid-state on-chip micro-capacitor performance. Synthesis temperatures in the range from 800 °C to 1000 °C are investigated. Capacitances and electrochemical stability of the films are evaluated using cyclic voltammetry, as well as galvanostatic measurements and electrochemical impedance spectroscopy in 0.5 M Na₂SO₄. We have shown that N-doping is an efficient way to improve the N-GLF capacitance. 900 °C is the optimal temperature for the N-GLF synthesis with the best electrochemical properties. The capacitance rises with increasing film thickness which also has an optimum (about 50 nm). The transfer-free acetonitrile-based CVD on Si yields a perfect material for microcapacitor electrodes. Our best value of the area-normalized capacitance (960 mF/cm²) exceeds the world's achievements among thin graphene-based films. The main advantages of the proposed approach are the direct on-chip performance of the energy storage component and high cyclic stability.

Laser-Induced Transient Self-Organization of TiNx Nano-Filament Percolated Networks for High Performance Surface-Mountable Filter Capacitors

Filter capacitors (FCs) are substantial for digital circuits and microelectronic devices, and thus more compact FCs are eternally demanded for system miniaturization. Even though microsupercapacitors are broadly regarded as an excellent candidate for future FCs, yet due to the limitation of available electrode materials, the capacitive performance of reported MSCs drops sharply under high-frequency alternating current. Herein, we present a unique laser-induced transient self-organization strategy, which synergizes pulsed laser energy and multi-physical field controlled coalescence processes, leading to the rapid and controllable preparation of titanium nitride ultrafine nano-filaments (diameter ≈3-5 nm) networks. Their chaotic fractal nanoporous structure, superior specific surface area, and excellent conductivity render these nanostructures promising candidates for FCs. Surface-mounted filter capacitors based on this electrode material exhibit ultra-long cycle-life (2 000 000 cycles) with record ultrahigh volumetric energy density of 9.17 mWh cm^-3 at 120 Hz in aqueous electrolyte, displaying advantages in function, size, and integrability compared with the state-of-the-art aluminum electrolytic capacitors. The method here provides a versatile toolbox for designing novel nanostructures with intriguing characteristics and insights for developing advanced and miniaturized filter and power devices.

Monolithic integrated micro-supercapacitors with ultra-high systemic volumetric performance and areal output voltage

Monolithic integrated micro-supercapacitors (MIMSCs) with high systemic performance and cell-number density are important for miniaturized electronics to empower the Internet of Things. However, fabrication of customizable MIMSCs in an extremely small space remains a huge challenge considering key factors such as materials selection, electrolyte confinement, microfabrication and device-performance uniformity. Here, we develop a universal and large-throughput microfabrication strategy to address all these issues by combining multistep lithographic patterning, spray printing of MXene microelectrodes and controllable 3D printing of gel electrolytes. We achieve the monolithic integration of electrochemically isolated micro-supercapacitors in close proximity by leveraging high-resolution micropatterning techniques for microelectrode deposition and 3D printing for precise electrolyte deposition. Notably, the MIMSCs obtained demonstrate a high areal-number density of 28 cells cm^-2 (340 cells on 3.5 × 3.5 cm²), a record areal output voltage of 75.6 V cm^-2, an acceptable systemic volumetric energy density of 9.8 mWh cm^-3 and an unprecedentedly high capacitance retention of 92% after 4000 cycles at an extremely high output voltage of 162 V. This work paves the way for monolithic integrated and microscopic energy-storage assemblies for powering future microelectronics.

Ultrafast materials synthesis and manufacturing techniques for emerging energy and environmental applications

Energy and environmental issues have attracted increasing attention globally, where sustainability and low-carbon emissions are seriously considered and widely accepted by government officials. In response to this situation, the development of renewable energy and environmental technologies is urgently needed to complement the usage of traditional fossil fuels. While a big part of advancement in these technologies relies on materials innovations, new materials discovery is limited by sluggish conventional materials synthesis methods, greatly hindering the advancement of related technologies. To address this issue, this review introduces and comprehensively summarizes emerging ultrafast materials synthesis methods that could synthesize materials in times as short as nanoseconds, significantly improving research efficiency. We discuss the unique advantages of these methods, followed by how they benefit individual applications for renewable energy and the environment. We also highlight the scalability of ultrafast manufacturing towards their potential industrial utilization. Finally, we provide our perspectives on challenges and opportunities for the future development of ultrafast synthesis and manufacturing technologies. We anticipate that fertile opportunities exist not only for energy and the environment but also for many other applications.

Effect of Surface Treatment on Performance and Internal Stacking Mode of Electrohydrodynamic Printed Graphene and Its Microsupercapacitor

Microelectronic devices are developing rapidly in portability, wearability, and implantability. This puts forward an urgent requirement for the delicate deposition process of materials. Electrohydrodynamic printing has attracted academic and industrial attention in preparing ultrahigh-density microelectronic devices as a new noncontact, direct graphic, and low-loss thin film deposition process. In this work, a printed graphene with narrow line width is realized by combining the electrohydrodynamic printing and surface treatment. The line width of printed graphene on the hydrophobic treatment surface reduced from 80 to 28 μm. The resistivity decreased from 0.949 to 0.263 Ω·mm. Unexpectedly, hydrophobic treatment can effectively induce random stacking of electrohydrodynamic printed graphene, which avoids parallel stacking and agglomeration of graphene sheets. The performance of printed graphene is thus effectively improved. After optimization, a graphene planar supercapacitor with a printed line width of 28 μm is successfully obtained. Its capacitance can reach 5.39 mF/cm² at 50 mV/s, which is twice higher than that of the untreated devices. The device maintains 84.7% capacitance after 5000 cycles. This work provides a reference for preparing microelectronic devices by ultrahigh precision printing and a new direction for optimizing two-dimensional material properties through stacking adjustment.

Facile Assembly of Hybrid Micro-Supercapacitors for a Sunlight-Powered Energy Storage System

Herein, hybrid micro-supercapacitors (MSCs), consisting of positive CoNi layer double hydroxides (LDHs) decorated on carbon nanotubes (CoNi LDHs@CNTs) and negative CNT electrodes, were assembled by facile drop-coated and electrodeposition methods. The as-fabricated MSCs were optimized in view of electrochemical performance, and the CoNi LDHs-2@CNTs//CNT MSC exhibited a favorable performance and was thus chosen to be the candidate for MSC device package. The packaged CoNi LDHs-2@CNTs//CNT MSC demonstrated a large areal capacitance of 11.0 mF·cm^-2 at a current density of 0.08 mA·cm^-2, a good rate performance (56% areal capacitance retained at a higher current density of 0.4 mA·cm^-2), and a favorable cycling stability and reversibility (92% of the original areal capacitance was retained after 5000 cycles). Furthermore, the MSC device recorded an energy density of 1.5 μWh·cm^-2 at a power density of 42.5 μW·cm^-2 and was successfully applied for the storage of energy supplied by solar cells to operate a red light-emitting diode. All these findings demonstrated the promising practical energy storage application of the as-fabricated hybrid MSC devices in the construction of sunlight-powered energy storage systems.

Engineering Interlaced Architecture of Pristine Graphene Anchored with 2-Amino-8-Naphthol 6-Sulfonic Acids for Printed Hybrid Micro-Supercapacitors with High Electrochemical Capability

All-printed flexible micro-supercapacitors (MSCs) based on two-dimensional (2D) nanomaterials with in-plane interdigital configurations are regarded as promising miniaturized power source units, but they chronically suffer from self-aggregation and inadequate matching of electrode materials, thus resulting in inefficient electrolyte ions intercalation. Herein, an innovative multicomponent interlaced architecture essentially consisting of 2-amino-8-naphthol 6-sulfonic acid (ANS)-anchored pristine graphene and highly conductive multiwalled carbon nanotubes is reported. The assembled and optimized Gr@ANS electrodes offer sufficient absorption/desorption and redox-active sites, delivering a high areal capacitance of 33.7 mF/cm² for screen-printed MSCs. Particularly, the well-modified Gr@ANS/CNTs-interlaced complex structure effectively prevents the usual restacking of the delaminated Gr@ANS nanosheets and maximizes ion accessibility in electrodes. Ascribed to the optimized electron-transferring kinetics, the achieved Gr@ANS/CNTs MSCs exhibit excellent capacitance (40.2 mF/cm² and 18.8 F/cm³), simultaneously significantly increasing the rate capability of Gr@ANS MSCs (from 3.9 to 60.0%). Arising from the multicomponent synergism, the all-solid-state MSCs exhibit outstanding bending stability and cycling performance (73.8% after 10 000 charge/discharge cycles). The new charge reservoir engineering evidenced in graphene-based micro-supercapacitors would serve as a stepping stone toward the scalable manufacture of hybrid energy storage micro-devices.

Laser Processing of Flexible In-Plane Micro-supercapacitors: Progresses in Advanced Manufacturing of Nanostructured Electrodes

Flexible in-plane architecture micro-supercapacitors (MSCs) are competitive candidates for on-chip miniature energy storage applications owing to their light weight, small size, high flexibility, as well as the advantages of short charging time, high power density, and long cycle life. However, tedious and time-consuming processes are required for the manufacturing of high-resolution interdigital electrodes using conventional approaches. In contrast, the laser processing technique enables high-efficiency high-precision patterning and advanced manufacturing of nanostructured electrodes. In this review, the recent advances in laser manufacturing and patterning of nanostructured electrodes for applications in flexible in-plane MSCs are comprehensively summarized. Various laser processing techniques for the synthesis, modification, and processing of interdigital electrode materials, including laser pyrolysis, reduction, oxidation, growth, activation, sintering, doping, and ablation, are discussed. In particular, some special features and merits of laser processing techniques are highlighted, including the impacts of laser types and parameters on manufacturing electrodes with desired morphologies/structures and their applications on the formation of high-quality nanoshaped graphene, the selective deposition of nanostructured materials, the controllable nanopore etching and heteroatom doping, and the efficient sintering of nanometal products. Finally, the current challenges and prospects associated with the laser processing of in-plane MSCs are also discussed. This review will provide a useful guidance for the advanced manufacturing of nanostructured electrodes in flexible in-plane energy storage devices and beyond.

Femtosecond Laser-Assisted Device Engineering: Toward Organic Field-Effect Transistor-Based High-Performance Gas Sensors

Organic electronic-based gas sensors hold great potential for portable healthcare- and environment-monitoring applications. It has recently been shown that introducing a porous structure into an organic semiconductor (OSC) film is an efficient way to improve the gas-sensing performance because it facilitates the interaction between the gaseous analyte and the active layer. Although several methods have been used to generate porous structures, the development of a robust approach that can facilely engineer the porous OSC film with a uniform pore pattern remains a challenge. Here, we demonstrate a robust approach to fabricate porous OSC films by using a femtosecond laser-processed porous dielectric layer template. With this laser-assisted strategy, various polymeric OSC layers with controllable pore size and well-defined pore patterns were achieved. The consequent porous p-type polymer-based device exhibits enhanced sensitivity to the ammonia analyte in the range from 100 ppb to 10 ppm with remarkable reproducibility and selectivity. The micropattern of the active layer was precisely controlled by generating various pore densities in the predecorated templates, which results in modulated ammonia sensitivities ranging from 30 to 65% ppm^-1. Furthermore, we show that this approach can be used to fabricate flexible gas sensors with enhanced sensing performance and mechanical durability, which indicate that this femtosecond laser-assisted approach is very promising for the fabrication of next-generation wearable electronics.

Research Progress on the Preparation and Applications of Laser-Induced Graphene Technology

Graphene has been regarded as a potential application material in the field of new energy conversion and storage because of its unique two-dimensional structure and excellent physical and chemical properties. However, traditional graphene preparation methods are complicated in-process and difficult to form patterned structures. In recent years, laser-induced graphene (LIG) technology has received a large amount of attention from scholars and has a wide range of applications in supercapacitors, batteries, sensors, air filters, water treatment, etc. In this paper, we summarized a variety of preparation methods for graphene. The effects of laser processing parameters, laser type, precursor materials, and process atmosphere on the properties of the prepared LIG were reviewed. Then, two strategies for large-scale production of LIG were briefly described. We also discussed the wide applications of LIG in the fields of signal sensing, environmental protection, and energy storage. Finally, we briefly outlined the future trends of this research direction.

Optical Modification of 2D Materials: Methods and Applications

2D materials are under extensive research due to their remarkable properties suitable for various optoelectronic, photonic, and biological applications, yet their conventional fabrication methods are typically harsh and cost-ineffective. Optical modification is demonstrated as an effective and scalable method for accurate and local in situ engineering and patterning of 2D materials in ambient conditions. This review focuses on the state of the art of optical modification of 2D materials and their applications. Perspectives for future developments in this field are also discussed, including novel laser tools, new optical modification strategies, and their emerging applications in quantum technologies and biotechnologies.

Ultrafast Shaped Laser Induced Synthesis of MXene Quantum Dots/Graphene for Transparent Supercapacitors

Ultratransparent electrodes have attracted considerable attention in optoelectronics and energy technology. However, balancing energy storage capability and transparency remains challenging. Herein, an in situ strategy employing a temporally and spatially shaped femtosecond laser is reported for photochemically synthesizing of MXene quantum dots (MQDs) uniformly attached to laser reduced graphene oxide (LRGO) with exceptional electrochemical capacitance and ultrahigh transparency. The mechanism and plasma dynamics of the synthesis process are analyzed and observed at the same time. The unique MQDs loaded on LRGO greatly improve the specific surface area of the electrode due to the nanoscale size and additional edge states. The MQD/LRGO supercapacitor has high flexibility and durability, ultrahigh energy density (2.04 × 10^-3  mWh cm^-2 ), long cycle life (97.6% after 12 000 cycles), and excellent capacitance (10.42 mF cm^-2 ) with both high transparency (transmittance over 90%) and high performance. Furthermore, this method provides a means of preparing nanostructured composite electrode materials and exploiting quantum capacitance effects for energy storage.

Fabrication Technologies for the On-Chip Integration of 2D Materials

With compact footprint, low energy consumption, high scalability, and mass producibility, chip-scale integrated devices are an indispensable part of modern technological change and development. Recent advances in 2D layered materials with their unique structures and distinctive properties have motivated their on-chip integration, yielding a variety of functional devices with superior performance and new features. To realize integrated devices incorporating 2D materials, it requires a diverse range of device fabrication techniques, which are of fundamental importance to achieve good performance and high reproducibility. This paper reviews the state-of-art fabrication techniques for the on-chip integration of 2D materials. First, an overview of the material properties and on-chip applications of 2D materials is provided. Second, different approaches used for integrating 2D materials on chips are comprehensively reviewed, which are categorized into material synthesis, on-chip transfer, film patterning, and property tuning/modification. Third, the methods for integrating 2D van der Waals heterostructures are also discussed and summarized. Finally, the current challenges and future perspectives are highlighted.

A Multidimensional Topotactic Host Composite Anode Toward Transparent Flexible Potassium-Ion Microcapacitors

Transparent flexible supercapacitors (TFSCs) are a tantalizing power supplier for future transparent flexible electronics. However, their energy density is far behind a practical level while maintaining high transparency. We report here a transparent flexible potassium-ion microcapacitor, and its high energy density (15.5 μWh cm^-2) roots in the battery-supercapacitor hybrid storage mechanism and much enlarged working voltage (3 V), outperforming the state-of-the-art TFSC, which is generally based on an aqueous electrolyte and an asymmetric pseudocapacitive mechanism. From an electrode material perspective, a multidimensional topotactic host composite anode is designed in which the component not only performs energy storage by synchronous and reversible uptake of potassium ions and electrons into its host structure, but also mutually compensates individual weakness in functional and structural aspects, efficiently constructing a three-dimensional potassium-ion diffusion and electron transport system. This conceptual exhibition provides design principles at material and device levels for high-performance TFSCs.

Throughput Improvement in Femtosecond Laser Ablation of Nickel by Double Pulses

In this study, femtosecond laser double pulses were tested to improve their nickel ablation efficiency. The experimental results indicated that compared with single pulses, double pulses with different delay times generated craters with larger diameters and depths. The results obtained for three sets of double pulses with different energy ratios indicated that double pulses with an energy ratio of 1:9 had the highest ablation efficiency, followed by those with energy ratios of 2:8 and 5:5. The double pulses with the aforementioned three energy ratios achieved the maximum ablation efficiency when the delay time was 3-4 ps. Compared with single pulses, double pulses with an energy ratio of 1:9 generated craters with an up to 34% greater depth and up to 14% larger diameter. In addition, an interference effect was observed with a double pulse delay time of 0 ps, which has seldom been reported in the literature. The double pulses were simulated using the two-temperature model. The simulation results indicated that double pulses with an energy ratio of 1:9 with a delay time of 4 ps can perform the strongest ablation. These simulation results are in line with the experimental results.

Tuning the Mechanical and Electrical Properties of Porous Electrodes for Architecting 3D Microsupercapacitors with Batteries-Level Energy

Microsupercapacitors (MSCs) are vital power sources for internet of things (IoTs) and miniaturized electronics. The performance of MSCs is often restricted by its low areal energy density, which is due to the low areal mass loading of active materials. Constructing thick planar microelectrode with fine structure and high aspect ratio is an efficient way to increase mass loading, but limited by the breakable nature of porous electrode materials. Here, it is found that the mechanical and electrical properties of porous electrodes, as well as their surface area utilization and internal ion diffusion pathway, can be synergistically tuned by infilling gel electrolyte into internal pores of porous electrode films. The tuned thick porous electrode films are robust enough to enable laser ablation of three dimensional (3D) microelectrodes for high mass loading and high aspect ratio. The areal capacitance of 3D microelectrodes is able to increase linearly with mass loading (or thickness) up to at least 13 mg cm^-2  (or 260 µm) for a value of up to 4640 mF cm^-2 based on active carbon. The 3D MSCs deliver areal energy density of 1318 μWh cm^-2 , which is comparable to the best of Li-ion 3D microbatteries while exhibiting superior electrochemical and mechanical stability.

Fabrication of nanogap structures through spatially shaped femtosecond laser modification with the assistance of wet chemical etching

Fabricating nanostructures with an extremely small feature size through a near-infrared femtosecond laser is a considerable challenge. In this Letter, we report a flexible, facile, and mask-free method that enables the formation of nanogap structures with a controllable size on silicon. This method involves spatially shaped femtosecond laser single-pulse modification assisted with chemical etching. Nanogaps obtained after etching can be divided into two categories, namely a ring dimer with a nanogap (type I) and Crack-nanogap (type II). The nanogap between the ring dimer could be reduced to 68 nm with a gradual increase in the laser fluence. For the Crack-nanogap obtained through crack propagation induced by stress release during a wet etching process, the smallest gap size is approximately 9 nm.

Preclinical assessment on neuronal regeneration in the injury-related microenvironment of graphene-based scaffolds

As the application of graphene nanomaterials gets increasingly attractive in the field of tissue engineering and regenerative medicine, the long-term evaluation is necessary and urgent as to their biocompatibility and regenerative capacity in different tissue injuries, such as nerve, bone, and heart. However, it still remains controversial about the potential biological effects of graphene on neuronal activity, especially after severe nerve injuries. In this study, we establish a lengthy peripheral nerve defect rat model and investigate the potential toxicity of layered graphene-loaded polycaprolactone scaffold after implantation during 18 months in vivo. In addition, we further identify possible biologically regenerative effects of this scaffold on myelination, axonal outgrowth, and locomotor function recovery. It is confirmed that graphene-based nanomaterials exert negligible toxicity and repair large nerve defects by dual regulation of Schwann cells and astroglia in the central and peripheral nervous systems. The findings enlighten the future of graphene nanomaterial as a key type of biomaterials for clinical translation in neuronal regeneration.