Ultrafast Femtosecond Laser Maskless Patterning for Multitype Microsupercapacitors

Downsizing electrode architectures provides great potential for the fabrication of microscale energy storage devices. With their extended voltage window and high energy density, asymmetric microsupercapacitors (MSCs) play an essential role in various applications. However, the ecient manufacturing of asymmetric MSCs remains challenging. Herein, maskless lithography–based ultrafast fabrication of multitype micron-sized planar MSCs in one step through temporally and spatially shaped femtosecond laser is presented. MSCs are only 10 × 10 µm 2 in size and have a minimum line width of 200 nm. MXene and 1T-MoS 2 can be combined with laser-induced MXene-derived TiO 2 and 1T-MoS 2 derived MoO 3 to form various types of asymmetric and symmetric MSCs in the same material system within seconds. The asymmetric MSC exhibits an ultrahigh speci (cid:0) c capacitance (220 mF cm −2 and 1101 F cm −3 ), cycling stability (98.3% capacitance retention after 15,000 cycles), energy density (0.495 Wh cm −3 ) and power density (28 kW cm −3 ). This versatile strategy overcomes the current limitations of MSC manufacturing. Multitype MSCs fabricated herein have high resolution, enhancing the feasibility and exibility of the preparation of microscale energy storage devices. The morphology and microstructures were characterized by scanning electron microscope (SEM) using SU8220 (Hitachi, Japan) by a Hitachi SEM in Tsinghua university. X-ray photoelectron spectroscopy (XPS) analysis was performed using a ESCALAB 250Xi spectrometer with a monochromatic Al Kα source (7.5 µm beam spot). Raman spectra were acquired using a Via-reex spectroscopy with the excitation laser line at 532 nm. The XRD patterns were conducted on a D8 Advance (Bruker) with CuKa radiation. Using an Olympus metallographic microscope can take optical microscopy images. The Confocal Laser Scanning Microscopy used an MPLAPONLEXT x20 lens. The Raman spectroscopy investigations were performed using a Renishaw inVia Reex spectrometer with laser wavelength of 532 nm. in a two-electrode cyclic (CV), galvanostatic charge/discharge electrochemical areal cm −2 ) per GCD Eqs. follows:


Introduction
The growing demand for miniaturized, multifunctional portable electronics has greatly stimulated the development of microintegrated energy systems. The microsupercapacitor (MSC) plays an integral role in microscale energy storage devices. [1] With technological advances, various types of MSCs have been developed. Unlike symmetric MSCs, asymmetric MSCs can be assembled using two electrode materials, providing a larger voltage window and signi cantly increasing the energy density. [2,3] Thus, the practical applications of MSCs can be extended. Substantial progress has been made for asymmetric MSCs in recent years. Conventional asymmetric MSCs are referred to as sandwich-type MSCs. Thinner, smaller, more exible planar asymmetric MSCs require multiple fabrication steps and are di cult to further downsize. [4,5] Speci cally, the preparation process is extremely complex because of the unique structure of the inconsistent electrode materials, and accurate control of the electrode materials is challenging. The minimum size of asymmetric supercapacitors remains at the micron or millimeter level. The precise control of electrode material assembly, as well as the simultaneous formation of patterns of two types of materials in one step, is challenging to accomplish through conventional methods such as electrodeposition, [6] inkjet printing, [7] laser etching, [8] and photolithography. [9] Pseudocapacitance materials are common asymmetric electrode materials, but due to their instability and poor electrical conductivity, their power density is low and their lifespan is short. In recent years, two-dimensional materials have attracted considerable scholarly attention because of their excellent electrochemical properties. 1T-MoS 2 and MXene, the most notable, have highly reversible surface redox reactions and favorable metallic conductivity. [10,11] A recent study reported that 1T-MoS 2 demonstrated excellent conductivity and a high cycle life as an electrode material for asymmetric supercapacitors. Moreover, the voltage window was large. [12] In other investigations, MXene materials were combined with various metal oxides and carbon-based materials to construct asymmetric supercapacitors, which achieved excellent electrochemical performance. [13,14] In this study, we present a method for the ultrafast fabrication of submicron-scale symmetric and asymmetric MSCs on the same 1T-MoS 2 /MXene thin lms by using temporally and spatially shaped femtosecond laser. Three types of MSCs, namely a 1T-MoS 2 / MXene symmetric MSC, a laser-induced symmetric MSC prepared on MXene-derived TiO 2 and 1T-MoS 2 -derived MoO 3 thin lms, and an asymmetric MSC prepared on 1T-MoS 2 /MXene/laser-induced MXene-derived TiO 2 and 1T-MoS 2 -derived MoO 3 thin lms, were fabricated. The composition of the laser-induced MoO 3 and TiO 2 thin lms was manipulated through laser pulse delay and energy. Using the proposed approach, more than 150 groups of MSCs could be fabricated every minute, and each MSC was only 10 × 10 µm 2 in size.

Discussion
The Preparation of Multitype MSCs First, 1T-MoS 2 /MXene hybrid thin lms of variable thickness were prepared through vacuum ltration. We transferred thin lms of differing thicknesses to the glass substrate. As shown in Figure 1a, a confocal spatial pulse shaping system for femtosecond lasers was constructed to achieve ultrafast, high-precision patterning. In this process, materials are subjected to laser ablation according to controllable energy. By designing any combination of light elds, various types of symmetric and asymmetric MSCs can be fabricated. Almost any material, including ultrahard, ultrastrong materials, can be subjected to such processing. [15] Phase-adjustable spatial light modulators (SLMs) were employed to focus the Gaussian femtosecond laser into a femtosecond laser with a varying spatial distribution. Through the design of distinct phases, arbitrary changes in the light eld were realized within an extremely short period to produce multiple types of MSCs. SLMs can load computer-generated holograms (CGHs) to focus light in space. Before the Gaussian laser entered the SLM, it was focused using a Michelson interferometer. The Gaussian femtosecond pulse was integrated into an evenly divided double pulse sequence with a pulse delay of 10 ps. The subsequent subpulses focused the laser on the material in the preceding sequence.
When the front sequence pulse contacted the material, numerous freely moving electrons were excited.
The subsequent pulse sequence further interacted with the seed electrons generated by the front sequence pulse before the material was modi ed or ablated, leading to the avalanche ionization of more free electron eruptions. This occurrence is because the pulse delay between the two pulse sequences is in the picosecond order, which is substantially shorter than the time required for material phase transition.
For our initial beam (800 nm, 35 fs), we customized a special algorithm to calculate the original incident beam, adjusting it according to our target light eld. The optimized GS algorithm ensured a more uniform light eld distribution. [16] In previous experiments using SLM, each pattern corresponded to a CGH. [17,18] However, considering the pattern processing of multiple types of MSCs, various patterns must be processed in the asymmetric MSCs in situ at the same time. Thus, the processing technology requires optimization. We overlaid the target pattern on multiple target images, and programming was applied to load various CGHs into SLMs to realize continuous changes in multiple light elds over a 0.001-s duration. Multiple spatially focused light elds were smoothly focused by the objective lens from the SLM outlet through the 4f relay system. As shown in Figure 1b extremely small (10 × 10 µm 2 ), had extremely high processing consistency, and could be rapidly prepared in a very short time (150 groups/min) across a large area (Figures 2b and 2c). The MSCs clearly exhibited regularity, and the minimum line width was continuous. The interdigital MSCs with differing shapes and ngers could be completely prepared, such that the in uence of ngers on electrochemical performance could be determined. MSCs of different shapes were prepared by controlling the shapes of the target light eld (Supplementary Figure 1). This enabled the controllable and personalized preparation of microscale electronics, and the exibility surpassed that achieved through conventional processing techniques.
Moreover, we could control the laser frequency in the actual processing procedure; laser pulses could be shot out of the laser extremely rapidly. In the processing of MSCs with a size of 10 × 10 µm 2 , the translational was set to move at a rate of 2000 um/s under a laser frequency of 200. Therefore, 200 subpulses could be used to pattern 200 symmetric MSCs in 1 s. However, because multiple patterned light elds are required to realize the fabrication of an asymmetric MSC, the maximum number of MSCs processed per second is 100. Supplementary Figure 2 presents MSCs arrays (with varying sizes and line widths) prepared through this method. As indicated in Supplementary Figure 3, we designed patterned MSCs with differing line widths by adjusting the patterns and parameters of the light eld with focused laser pulses. These line widths were adjustable from the micron scale (5 µm) to the nanometer scale (200 nm). Furthermore, we achieved ultrahigh-resolution machining by setting a delay in temporally and spatially shaped femtosecond laser to control pulse shaping near the ablation threshold of the material. We employed femtosecond laser pulses to realize one-step pattern processing of various electrode material systems because this technology can be used to process almost any material.
As shown in Figure 2d, regular pattern processing was conducted on various materials (a metal-organic framework, graphene, WS 2 , MoTe, MnO 2 , and RuO 2 ). Raman characterization of the laser-patterned area con rmed the complete removal of the material through laser ablation. This demonstrates that our technology can not only be applied to the pattern processing of two-dimensional materials but also be employed for the high-precision processing of metal oxide materials. These results indicate that our technology is promising for the preparation of microelectronics and microscale energy storage devices. We conducted a review of technologies used in the processing of asymmetric supercapacitors.
Supplementary Table 1 presents a comparison of our technology with other processes in terms of the size and the maximum resolution of the asymmetric supercapacitors fabricated. Our asymmetric MSCs are at the micron scale, which is dozens or even hundreds of times smaller than conventional asymmetric  [19] In the highresolution transmission electron micrographs of typical orthogonal MoO 3 nanorods, lattice fringes are clearly visible. The distance between adjacent fringes is approximately 0.23 nm, indicating that the nanorods grew in the (200) direction. [20] MT was found among laser-induced materials, but the morphology differed due to the in uence of laser power and pulse delay. The transmission electron micrographs revealed that the corresponding metal oxides were formed during the laser ablation of MXene/1T-MoS 2 . We speculate that the temporally and spatially shaped femtosecond laser rst excited a large number of free electrons. After laser pulse bombardment, these free electrons increased in number. The extremely high instantaneous power of the femtosecond laser pulses generated defects in the Mo-S and Ti-C bonds. The numerous free electrons facilitated the combination of the femtosecond laser pulses with oxygen in the air. Moreover, the femtosecond laser pulses ionized to the oxygen to produce oxygen bonds. Thus, the original MXene material was easily transformed into metal oxide.
To further explore the effect of laser ablation on MXene/1T-MoS 2 , X-ray photoelectron spectroscopy (XPS) was conducted. Studies have reported that the binding energy of 1T-MoS 2 is almost 0.9 eV lower than that of 2H-MoS2 in non-laser-processed materials. [19,21] As presented in Figure 3a, the high-resolution XPS spectra of Mo 3d could be deconvoluted into peaks assigned to Mo 3d 3/2 and Mo 3d 5/2 . The peaks at 231.6, 232.8, 234.6, and 235.8 eV in various MT thin lms indicated that the Mo 3d 5/2−3/2 doublets corresponded to MoO 3 and MoS 2 (with Mo 5+ 3d 5/2 peaks at 231.6 eV, Mo 5+ 3d 3/2 peaks at 234.6 eV, Mo 6+ 3d 5/2 peaks at 232.8 eV, and Mo 5+ 3d 5/2 peaks at 235.8 eV, respectively). [19,24] . The content of Mo in distinct valence states could be summarized from XPS analysis. The Ti2p spectra con rmed the presence of TiO 2 . The peaks centered at 455.1 and 461.2 eV (Figure 3b) corresponded to Ti-C bonds. The peaks centered at 458.5 and 464.4 eV were assigned to Ti-O 2p 3/2 and Ti-O 2p 1/2 , revealing that the oxygen in TiO 2 resulted in the formation of C-Ti-O. [25,26] As shown in Table 1, the proportion of Mo uctuated with changes in laser power and pulse delay, con rming that the composition of mixed materials and the content of MoO 3 can be adjusted by modifying laser parameters. Results regarding the unprocessed MXene hybrid materials and the TM materials laser processed under various parameters were also summarized. After laser ablation, the Ti-C bond in MXene was substantially reduced. By contrast, the Ti-O bond was considerably increased, indicating the production of titanium oxide. As displayed in Figure 3c

Effects of Laser Parameters on Materials and Their Electrochemical Properties
When focused laser pulses are applied to MXene and 1T-MoS 2 composite materials, they not only cause changes in the material properties but also produce new laser-induced metal oxide materials. Controlling these composite materials through laser parameters and determining the optimal parameters are of great research relevance. In this study, as shown in Figure 4a, we analyzed changes in the Mo content in the composite material by adjusting the laser power and pulse delay. As the laser power was increased, the proportion of Mo 5+ and Mo 6+ increased gradually, whereas the Mo 4+ content initially decreased substantially and then remained stable. These results can be explained as follows: As the laser pulses acted on the material, Mo 4+ was oxidized and modi ed, leading to an increase in the valence state. Taken together with the XPS data, these results suggest that the modi ed Mo formed a more stable bond with oxygen, generating molybdenum oxide. We also analyzed the mixed materials generated by laser-induced MXene targets. As presented in Figure 4b, the proportion of Ti-C bonds in MXene decreased as the laser power was increased. At the same time, the Ti-O bonds increased gradually. This is in line with the premise that the laser pulses acted on 1T-MoS. In sum, metal oxides were formed during laser processing. When the laser power remained unchanged but the pulse delay was adjusted, a slight change was noted in the composite material. This is mainly related to the ionization of electrons and materials under the pulse delay. An increase in the pulse delay resulted in increased valence states and a more uniform distribution of Mo and Ti in the composite material. This also con rms that the pulse delay excited more other studies. [27,28] Small peaks of molybdenum oxide near 263, 342 and 831 cm −1 were assigned to the orthorhombic MoO 3 compound. [29] These characteristic peaks were located at 150, 198, 401, 515, and processed under various laser parameters, and the cyclic voltammetry (CV) curves are shown in Figure  4e. The MSCs had excellent electrochemical performance, which may be due to the laser ablationinduced production of multivalent molybdenum oxide in the hybrid materials. The multivalent metal oxides affected the electrochemical performance of the materials. Because of the material modi cation threshold, the femtosecond laser pulses fully oxidized the material. Moreover, to maximize electrochemical performance, the electrode material on the surface was not removed. Figure 4f demonstrates the in uence of laser parameters, including the laser pulse delay, on MSC performance.  3 MSCs. This is mainly attributable to the excellent conductivity and capacitance properties of two-dimensional materials; the conductivity of metal oxides is slightly inadequate in comparison. The galvanostatic charge-discharge (GCD) pro les of the two types of MSCs (Figures 5d and 5e) are consistent with previous results. A performance comparison of the two MSCs with differing electrode materials was conducted on the basis of the CGD pro les. To clearly observe the differences in performance, we compared the CV curves generated at the same scan rate and the GCD pro les established at the same current density (Figures 5g-5i).

Electrochemical Performance Of The Multitype Mscs
Next, the asymmetric MSCs were subjected to comprehensive electrochemical testing. As shown in Figure   6a, favorable capacitance characteristics were retained even after the voltage window was expanded from 1.2 to 1.8 V in 1M H 2 SO 4 aqueous electrolyte. This large voltage window contributed to the high energy density of the asymmetric MSCs. Through our approach, the shapes, number of ngers, and microscopic size of the interdigitated MSCs were controlled. As presented in Figure 2, interdigitated MSCs with various numbers of ngers were fabricated, and the in uence of the number of ngers on electrochemical performance was investigated. Curves in GCD pro les generated under the same current density of 1.8 V indicated favorable characteristics. The GCD pro les in Figure 6b indicated that MSCs with more ngers outperformed those with fewer ngers; this is related to the area of the active interface site in contact with the electrolyte. Multiple ngers can increase electrode-electrolyte contact and facilitate rapid charge transfer, thus enhancing electrochemical performance. CV curves were measured according to the change in scan rates. A rectangular shape and similar curves were noted (Figure 6c). The speci c capacitance results support that MSCs with more indexes have more favorable electrochemical performance. We examined the electrochemical properties of MSCs with four ngers. Figures 6d and 6e display the GCD pro les and CV curves corresponding to these MSCs under various current densities and scan rates, respectively. We determined the areal and volumetric capacitance of the MXene-derived  (Figure 6h). Notably, the MSCs retained more than 98.8% of the initial capacitance after 15,000 cycles. For comparison, we extracted several GCD pro les from the loop. They were almost consistent under a voltage window of 1.8 V. CV curves of asymmetric MSCs under differing bending states were generated (Supplementary Figure 10). The CV curves were generally consistent, indicating that the MSCs had excellent exibility and exural resistance. Figure 6i presents a Ragone plot comparing the energy and power density of our MSCs and other energy storage devices. [16,[31][32][33][34] The energy density of 0.495 Wh cm −3 achieved in the present study is several orders of magnitude higher than those of other capacitors or batteries. It is also substantially higher than those of MSCs presented in previous studies. In addition, our MSCs exhibited an excellent power density of 28295 W cm −3 , which is attributable to its favorable capacitance characteristics under a high scan rate. In sum, our MSCs have high potential for application to microscale energy storage devices.

Conclusion
Through our simple maskless patterning approach, high-performance multitype MSCs were prepared. Leveraging the unique advantages of temporally and spatially shaped femtosecond laser, the ultrafast fabrication of multipatterned MSCs was realized. Our method can be applied to various material systems, including to the construction of asymmetric electrode structures from laser oxidation materials. This is the rst speci c mention of micromachining and packaging in this paper. Are you referring to the proposed ultrafast fabrication method? Please review. This appears to better re ect your intended meaning. Please review. This is the idiomatic term. Please review. The meaning of "large cycles" is unclear. Please review this change.

MXene/1T-MoS 2 thin lm Preparation
MXene dispersion (2.5 mg mL −1 , 200-500 nm) purchased from Nanjing/Jiangsu XFNANO Materials Tech Co., Ltd was mixed with the suspended chemically exfoliated single-layer 1T-MoS 2 nanosheets dispersion purchased from Nanjing/Jiangsu XFNANO Materials Tech Co., Ltd. The two solutions underwent exfoliation for 5h, separately. Then, the two diluted mixed solutions were mixed together, treated by sonication for 2 h and stirred for 1 h. The prepared mixed solution was vacuum ltered by ber lter. About 6 h of ltration, a layer of mixed lm was produced, then it was vacuum-dried. Nitrocellulose membrane for vacuum ltration was purchased from Merck Millipore LTD. Sulfuric acid (95%-98%) was obtained from Sigma Aldrich and used to dissolve the cellulose lm when transferring the mixed lm. In a simple vacuum ltration process, MXene and monolayer MoS 2 nanosheets are ltered through a membrane with an aperture of 25 nm to form a stacked MXene/metal 1T-MoS 2 membrane. The thickness of this re-stacked lm is controllable, depending on the volume of the ltered solution. In our test, the thickness of the composite lm prepared by us is 1μm.
The Shaped femtosecond laser A Titanium sapphire laser regeneration ampli cation system was used to transmit a Gaussian beam with a central wavelength of 800 nm and a pulse duration of 35 fs. Holoeye Pluto (spatial light modulator) can receive the phase difference distribution of the load and re ect the beam away. The designed electrode shape determines the intensity distribution by locating a 256×256 pixel region to a black 1080×1920 background image. We use an improved Gaussian algorithm to optimize the algorithm by increasing the number of iterations and using a function to optimize the distance between the beam spots. So we can get different expected light elds. Then, the gray phase hologram is loaded onto SLM to transform the light eld of any geometry. The shape beam is focused by an Olympus objective lens (20×, NA = 0.45). The sample was placed horizontally on the six-axes translation stage (M840.5DG, PI, Inc.).
Characterization of laser-induced MXene/1T-MoS 2 The morphology and microstructures were characterized by scanning electron microscope (SEM) using SU8220 (Hitachi, Japan) by a Hitachi SEM in Tsinghua university. X-ray photoelectron spectroscopy (XPS) analysis was performed using a ESCALAB 250Xi spectrometer with a monochromatic Al Kα source (7.5 µm beam spot). Raman spectra were acquired using a Via-re ex spectroscopy with the excitation laser line at 532 nm. The XRD patterns were conducted on a D8 Advance (Bruker) with CuKa radiation. Using an Olympus metallographic microscope can take optical microscopy images. The Confocal Laser Scanning Microscopy used an MPLAPONLEXT x20 lens. The Raman spectroscopy investigations were performed using a Renishaw inVia Re ex spectrometer with laser wavelength of 532 nm.

Electrochemical characterization of the result micro-supercapacitors
Further analysis was performed to determine the current density using the software package NanoScope Analysis. Electrochemical testing was performed on a CHI760E electrochemical workstation connected through a Probe Station with polyamide-coated platinum probes (tip diameter, approximately 5 µm) as the current collectors. To ensure a stable electrochemistry environment, the open-circuit potential (Eocp) measurements were tested for one hour until the uctuation was of less than 10 mV in 10 minutes before every electrochemistry measurements. The electrochemical performance of the MSCs was measured in a two-electrode system, and analysed according to the cyclic voltammetry (CV), galvanostatic charge/discharge (GCD) and electrochemical impedance spectra (EIS). The areal capacitance (mF cm −2 ) per electrode was derived from the CV and GCD tests by using Eqs. (1) and (2), respectively, as follows: where I, ϑ and V represent the current applied, scanning rate and voltage (Vf and Vi are the nal voltage and initial voltage).
where I is the discharge current, and dV/dt is the slope of the discharge curve. Cycling stability measurements were performed by repeating constant current charge-discharge at 1 mA for 12,000 cycles. The energy densities (mWh cm −2 ) of the supercapacitors were calculated according to the following equations: where ∆E represents the operating voltage window. Therefore, the power density (μWh cm −2 ) of the obtained supercapacitor was obtained as follows: where t represents the discharge time (t = ∆V/ϑ).

Declarations Data availability
All relevant data that support the plots within this article and other ndings of this study are available from the corresponding authors upon request. Table   Table 1 is available in the supplementary les section. Figure 1 Schematic of the SLM-based maskless patterning method for the ultrafast manufacturing of multitype MSCs. a) The original Gaussian laser is transformed by the Michelson interferometer into a double pulse with a pulse delay. It then passes through the SLM and is transported to the objective lens by the 4f system to realize micro/nano processing. b) The Schematic of the laser-induced synthesis of materials for different MSCs. c) The magni ed image of the objective lens and the processed sample can be processed within an extremely short period of time by controlling the 1, 2, and 3 subpulses to obtain various types of MSCs.