A roll-to-roll sustainable multilayer deposition assembly method of nanomaterials

Abstract

The application discloses a kind of nanometer material's roll-to-roll sustainable multilayer deposition assembly method, first two-dimensional nanometer material to be transferred is dispersed in volatile organic solvent and homogenized, and the dispersion of sample is obtained;Based on injection / extrusion pump with constant volume flow sampling, and glass flow guide is arranged below the sampling port to reduce droplet into interface disturbance, and induce laminar flow to develop;Then in situ observation is arranged on the sample side of Brusen angle microscope BAM, when continuous dense film appears, start roll-to-roll traction;Along the direction of film movement, heating unit is configured to dry with speed linkage to fix film layer structure;Finally, under the condition of constant tension and damping vibration suppression, film layer is uniformly wound;Afterwards, the wound film is returned to the sample side by reversing the drive of the winding and unwinding mechanism, and the above process is repeated to achieve the multilayer continuous deposition of two-dimensional sheet nanometer material on the base without interruption.

Description

Technical Field

[0001] This invention relates to the field of nanomaterial thin film preparation and interface self-assembly technology, specifically to a roll-to-roll sustainable multilayer deposition and assembly method for nanomaterials based on Langmuir technology. This method utilizes the liquid-gas interfacial tension driving principle and employs a roll-back deposition process to achieve continuous, controllable, and large-area multilayer deposition of two-dimensional sheet nanomaterials (such as graphene oxide, MXene, etc.) on flexible or rigid substrates, belonging to the field of nanofabrication and flexible electronic device fabrication. Background Technology

[0002] Langmuir–Blodgett (LB) thin film technology is a self-assembly deposition method for molecules or nanosheets based on the liquid-gas interface, enabling the ordered construction of thin films at the molecular level. This technology has broad application prospects in flexible electronics, sensors, optoelectronic devices, and membrane separation.

[0003] In the preparation of two-dimensional nanomaterials (such as graphene oxide, MXene, and carbon nanosheets), Langmuir technology offers significant advantages over traditional methods like chemical vapor deposition (CVD and PVD). First, its self-assembly characteristics based on the liquid-gas interface enable highly oriented and densely packed two-dimensional sheet materials on a water surface, facilitating the formation of single-layer or multi-layer films with excellent continuity and large-area uniformity. Second, the mild processing conditions of Langmuir technology avoid the damage to flexible substrates or organic functional groups caused by high-temperature and high-energy environments, making it particularly suitable for solution-processable two-dimensional material systems. Third, the LB method allows for precise control of film thickness and layer number by adjusting parameters such as spreading concentration, surface pressure, and transfer rate, providing unique controllability for the functional assembly of two-dimensional materials. Compared to chemical vapor deposition, it consumes less energy, has a smaller environmental impact, and is compatible with various solution systems and heterogeneous interface structures, thus holding significant potential in the fabrication of flexible electronics, transparent conductive films, and optical components.

[0004] However, traditional Langmuir nanofilm deposition techniques have certain limitations. Both vertical sampling (Langmuir-Blodgett technique) and horizontal sampling (Langmuir-Schaefer technique) suffer from low production efficiency and low reproducibility, limiting the deposition and assembly of Langmuir-based nanomaterials to the laboratory stage and hindering large-scale industrial applications. Furthermore, current roll-to-roll production methods for Langmuir technology have numerous limitations: Existing Langmuir roll-to-roll deposition technology cannot achieve truly continuous film deposition. Most Langmuir roll-to-roll instruments currently in use employ a barrier-driven method for transferring nanomaterials. Films deposited in this way require periodic repositioning, and the resulting liquid surface disturbances during repositioning cause periodic local defects on the nanofilms, making true large-area production impossible.

[0005] Multilayer deposition of a single nanomaterial is not feasible. Existing roll-to-roll techniques focus only on single-layer film deposition of a single material; however, no clear and efficient solution has yet been proposed for multilayer deposition of a single material.

[0006] Deposition parameters are difficult to quantify, have low reproducibility, and result in poor film quality stability. In traditional Langmuir roll-to-roll systems, deposition quality relies heavily on operator experience, lacking a unified quantitative model for the coupling relationships between multiple factors such as liquid surface tension, transfer angle, film / feed rate ratio, solvent evaporation rate, and diffusion concentration. Because these parameters interact and change dynamically in real time, it is difficult to establish a stable control window, leading to significant fluctuations in film thickness, coverage, and uniformity with each deposition.

[0007] Therefore, I propose a sustainable assembly method for roll-to-roll continuous deposition of nanomaterials driven by a liquid surface tension field under barrier-free conditions. This method should possess characteristics such as low disturbance, controllable parameters, long-term operational stability, and multi-material compatibility, in order to overcome the scalability bottleneck of Langmuir technology in engineering applications. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by proposing a roll-to-roll sustainable multilayer deposition and assembly method for nanomaterials. This method uses the surface tension of organic solvents on the liquid surface as the driving force to achieve continuous, uniform, controllable, and reproducible deposition and assembly of two-dimensional nanomaterial films on flexible or rigid substrates. Furthermore, it utilizes a "rollback" technique to achieve multilayer continuous deposition and production of single nanomaterials, and is equipped with real-time monitoring / local evaluation and parameter quantification models to support long-term stable industrial production.

[0009] The objective of this invention is achieved through the following technical solution: a roll-to-roll sustainable multilayer deposition assembly method for nanomaterials, the method comprising: S1 Sample preparation: The two-dimensional nanomaterials to be transferred are dispersed in a volatile organic solvent and homogenized to obtain the dispersion for injection; S2 injection: Based on the injection / extrusion pump, the sample is injected at a constant volumetric flow rate, and a glass guide plate is placed below the injection port to reduce the disturbance of the droplet at the interface and induce laminar flow. S3 Online Observation and Start-up: Brewster Angle Microscope (BAM) is set up on the sample receiving side for in-situ observation. When a continuous dense film appears, roll-to-roll traction is started. S4 Directional Drying: Heating units are configured along the direction of film movement to perform speed-dependent drying in order to fix the film structure; S5 Film winding collection: The film layer is uniformly wound up under constant tension and damping vibration suppression conditions; S6 Secondary roll-back coating: The reverse drive winding and unwinding mechanism returns the wound film to the sample feeding side, repeating steps S1–S5 to achieve multi-layer continuous deposition of two-dimensional sheet nanomaterials on the substrate without interruption.

[0010] Furthermore, by increasing the injection volume flow rate Dispersion concentration Roll-to-roll linear speed With effective film width Combination is defined as surface density The overall parameters, and in The target range serves as the control benchmark for process tuning and cross-device migration, thereby enabling quantifiable control of film thickness, coverage, and number of layers.

[0011] Furthermore, the online observation uses the density threshold of the BAM (Body Aperture AM) as the trigger signal for the start-up and operation process. Once a continuous and dense interfacial film is observed at the sample collection point, roll-to-roll traction is initiated, causing the film to enter a stable continuous transfer state. The BAM image serves as an online quality signal for triggering and correcting subsequent parameters. The injection volumetric flow rate is then determined based on the characteristics of the BAM image. relative to the roll linear speed Through coordinated fine-tuning, a stable online closed-loop interface is formed at the forefront.

[0012] Furthermore, the glass guide plate mentioned in step S2 is a transparent flat plate structure, located below the injection port and tilted at a 30° angle towards the liquid surface in the tank, so as to expand the injection cross section and suppress the disturbance caused by the material entering the interface.

[0013] Furthermore, carbon fiber heating lamps (or equivalent heat sources) are arranged above the membrane along its movement direction to rapidly and directionally dry the newly transferred wet membrane, stabilizing the solvent evaporation rate and fixing the membrane structure, reducing the risk of stacking and pinholes; the drying temperature and... Interlocking control is used to avoid heat buildup and warping.

[0014] Furthermore, the winding and unwinding mechanism includes a constant tension and damping vibration suppression unit, an active wheel connected to a stepper motor, and a collection wheel that is a feeding wheel. By adding an elastic band to the collection wheel, friction is increased to achieve motion damping, thereby reducing the coupling of mechanical vibration and liquid surface disturbance and improving the consistency of film thickness / coverage.

[0015] Furthermore, by pulling the groove on the support, the deposition angle between the material and the thin film substrate can be changed, thereby achieving infinitely efficient adjustment of the deposition angle.

[0016] Furthermore, in step S1, ultrasonic crushing / dispersion is preferably used to obtain a stable colloidal dispersion, with particle size and concentration meeting the uniformity requirements for interfacial spreading and subsequent transfer.

[0017] Furthermore, a level is installed at the center of the support, and the four supporting legs of the support can be individually adjusted in height by rotation, achieving rapid leveling before material deposition. Compared with the prior art, the present invention has the following outstanding advantages: 1. Truly sustainable roll-to-roll deposition: Using tension-driven deposition instead of barrier reset eliminates surface disturbance during reset, enabling uninterrupted continuous production; 2. Low disturbance and stable interface: Glass guide plate + parameter linkage control Q_"in" and v_"r2r" enter the steady-state transition region under the BAM triggering mechanism, suppressing leading-edge instability and local stacking; 3. Rapid stacking of multiple layers of a single material: N-layer continuous deposition is achieved through rollback technology, which significantly shortens the cycle time and improves thickness controllability and interface integrity; 4. Parameters are quantifiable and processes are reproducible: Using σ (surface density) as the overarching parameter, supplemented by BAM / SEM to achieve closed-loop indexing, a clear operable window and tolerance band are provided, and cross-batch consistency is significantly improved; 5. Long-term stability and engineering applicability: Through the coordinated optimization of rollers / transmission / damping and temperature control, long-term continuous operation and film uniformity are significantly improved, laying the foundation for large-scale application. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 This is a schematic diagram of a roll-to-roll sustainable multilayer deposition assembly method for nanomaterials.

[0020] Figure 2 Graphene oxide samples obtained using the conventional Langmuir Blodgett horizontal deposition method ( Figure 4 (ab) and samples prepared using roll-to-roll persistent deposition assembly method ( Figure 4 Compare with cd in the middle.

[0021] Figure 3 The image shows an aluminum film coated with continuous graphene oxide material, prepared using the method of this invention, and SEM images of samples taken at various locations.

[0022] Figure 4 For the monolayer graphene oxide nanofilm prepared using the method of the present invention ( Figure 4 a) and bilayer graphene oxide nanofilms prepared using the rollback technique ( Figure 4 (b) in the middle.

[0023] Figure 5 The comparison images before and after SEM image processing allow for analysis of the film coverage.

[0024] Figure 6 These are thin film samples with different numbers of layers obtained after 1-4 roll-ups.

[0025] Figure 7 This is a schematic diagram illustrating the stepless adjustment of the deposition angle achieved by pulling the tank body. Detailed Implementation

[0026] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described below with reference to the accompanying drawings and examples. It should be understood that the specific examples described herein are merely illustrative and not intended to limit the invention.

[0027] This invention provides a roll-to-roll sustainable multilayer deposition and assembly method for nanomaterials, used for roll-to-roll sustainable deposition and secondary rollback coating of graphene oxide (GO) as the material, such as... Figure 1 As shown, unlike traditional barrier-driven systems, this method uses tension-driven technology instead of mechanical barrier-driven technology. It employs a barrier-free Langmuir roll-to-roll device, with the driving force derived from liquid surface tension and roll-up / unrolling traction. Continuous sample feeding via an injection / extrusion pump and constant-speed roll-up are achieved. Through coordinated control of the sample feeding rate and roll-up linear velocity, interfacial stability is maintained, interfacial disturbances are suppressed, and a reproducible process window is established. A Brewster angle microscope (BAM) is used at the roll-up end for in-situ triggering and monitoring, while a carbon fiber heating lamp is used at the drying end for directional drying. The entire system features vibration suppression and constant tension structures. Online BAM triggering and monitoring, along with offline SEM / electrical observation, form a quality closed loop for parameter tuning and establishing a reproducible window. To ensure stability during long-term continuous operation, this invention preferably employs structural improvements such as high-strength roller materials and load-equalizing supports, optimized transmission / tensioning subsystems, roller damping for vibration suppression, and improved heating unit energy efficiency and temperature field homogenization. These improvements significantly reduce the coupling effect of mechanical vibration and liquid surface disturbance, enhancing the consistency of film thickness / coverage and long-term stability.

[0028] The specific implementation steps of the method of the present invention are as follows: S1 Sample Preparation (GO Dispersion Preparation) Weigh 18 mg of monolayer GO and disperse it in methanol to a target concentration of 0.5 mg / mL. Homogenize the mixture for the first time using an ultrasonic cell disruptor, then add an equal volume of deionized water for a second homogenization (using the same power and duration as the first homogenization) to achieve better dispersion stability and wettability for interfacial spreading while preserving the flake size. Allow the resulting dispersion to stand to remove bubbles before use.

[0029] S2 injection (continuous feeding + flow control) The dispersion is injected into an injection / extrusion pump, precisely driven by a stepper motor to achieve a constant volumetric flow rate. A glass guide vane is installed below the inlet to allow the liquid flow into the tank to spread into a near-laminar flow on the liquid surface, significantly reducing the disturbance at the droplet inlet interface. In this embodiment, to achieve the target surface density (see below), the typical settings are as follows: Injection flow rate : 0.10–15 mL / min; Effective film width 125 mm - 500 mm (effective opening between guide vane and trough); Roll-to-roll linear speed : 0.40–1.2 m / min.

[0030] Note: The above parameters are jointly tuned using the BAM trigger threshold and SEM coverage regression to ensure entry into a stable and continuous transfer zone.

[0031] S3 Online Observation (BAM-triggered Steady-State Transition) See Figure 5 In situ observations were performed using a Brewster angle microscope (BAM) on the sample receiving side; when a continuous, dense, and slowly moving interfacial film appeared in the BAM image (see... Figure 5 (The density state shown in b) initiates winding and unwinding to achieve steady-state continuous transfer. BAM observation data is also used for small-amplitude linkage regulation. and To maintain a dense and stable interface front.

[0032] S4 Directional Drying (Linked Linear Speed) Carbon fiber heating lamps are positioned above the interface film's operating path to directionally dry the wet film, thereby fixing the structure, stabilizing volatilization, and suppressing the risks of stacking and pinholes; temperature and linear velocity are linked (e.g., 120 °C, depending on the speed). (Fine-tuning within ±10 °C) ensures no heat buildup and warping.

[0033] S5 film collection (constant tension + vibration suppression) The dried and shaped film is wound up and evenly stacked on a winding shaft for collection. By adding an elastic band to the collection wheel, friction is increased to achieve motion damping. This constant tension and damping vibration suppression method ensures the consistency of linear speed and the temporal consistency of thickness / coverage, and the interlayer stacking is uniform, meeting the stability requirements of long-term continuous operation.

[0034] Surface density target and parameter generalization: To avoid empirical operation, sample introduction, linear velocity, and effective width are normalized, and the generalized quantity surface density is defined. (Mass flow rate of deposition per unit area), serving as a benchmark for production parameter tuning and cross-device migration, exhibits a monotonically coupled relationship with coverage, film thickness, and number of layers. It is constructed using surface flux and linear velocity. This method aims to guide parameter tuning and capacity scaling for different non-standard tanks and material systems; the optimal method was determined through multiple experiments in this embodiment. The target is approximately 136 mg / m³. 2 (Regarding the current GO system and target coverage / electrical performance indicators). In practice, this will be achieved through coordinated efforts. , , Effective membrane width Maintaining a closed loop between BAM triggering and SEM regression Stabilize within the target bandwidth to obtain a single-layer film with ≥85% coverage and low defect rate. Online linkage using the BAM criterion (density). , Fine-tuning; offline SEM is used for acceptance and regression to form a unified evaluation matrix of coverage and uniformity, and then the target interval and control bandwidth of σ are updated in reverse to establish a reproducible process window.

[0035] Specific surface density The calculation formula is as follows: The secondary roll-back deposition involves the rapid stacking of multiple layers of the same material. Specifically, after completing steps S1-S5, the drive wheel direction is reversed to roll the wound film back to the sample inlet, and steps S1-S5 are repeated to achieve the second layer deposition. To avoid brittle fracture caused by the accumulation of interlayer roughness and pore closure, this embodiment incorporates the following during the second deposition: Maintain at 90–100% of the initial target (preferably the same, but can be slightly reduced to ~0.9×), and keep the remaining parameters (base-liquid surface angle) unchanged. Drying temperature The BAM threshold remains unchanged. The rollback path requires no disassembly or reset, significantly shortening interlayer cycle time and reducing interface disturbance accumulation.

[0036] After the secondary coating is completed, samples are taken every 10 cm along the strip, and surface morphology is captured using SEM. To avoid subjective judgment, this invention employs an automated coverage evaluation method to segment the samples into substrate / single-layer / multi-layer regions and perform coverage statistics. An automatic image processing method is used to evaluate the coverage of the offline SEM images. This method includes: automatic ROI cropping and interference band removal, contrast-limited adaptive histogram equalization (CLAHE) and Gaussian denoising, and feature construction. (Brightness, texture smoothness = 1 − local variance, edge sparsity = 1 − gradient magnitude), EM / GMM or K-means unsupervised clustering and identification of basis clusters based on brightness and smoothness weights, differentiation of single-layer and multi-layer in non-basis regions using Otsu threshold, morphological opening and closing and minimum connected component screening, statistical analysis of basis / single-layer / multi-layer ratios and total coverage, and output of color overlay images and masks for each category. Its core principle is as follows (interfacing with production closed loop): 1. ROI Acquisition and Interference Removal: Automatically detects and trims the effective area (removing interference bands such as scale bars / footers); 2. Enhancement and Feature Construction: Grayscale images are subjected to Gaussian noise reduction and CLAHE adaptive contrast processing; three types of features are extracted: brightness (Normalized intensity); Texture smoothness (=1−local variance), used to distinguish the difference in roughness between the substrate and the lamellar layer; Edge sparsity (=1 − gradient magnitude), used to characterize the density at the edge of the sheet; Combination features are .

[0037] 3. Unsupervised clustering and basis identification: EM / GMM (alternate K-means) is used to cluster pixel features (K=3); basis clusters are automatically selected by basis scores with brightness as the main weight and smoothness as the weight; if the cluster area is too large / too small, a backoff strategy is triggered to ensure robust basis identification.

[0038] 4. Single-layer / multi-layer partitioning: Apply Otsu self-thresholding binary division to the enhanced grayscale in the non-substrate region to obtain single-layer and multi-layer masks; 5. Morphological and Connected Component Removal: Opening and closing operations and minimum area threshold are used to remove pseudo-small spots and obtain topologically consistent regions; 6. Statistics and Output: Calculate the base, single-layer, multi-layer ratios and total coverage, and export color overlay maps, mask maps for each category and ROI maps as inputs for batch comparison and regression.

[0039] This method, together with the online BAM criterion, forms an online-offline closed loop. In the interim study, it was used as an "automated quantitative method for coverage," unifying the statistical caliber of SEM images across batches and providing feedback. Control bandwidth.

[0040] See Figure 2 and Figure 6 This invention provides a single-layer deposition on... A schematic diagram showing a dense GO film with a coverage of ≥85% is provided. This invention reveals that the graphene oxide film prepared by this method and the graphene oxide film prepared by the traditional Langmuir-Blodgett method have very similar coverage, both greater than 85%. At the same time, the film prepared by this method achieves better monolayer properties (graphene oxide materials with different numbers of layers exhibit different colors under SEM, which can be combined with image analysis methods to distinguish between monolayer and multilayer regions). See Figure 3 In evaluating the stability of continuous deposition of nanomaterials, this invention uses a single layer of nano-graphene oxide material as the research object. A sustainable deposition experiment was conducted on an aluminum film 13cm wide and 50cm long. The final sampling results show that the method exhibits good stability and coverage in the continuous deposition of nanomaterials.

[0041] See Figure 4 After the second rollback, the coverage was further improved and the defect rate was controllable. The consistency between BAM triggering and SEM automatic evaluation was good. With the vibration suppression and constant tension design, the temporal consistency of film thickness and coverage was significantly improved under continuous long-term operation, forming a reproducible practical window.

[0042] See Figure 7 This equipment can adjust the horizontal distance between the roller that fixes the film in the tank and the guide roller on the right side by pulling the tank body, thereby achieving stepless adjustment of the deposition angle.

[0043] The above embodiments are used to explain and illustrate the present invention, but not to limit the present invention. Any modifications and changes made to the present invention within the spirit and scope of the claims shall fall within the protection scope of the present invention.

Claims

1. A roll-to-roll sustainable multilayer deposition assembly method for nanomaterials, characterized in that: The method includes: S1 Sample preparation: The two-dimensional nanomaterials to be transferred are dispersed in a volatile organic solvent and homogenized to obtain the dispersion for injection; S2 injection: Based on the injection / extrusion pump, the sample is injected at a constant volumetric flow rate, and a guide vane is set below the injection port to reduce the disturbance of the droplet at the interface and induce laminar flow. S3 Online Observation and Start-up: In-situ observation is conducted on the sample receiving side. When a continuous dense film appears, roll-to-roll traction is initiated. S4 Directional Drying: Heating units are configured along the direction of film movement to perform speed-dependent drying in order to fix the film structure; S5 Film winding collection: The film layer is uniformly wound up under constant tension and damping vibration suppression conditions; S6 Secondary roll-back coating: The reverse drive winding and unwinding mechanism returns the wound film to the sample feeding side, repeating steps S1–S5 to achieve multi-layer continuous deposition of two-dimensional sheet nanomaterials on the substrate without interruption.

2. The method according to claim 1, characterized in that: By increasing the injection volume flow rate Dispersion concentration Roll-to-roll linear speed With effective film width Combination is defined as surface density The overall parameters, and in The target range serves as the control benchmark for process tuning and cross-device migration, thereby enabling quantifiable control of film thickness, coverage, and number of layers.

3. The method according to claim 1, characterized in that: Online observation uses the density threshold of Brewster's angle microscope (BAM) as the trigger signal for the start-up and operation process, and the injection volume flow rate is determined based on BAM image features. relative to the roll linear speed Through coordinated fine-tuning, a stable online closed-loop interface is formed at the forefront.

4. The method according to claim 1, characterized in that: The guide plate mentioned in step S2 is a transparent flat plate structure, located below the injection port and set at an angle pointing towards the liquid surface in the tank, so as to expand the injection cross section and suppress the disturbance caused by the material entering the interface.

5. The method according to claim 1, characterized in that: The drying temperature of step S4 directional drying and Interlocking control is used to avoid heat buildup and warping.

6. The method according to claim 1, characterized in that: The winding and unwinding mechanism includes a constant tension and damping vibration suppression unit, an active wheel connected to a stepper motor, and a collection wheel that is a feeding wheel. By adding an elastic band to the collection wheel, friction is increased to achieve motion damping, thereby reducing the coupling of mechanical vibration and liquid surface disturbance and improving the consistency of film thickness / coverage.

7. The method according to claim 1, characterized in that: By pulling the groove on the support, the deposition angle between the material and the thin film substrate can be changed, thereby achieving infinitely efficient adjustment of the deposition angle.

Images