Self-supporting membrane filter sheet stripping system and method

Abstract

A self-supporting membrane filter sheet demolding system and method, comprising a fixing device, a clamping device and a liquid discharge device. The fixing device adopts a mounting ring, the clamping device adopts a single-sided clamping groove, and the liquid discharge device adopts a liquid discharge funnel with a fine hole filter plate. The vertical demolding balances the influence of the fluid on both sides of the membrane surface on the membrane during the demolding process, so that the external force on both sides of the membrane surface remains dynamic symmetry during the liquid surface drop process, thereby achieving balance and offset, while effectively avoiding the adverse effects of liquid surface tension changes. The clamping device adopts a single-sided clamping groove and a bottom hollow design, so that the filter sheet substrate can be uniformly dissolved and quickly removed. During the liquid discharge process, the filter plate with fine holes slows down the liquid flow to protect the membrane from the influence of liquid flow disturbance. Compared with the traditional floating method demolding mode, the present application reduces manual operation, reduces solution disturbance, has better controllability and anti-interference, and improves the preparation success rate of the self-supporting membrane filter sheet.

Description

Technical Field

[0001] This invention belongs to the field of precision optical components, specifically relating to a vertical membrane removal system and method for a self-supporting thin film filter. Background Technology

[0002] Self-supporting thin-film filters are important optical components in short-wavelength research, with film thicknesses typically on the order of hundreds of nanometers. The conventional fabrication process involves first depositing a film of the desired thickness onto a soluble substrate or a "release agent" using methods such as magnetron sputtering or electron beam evaporation. The substrate or "release agent" is then dissolved to obtain the self-supporting thin-film filter. Compared to filters with additional support structures, self-supporting filters generally suffer from lower mechanical strength, and the film typically experiences significant internal stress during fabrication, making it highly susceptible to breakage during release. Therefore, effective release devices and systems, as well as the reliability of release methods, are crucial for improving the success rate of self-supporting thin-film filter fabrication.

[0003] The most common method for film removal is the flotation method. This method involves slowly immersing the substrate coated with the film in a solution at a certain angle. As the substrate dissolves, the film gradually separates from the substrate at the interface between the liquid surface and the air. Once the substrate is completely detached, the film floats on the surface, and is then retrieved from the solution using an auxiliary structure such as a mounting ring. The main drawbacks of this method are: 1) It requires manual operation, resulting in poor controllability and repeatability, making it difficult to precisely control the substrate tilt angle and the rate of film separation; 2) During the retrieval of the film using the mounting ring, the film is highly susceptible to damage from external forces.

[0004] Anna Stolarz et al.'s paper (Stolarz A, Maier-Komor P. "Large-area thin self-supporting carbon foils with MgO coatings". Nuclear Instruments and Methods in Physics Research Section A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2002, 480(1):194-198) proposed a relatively reliable improved floating method device system: in an empty liquid tank, the substrate coated with a thin film is placed at an angle on a support, and the flow rate of the liquid injected into the tank is controlled by a separating funnel. This device basically alleviates the problem of difficulty in controlling the tilt angle and the film removal rate; however, during the process of retrieving the film after removal, the device failed to propose an improvement scheme for the problem that the film is very easy to break when it comes into contact with the mounting structure.

[0005] The utility model patent CN207915878U from the Laser Fusion Research Center of the China Academy of Engineering Physics discloses a large-size ultrathin thin film stripping-retrieval device. This device achieves the film retrieval process by adjusting the positions of each moving unit and the angles of the rotating unit and the clamp, and the operation is simple and controllable. However, this device is mainly related to devices in the field of nuclear fusion, and the film stripping-retrieval process is for films made of organic polymer materials, and the retrieval process cannot obtain self-supporting films. Therefore, this device is not suitable for the preparation and research of self-supporting thin film filters based on metal or inorganic materials in the field of short-wavelength devices.

[0006] In addition to the aforementioned flotation method, there is an improved method for removing the film, the steps of which are as follows: First, the auxiliary structure, such as the mounting ring coated with adhesive, is bonded to the substrate (the coated side) with the film. Then, the entire assembly is placed in a solution. After the substrate dissolves and detaches, the film is removed from the solution as a whole using the mounting ring bonded to it. Alternatively, the solution can be drawn with a syringe to lower the liquid level until the film is completely exposed to the air. The main advantage of this method is that it avoids the manual operation of retrieving the film with the mounting ring in the flotation method and eliminates the adverse effect of applying additional stress to the film when the mounting ring is in contact with it. A 2006 paper from Tongji University (“Preparation and Measurement of Self-Supported Zr Filter Film for Soft X-ray Lasers” - *High Power Laser and Particle Beams*, Vol. 18, No. 6) was among the first to apply this method to the preparation of self-supported thin-film filters. However, this membrane removal method shares a common drawback with the floating method: during the membrane removal and removal process, the membrane, substrate, and mounting ring are all randomly tilted or nearly level in the solution. This results in uneven liquid flow rates and inconsistent liquid pressures on both sides of the membrane, as well as asymmetrical surface tensions on both sides during membrane removal. Such random unevenness and asymmetrical forces make the hundred-nanometer-scale membrane extremely prone to damage during this membrane removal process, greatly reducing the success rate of self-supporting membrane filter fabrication. Summary of the Invention

[0007] The purpose of this invention is to overcome the shortcomings of the prior art and propose a vertical membrane removal device system and method for self-supporting membrane filters: a mounting ring serves as a fixing device, a mold including a single-sided clamping groove and a hollow base serves as a clamp, and a drainage funnel with a fine-pore filter plate serves as a drainage device; the clamp keeps the membrane, substrate, and mounting ring upright, and the flow rate of the solution is controlled by the fine-pore filter plate and valve of the drainage funnel. This membrane removal method, used in solution environments and capable of stably removing soluble substrates from the membrane while ensuring membrane integrity, yields stable and practical self-supporting membrane filters at the hundred-nanometer scale.

[0008] The technical solution of the present invention is as follows:

[0009] A vertical membrane removal system for a self-supporting membrane filter is characterized by comprising a fixing device, a clamping device, and a draining device; the fixing device (mounting ring) is provided with a groove for filling adhesive to fix the membrane filter; the clamping device is used to vertically embed into the fixing device to clamp it; the draining device has a space to accommodate the fixing device, the clamping device, and the removal solution, and is provided with a valve device to control the outflow rate of the removal solution.

[0010] The mounting ring is a hollow ring with the same outer diameter as the membrane diameter, and a semi-circular groove is provided on one side of the ring surface for filling with adhesive; in addition, the mounting ring also serves to provide auxiliary support for the membrane at the edge of the membrane, while ensuring that the actual working area of ​​the membrane filter does not come into contact with the outside world.

[0011] The clamping device includes a clamp, a base, and an operating rod. The clamp has a slot for fixing a mounting ring on one side and is machined with negative tolerance. The base has a hollow design, with a threaded hole on the narrow side of the slot and an operating rod with a thread on one end.

[0012] The drainage device can be designed as a funnel with a flow-limiting valve, and a filter plate with fine pores is provided in the funnel.

[0013] The workflow of this invention is as follows:

[0014] 1) First, use epoxy resin adhesive to fill the semi-circular groove on the mounting ring by scraping; then, adhere the mounting ring to the film surface with the substrate. After the resin has cured for about two hours, you can use tweezers to pick up the glued mounting ring (and the film substrate) as a whole and embed it into the slot on the fixture.

[0015] 2) Use the draining device, close the flow-limiting valve at its bottom, and inject enough liquid into it to ensure that the liquid level completely covers the top of the installation ring that will be placed next.

[0016] 3) Using the operating lever, slowly and vertically place the clamp with the mounting ring and the film substrate into the draining device. At this time, the mounting ring on the clamp should always maintain a certain angle (range of 80-100 degrees) with the liquid surface, preferably 90° (perpendicular to the liquid surface).

[0017] 4) After the clamp is placed, wait for the substrate to dissolve naturally in the liquid until it detaches from the membrane surface. At this point, open the flow limiting valve to drain the liquid and adjust the flow rate appropriately. After the liquid has slowly drained or the liquid level is far below the bottom of the mounting ring, the clamp can be removed from the draining device. Finally, remove the membrane with the mounting ring from the clamp. At this point, the membrane removal process is complete.

[0018] The technical effects of this invention are:

[0019] 1) Effects and advantages of vertical demolding design: The membrane is always in a vertical state. Especially during the liquid drainage process, the pressure on both sides of the membrane surface is dynamically symmetrical and always consistent, thereby achieving balance and cancellation, which greatly reduces the disturbance of the membrane caused by the fluid on both sides of the membrane surface. In particular, it effectively alleviates the adverse effects of changes in the surface tension of the liquid on both sides of the membrane surface when the liquid level drops. At the same time, it also reduces the disturbance of the self-supporting membrane surface by various (random) factors during the demolding process, effectively avoiding membrane damage and thus greatly improving the success rate of the demolding process.

[0020] 2) The slot and bottom hollow design in the fixture: This design ensures smooth liquid flow, ensures uniform dissolution of the substrate and consistency of liquid flow rate on both sides of the film surface as much as possible, and the bottom hollow design can reduce the disturbance when the fixture is placed on the liquid surface.

[0021] 3) Groove design of the mounting ring: This design makes the coating process more stable, uniform and controllable, and improves the repeatability of the process, effectively avoiding the random overflow problem that often occurs when coating directly; any glue that overflows onto the membrane will directly reduce the actual effective working area of ​​the final finished membrane filter.

[0022] 4) Single-sided fixing slot design in the fixture: This design allows the slot to make physical contact only with the mounting ring, thereby achieving clamping and vertical fixation and ensuring the hydraulic balance on both sides of the film surface; more importantly, this design can achieve natural separation between the undissolved remaining part of the substrate and the film after the contact surface between the soluble substrate and the film is dissolved, with the assistance of the substrate's gravity, which greatly reduces the total time required for the entire demolding process.

[0023] 5) Fine-pore filter plate design in the drainage device: This design allows the liquid flow and its velocity generated during drainage to be evenly distributed on the horizontal surface. In particular, it effectively reduces any random disturbances caused by the fluid when the liquid level drops, thereby avoiding the adverse effects of these disturbances on the success rate of membrane demolding.

[0024] 6) Compared with the existing membrane removal methods and devices, the present invention maintains an optimized fixed angle between the membrane surface and the liquid surface throughout the entire membrane removal process and the integration process of the self-supporting membrane. This minimizes the adverse effects caused by the imbalance of liquid flow rate and pressure on both sides of the membrane and the asymmetry of liquid surface tension, resulting in better controllability and repeatability. It also eliminates random interference from human operation and greatly improves the success rate of self-supporting membrane filter preparation and the yield of finished products. Attached Figure Description

[0025] Figure 1 This is a schematic diagram of the vertical membrane removal system for the self-supporting thin film filter of Embodiment 1 of the present invention.

[0026] Figure 2 This is a schematic diagram of the clamping device in Example 1.

[0027] Figure 3 This is a top view of the draining funnel with a circular fine-pore filter plate of Example 1.

[0028] Figure 4 This is a front view of the mounting ring in Example 1.

[0029] Figure 5 This is a comparison image of the vertically delaminated sample (left image) and the traditional floating method delaminated sample (right image) from Example 1.

[0030] Figure 6 This is a schematic diagram of the clamping device in Example 2.

[0031] Figure 7 This is a top view of the draining funnel with a rectangular fine-pore filter plate in Example 2.

[0032] Figure 8 This is a front view of the mounting frame in Example 2. Detailed Implementation

[0033] To more clearly illustrate the structural details and technical solutions of the present invention, the present invention will be further described below in conjunction with embodiments and accompanying drawings.

[0034] A vertical membrane removal system for a self-supporting membrane filter includes a fixing device, a clamping device, and a draining device. The fixing device (mounting ring) has a groove for filling with adhesive to fix the membrane filter. The clamping device is used to vertically embed into the fixing device to clamp it. The draining device has a space to accommodate the fixing device, the clamping device, and the removal solution, and is equipped with a valve device to control the outflow rate of the removal solution.

[0035] Example 1

[0036] Please see Figures 1 to 4 , Figure 1 This is a schematic diagram of the vertical membrane removal system for the self-supporting thin film filter of Embodiment 1 of the present invention. Figure 2 This is a schematic diagram of the clamping device in Example 1. Figure 3 This is a top view of the draining funnel with a fine-pore filter plate in Example 1. Figure 4This is a front view of the mounting ring in Example 1. As shown in the figure, the fixing device in this example uses mounting ring 1, which is a hollow ring with an outer diameter the same as the membrane diameter. A semi-circular groove is provided on one side of the ring surface for filling with adhesive for fixing. This provides auxiliary support for the edge of the membrane filter and ensures that the actual working area of ​​the membrane filter is not in contact with the outside environment. The mounting ring can be made of polytetrafluoroethylene (PTFE), which has the advantages of being acid and alkali resistant and resistant to various organic solvents.

[0037] In this embodiment, the clamping device can be made of aluminum with an anti-corrosion coating, which ensures mechanical strength while also being stable in complex solution environments. It mainly consists of three parts:

[0038] A clamp 2 with a single-sided fixing groove 3 is used to fix the mounting ring. This groove 3 is machined with negative tolerances and designed to make contact only with the mounting ring for clamping and fixing; generally, there are no clamping restrictions on the substrate. The shape of the groove can be flexibly adjusted according to the shape characteristics of the release element.

[0039] The base 4, which provides stable support, adopts a large-area hollow design to ensure the stability of the liquid flow on both sides of the membrane as much as possible.

[0040] The control lever 5, used for transfer and control, is connected to the base at the bottom through conventional inlay structures such as threads, which allows for easy assembly and disassembly with bases of various custom fixture sizes and shapes.

[0041] A method for demolding a self-supporting film using the demolding system of the embodiment includes the following steps:

[0042] Step 1: Use a scraper to fill the groove of the mounting ring 1 with adhesive, and then directly bond the mounting ring 1 to the film surface with the soluble substrate. Epoxy resin adhesive is preferred. After two hours of polymerization and curing at room temperature, the bonded material can be picked up with tweezers and vertically fixed to the mounting ring and film substrate using clamp 2.

[0043] Step 2: Using the drain funnel 6, close its flow limiting valve 8, and add liquid so that the liquid level completely covers the top of the membrane to be placed.

[0044] Step 3: Use the operating lever to slowly lower the clamp, mounting ring, and film substrate into the liquid. At this time, the film on the clamp should always be perpendicular to the liquid surface (at a 90° angle).

[0045] Step 4: Wait until the soluble substrate dissolves and detaches. At this time, open the control funnel valve 8 to drain the liquid and adjust the flow rate appropriately. After the liquid has slowly drained or the liquid level is far below the bottom of the mounting ring, remove the clamp from the draining device. Finally, remove the film with the mounting ring from the clamp to complete the film removal.

[0046] As a comparison with the results of membrane removal using the traditional flotation method:

[0047] Figure 5 The left image shows a photograph of a sample successfully demembraned using the vertical demembranes removal method in Example 1. This contrasts sharply with the photograph of a sample (right image) obtained using the traditional floating method, where the membrane layer is ruptured in multiple places. Clearly, the vertical demembranes removal system and method of this invention are more effective and reliable, resulting in a more intact membrane surface and a higher success rate in filter preparation.

[0048] Example 2

[0049] To meet the diverse needs and application scenarios of membrane filter sheets, the design of the fixing, clamping, and drainage devices in the corresponding vertical membrane removal system can employ various combinations of shapes. For example, when performing membrane removal operations on membrane filter sheets with rectangular (square) substrates, the shape design of the fixing, clamping, and drainage devices in the vertical membrane removal system can refer to... Figures 6 to 8 As shown.

[0050] Figure 6 This is a schematic diagram of the rectangular clamping device, which uses a circular hollow base (or the one in Embodiment 1). Figure 2 Similarly, a rectangular hollow base (4) is selected. Figure 7 This is a top view of a draining funnel with a rectangular (square) fine-pore filter plate. Figure 8 The following is a front view of the mounting frame used in Embodiment 2: The mounting frame is a rectangular (square) frame with the same outer side length as the film side length; as can be seen from the figure, the mounting frame can also be designed without any grooves.

[0051] The function of each part of the vertical demolding system in this embodiment 2 and the specific operating steps of the vertical demolding method are the same as those in embodiment 1 above.

Claims

1. A membrane removal system for a self-supporting thin-film filter, characterized in that, Includes fixing devices, clamping devices, and drainage devices; The fixing device is provided with a groove for filling adhesive, thereby fixing the membrane filter sheet; The clamping device is used to vertically embed into the fixing device to achieve vertical clamping of it; The aforementioned draining device has a space to accommodate the fixing device, clamping device, and stripping solution, and is equipped with a valve device that can control the outflow rate of the stripping solution. The fixing device is a mounting ring (1), which is a hollow ring with the same outer diameter as the membrane diameter, and has a semi-circular groove on one side of the ring surface for filling with adhesive; at the same time, it provides auxiliary support for the edge of the membrane filter to ensure that the actual working area of ​​the membrane filter is not in contact with the outside world. The clamping device includes a clamp (2), a base (4), and an operating lever (5); The clamp (2) is concave and has a slot (3) to allow the mounting ring (1) to be embedded and fixed. The clamp (2) is fixed in the middle of the base (4), and the two sides of the base (4) are hollowed out to ensure the stability of the flow of the membrane filter solution on both sides; The operating lever (5) is connected to the base (4), and the other end extends out of the draining device for hand-held use; By controlling the operating lever (5), the membrane filter is immersed in the stripping solution in the draining device, and the membrane filter is kept at a certain angle to the plane of the stripping solution, with the angle ranging from 80 to 100 degrees.

2. The membrane removal system for the self-supporting thin-film filter according to claim 1, characterized in that, The slot (3) is machined with negative tolerance and only makes contact with the mounting ring to achieve clamping and fixing.

3. The membrane removal system for the self-supporting thin-film filter according to claim 1, characterized in that, The drainage device is a funnel (6), which has a filter plate (7) inside and a valve (8) at the bottom.

4. The membrane removal system for the self-supporting thin-film filter according to claim 3, characterized in that, The filter plate (7) has fine pores.

5. The membrane removal system for a self-supporting thin-film filter according to any one of claims 1-4, characterized in that, When the clamping device and the draining device are used together, multiple clamping devices can be used simultaneously in the same draining device to perform batch demolding.

6. A vertical membrane removal method for a self-supporting thin-film filter, comprising using the apparatus as described in any one of claims 1-5, characterized in that, Includes the following steps: Adhesion and fixing: Use a scraper to scrape the adhesive into the groove of the mounting ring (1), and then align the mounting ring (1) with the surface of the membrane filter with the soluble substrate and bond it so that the membrane filter contacts the adhesive in the groove of the mounting ring (1) to achieve adhesion and fixing; Dissolution: The mounting ring (1) with the membrane filter and soluble substrate is embedded and fixed in the slot (3) of the clamp (2); By moving the operating lever (5), the clamping device is slowly placed into the draining device containing the stripping solution and kept perpendicular to the liquid surface until the membrane filter is completely immersed in the stripping solution. Then wait for the soluble substrate to dissolve and fall off. Drainage: Control the flow rate of the stripping solution by rotating valve (8) to ensure that the liquid level drops slowly and uniformly until the membrane filter is completely removed from the slowly falling liquid level; at this point, the membrane removal process of the membrane filter is completed and the membrane is completely exposed to the air; After the stripping solution has been completely drained, move the operating lever (5) to remove the clamping device from the draining device.

7. The vertical membrane removal method for a self-supporting thin-film filter according to claim 6, characterized in that, The adhesive is an epoxy resin adhesive, which is polymerized and cured at room temperature.

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