A flexible sensor for a vacuum sheet transfer robot and a method of manufacturing and use thereof

Abstract

The present application relates to the technical field of sensors, more particularly to a flexible sensor for a vacuum sheet conveying manipulator, a preparation method of the flexible sensor, a vacuum chuck and a vibration detection and active vibration suppression system, and the technical scheme points are that the flexible sensor comprises at least two layers of flexible substrates, liquid metal circuits and a vacuum packaging layer, and the two layers of liquid metal circuits arranged oppositely are orthogonal to each other to form a capacitive sensing unit; the flexible sensor is embedded in the vacuum chuck and connected with a signal processing unit and a main controller to realize the collection of the vibration signal of the vacuum sheet conveying manipulator, vibration decoupling analysis and active vibration suppression control. The present application has the advantages of good adaptability to a vacuum environment, high vibration detection sensitivity, and the ability to realize multi-directional vibration decoupling and active vibration suppression.

Description

Technical Field

[0001] This invention relates to the field of sensor technology, and more specifically, to a flexible sensor for a vacuum transfer robot, its fabrication method, and its application. Background Technology

[0002] Dry etching is a core process in display panel manufacturing, accounting for over 90% of the market. In the G8.6 generation AMOLED production line, vacuum handling robots are responsible for the high-precision transfer of large-size glass substrates between multiple high-vacuum process chambers. Because the glass substrates are only about 0.5mm thick and have dimensions as large as 2200mm × 2250mm, the vibrations generated during robot operation can cause substrate bending, deformation, and positional shifts, directly affecting the accuracy and uniformity of the etching pattern. In severe cases, it can even cause the substrate to shatter, resulting in significant economic losses.

[0003] Currently, vibration monitoring technology is mainly divided into three categories: traditional rigid vibration sensors, ordinary flexible strain sensors, and triboelectric nanogenerator sensors. However, all of them have limitations in the application scenarios of vacuum transfer robotic arms. Traditional rigid sensors, such as piezoelectric ceramic sensors, MEMS accelerometers, and fiber optic sensors, need to be mounted on the joints, support arms, or motor ends of the robotic arm and cannot be directly attached to the surface of thin forks. Their sensitivity is generally above 10mg, making it difficult to capture micro-vibration signals below 1mg. Furthermore, they suffer from complex cable arrangements and high outgassing rates in high vacuum environments. Ordinary flexible strain sensors, made from materials such as conductive fibers, carbon nanotubes, and graphene, possess a certain degree of flexible attachment capability, but suffer from insufficient sensitivity, poor cycle stability, and a lack of specific vacuum environment adaptation design. The risk of material outgassing is significant, making it difficult to meet the cleanroom requirements of semiconductor processes. Triboelectric nanogenerator sensors can convert mechanical vibration into electrical signals for energy harvesting and detection. However, existing structures mostly employ rigid or semi-rigid structures, making it difficult to fit the complex curved surfaces of forks, and the sensitive layer's response sensitivity to micro-deformation is insufficient.

[0004] In addition, existing technical solutions such as CN223283754U, CN108560250A and CN121558168A, although they propose flexible vibration sensing structures or piezoresistive detection schemes respectively, generally suffer from problems such as large structural thickness, mismatch of the attachment interface, insufficient sensitivity of micro-vibration detection and poor adaptability to vacuum environment. In particular, they are difficult to meet the application requirements of in-situ, high-precision, multi-modal vibration detection at the contact interface between vacuum chuck and plate fork.

[0005] In summary, existing vibration sensors generally suffer from poor structural adaptability, difficulty in achieving bonding and integration with forks or vacuum chucks when used in G8.6 and above generation large-size vacuum handling robots for handling ultra-thin substrates, insufficient sensitivity in micro-vibration detection, and poor compatibility with high vacuum clean environments, making it difficult to meet the requirements for high-precision in-situ vibration monitoring. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a flexible sensor for vacuum transfer manipulators, its preparation method, and its application. This sensor has the advantages of good adaptability to vacuum environments, high vibration detection sensitivity, and the ability to achieve multi-directional vibration decoupling and active vibration suppression.

[0007] The above-mentioned technical objective of the present invention is achieved through the following technical solution: a flexible sensor for a vacuum transfer robot, comprising: at least two flexible substrates, each of which is provided with a closed microchannel; a liquid metal circuit filled inside the closed microchannel; and a vacuum encapsulation layer formed on the outside of the liquid metal circuit to seal the liquid metal circuit and make the flexible sensor suitable for operation in a vacuum environment.

[0008] The closed microchannels within each layer of the flexible substrate are arranged in an interdigital pattern. The extension directions of the two opposing liquid metal circuits are orthogonal to each other and are stacked on top of each other with the flexible substrate to form a capacitive sensing unit. The capacitive sensing unit is used to convert the elastic deformation of the flexible substrate into a capacitance change signal to realize vibration detection during the vacuum transfer process.

[0009] In one embodiment, the flexible substrate is a polyimide film or a modified material thereof, and the vacuum encapsulation layer is parylene or a derivative thereof.

[0010] Based on the same inventive concept, the present invention also provides a method for fabricating a flexible sensor, which includes the following steps:

[0011] S1. Prepare a flexible substrate with microchannel grooves on its surface;

[0012] S2. Cover the surface of the flexible substrate with a blank cover to seal it, so that the microchannel groove forms a closed microchannel, and open an inlet and an outlet at both ends of the closed microchannel.

[0013] S3. Liquid metal is filled into the sealed microchannel through the inlet and outlet to form a liquid metal circuit.

[0014] S4. The flexible substrate filled with liquid metal is subjected to vacuum-compatible encapsulation treatment, so that a vacuum encapsulation layer is formed on the outside of the liquid metal circuit to seal the liquid metal circuit and obtain a single-layer sensing semi-finished product.

[0015] S5. Align and stack the two sets of single-layer sensing semi-finished products, arrange the two sets of liquid metal circuits orthogonally, and then fix and encapsulate them to obtain the flexible sensor.

[0016] In one embodiment, step S1 specifically includes:

[0017] S11. Using electrohydrodynamic near-field direct writing technology, a microchannel male mold pattern with an interdigitated structure is printed on a rigid substrate using polycaprolactone as raw material. After cooling and shaping, a release agent is coated on the surface of the male mold.

[0018] S12. Prepare a modified polyimide solution and perform vacuum degassing treatment on the modified polyimide solution;

[0019] S13. Assemble and fix the microchannel male mold and the base mold to form a casting cavity, inject the degassed polyimide solution into the cavity, remove the solvent by vacuum and solidify the polyimide solution to form a mold, and obtain a flexible base with the microchannel grooves after demolding.

[0020] In one embodiment, step S1 specifically includes: using a femtosecond laser direct writing process to directly etch microchannel trenches on the surface of a flexible thin film to obtain the flexible substrate with microchannel trenches.

[0021] In one embodiment, in step S2, the inner wall of the microchannel trench is hydrophilically modified before sealing; in step S3, liquid metal is filled by differential pressure injection and pressure is maintained to eliminate dead corners; in step S4, the vacuum encapsulation layer is formed by parylene vacuum vapor deposition process, and vacuum annealing is performed after encapsulation to eliminate film internal stress.

[0022] Based on the same inventive concept, the present invention also provides a vacuum suction cup with vibration monitoring function, including a suction cup body and the above-mentioned flexible sensor; the flexible sensor is embedded in the adsorption surface of the suction cup body, and the sensing surface of the flexible sensor is flush with the adsorption surface of the suction cup body.

[0023] The flexible sensor is covered by a flexible shell, and the flexible substrate is fitted to the flexible shell.

[0024] The liquid metal circuit is led out to the outside of the suction cup body through a sealed wire disposed inside the suction cup body.

[0025] Based on the same inventive concept, the present invention also provides a vibration detection and active vibration suppression system for a vacuum transfer robot, including a vacuum suction cup as described above, a signal processing unit connected to the vacuum suction cup, and a main controller communicatively connected to the signal processing unit;

[0026] The signal processing unit is used to acquire the capacitance change signal output by the flexible sensor and convert it into a digital signal;

[0027] The main controller is used to extract capacitance features corresponding to different vibration directions based on the digital signal, and decouple the capacitance features by combining the orthogonal arrangement of the liquid metal circuit to obtain the corresponding vibration parameters; the main controller generates control signals according to the vibration parameters to adjust the motion parameters of the vacuum transfer robot and realize active vibration suppression.

[0028] The vibration parameters include vibration components in the vertical, lateral, longitudinal, and torsional directions.

[0029] In one embodiment, the signal processing unit includes a capacitance detection front-end module, a signal amplification module, a filtering module, and an analog-to-digital conversion module connected in sequence.

[0030] The capacitance detection front-end module is used to acquire the capacitance change signal output by the flexible sensor and output an analog electrical signal. The signal amplification module is used to amplify the analog electrical signal. The filtering module is used to filter out noise in the amplified analog electrical signal. The analog-to-digital conversion module is used to convert the processed analog signal into a digital signal.

[0031] In one embodiment, the capacitance detection front-end module uses a differential acquisition method to acquire the capacitance change signal output by the flexible sensor.

[0032] The aforementioned flexible sensor for a vacuum transfer robot, its fabrication method, vacuum chuck, and vibration detection and active vibration suppression system have the following beneficial effects:

[0033] Firstly, it boasts high detection accuracy and strong multimodal vibration recognition capability. This invention embeds a flexible sensor into the adsorption surface of a vacuum suction cup, enabling in-situ vibration detection at the interface between the glass substrate and the suction cup. This reduces signal attenuation and distortion caused by the detection position deviating from the vibration source in traditional sensors. Simultaneously, a capacitive sensing unit is formed by two layers of liquid metal circuits arranged orthogonally, which can identify four vibration modes: vertical, lateral, longitudinal, and torsional. This enables the detection of multi-directional vibration states of the glass substrate, improving vibration detection accuracy and multimodal vibration recognition capability.

[0034] Secondly, the fabrication process is simple and suitable for mass production. This invention uses near-field direct writing or femtosecond laser direct writing technology to fabricate microchannels, and combines liquid metal filling and vacuum-compatible encapsulation technology to complete the fabrication of flexible sensors. It does not require complex nanomaterial synthesis processes, the process flow is simple, it is easy to achieve standardization and mass production, and the material and manufacturing costs are low, which is conducive to industrialization and application.

[0035] Third, it exhibits good adaptability to vacuum environments and high system reliability. This invention employs a vacuum-compatible low-outgas material system and packaging structure to construct a flexible sensor, reducing the risk of small molecule volatile pollution. The sensor's embedding in the suction cup does not compromise the airtightness of the vacuum adsorption. Combined with differential signal acquisition, it improves the system's anti-electromagnetic interference capability, simplifies wiring design within the vacuum chamber, and reduces the impact on equipment operation, making it suitable for the demanding high-cleanliness and high-vacuum conditions of semiconductor manufacturing.

[0036] Fourth, it has a fast response speed, enabling real-time vibration detection and active vibration suppression. This invention uses liquid metal circuits, which are free from metal fatigue and response hysteresis, and have excellent dynamic response capabilities. By extracting features and decoupling vibration from the capacitance change signal output by the flexible sensor, the vibration parameters corresponding to the glass substrate are obtained, and the motion parameters of the vacuum transfer robot are adjusted in real time accordingly to achieve active vibration suppression and improve the stability of the transfer process. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the vacuum plate transfer robot in this embodiment;

[0038] Figure 2 This is a schematic diagram of the process for fabricating a flexible sensor based on the EHD near-field direct writing technology in this embodiment;

[0039] Figure 3 This is an exploded view of the vacuum chuck in this embodiment;

[0040] Figure 4 This is a flowchart of vibration signal processing and parameter mapping in this embodiment;

[0041] Figure 5 This is a flowchart of the vibration detection and active vibration suppression system in this embodiment.

[0042] In the diagram: 1. Fork; 2. Vacuum suction cup; 21. Suction cup vent; 22. Flexible shell; 23. PI flexible substrate; 24. EGaIn liquid metal circuit; 25. Parylene F vacuum encapsulation layer; 26. Suction cup base. Detailed Implementation

[0043] The present invention will now be described in detail with reference to the accompanying drawings and embodiments.

[0044] like Figure 3 As shown, the present invention provides a flexible sensor for a vacuum transfer robot, comprising at least two flexible substrates, a liquid metal circuit and a vacuum encapsulation layer.

[0045] Each layer of the flexible substrate contains a closed microfluidic channel, and the liquid metal circuit fills the interior of the closed microfluidic channel, thereby forming a flexible conductive path. Compared with flexible sensing structures using solid metal electrodes, the liquid metal used in this invention has good fluidity and deformability, which can reduce the risk of decreased conductivity due to crack propagation caused by material fatigue during repeated deformation. When the flexible substrate is subjected to mechanical forces such as bending, stretching, or compression, the liquid metal circuit can deform synchronously with the flexible substrate and maintain continuous conductivity, improving the stability of the sensor during vibration detection.

[0046] A vacuum encapsulation layer is formed on the outside of the liquid metal circuit to seal the liquid metal circuit, prevent the liquid metal from directly contacting the external environment, and reduce the risk of volatile pollution generated by the flexible sensor during operation in a vacuum environment, making the flexible sensor suitable for the working environment of a vacuum transfer robot.

[0047] In this system, the sealed microchannels within each layer of the flexible substrate are arranged in an interdigital pattern. The two opposing layers of liquid metal circuits extend orthogonally to each other and are stacked on top of and below the flexible substrate to form a capacitive sensing unit. When the glass substrate vibrates during vacuum transfer, the vibration acts on the flexible sensor, causing elastic deformation of the flexible substrate. This, in turn, changes the coupling area, spacing, or relative positional relationship between the two layers of liquid metal circuits, causing the capacitive sensing unit to output a capacitance change signal corresponding to the vibration state. By collecting and analyzing the capacitance change information corresponding to electrodes in different directions, the vibration state of the glass substrate in multiple directions, including vertical, horizontal, longitudinal, and torsional directions, can be detected, providing a data basis for subsequent vibration decoupling processing.

[0048] In this embodiment, the flexible sensor can be configured as a two-layer or multi-layer flexible substrate structure according to vibration detection requirements. In the multi-layer structure, at least two opposing flexible substrate layers contain liquid metal circuits, and the relative displacement change between the two liquid metal circuit layers forms a capacitive sensing unit, realizing the conversion of mechanical vibration signals into electrical signals. When multiple capacitive sensing units are provided, each capacitive sensing unit can be arranged along the stacking direction to improve vibration detection sensitivity or realize multi-dimensional vibration detection.

[0049] It should be noted that, in vacuum cleanroom applications, while multilayer flexible substrate structures can achieve different performance requirements through material composites, the interlayer encapsulation structure may increase the risk of gas release and cause losses in the transmission of mechanical vibration signals between different material layers. Therefore, this embodiment preferably adopts a two-layer flexible substrate structure to meet the vibration detection requirements while also considering the vacuum compatibility, structural reliability, and detection accuracy of the flexible sensor.

[0050] In this embodiment, the material of the liquid metal circuit is selected from one or more of room temperature liquid metal alloys and liquid metal composite materials doped with nano-conductive particles, which can further optimize the conductivity and sensing sensitivity of the electrodes. Specifically, the room temperature liquid metal alloy is at least one of gallium indium alloy (EGaIn), gallium indium tin alloy, and gallium zinc alloy; the nano-conductive particles include at least one of nano-copper particles and nano-silver particles.

[0051] In this embodiment, the flexible substrate is a polyimide (PI) film or a modified material thereof. Polyimide materials possess excellent flexibility, temperature resistance, and adaptability to vacuum environments, meeting the application requirements of vacuum transfer robots in confined internal spaces and high-cleanliness environments. Specifically, the outgassing rate of semiconductor-grade polyimide films can be as low as 5 × 10⁻⁶. -9 With a Pa·m³ / (s·cm²), total mass loss (TML) ≤ 0.1%, and condensable volatile matter (CVCM) ≤ 0.01%, these performance indicators are far superior to those of conventional flexible substrates such as polydimethylsiloxane (PDMS), and can meet the requirements of high-cleanliness and high-reliability applications such as semiconductor vacuum equipment and aerospace.

[0052] In this embodiment, the vacuum encapsulation layer is parylene or a derivative thereof. Parylene can be formed into a continuous, dense, pinhole-free thin film structure using a vacuum vapor deposition process, with an outgassing rate as low as 2×10⁻⁶. -9 With a strength of Pa·m³ / (s·cm²), a total mass loss (TML) ≤0.05%, and near-zero volatile matter concentration (CVCM), parylene is a typical flexible encapsulation material suitable for vacuum clean environments. In practical applications, parylene can be selected from at least one of the following: general-purpose monochloroparylene (Parylene C), high-temperature resistant dichloroparylene (Parylene D), and UV-resistant tetrafluoroparylene (Parylene F). In this embodiment, Parylene F is preferred as the encapsulation material for sealing liquid metal circuits, preventing liquid metal leakage, and meeting the requirements for long-term use in vacuum environments.

[0053] Based on the same inventive concept, such as Figure 2As shown, the present invention also provides a method for fabricating a flexible sensor, which is used to fabricate the above-mentioned flexible sensor. The fabrication method includes the following steps:

[0054] S1. Prepare a flexible substrate with microchannel grooves on its surface.

[0055] This step is the microfluidic structure forming process. For different mass production scales and customization needs, this embodiment provides two process solutions that can be implemented in parallel.

[0056] In one embodiment, step S1 is achieved through a near-field direct-write positive mold casting process, which is suitable for batch production needs, and specifically includes the following sub-steps:

[0057] S11. Using electrohydrodynamics (EHD) near-field direct writing technology, polycaprolactone (PCL) is used as raw material to print a microchannel male mold pattern with interdigitated structure on a rigid substrate. After cooling and shaping, a release agent is coated on the surface of the male mold.

[0058] Specifically, EHD near-field direct writing technology can achieve pattern printing with micron-level precision, accurately replicating the fine morphology of interdigitated microchannels; polycaprolactone material cools and solidifies quickly after melting and printing, with stable molding dimensions, and can be reused as a male mold, effectively reducing the mold cost for mass production; the release agent can ensure the integrity of the microchannel groove morphology during subsequent demolding, avoiding defects such as sidewall defects and pattern stretching.

[0059] S12. Prepare the modified polyimide solution and perform vacuum degassing treatment on the modified polyimide solution.

[0060] Specifically, the modified polyimide solution uses an alcohol-soluble or ester-soluble low-boiling-point solvent system, which is suitable for low-temperature curing processes and avoids the melting and deformation of the microchannel positive mold caused by high temperature. The micro air bubbles in the modified polyimide solution are removed by vacuum degassing to avoid pinholes and defects in the substrate after casting and curing, thus ensuring the mechanical uniformity and vacuum sealing performance of the flexible substrate.

[0061] S13. Assemble and fix the microchannel male mold and the base mold to form a casting cavity. Inject the degassed polyimide solution into the cavity. Remove the solvent under vacuum and allow the polyimide solution to solidify and form a mold. After demolding, a flexible base with microchannel grooves is obtained.

[0062] Specifically, by using vacuum solvent removal curing, polyimide film curing can be completed at low temperature, avoiding damage to the positive mold structure caused by high temperature processes. At the same time, the cured polyimide substrate has good density and low outgassing rate, which fully meets the material requirements of vacuum working conditions.

[0063] In another implementation, step S1 is achieved by femtosecond laser direct writing, which is suitable for rapid sample verification and small-batch customized chemical conditions. Specifically, the femtosecond laser direct writing process is used to directly etch microchannel trenches on the surface of the flexible film to obtain a flexible substrate with microchannel trenches.

[0064] Specifically, femtosecond laser etching is a cold processing technology. During the etching process, the heat-affected zone of the polyimide film is extremely small, which will not cause thermal deformation or thermal degradation of the substrate material. This ensures that the groove edges are neat and the dimensional accuracy is controllable. This process does not require the preparation of molds and casting cavities, has a short process flow, flexible pattern adjustment, and can quickly iterate microchannel structures with different parameters, shortening the R&D cycle. It can also produce ultra-thin sensor devices, which are suitable for the embedded integration requirements of vacuum chuck 2.

[0065] S2. Cover the surface of the flexible substrate with a blank cover to seal it, so that the microchannel grooves form a closed microchannel, and open the sample inlet and the sample outlet at both ends of the closed microchannel.

[0066] Furthermore, before sealing, the inner wall of the microchannel trench is hydrophilically modified to increase the surface energy of the inner wall, improve the interfacial wetting state between the liquid metal and the inner wall of the microchannel, avoid bubbles and flow interruption during the filling process, and ensure the continuity of the liquid metal circuit.

[0067] In practice, the sealing method can be selected according to the substrate process: for near-field direct writing casting substrates, vacuum-grade flexible adhesive is used for edge sealing in conjunction with U-shaped clamps, which has strong process tolerance and is suitable for batch preparation; for femtosecond laser direct writing ultrathin substrates, oxygen plasma bonding sealing is preferred, which has high bonding strength and no additional adhesive, thus avoiding adhesive outgassing and contamination of the vacuum environment.

[0068] S3. Liquid metal is filled into the closed microchannel through the inlet and outlet to form a liquid metal circuit.

[0069] Specifically, this step uses a differential pressure injection method to fill liquid metal and maintains pressure to eliminate filling dead zones. By creating a stable pressure difference through vacuuming at the sample outlet and applying positive pressure at the sample inlet, the liquid metal is driven to quickly and smoothly fill the entire microchannel. Maintaining pressure eliminates corner filling dead zones, avoids electrode open circuits, and ensures high yield in batch production.

[0070] S4. Vacuum-compatible encapsulation is performed on the flexible substrate after filling with liquid metal, so that the vacuum encapsulation layer is formed on the outside of the liquid metal circuit to seal the liquid metal circuit and obtain a single-layer sensing semi-finished product.

[0071] Specifically, a continuous and dense vacuum encapsulation layer is formed on the surface of a flexible substrate using a parylene vacuum vapor deposition process, which isolates the liquid metal circuit from the external environment. After encapsulation, the single-layer sensor semi-finished product is subjected to vacuum annealing to release the film internal stress generated during the encapsulation process and improve the structural stability of the vacuum encapsulation layer.

[0072] S5. Align and stack the two sets of single-layer sensor semi-finished products, arrange the two sets of liquid metal circuits orthogonally, and then fix and encapsulate them to obtain a flexible sensor.

[0073] Specifically, during the alignment process, the orthogonal angle and interlayer spacing of the two liquid metal circuits are controlled to ensure that the two liquid metal circuits are positioned relative to each other and maintain stable initial structural parameters. Since a vacuum encapsulation layer is formed on the surface of each single-layer sensing semi-finished product, when two sets of single-layer sensing semi-finished products are stacked, the vacuum encapsulation layer region between the two opposing liquid metal circuits serves as an intermediate dielectric layer, enabling the two liquid metal circuits to form a capacitive sensing unit. Vacuum-compatible bonding technology is used to fix the layers, preventing interlayer delamination under high vacuum and repeated deformation conditions, thus improving structural reliability. In this embodiment, the liquid metal circuit adopts a micro-channel structure, enabling the fabrication of linewidths of 20–50 μm. The overall thickness of the fabricated flexible sensor is ≤500 μm, meeting the requirements of a vacuum transfer robot for detecting micro-vibrations on extremely thin glass substrates.

[0074] The above preparation method will be further illustrated by the following two sets of examples:

[0075] Example 1: Preparation method of positive mold based on EHD near-field direct writing

[0076] 1. Preparation of near-field direct-write microchannel positive mold: Using EHD near-field direct-write technology and PCL as the raw material, a 50μm linewidth interdigitated microchannel positive mold pattern was printed on a clean glass substrate. Process parameters were set as follows: applied voltage 2.3kV, supply gas pressure 30kPa, nozzle-to-substrate distance 0.8mm, nozzle temperature 70℃, substrate moving speed 20mm / s, and acceleration 100mm / s². After printing, the substrate was placed in a clean environment for natural cooling and setting, then transferred to a fume hood. A thin layer of ultra-thin dry fluorinated release agent was uniformly sprayed onto the positive mold surface and allowed to stand for 10 minutes to allow complete solvent evaporation. This spraying-standing process was repeated twice to ensure the surface of the microchannel protrusions was completely covered by the release agent.

[0077] 2. Selection, preparation, and degassing of the soluble PI solution: To avoid melting and deformation of the microchannel positive mold due to high-temperature curing, an alcohol-soluble / ester-soluble modified PI solution was selected. The solvent system used was a mixture of low-boiling-point ethanol and propylene glycol methyl ether (PM). A PI solution with a solid content of 10 wt% and a viscosity of 400-600 mPa·s was prepared. The prepared PI solution was then subjected to vacuum degassing treatment at room temperature for 15 minutes to remove tiny air bubbles from the solution.

[0078] 3. PI Substrate Casting, Curing, and Demolding: The prepared microchannel male mold and PI substrate mold are assembled and fixed on a clean horizontal platform. The degassed PI solution is slowly injected along the inner wall of the mold. The cast mold is placed in a 25℃ vacuum drying oven. First, a vacuum is drawn for 5 minutes to remove the gas inside the cavity. Then, the pressure is slowly released to -0.1MPa and maintained for 4 hours to remove the solvent and solidify the PI solution. After vacuum curing, the mold is removed and allowed to stand at room temperature for 30 minutes to fully set before demolding, resulting in a flexible PI substrate with microchannel grooves on the surface.

[0079] 4. Microchannel inner wall pretreatment: Prepare a 2 mg / mL dopamine hydrochloride solution and adjust the pH to 8.5 using Tris-HCl buffer. Inject the dopamine hydrochloride solution into the microchannel of the flexible PI substrate and let it stand at room temperature in the dark for 4-6 hours to form an ultrathin hydrophilic film on the inner wall of the microchannel. Then rinse the residual solution in the channel with anhydrous ethanol and dry it at 60℃ to complete the modification treatment, thereby reducing the contact angle between the PI surface and the liquid metal. Cover the modified flexible PI microchannel surface with a blank PI cover sheet and seal it with U-clamps. Make holes at both ends of the microchannel as the inlet and outlet of the liquid metal.

[0080] 5. Differential Pressure Filling of Liquid Metal: Connect Luer connectors and PTFE tubing to two ports of the flexible PI microfluidic mold. One end serves as the inlet, connected to a centrifuge tube containing pretreated liquid metal; the other end serves as the outlet, connected to a waste collection bottle, and then connected to a precision vacuum valve, vacuum container, and vacuum pump via the PTFE tubing. All connections are sealed with vacuum grease to ensure no leaks. Close the vacuum valve and start the vacuum pump to evacuate the vacuum container to a -0.1MPa ultimate vacuum. Slowly open the vacuum valve to create a differential pressure, driving the liquid metal towards the outlet. When the liquid metal completely fills the channel and reaches the outlet, immediately close the vacuum valve and maintain the pressure for 1-2 minutes to eliminate dead zones at the channel corners, forming a continuous liquid metal circuit.

[0081] 6. Parylene F Vacuum Encapsulation: After vacuum drying pretreatment of the flexible substrate filled with liquid metal, it is placed in the deposition chamber. After sealing the chamber, the vacuum system is activated, evacuated to a high vacuum and stabilized at ≤1 Pa. Pressure holding and leak testing confirm that there is no gas leakage in the chamber. The pyrolysis chamber is heated to 680-720℃ and held at a constant temperature to completely pyrolyze the Parylene F dimer into active monomers. High-purity Parylene F raw material is accurately weighed according to the target encapsulation thickness of 5-10 μm. The vaporization chamber is heated to 140-150℃ using a stepped heating method to control a stable sublimation rate. In the room temperature deposition chamber below 30℃, the active monomers are deposited on the surface of the flexible substrate filled with liquid metal circuits, forming a tight-sealed encapsulation film on the outside of the liquid metal circuits. After the raw material is completely sublimated, the temperature is gradually reduced, and inert gas is slowly introduced to restore normal pressure before discharging. The mask in the electrode area is removed. Subsequently, the sample is placed in a vacuum annealing environment at 60℃ for 1-2 hours to eliminate the internal stress of the encapsulation film, obtaining a single-layer sensor semi-finished product.

[0082] 7. Double-layer orthogonal alignment and encapsulation: Another set of single-layer sensor semi-finished products with liquid metal circuit and encapsulation layer structure is prepared using the same process. After vacuum drying, flexible epoxy adhesive is uniformly thinly coated on the edge area of ​​both sets of samples. The liquid metal circuits of the two sets of samples are vertically placed and aligned and bonded. They are then placed in a 40℃ oven for curing for 30 minutes to ensure complete sealing between layers and no damage to the internal liquid metal circuit, finally obtaining a flexible sensor.

[0083] Example 2: Fabrication method based on femtosecond laser direct writing process

[0084] 1. Femtosecond laser etching of microchannels: Semiconductor-grade PI thin film is used as the substrate, and interdigitated microchannel trenches are directly etched on the surface of the thin film using a femtosecond laser direct writing process. The trench linewidth is controlled to be 20-50μm, and the linewidth accuracy is controlled at the 10μm level. After etching, the substrate is ultrasonically cleaned to remove etching residues and surface particles, resulting in a flexible PI substrate with microchannel trenches.

[0085] 2. Oxygen Plasma Bonding and Sealing of Openings: The etched PI substrate undergoes hydrophilic modification of its inner wall. A 2 mg / mL dopamine hydrochloride solution is prepared, and the pH is adjusted to 8.5 using Tris-HCl buffer. After being injected into the microchannels, the solution is allowed to stand at room temperature in the dark for 4-6 hours, rinsed with anhydrous ethanol, and dried at 60°C. Subsequently, the substrate and a blank PI cover plate are subjected to oxygen plasma surface activation treatment. After precise alignment, oxygen plasma bonding is used to achieve sealing, forming a closed microchannel. After bonding, inlet and outlet ports are opened at both ends of the microchannel.

[0086] 3. The subsequent liquid metal differential pressure filling, Parylene F vacuum encapsulation, and double-layer orthogonal alignment encapsulation processes are consistent with steps 5-7 in Example 1, and finally a flexible sensor suitable for embedding inside the vacuum chuck 2 is obtained.

[0087] Based on the same inventive concept, the present invention also provides a vacuum suction cup 2 with vibration monitoring function, including a suction cup body and the above-mentioned flexible sensor;

[0088] Specifically, such as Figure 3 As shown, the suction cup body includes a suction cup base 26, a flexible outer shell 22 covering the periphery of the flexible sensor, and a suction cup vent 21 communicating with the suction cup base 26. The flexible sensor is embedded inside the adsorption surface of the suction cup base 26, with its sensing surface flush with the adsorption surface. The flexible outer shell 22 is fitted to the periphery of the flexible sensor to buffer stress concentration between the sensor and the suction cup mounting structure, and to improve the structural reliability of the integrated sensor.

[0089] The flexible sensor comprises two stacked PI flexible substrates 23, an EGaIn liquid metal circuit 24 disposed within each PI flexible substrate 23, and a Parylene F vacuum encapsulation layer 25 formed on the outer surface of the EGaIn liquid metal circuit 24. The Parylene F vacuum encapsulation layer 25 seals the EGaIn liquid metal circuit 24. When the two PI flexible substrates 23 are stacked, the Parylene F vacuum encapsulation layer 25 located between the two EGaIn liquid metal circuits 24 serves as an intermediate dielectric layer to form a capacitive sensing unit. Due to the flexibility of the Parylene F material, its thickness changes with the deformation of the flexible substrate when subjected to vibration or pressure, causing a change in the spacing between the two EGaIn liquid metal circuits 24, thereby inducing a change in capacitance. Vibration signal detection is achieved by detecting this change in capacitance.

[0090] In one embodiment, the flexible sensor adapter suction cup structure is designed as a ring with an outer diameter of 39mm, an inner diameter of 28mm, and a thickness of 6mm. Multiple ring sensors are arranged in an array to achieve multi-point vibration detection on the entire adsorption surface, thereby improving the monitoring coverage and accuracy of large-size glass substrates.

[0091] The flexible sensor is surrounded by a flexible shell 22, and the flexible substrate is attached to the flexible shell 22. Specifically, the flexible shell 22 is a circular silicone shell made of low-volatility, vacuum-compatible flexible silicone rubber, which can buffer the stress at the embedding edge, ensure synchronous deformation of the sensor, and help improve the side vacuum sealing. After the shell is encapsulated, it forms a suction cup integrated liquid metal capacitive sensing unit, which can be directly assembled into the suction cup embedding groove.

[0092] The liquid metal circuit is led out to the outside of the suction cup body through a sealed wire located inside the suction cup body for connecting to an external signal acquisition device. Specifically, the sealed wire is preferably made of multi-strand stranded gold-plated oxygen-free high-conductivity copper (OFHC) core material, which has both low resistance and high anti-interference characteristics. The wire is concealed along a dedicated wiring groove inside the suction cup body, without damaging the original vacuum circuit structure and sealing performance of the suction cup. This ensures stable signal transmission while maintaining the vacuum cleanliness of the chamber and avoiding additional gas release contamination.

[0093] Furthermore, a connection structure is provided between the liquid metal circuit and the sealed wire; the connection structure includes a conductive connection layer and a sealing layer disposed outside the conductive connection layer. The conductive connection layer uses Ep-Tek H20E conductive adhesive to achieve a low-resistance and reliable connection, avoiding the impact of contact resistance fluctuations on detection accuracy; the sealing layer is formed by Parylene C vapor deposition, covering the connection node to isolate it from the outside environment, preventing liquid metal leakage and oxidation in a vacuum environment, and ensuring long-term working stability.

[0094] Based on the same inventive concept, such as Figure 4 and Figure 5 As shown, this invention also provides a vibration detection and active vibration suppression system for a vacuum sheet transfer robot, including the aforementioned vacuum suction cup 2, a signal processing unit connected to the vacuum suction cup 2, and a main controller communicatively connected to the signal processing unit. This system uses orthogonally arranged liquid metal capacitive sensors as its core, and forms a complete vibration suppression link through signal acquisition, feature decoupling, and motion closed-loop control, enabling real-time vibration monitoring and active suppression throughout the entire vacuum sheet transfer process.

[0095] Furthermore, the signal processing unit is used to acquire the capacitance change signal output by the flexible sensor and convert it into a digital signal that can be recognized by the main controller. Specifically, the signal processing unit includes a capacitance detection front-end module, a signal amplification module, a filtering module, and an analog-to-digital conversion module connected in sequence. The capacitance detection front-end module acquires the capacitance change signal output by the flexible sensor and outputs an analog electrical signal; the signal amplification module amplifies the analog electrical signal to improve the detection sensitivity of weak vibration signals; the filtering module filters out noise from the amplified analog electrical signal, retaining the valid signal corresponding to the vibration state; and the analog-to-digital conversion module converts the processed analog signal into a digital signal and transmits it to the main controller.

[0096] Furthermore, the capacitance detection front-end module employs a differential acquisition method to acquire the capacitance change signal output by the flexible sensor. Specifically, the capacitance detection front-end module uses a high-resolution capacitance detection chip to acquire the capacitance signals of the upper and lower electrodes of each sensing unit in differential acquisition mode, achieving a resolution of up to 1aF. This allows for precise capture of capacitance changes at the fF level caused by micro-vibrations. The sampling rate is set to 2kHz to meet the vibration dynamic monitoring requirements during high-speed wafer transfer.

[0097] In one implementation, the signal processing unit completes the initial acquisition and differential conversion of the capacitance signal through a high-resolution capacitance detection chip, outputs a weak differential analog electrical signal, amplifies the weak differential analog electrical signal through a low-noise instrumentation amplifier, filters out high-frequency electromagnetic interference and low-frequency harmonic noise in the vacuum environment through a fourth-order Butterworth bandpass filter, and finally converts the analog electrical signal into a digital signal through a high-precision analog-to-digital converter, and transmits it to the main controller through a shielded isolation link.

[0098] In one embodiment, the system adopts a vacuum-sealed air-to-air connector transmission scheme. The digital signal output by the analog-to-digital converter module is connected to the vacuum-sealed air-to-air connector through a shielded isolation link, and then transmitted to the main controller outside the vacuum chamber via the vacuum-sealed air-to-air connector.

[0099] Furthermore, the main controller is used to extract the capacitance features corresponding to different vibration directions based on digital signals, and to decouple the capacitance features by combining the orthogonal arrangement of the liquid metal circuit to obtain the corresponding vibration parameters; the main controller generates control signals according to the vibration parameters to adjust the motion parameters of the vacuum transfer robot and realize active vibration suppression; wherein, the vibration parameters include vibration components in the vertical, horizontal, longitudinal and torsional directions.

[0100] Specifically, based on the structural characteristics of the cross-finger electrodes and the array layout of the sensing units, the main controller extracts the core features corresponding one-to-one with the vibration parameters from the preprocessed capacitance signal, thereby decoupling the vibration state. The mapping relationship of vibration feature quantities in each direction is as follows:

[0101] Vertical vibration characteristic quantity: That is, the relative rate of change of capacitance between the vertically parallel interdigitated fingers is only related to the change in electrode spacing, corresponding to the vibration deformation in the vertical direction.

[0102] Lateral vibration characteristic quantities: That is, the relative rate of change of capacitance of the interdigitated electrodes in the X-axis direction is related to the change of the transverse facing area of ​​the electrodes, corresponding to transverse vibration in the X-axis direction;

[0103] Longitudinal vibration characteristic quantity: That is, the relative rate of change of capacitance of the interdigitated electrodes in the Y-axis direction, which is related to the change of the longitudinally facing area of ​​the electrodes, corresponding to the longitudinal vibration of the Y-axis;

[0104] in , , These represent the vibration characteristic quantities in the vertical, horizontal, and longitudinal directions, respectively. , , These represent the static initial capacitances of the sensitive interdigital electrode pairs in the Z, X, and Y directions, respectively. , , These represent the absolute changes in capacitance of the flexible sensor in the vertical, horizontal, and longitudinal directions, respectively. For torsion detection of the substrate, a four-point difference method based on vertical displacement is used to detect the out-of-plane warping torsion of the glass substrate (bending torsion around the X-axis, i.e., diagonal / lateral warping deformation of the substrate): Data from four sensors symmetrically distributed in a rectangle below the glass substrate are collected as follows:

[0105]

[0106]

[0107]

[0108] The torsional characteristic about the X-axis is:

[0109]

[0110] That is, the sum of the vertical displacements of the two rear forks is subtracted from the sum of the vertical displacements of the two front forks. When the whole vertical translation occurs, the four characteristic quantities change synchronously, and the common-mode displacement interference can be effectively suppressed through differential operation; when the substrate warps back and forth around the X-axis, the vertical displacements of the front and rear sides are reversed, the differential signals are superimposed and amplified, and the signal-to-noise ratio is significantly improved.

[0111] The torsional characteristic about the Y-axis is:

[0112]

[0113] That is, subtract the sum of the vertical displacements of the two right forks from the sum of the vertical displacements of the two left forks. Similarly, this can reduce common-mode interference such as overall vertical translation, temperature drift, and dielectric constant fluctuations, while retaining only the torsional component of warping around the Y-axis.

[0114] After signal preprocessing, the relative capacitance changes in the lateral, longitudinal, and vertical directions of each flexible sensing unit distributed on the four forks are calculated. These changes are then mapped using pre-calibrated displacement conversion coefficients to obtain the three-dimensional real-time vibration displacement of the glass substrate at each support point. Based on this, and taking advantage of the rectangular symmetrical spatial layout of the four forks, the vertical vibration displacements of different forks are grouped and differentially calculated to obtain the forward and backward warping torsion angles of the glass substrate around the X-axis and the left and right warping torsion angles around the Y-axis.

[0115] In practical applications, such as Figure 1As shown, the vacuum transfer robot includes a robot body, multiple forks 1, and vacuum suction cups disposed at the ends of each fork 1. The multiple forks 1 are arranged side-by-side along the robot body to carry and transport glass substrates. Each fork 1 has at least one vacuum suction cup at its end, which generates negative pressure through a vacuum path to adsorb and fix the glass substrate, thus completing the transfer of the glass substrate between different workstations. When the vacuum transfer robot transports the glass substrate, the vibration generated by the glass substrate is transmitted to the flexible sensor via the vacuum suction cups 2, causing elastic deformation of the flexible substrate. This, in turn, causes changes in the vertical spacing and horizontal facing area between the upper and lower orthogonally arranged liquid metal interdigitated electrodes, outputting capacitance change signals corresponding to the vibration amplitude, frequency, and direction, providing a data basis for vibration parameter calculation.

[0116] After completing the vibration parameter calculation, the main controller generates corresponding control signals based on the real-time vibration parameters to adjust the motion parameters of the vacuum wafer transfer robot, including adjusting the acceleration and deceleration curves of the robot's end effector, compensating for motion trajectory deviations, adjusting output torque, and correcting the suction cup posture, thereby actively offsetting the displacement fluctuations caused by vibration and realizing closed-loop active vibration suppression in the wafer transfer process.

[0117] In one specific implementation, the workflow of the vibration detection and active vibration suppression system is as follows:

[0118] 1. The vacuum suction cup 2 adsorbs the glass substrate, and the liquid metal flexible sensor undergoes initial deformation under the pressure of the glass substrate, thus completing the initial capacitance value calibration of the system;

[0119] 2. The vacuum transfer robot handles the glass substrate. The vibration generated during the handling process causes the flexible substrate of the flexible sensor to undergo corresponding compression and stretching deformation, and the sensor outputs a capacitance change signal.

[0120] 3. The signal processing unit sequentially completes signal acquisition, amplification, filtering, and analog-to-digital conversion to obtain a digital signal;

[0121] 4. The main controller extracts features and performs decoupling calculations on the digital signals using a preset vibration mapping model to obtain the real-time vibration parameters of the glass substrate;

[0122] 5. The main controller feeds back the vibration parameters to the motion control link in real time. By analyzing and processing the vibration parameters, it generates corresponding vibration reduction adjustment strategies and then outputs control signals to adjust the acceleration, output torque and other motion parameters of the vacuum plate transfer robot accordingly, so as to achieve active vibration reduction.

[0123] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention. Therefore, the scope of protection of this patent should be determined by the appended claims.

Claims

1. A flexible sensor for a vacuum transfer robot, characterized in that, include: At least two flexible substrates, each of which contains a closed microchannel; Liquid metal circuitry is filled inside the sealed microchannels; A vacuum encapsulation layer is formed on the outside of the liquid metal circuit to seal the liquid metal circuit and make the flexible sensor suitable for operation in a vacuum environment; The closed microchannels in each layer of the flexible substrate are arranged in an interdigital pattern, and the extension directions of the two layers of liquid metal circuits arranged opposite each other are orthogonal to each other, and they are stacked on top of each other with the flexible substrate to form a capacitive sensing unit. The capacitive sensing unit is used to convert the elastic deformation of the flexible substrate into a capacitance change signal to realize vibration detection during the vacuum transfer process.

2. The flexible sensor according to claim 1, characterized in that, The flexible substrate is a polyimide film or a modified material thereof, and the vacuum encapsulation layer is parylene or a derivative thereof.

3. A method for fabricating a flexible sensor, characterized in that, The method for fabricating the flexible sensor according to claim 1 or 2 includes the following steps: S1. Prepare a flexible substrate with microchannel grooves on its surface; S2. Cover the surface of the flexible substrate with a blank cover to seal it, so that the microchannel groove forms a closed microchannel, and open an inlet and an outlet at both ends of the closed microchannel. S3. Liquid metal is filled into the sealed microchannel through the inlet and outlet to form a liquid metal circuit. S4. The flexible substrate filled with liquid metal is subjected to vacuum-compatible encapsulation treatment, so that a vacuum encapsulation layer is formed on the outside of the liquid metal circuit to seal the liquid metal circuit and obtain a single-layer sensing semi-finished product. S5. Align and stack the two sets of single-layer sensing semi-finished products, arrange the two sets of liquid metal circuits orthogonally, and then fix and encapsulate them to obtain the flexible sensor.

4. The method for fabricating a flexible sensor according to claim 3, characterized in that, Step S1 specifically includes: S11. Using electrohydrodynamic near-field direct writing technology, a microchannel male mold pattern with an interdigitated structure is printed on a rigid substrate using polycaprolactone as raw material. After cooling and shaping, a release agent is coated on the surface of the male mold. S12. Prepare a modified polyimide solution and perform vacuum degassing treatment on the modified polyimide solution; S13. Assemble and fix the microchannel male mold and the base mold to form a casting cavity, inject the degassed polyimide solution into the cavity, remove the solvent by vacuum and solidify the polyimide solution to form a mold, and obtain a flexible base with the microchannel grooves after demolding.

5. The method for fabricating a flexible sensor according to claim 3, characterized in that, Step S1 specifically includes: using femtosecond laser direct writing technology to directly etch microchannel trenches on the surface of a flexible thin film to obtain the flexible substrate with microchannel trenches.

6. The method for fabricating a flexible sensor according to claim 3, characterized in that, In step S2, the inner wall of the microchannel groove is subjected to hydrophilic modification treatment before sealing; In step S3, liquid metal is filled using differential pressure injection, and pressure is maintained to eliminate filling dead zones; In step S4, the vacuum encapsulation layer is formed using a parylene vacuum vapor deposition process. After encapsulation, vacuum annealing is performed to eliminate internal stress in the film.

7. A vacuum suction cup with vibration monitoring function, characterized in that, Includes a suction cup body and a flexible sensor as described in claim 1 or 2; The flexible sensor is embedded inside the adsorption surface of the suction cup body, and the sensing surface of the flexible sensor is flush with the adsorption surface of the suction cup body. The flexible sensor is covered by a flexible shell, and the flexible substrate is fitted to the flexible shell. The liquid metal circuit is led out to the outside of the suction cup body through a sealed wire disposed inside the suction cup body.

8. A vibration detection and active vibration suppression system for a vacuum plate transfer robot, characterized in that, Includes the vacuum suction cup as described in claim 7, a signal processing unit connected to the vacuum suction cup, and a main controller communicatively connected to the signal processing unit; The signal processing unit is used to acquire the capacitance change signal output by the flexible sensor and convert it into a digital signal; The main controller is used to extract capacitance features corresponding to different vibration directions based on the digital signal, and decouple the capacitance features by combining the orthogonal arrangement of the liquid metal circuit to obtain the corresponding vibration parameters; the main controller generates control signals according to the vibration parameters to adjust the motion parameters of the vacuum transfer robot and realize active vibration suppression. The vibration parameters include vibration components in the vertical, lateral, longitudinal, and torsional directions.

9. The vibration detection and active vibration suppression system according to claim 8, characterized in that, The signal processing unit includes a capacitance detection front-end module, a signal amplification module, a filtering module, and an analog-to-digital conversion module connected in sequence. The capacitance detection front-end module is used to acquire the capacitance change signal output by the flexible sensor and output an analog electrical signal. The signal amplification module is used to amplify the analog electrical signal. The filtering module is used to filter out noise in the amplified analog electrical signal. The analog-to-digital conversion module is used to convert the processed analog signal into a digital signal.

10. The vibration detection and active vibration suppression system according to claim 9, characterized in that, The capacitance detection front-end module uses a differential acquisition method to acquire the capacitance change signal output by the flexible sensor.

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