Intelligent micro-clamping system and construction method and control method thereof

Abstract

The invention relates to the technical field of micro-operation and intelligent sensing cross equipment, in particular to an intelligent micro-clamping system and a construction method and a control method thereof. The intelligent micro-clamping system comprises a liquid metal pressure sensor, a clamping device, an electromagnetic driving device and a controller. The liquid metal pressure sensor is used for sensing the pressure of an object in real time. The clamp holder comprises a plurality of clamping jaws. The electromagnetic driving device is used for generating a directional magnetic field and providing constant current. The clamp holder drives the clamping jaws to open outwards to the maximum angle through the shape memory compound under the action of a directional magnetic field, and drives the clamping jaws to bend inwards to be closed to the same point after the resistance wire is heated to the temperature higher than the glass-transition temperature through constant current and the magnetic field is removed. And the controller is used for controlling the clamping device to execute clamping and releasing actions. According to the intelligent micro-clamping system, when an object is clamped, the pressure borne by the object can be sensed in real time, and meanwhile lossless clamping of the object is achieved as far as possible.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of micro-operation and intelligent sensing cross-device, and particularly relates to an intelligent micro-gripping system and a construction method and a control method thereof. BACKGROUND

[0002] Traditional micro-grippers are generally based on micro-electro-mechanical system (MEMS) technology, which adopts silicon-based materials and electrostatic or piezoelectric driving methods, has high machining precision and fast response speed, and is widely used in micro-assembly and biological operation fields. However, such grippers rely on rigid materials and open-loop control mode, and cannot realize real-time sensing of contact force, which easily leads to mechanical damage of the operation object (such as cells and microchips), and the performance of such grippers is significantly reduced in high-temperature and strong-magnetic-field environments. Therefore, flexible pressure sensors are found, which adopt polymer-based piezoresistive materials and realize sensing by resistance change caused by pressure. Such sensors have the advantages of being bendable and adaptive to cavities, but have problems such as large hysteresis error, narrow temperature resistance range and resolution priority, which makes it difficult to meet the high-precision detection requirements of micro-force in micro-operation. Even if the micro-gripper equipped with flexible sensors still has problems such as lack of real-time sensing ability, easy to cause damage to the operation object, and insufficient environmental adaptability. SUMMARY

[0003] In order to solve the technical problems of lack of real-time sensing ability and easy to cause damage to the gripped object when the micro-gripper is gripped in the prior art, the present application provides an intelligent micro-gripping system and a construction method and a control method thereof.

[0004] The application adopts the following technical scheme: an intelligent micro-gripping system comprises a liquid metal pressure sensor, a gripper, an electromagnetic driving device and a controller. The liquid metal pressure sensor is used for placing an object to be gripped and for sensing the pressure of the object in real time. The gripper is used for gripping the object placed on the liquid metal pressure sensor. The gripper comprises a plurality of expandable or closable clamping jaws. Each clamping jaw comprises a magnetic shape memory composite and a resistance wire embedded in the shape memory composite. The electromagnetic driving device comprises a magnetic field generating device for generating a directional magnetic field and a power supply for providing a constant current; the gripper is driven by the shape memory composite to expand outward to a maximum angle under the action of the directional magnetic field, and is driven to bend inward to a same point after the resistance wire is heated to a temperature higher than the glass transition temperature by the constant current and the magnetic field is removed. The controller is used for controlling the gripper to perform gripping and releasing actions. When performing the gripping operation, the controller controls the gripper to move towards the object while collecting the pressure value of the liquid metal pressure sensor, and controls the gripper to move upward by a preset distance and then starts the power supply when the pressure value exceeds a set pressure threshold, and removes the magnetic field when the resistance wire is powered and heated to a temperature higher than the glass transition temperature. When performing the releasing action, the controller first turns off the power supply and then starts the magnetic field generating device.

[0005] As a further improvement of the application, the liquid metal pressure sensor comprises a substrate and a protective layer, and a liquid metal conductive layer in a serpentine structure is arranged on one side of the substrate close to the protective layer; the protective layer is used for encapsulating the liquid metal conductive layer on the surface of the substrate; and the two ends of the liquid metal conductive layer are electrically connected to the controller.

[0006] As a further improvement of the application, the substrate is made of a PDMS film, the protective layer is made by spin coating a PDMS prepolymer onto the surface of the liquid metal conductive layer and solidifying, the thickness of the substrate is 0.5-1 mm, and the width of the liquid metal conductive layer is 25 μm.

[0007] As a further improvement of the application, the intelligent micro-gripping system further comprises a driving member connected to the gripper, and the controller controls the movement of the gripper through the driving member.

[0008] The application further provides a construction method of the intelligent micro-gripping system, which comprises: respectively constructing the liquid metal pressure sensor and the gripper as described above. The constructed liquid metal pressure sensor and the magnetic field generating device are respectively placed on an XYZ high-precision moving platform, and the constructed gripper is connected to the Z-axis moving part of the XYZ high-precision moving platform. The controller is electrically connected to the resistance wire on the gripper, the XYZ high-precision moving platform and the liquid metal pressure sensor.

[0009] As a further improvement of the application, one end of the liquid metal pressure sensor is connected to the input end of the controller through an amplification circuit; one end of the power supply is connected to the output end of the controller through a PWM signal, and the other end of the power supply is connected to the resistance wire; one end of the driving member is connected to the controller, and the other end of the driving member is connected to the holder.

[0010] As a further improvement of the application, the holder is constructed as follows: a PDMS film is flatly pasted on a glass slide substrate, and a layer of water-soluble adhesive tape is covered on the surface to obtain an intermediate sample. A femtosecond laser system is used to control and focus the light speed through diaphragms, half-wave plates, Glan prisms and high-speed galvanometer mirrors, and then the laser is focused on the intermediate sample through an f-theta field lens. The laser power is 300 mW, the scanning speed is 25 mm / s, and the surface of the intermediate sample is scanned according to the preset serpentine path, and the scanning is repeated multiple times to obtain the scanned intermediate sample. The scanned intermediate sample is ultrasonically cleaned, and then the ultrasonically cleaned intermediate sample is contacted with the liquid metal bath until the liquid metal fills the unscanned area of the intermediate sample, so that the liquid metal forms a liquid metal conductive layer on the intermediate sample. Copper foil electrodes are pasted on both ends of the liquid metal conductive layer, and PDMS prepolymer is spin-coated on the surface of the intermediate sample filled with liquid metal and solidified to obtain the liquid metal pressure sensor.

[0011] As a further improvement of the application, the holder is constructed as follows: a femtosecond laser is used to process a jaw mold pattern on a silica gel film. Shape memory epoxy resin, curing agent and Fe3O4 particles are mixed in a mass ratio of 3:1:4, and then vacuum degassing is performed to obtain a magnetic shape memory composite. The shape memory composite is poured into the mold, and after embedding the resistance wire, vacuum degassing, curing and demolding are performed in sequence to obtain the jaw. According to the above steps, a plurality of jaws are prepared, and the ends of the plurality of jaws are pasted to the same place to obtain the holder.

[0012] The application further comprises a control method of the intelligent micro-gripping system, which adopts the intelligent micro-gripping system as described above. The control method comprises: starting the magnetic field generating device, so that each gripper of the gripper is in a maximum open state; moving the gripper to directly above the liquid metal pressure sensor containing the to-be-gripped object through the controller. Sending a lowering instruction to the controller, and the controller controls the driving member to move the gripper downward and simultaneously acquires the pressure value of the liquid metal pressure sensor, and makes a judgment: if the pressure value is greater than a preset pressure threshold, the driving member moves the gripper upward by a preset distance. After the gripper moves upward by the preset distance, the power supply is started to heat the resistance wire until the temperature of the resistance wire is greater than the glass transition temperature, the magnetic field generating device is turned off, and the plurality of grippers on the gripper rapidly shrink and close to complete the grabbing of the to-be-gripped object located on the liquid metal pressure sensor.

[0013] As a further improvement of the application, the control method further comprises, when it is required to release the gripped object, first moving the gripped object to a preset placement point through the gripper. The power supply is turned off and the magnetic field generating device located at the placement point is started, and the plurality of grippers on the gripper are all expanded under the action of the magnetic field, thereby completing the release of the object.

[0014] The technical scheme provided by the application has the following beneficial effects: (1) The intelligent micro-gripping system provided by the application can realize the perception of the real-time contact force of the gripper to the object in the micro-newton force level when the gripper contacts the object during gripping, so that the liquid metal pressure sensor can sensitively and in real time perceive the contact force of the gripper to the object during movement, thereby avoiding damage to the object caused by the gripper during gripping. In combination with the gripper provided by the application, the gripper has a certain flexibility, thereby further avoiding damage to the object caused by the gripper during gripping, so as to realize real-time perception of the object to be gripped and non-destructive gripping as much as possible.

[0015] (2) The intelligent micro-gripping system provided by the application is made of a flexible material system, so that the intelligent micro-gripping system constructed by the application can stably work in a temperature range of -20℃ to 120℃, vacuum, strong magnetic field and other special environments. At the same time, the liquid metal pressure sensor can sensitively perceive the contact force between the gripper and the object, thereby avoiding damage to the object during gripping. Therefore, the intelligent micro-gripping system provided by the application can realize non-destructive gripping in a wide temperature range, and solves the problems of non-destructive grabbing and environmental adaptability in precise operation.

[0016] (3) The control method of the intelligent micro-gripping system provided by the application, through the controller, the gripper, the electromagnetic driving device and the liquid metal pressure sensor are electrically connected respectively, so that the controller first controls the gripper to slowly move towards the to-be-gripped object located on the liquid metal pressure sensor before gripping, and simultaneously senses the pressure value of the liquid metal pressure sensor in real time, and when the contact force between the gripper and the object is greater than 0.0168kPa, the gripper is controlled to move upward by a preset distance (such as 0.1mm), this setting can determine that the gripper has contacted the object, and since the pressure threshold is set to 0.0168kPa, even if the gripper contacts the object, since the contact force is very small, the object will not be damaged basically. In addition, when the pressure value (contact force between the gripper and the object) sensed by the liquid metal pressure sensor is greater than 0.0168kPa, the controller can immediately control the gripper to move upward, which can further avoid the gripper from touching the object and causing damage to the object while keeping the gripper capable of gripping the object. Therefore, the gripper of the present application can realize non-destructive and rapid gripping of the object. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 The structure schematic diagram of the intelligent micro-gripping system provided in embodiment 1 of the application is built in the actual use process.

[0018] Figure 2 The frame diagram of the intelligent micro-gripping system provided in embodiment 1 of the application when each component is connected.

[0019] Figure 3 The pictures of the liquid pressure sensor provided in embodiment 1 of the application in different states during preparation.

[0020] Figure 4 The step flow chart of the control method of the intelligent micro-gripping system in embodiment 2 of the application.

[0021] Figure 5 The pictures of the gripper of the intelligent micro-gripping system provided by the application in the process of gripping 100μm microspheres.

[0022] Figure 6 The pictures of the gripper of the intelligent micro-gripping system provided by the application in the process of gripping 5μL droplets.

[0023] Figure 7 The pictures of the gripper of the intelligent micro-gripping system provided by the application in the process of gripping biological samples.

[0024] Figure 8 The pictures of the gripper of the intelligent micro-gripping system provided by the application in the process of gripping 10 grams of weights.

[0025] Figure 9 Pictures taken by the gripper of the intelligent micro-gripping system provided by the present application in the process of clamping 100 grams of gualou stone.

[0026] Figure 10 Pictures taken by the gripper of the intelligent micro-gripping system provided by the present application in the process of clamping other different objects. DETAILED DESCRIPTION

[0027] Hereinafter, the present application will be further described in conjunction with specific embodiments, and it should be noted that the following described embodiments or technical features can be combined in any manner to form new embodiments without conflict.

[0028] In the description of the present application, it should be noted that, for orientation words, such as the terms "center", "transverse", "longitudinal", "length", "width", "thickness", "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", etc. indicate the orientation and positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and cannot be understood as limiting the specific protection scope of the present application. The terms "first", "second", etc. in the specification and claims of the present application are used to distinguish similar objects, and do not necessarily describe a specific order or sequence. The terms "include" and "have" and any variations thereof in the specification and claims of the present application are intended to cover non-exclusive inclusion, for example, a process, method, system, product or device that includes a series of steps or units does not necessarily limit to those steps or units clearly listed, but can include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0029] Embodiment 1 The present embodiment provides an intelligent micro-gripping system, please refer to Figure 1 and Figure 2 which includes a liquid metal pressure sensor, a gripper, an electromagnetic driving device, and a controller.

[0030] The liquid metal pressure sensor is used to place the object to be gripped and to sense the pressure of the object in real time. The thickness of the liquid metal pressure sensor can be 25 μm, and the resolution can be 0.0168 kPa. The liquid metal pressure sensor is electrically connected to the controller, and the liquid metal pressure sensor is used to convert the weak resistance change signal sensed into a voltage signal of the order of volts through an amplification circuit and deliver it to the controller for processing. The controller converts the input voltage signal into a pressure value.

[0031] One end of the liquid metal pressure sensor can be connected to the controller through an amplification circuit. In the present solution, the amplification circuit can include a Wheatstone bridge and an instrument amplifier. The output end of the liquid metal pressure sensor can be connected to a high-precision Wheatstone bridge, and the differential signal output by the Wheatstone bridge can be connected to the input end of an instrument amplifier (such as ADI's AD620), and the gain of the instrument amplifier is set to 1000 times. Through the above operation, the weak resistance change signal (0.1 mΩ level) sensed by the liquid metal pressure sensor can be amplified to a voltage signal of the order of volts. The output end of the instrument amplifier can be connected to the analog-to-digital converter (ADC) pin of the controller, and through the analog-to-digital converter pin, the analog voltage signal can be converted into a digital signal for the processor in the controller to judge.

[0032] The liquid metal pressure sensor can be made by femtosecond processing. Please refer to Figure 3 , and the specific processing method can be as follows: (1.1) Prepare a PDMS film with a thickness of 0.5-1 mm, and paste it flat on a glass slide substrate, and then cover a layer of water-soluble tape on the surface of the PDMS film, as shown in Figure 3 part (a); (1.2) Use a femtosecond laser system with a center wavelength of 800 nm, a pulse width of 100 fs, and a repetition frequency of 1 kHz, and control the light speed and focus through an aperture, a half-wave plate, a Glan prism, and a high-speed galvanometer. Finally, through an f-theta field lens (focal length 100 mm), the laser spot diameter is about 30 pm, and the laser is focused on the surface of the PDMS film. (1.3) Control the laser power at 300 mW, and the scanning speed is 25 mm / s. On the surface of the PDMS film covered with water-soluble tape, a serpentine path with a preset line width of 25 pm is scanned, and after 6 cycles, the scanned intermediate sample is obtained, as shown in Figure 3 part (b). The area treated by laser has a micro-nano rough structure, which significantly reduces the adhesion of liquid metal, while the untreated area maintains high adhesion. (1.4) After scanning processing, the scanned intermediate sample is placed in deionized water for ultrasonic cleaning. The purpose of ultrasonic cleaning is to completely remove the water-soluble tape remaining on the PDMS film and expose the patterned area with different adhesion. (1.5) Contact the ultrasonic cleaned intermediate sample with liquid metal; the liquid metal bath is contacted for 30 seconds, as shown in Figure 3As shown in the middle (c) part, during the process, the liquid metal will only select the high-adhesion area of the middle sample that has not been treated by laser, so that the liquid metal forms a continuous liquid metal conductive layer on the middle sample (i.e. PDMS film), thereby realizing the selective transfer of the liquid metal to the middle sample. Figure 3 As shown in the middle (d) part. By the above method, a liquid metal conductive layer with a width of 25 μm can be prepared. Among them, the liquid metal can be selected from any one of gallium-indium alloy, Galinstan alloy (i.e. gallium-indium-tin alloy) or other metals. The PDMS prepolymer can be prepared by mixing the curing agent and the crosslinking agent at a mass ratio of 10:1. The curing agent can be selected from epoxy resin, and the crosslinking agent can be selected from ethylenediamine.

[0033] The liquid metal pressure sensor can sensitively and in real time perceive the contact force between the holder and the article. The core principle lies in the rapid response characteristics of the liquid metal conductive layer and the high efficiency of the signal processing chain. Specifically, when the holder moves downward and contacts the article, the pressure applied to the surface of the liquid metal pressure sensor will immediately cause a micro-deformation of the PDMS substrate. This deformation is transmitted to the liquid metal conductive layer in a serpentine structure, causing an instantaneous change in its geometric shape (such as length, cross-sectional area or contact resistance). Since the liquid metal (such as gallium-indium alloy) has extremely high conductivity and fluidity, its resistance value will quickly adjust with the change in pressure, with a response time of milliseconds, thereby realizing real-time monitoring of the contact force.

[0034] In addition, the design of the serpentine structure not only improves the sensitivity of the liquid metal pressure sensor (with a resolution of 0.0168 kPa), but also enhances the significance and stability of signal changes by increasing the length and tortuosity of the conductive path, ensuring that even small pressure changes can be effectively captured. The low elastic modulus and fast recovery characteristics of the PDMS material further ensure that the sensor can immediately recover to its initial state after the pressure is removed, supporting continuous and dynamic force perception.

[0035] In terms of signal processing, the resistance change of the liquid metal conductive layer is converted into a voltage signal in real time through a Wheatstone bridge and an instrument amplifier (such as AD620), and is digitized at a high sampling rate (e.g. thousands of times per second) through the analog-to-digital converter (ADC) of the controller. This complete "sensing-amplifying-processing" chain ensures that the pressure data can be acquired and judged by the controller in real time, thereby realizing real-time feedback and control of the contact force during the movement of the holder, avoiding damage to the article.

[0036] The gripper is used for clamping objects placed on a liquid metal pressure sensor. The gripper comprises a plurality of expandable or closable clamping jaws, each of which comprises a magnetic shape memory composite and an embedded resistance wire in the shape memory composite. The magnetic shape memory composite can expand outward under the action of a magnetic field to open the gripper to the maximum angle, and the resistance wire can rapidly shrink and close under the driving of the shape memory effect of the shape memory composite when heated to a temperature above the glass transition temperature (80℃) and the magnetic field is removed, thus completing the grabbing. In this scheme, the number of clamping jaws can be four, and one end of the four clamping jaws can be pasted at the same place, and the other end of the four clamping jaws can be expanded or closed to the same point. If the gripper clamps the object, the closed clamping jaws are expanded to release the clamped object; if clamping is required, the clamping jaws are changed from expansion to closure to achieve grabbing. The clamping jaws can be arc-shaped structures, semicircular arc-shaped structures or other common structures.

[0037] The construction method of the gripper is as follows: (2.1) four specific curved groove patterns are etched on a silica gel film by femtosecond laser to form a negative mold of four clamping jaws. The power of the femtosecond laser is 88 mW, the pulse width is 75 fs, and the scanning speed is 20 mm / s. (2.2) The shape memory epoxy resin, curing agent and Fe3O4 particles are mixed uniformly in a mass ratio of 3:1:4 to obtain a mixture, and vacuum degassing is performed for 10 minutes to remove air bubbles introduced during mixing. (2.3) The vacuum-deaerated mixture is poured into the mold, and a 40-μm nichrome resistance wire is embedded at the center of the mixture in the mold, and then secondary vacuum degassing is performed. (2.4) After the sample is cured at 80℃ for 2 hours and cooled to room temperature, it is carefully demolded to obtain four clamping jaws. (2.5) The ends of the four prepared clamping jaws are adhered together by a small amount of epoxy resin to obtain a gripper with a claw-shaped structure.

[0038] In this scheme, a femtosecond laser processing system, a three-dimensional moving platform and a control software system are used during the femtosecond laser processing operation. The femtosecond laser processing system can include a Spectra-Physics Solstice Ace femtosecond laser (80L8TICE-ACE-100F-1K), a high-speed galvanometer scanning system and an f-theta field lens. The three-dimensional moving platform can be used for precise positioning of the sample to realize three-dimensional movement control during processing. The control software system can use the CSMark control system to control the processing path and parameter settings. In this scheme, since no improvement is made to the devices, methods and control parts during the femtosecond laser processing, the femtosecond laser processing operation is not described in detail.

[0039] An electromagnetic drive device includes a magnetic field generator for producing a directional magnetic field and a power supply providing a constant current. In this embodiment, the magnetic field generator can be a magnet or other device capable of generating a magnetic field. The power supply can be a constant current drive circuit composed of MOSFETs (such as the IRF540N). This circuit converts the PWM signal from the controller into a precise current output, thereby providing a drive current of 0.05A to 0.30A to the resistance wire. Under the action of the directional magnetic field, the gripper uses a shape memory compound to drive each jaw to open outward to its maximum angle. After the resistance wire is heated to a temperature above its glass transition temperature by a constant current and the magnetic field is removed, the gripper drives each jaw to bend inward and close to the same point.

[0040] The controller is used to control the gripper to perform gripping and releasing actions. During gripping, the controller moves the gripper directly above the object, then moves it downwards while simultaneously acquiring the pressure value from the liquid metal pressure sensor. When the pressure value exceeds a set threshold, the controller moves the gripper upwards a preset distance and then activates the power supply. The power supply provides a constant current to the resistance wire, heating it. The controller also removes the magnetic field when the resistance wire is heated to a temperature above its glass transition temperature. At this point, the gripper's jaws close due to the shape memory effect of the shape memory compound, achieving gripping. During releasing, the controller first shuts off the power and then activates the magnetic field generator. Under the influence of the magnetic field generated by the generator, each jaw on the gripper expands outwards to its maximum angle, releasing the object. The controller can use an STMicroelectronics STM32F407ZGT6 microcontroller as its core processing unit. The pulse width modulation (PWM) output pin of the STM32F407ZGT6 microcontroller is connected to a constant current drive circuit composed of MOSFETs (such as IRF540N). This constant current circuit can convert the PWM signal from the MCU into a precise current output, thereby providing a constant drive current for the resistance wire embedded in the clamp.

[0041] In the scheme, the constructed liquid metal pressure sensor can realize the perception of the real-time contact force of the gripper when it contacts the article during clamping, reaching the micro-newton level, so that the liquid metal pressure sensor can sensitively perceive the contact force when the gripper moves to the article, thereby avoiding damage to the article caused by the gripper during clamping. In combination with the gripper provided in the scheme, the gripper has a certain flexibility, thereby further avoiding damage to the article caused by the gripper during clamping, so as to realize non-damage clamping of the article as much as possible. Furthermore, the magnetic field generated by the electromagnetic driving device and the current are used for double control driving to control the opening or closing of the multiple gripper claws of the gripper. The control makes the gripper respond quickly during opening or closing, thereby improving the clamping and releasing speed of the gripper. Under the synergistic action of the liquid metal pressure sensor and the electromagnetic driving device, not only can the micro-newton contact force of the article be perceived during clamping to realize non-damage clamping of the article, but also the electromagnetic double control can be combined to drive the gripper to quickly open and close, so as to improve the clamping and releasing speed of the gripper. In addition, the controller is electrically connected with the gripper, the electromagnetic driving device and the liquid metal pressure sensor respectively. Before clamping, the controller controls the gripper to slowly move to the article to be clamped on the liquid metal pressure sensor while sensing the pressure value of the liquid metal pressure sensor in real time. When the contact force of the gripper and the article is greater than 0.0168kPa, the controller controls the gripper to move upward by a preset distance (such as 0.1mm). This setting can determine that the gripper has contacted the article, and since the pressure threshold is set to 0.0168kPa, even if the gripper contacts the article, the contact force is very small, so the article is basically not damaged. In addition, when the pressure value (contact force of the gripper and the article) sensed by the liquid metal pressure sensor is greater than 0.0168kPa, the controller can immediately control the gripper to move upward, which can further avoid damage to the article caused by the gripper touching the article while keeping the gripper clamping the article. Therefore, the gripper of the scheme can non-damage and quickly clamp the article.

[0042] The liquid metal pressure sensor and the gripper in the scheme are made of flexible material system, so that the intelligent micro-gripping system constructed by the scheme can stably work in the temperature range of-20℃~120℃ and in special environments such as vacuum and strong magnetic field. At the same time, the liquid metal pressure sensor can sensitively perceive the contact force between the gripper and the article, thereby avoiding damage to the article during clamping, so that the intelligent micro-gripping system provided by the scheme can non-damage clamping in a wide temperature range, solving the problems of non-damage gripping and environmental adaptability in precise operation.

[0043] The intelligent micro-gripping system further comprises a driving member connected with the gripper, and the controller controls the movement of the gripper through the driving member. The driving member can be an XYZ high-precision moving platform, thereby realizing the movement of the gripper along the X-axis, Y-axis and Z-axis directions respectively.

[0044] In some other schemes, the intelligent micro-gripping system further comprises a support frame capable of moving along the X-axis and Y-axis, and a two-phase four-wire stepping motor can be arranged on the support frame. The stepping motor is connected with the gripper and is used to drive the gripper to move along the Z-axis direction. Specifically, the STM32F407ZGT6 microcontroller is connected to a stepping motor driver (such as TB6600) through pulse (PUL) and direction (DIR) signal pins. The driver drives a two-phase four-wire stepping motor to drive the gripper to make precise Z-direction displacement, thereby avoiding damage to the object as much as possible when the object is gripped.

[0045] The intelligent micro-gripping system can further comprise a display screen. The display screen can be a 7-inch capacitive touch screen. The display screen can communicate with the controller through UART to display the state and pressure curve of the intelligent micro-gripping system in real time, and can allow the user to set the related parameters of the intelligent micro-gripping system through the display screen.

[0046] It can be understood that the intelligent micro-gripping system provided by the scheme can be applied to a scene requiring high precision and capable of performing non-destructive operation on objects of multiple shapes. The gripper prepared by doping Fe3O4 particles in a shape memory polymer (SMP) and embedding a resistance wire can be unfolded under a magnetic field and closed after the magnetic field is removed when the temperature is higher than the glass transition temperature through electrical heating, so that the gripper can be quickly opened and closed. In actual use, the gripper can perform non-destructive grabbing at a load weight ratio of 2380:1.

[0047] Based on the above-mentioned structure of the intelligent micro-gripping system, the embodiment further provides a method for constructing the intelligent micro-gripping system, which comprises: first constructing the liquid metal pressure sensor and the gripper according to the method described above, and selecting the following objects: an XYZ high-precision moving platform, a controller, an electromagnetic driving device, a Wheatstone bridge and an instrument amplifier. The power supply in the electromagnetic driving device can be a constant current driving circuit composed of MOSFET (such as IRF540N), the magnetic field generating device can be a magnet, the controller can be an STM32F407ZGT6 microcontroller with a touch screen, and the model of the instrument amplifier can be AD620.

[0048] The output of the constructed liquid metal pressure sensor is connected to a high-precision Wheatstone bridge. The differential signal output from the high-precision Wheatstone bridge is then connected to the input of an instrumentation amplifier, with its gain set to 1000. The Wheatstone bridge and instrumentation amplifier amplify the weak resistance change signal (0.1mΩ level) sensed by the liquid metal pressure sensor into a voltage signal in the volt range. The output of the instrumentation amplifier is connected to the analog-to-digital converter (ADC) pin of the STM32F407ZGT6 microcontroller, thus converting the analog voltage signal into a digital signal for the processor to process. The pulse width modulation (PWM) output pin of the STM32F407ZGT6 microcontroller is also connected to a constant current drive circuit composed of MOSFETs (such as the IRF540N). This constant current drive circuit converts the PWM signal from the STM32F407ZGT6 microcontroller into a precise current output, providing a drive current of 0.05A to 0.30A (preferably 0.25A) to the nickel-chromium alloy resistance wire embedded in the clamp. The STM32F407ZGT6 microcontroller is also used to electrically connect to the stepper motor controlling the Z-axis movement on the XYZ high-precision moving platform. The gripper is mounted on the XYZ high-precision moving platform and connected to the stepper motor. In practical applications, the controller can control the movement of the gripper through the XYZ high-precision moving platform. Furthermore, in this solution, a stepper motor driver (such as the TB6600) can be connected via pulse (PUL) and direction (DIR) signal pins. This driver drives a two-phase four-wire stepper motor, causing the gripper to make precise Z-axis displacement, achieving a Z-axis movement accuracy of ±5μm. This design further improves the Z-axis movement accuracy of the gripper, facilitating precise adjustment of the gripper's Z-axis position during actual operation and further preventing damage to the object during gripping.

[0049] Example 2 Example 2, based on Example 1, provides a control method for an intelligent micro-gripping system. Please refer to [link / reference]. Figure 4 It includes: (a) Set the controller parameters: pressure threshold 0.0168 kPa, heating current 0.25 A, heating time 0.9 s, and the preset distance for the clamp to move upward is 0.1 mm.

[0050] (ii) Activate the magnetic field generating device so that each jaw of the gripper is in the maximum open state, and move the gripper directly above the liquid metal pressure sensor containing the item to be gripped by the controller.

[0051] (III) sending a descending instruction to the controller, the controller controlling the driving member to drive the gripper to move downward and simultaneously acquiring the pressure value of the liquid metal pressure sensor, and making the following judgment: if the pressure value is greater than the preset pressure threshold, the driving member drives the gripper to move upward by 0.1 mm.

[0052] (IV) after the gripper moves upward by 0.1 mm, starting the power supply to heat the resistance wire for 0.9 s, then closing the magnetic field generating device, and the plurality of clamping jaws on the gripper rapidly contract and close to complete the grabbing of the to-be-clamped object located on the liquid metal pressure sensor.

[0053] (V) when the clamped object needs to be released, first move the clamped object to a preset placement point through the gripper. Turn off the power supply and start the magnetic field generating device at the placement point, and the plurality of clamping jaws on the gripper are all expanded under the action of the magnetic field, thereby completing the release of the object.

[0054] In this scheme, through a series of pre-experiments, it is found that under the condition of heating current of 0.25 A and heating time of 0.9 s, the plurality of clamping jaws on the gripper will completely close under the shape memory effect after the magnetic field is removed. The magnetic field generating device in this scheme can use a magnet, which can be removed manually in the actual application process. In addition, the magnetic field generating device in this scheme can also be an electromagnet, which can also be electrically connected with the controller, and can generate a magnetic field by being controlled to be powered on when the magnetic field is needed, and can also remove the magnetic field by turning off the power supply of the electromagnet through the controller when the magnetic field needs to be removed. In this scheme, by setting the controller, the intelligent micro-gripping system provided by this scheme can realize the integration of "sensing, driving and control", so that the intelligent micro-gripping system can realize stable and lossless gripping of small objects.

[0055] Performance test In order to verify the gripping performance of the intelligent micro-gripping system provided in this embodiment, the technical personnel constructed the intelligent micro-gripping system to grab different micro-objects. The pictures obtained are as shown in Figures 5 to 10 Figure 5 is the picture taken during the process of gripping 100 μm microspheres by the gripper in this scheme, from left to right are the picture before gripping 100 μm microspheres, the picture taken during gripping 100 μm microspheres, and the picture taken after gripping 100 μm microspheres. Figure 6 is the picture taken at different stages during the process of gripping 5 μL droplets by the gripper provided in this scheme, from left to right are the picture taken when gripping 5 μL droplets, the picture taken when gripping 5 μL droplets, and the picture taken after placing the gripped 5 μL droplets back. Figure 7 ​The pictures taken by the gripper when clamping the biological sample are shown from left to right as the picture taken when just clamping the biological sample, the picture taken when clamping the biological sample, and the picture taken after releasing the clamped biological sample. Figure 8 The pictures taken by the gripper when clamping the 10 gram weight are shown from left to right as the picture taken before clamping the 10 gram weight, the picture taken when just clamping the 10 gram weight, and the picture taken after clamping the 10 gram weight. Figure 9 The pictures taken by the gripper when clamping the 100 gram Shoushan stone are shown from left to right as the picture taken when just clamping the 100 gram Shoushan stone, the picture taken after clamping the 100 gram Shoushan stone, and the picture taken after releasing the clamped 100 gram Shoushan stone. Figure 10 The pictures taken by the gripper when clamping other different shaped objects are shown. It can be seen from the pictures taken in the actual clamping operation that the gripper can stably and effectively clamp different shaped objects, even liquid drops and biological samples. In addition, when clamping the liquid drop by the gripper, a hydrophobic agent needs to be sprayed on the surface of the liquid drop. The purpose of spraying the hydrophobic agent is to maintain the shape of the liquid drop. The clamping force of the gripper is small, and the surface tension of the liquid drop is not damaged when clamping the liquid drop, so that the liquid drop can be stably clamped.

[0056] The above describes the basic principles, main features and advantages of the present application. It should be understood by those skilled in the art that the present application is not limited to the above embodiments, and the above embodiments and descriptions in the specification are only the principles of the present application. Various changes and improvements can be made without departing from the spirit and scope of the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. An intelligent micro-clamping system, characterized in that, It includes: Liquid metal pressure sensors are used to hold objects and sense their pressure in real time. A gripper for holding an object placed on a liquid metal pressure sensor; the gripper includes multiple expandable or closable jaws; each jaw includes a magnetic shape memory compound and a resistance wire embedded in the shape memory compound; An electromagnetic drive device includes a magnetic field generator for generating a directional magnetic field and a power supply for providing a constant current; under the action of the directional magnetic field, the gripper drives each gripper to open outward to the maximum angle through a shape memory compound, and after the resistance wire is heated to a temperature higher than the glass transition temperature by a constant current and the magnetic field is removed, it drives each gripper to bend inward and close to the same point. The controller is used to control the gripper to perform gripping and releasing actions. When performing the gripping operation, the controller controls the gripper to move towards the object while collecting the pressure value of the liquid metal pressure sensor. When the pressure value exceeds the set pressure threshold, the controller controls the gripper to move upward a preset distance and then starts the power supply. The controller also removes the magnetic field when the resistance wire is heated to a temperature higher than the glass transition temperature. When performing the releasing action, the controller first turns off the power supply and then starts the magnetic field generating device.

2. The intelligent micro-clamping system as described in claim 1, characterized in that, The liquid metal pressure sensor includes a substrate and a protective layer. A serpentine liquid metal conductive layer is provided on the side of the substrate near the protective layer. The protective layer is used to encapsulate the liquid metal conductive layer on the surface of the substrate. The two ends of the liquid metal conductive layer are electrically connected to the controller.

3. The intelligent micro-clamping system as described in claim 2, characterized in that, The substrate is made of PDMS film, and the protective layer is made by spin-coating PDMS prepolymer onto the surface of the liquid metal conductive layer and curing it; the thickness of the substrate is 0.5-1 mm; and the width of the liquid metal conductive layer is 25 μm.

4. The intelligent micro-clamping system as described in claim 1, characterized in that, The intelligent micro-gripping system also includes a drive component connected to the gripper, and the controller controls the movement of the gripper through the drive component.

5. A method for constructing an intelligent micro-clamping system, characterized in that, It includes: Construct the liquid metal pressure sensor and the clamp as described in any one of claims 1-4, respectively; The constructed liquid metal pressure sensor and magnetic field generator are placed on the XYZ high-precision moving platform, and the constructed clamp is connected to the Z-axis moving part of the XYZ high-precision moving platform. The controller is electrically connected to the resistance wire on the clamp, the XYZ high-precision moving platform and the liquid metal pressure sensor.

6. The method for constructing the intelligent micro-clamping system as described in claim 5, characterized in that, The output of the liquid metal pressure sensor is connected to the input of the controller via an amplifier circuit; one end of the power supply is connected to the output of the controller via a PWM signal, and the other end of the power supply is electrically connected to the resistance wire; one end of the drive is connected to the controller, and the other end of the drive is connected to the clamp.

7. The method for constructing the intelligent micro-clamping system as described in claim 5, characterized in that, The clamp is constructed as follows: a PDMS film is flatly pasted onto a glass slide substrate, and a layer of water-soluble adhesive tape is covered on its surface to obtain an intermediate sample; A femtosecond laser system is used, and the speed of light is controlled and focused by an aperture, a half-wave plate, a Glan prism and a high-speed galvanometer. Then, the laser is focused onto the intermediate sample by an f-theta field mirror. The intermediate sample was scanned and processed on its surface using a laser with a power of 300mW and a scanning speed of 25mm / s, following a preset serpentine path. This process was repeated multiple times to obtain the scanned intermediate sample. The intermediate sample after scanning is ultrasonically cleaned, and then the ultrasonically cleaned intermediate sample is brought into contact with a liquid metal bath until the liquid metal fills the unscanned area on the intermediate sample, thereby forming a liquid metal conductive layer on the intermediate sample. Copper foil electrodes are attached to both ends of the liquid metal conductive layer, and PDMS prepolymer is spin-coated onto the surface of an intermediate sample filled with liquid metal and then cured to obtain a liquid metal pressure sensor.

8. The method for constructing the intelligent micro-clamping system as described in claim 5, characterized in that, The method for constructing the gripper is as follows: Femtosecond laser is used to process the gripper mold pattern on a silicone film; Shape memory epoxy resin, curing agent and Fe3O4 particles were mixed in a mass ratio of 3:1:4 and then vacuum degassed to obtain a magnetic shape memory composite. The shape memory composite is poured into a mold, and after embedding the resistance wire, vacuum degassing, curing and demolding are performed in sequence to obtain the gripper. By following the steps described above, multiple grippers are made, and the ends of the grippers are glued to the same location to obtain the gripper.

9. A control method for an intelligent micro-gripping system, characterized in that, It employs the intelligent micro-gripping system as described in any one of claims 1-4; the control method includes: Activate the magnetic field generator so that each gripper of the clamp is in its maximum open state; use the controller to move the clamp to directly above the liquid metal pressure sensor containing the item to be clamped; A descent command is sent to the controller. The controller controls the drive to move the gripper downwards and simultaneously acquires the pressure value from the liquid metal pressure sensor. The controller then makes the following judgment: if the pressure value is greater than the preset pressure threshold, the drive moves the gripper upwards a preset distance. After the gripper moves upward a preset distance, the power supply is turned on to heat the resistance wire until the temperature of the resistance wire is greater than the glass transition temperature. Then, the magnetic field generating device is turned off, and the multiple grippers on the gripper quickly retract and close to complete the gripping of the object to be gripped on the liquid metal pressure sensor.

10. The control method for the intelligent micro-clamping system as described in claim 9, characterized in that, The control method further includes, when it is necessary to release the clamped item, first moving the clamped item to a preset placement point using the clamp; turning off the power and activating the magnetic field generator located at the placement point, so that the multiple grippers on the clamp unfold under the action of the magnetic field, thereby completing the release of the item.

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