A liquid nitrogen slush freezing device for sample freezing and storage and methods of use thereof

Abstract

The application provides a liquid nitrogen slush freezing device for sample freezing and storage and a use method thereof. The device comprises a liquid nitrogen slush tank body, a slush tank sealing cover, a movable sealing baffle, a sample feeding rod, a sample rack, a sample storage liquid nitrogen pool and a vacuum pump. The slush tank sealing cover is sealingly connected to the top of the liquid nitrogen slush tank body, and the movable sealing baffle is sealingly inserted between the liquid nitrogen slush tank body and the slush tank sealing cover. The liquid nitrogen slush tank body comprises an inner layer foam heat insulation tank body and an outer layer metal tank body. The sample rack is connected below the sample feeding rod. The sample feeding rod is inserted into the liquid nitrogen slush tank body through the slush tank sealing cover. The vacuum pump is connected to the liquid nitrogen slush tank body. The application utilizes liquid nitrogen slush to rapidly and efficiently freeze and fix the water-containing sample, avoids the generation of ice crystals in the sample, retains the real microstructure of the sample, ensures that the sample is not in contact with air during the whole freezing and storage process, and avoids the formation of surface condensation ice crystals.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of cryogenic scanning electron microscopy, in particular, especially relates to a liquid nitrogen slush freezing device for sample freezing and storage and a use method thereof. BACKGROUND

[0002] Cryogenic scanning electron microscopy is an irreplaceable means for observing the real microstructure and structure of samples containing liquid and not resistant to electron beam irradiation, and is a very important characterization method in the research fields of medicine, life science, material, energy and chemical industry. The core link is the freezing fixation technology of the sample. The existing freezing methods include boiling liquid nitrogen freezing method, liquid nitrogen slush freezing method, liquid propane / ethane freezing method and high pressure freezing method. The latter two methods are mainly used for freezing fixation of transmission electron microscopy samples and are expensive.

[0003] The boiling liquid nitrogen method is the preferred freezing scheme for beginners of cryogenic scanning electron microscopy because of its lowest cost and simple operation, but its shortcomings are also very obvious: the Leidenfrost phenomenon greatly reduces the freezing rate of the sample in the boiling liquid nitrogen, and it is difficult for water molecules in the sample to form an ideal glassy structure, and large ice crystals are easily formed to destroy the real microstructure and structure of the sample. The liquid nitrogen slush freezing method can effectively avoid this phenomenon, but some commonly used commercial scanning electron microscope freezing transmission equipment does not come with a liquid nitrogen slush freezing device, and users can only choose the boiling liquid nitrogen freezing method, which has poor freezing effect and limited application range, and needs to be improved. SUMMARY

[0004] According to the above technical problems, a liquid nitrogen slush freezing device for sample freezing and storage and a use method thereof are provided. The present application solves the problem of low freezing rate of boiling liquid nitrogen and easy formation of sample ice crystals. Through the design of the movable bottom of the liquid nitrogen slush tank, the frozen sample falls directly into the sample storage liquid nitrogen pool from the liquid nitrogen slush, without contacting the air, and avoids the formation of condensed ice crystals on the surface of the sample. The device can be used with a commercial scanning electron microscope freezing transmission system to provide a convenient and efficient liquid nitrogen slush freezing scheme for users.

[0005] The technical means adopted by the present application are as follows:

[0006] A liquid nitrogen slush freezing device for sample freezing and storage, comprising a liquid nitrogen slush tank body, a slush tank sealing cover, a movable sealing baffle, a sample feeding rod, a sample rack, a sample storage liquid nitrogen pool and a vacuum pump, the slush tank sealing cover is sealingly connected with the top of the liquid nitrogen slush tank body, the movable sealing baffle is sealingly inserted between the liquid nitrogen slush tank body and the slush tank sealing cover, and the liquid nitrogen slush tank body, the slush tank sealing cover and the movable sealing baffle constitute a liquid nitrogen slush tank with a closed space in the inside;

[0007] The liquid nitrogen slush tank body is a cylindrical tank body with a double-layer structure, comprising an inner foam heat insulation tank body and an outer metal tank body, the foam heat insulation tank body is arranged below the inside of the metal tank body, and the foam heat insulation tank body is designed as a movable bottom, and the bottom of the metal tank body is designed as a detachable bottom.

[0008] The sample rack is connected below the sample feeding rod, the sample feeding rod is inserted into the inside of the liquid nitrogen slush tank body through the slush tank sealing cover, and is used for pushing the sample rack with the sample to be frozen into the liquid nitrogen slush tank body for freezing.

[0009] The vacuum pump is connected with the liquid nitrogen slush tank body, and is used for vacuumizing the inside of the liquid nitrogen slush tank body; and the sample storage liquid nitrogen pool is a heat insulation foam pool, which is used for containing the frozen sample discharged from the bottom of the liquid nitrogen slush tank body, and provides a liquid nitrogen freezing and preservation environment for the frozen sample.

[0010] Further, a gap is arranged between the outer wall of the foam heat insulation tank body and the inner wall of the metal tank body, and the gap is filled with air.

[0011] The bottom of the foam heat insulation tank body is provided with a foam bottom plate designed as a movable bottom, and the foam bottom plate is arranged in the foam heat insulation tank body through interference fit; the foam bottom plate is connected with a pulling rope, which is used for pulling out the foam bottom plate from the bottom of the foam heat insulation tank body.

[0012] One side of the outer wall of the metal tank body is provided with a protruding vacuum interface, the vacuum interface is connected with the vacuum pump through a pipeline, a vacuum gauge is arranged on the pipeline, the other side of the outer wall of the metal tank body is provided with a protruding air release valve for connecting the atmosphere to break the vacuum; and a handle is arranged on the outer side of the metal tank body for holding the tank body.

[0013] Further, a first circular hole is arranged in the bottom of the metal tank body, a metal bottom plate is connected in the first circular hole, the metal bottom plate is a circular metal plate designed as a shoulder, a first groove is arranged on the outer circle of the shoulder, an annular metal bottom plate sealing ring is arranged in the first groove, the metal bottom plate sealing ring is in close contact with the inner wall of the first circular hole, and is used for realizing the radial sealing of the metal bottom plate and the bottom of the metal tank body.

[0014] Further, the top opening of the metal tank body is provided with a metal tank body flange interface for cooperating with the snow slush tank sealing cover and the movable sealing baffle to realize the sealing of the liquid nitrogen snow slush tank body;

[0015] The upper surface of the metal tank body flange interface is provided with a first flange interface groove penetrating the whole interface plane, for sliding insertion of the movable sealing baffle; the two sides of the first flange interface groove are provided with annular lateral protruding portions, and a plurality of first flange interface screw holes are arranged on the annular lateral protruding portions, for bolt connection and fixation with the snow slush tank sealing cover;

[0016] A groove is opened on the surface of the first flange interface groove, and a flange interface sealing ring is placed in the groove, which is in close contact with the lower surface of the movable sealing baffle, for realizing the axial sealing between the movable sealing baffle and the metal tank body.

[0017] Further, the snow slush tank sealing cover is a metal cover, which is composed of a detachable top cover and a lower cover body; the detachable top cover has a shoulder for positioning and realizing the cooperative connection with the cover body;

[0018] A second circular hole is arranged in the center of the detachable top cover for insertion of the sample injection rod; one side of the second circular hole is provided with an anti-falling mechanism, which includes a clamping groove, a spring and a resistance push block; the clamping groove is opened in the top of the detachable top cover; one end of the spring is fixed in the clamping groove, and the other end of the spring is fixedly connected with the resistance push block; the resistance push block slides in the clamping groove; under the elastic force of the spring, the resistance push block pushes the sample injection rod, preventing the sample injection rod from falling under the action of gravity;

[0019] The bottom of the cover body is provided with a sealing cover flange interface, which cooperates with the metal tank body flange interface of the metal tank body to realize the fixed connection of the liquid nitrogen snow slush tank body and the snow slush tank sealing cover;

[0020] The lower surface of the sealing cover flange interface is provided with a second flange interface groove penetrating the whole interface plane, for sliding insertion of the movable sealing baffle;

[0021] The two sides of the second flange interface groove are provided with annular lateral protruding portions, and a plurality of second flange interface screw holes are arranged on the annular lateral protruding portions, for bolt connection and fixation with the metal tank body flange interface of the metal tank body.

[0022] Further, the movable sealing baffle is a metal plate, and the two ends are circular arc-shaped, and the radii of the two ends are consistent with the circular edges of the metal tank body flange interface of the metal tank body and the sealing cover flange interface of the metal tank body; the width of the movable sealing baffle matches the width of the first flange interface groove of the metal tank body flange interface;

[0023] The mobile sealing baffle is provided with a mobile sealing baffle hole with a diameter consistent with the inner diameter of the metal can body, and the mobile sealing baffle hole is in different positions by pulling the mobile sealing baffle, so that the switching between the communication and isolation states between the snow mud sealing can body and the sealing cover is realized.

[0024] Further, the sample feeding rod comprises a rod body which is a metal round rod, a top of the rod body is provided with a character-shaped sample feeding rod handle, and a bottom of the rod body is provided with a fixing head for fixing the sample rack; the fixing head is an S-shaped detachable metal hook, a center position of the fixing head is provided with a fixing head screw hole, and a bottom end of the rod body is provided with a sample feeding rod screw hole, and the fixing head is fixed to the bottom end of the rod body through the fixing head screw hole, a screw and the sample feeding rod screw hole.

[0025] Further, a main body of the sample rack is a rectangular metal base, a middle position of the base is provided with a square sample rack groove which penetrates through the whole base from front to back, a center position of the sample rack groove is provided with a sample rack hole for placing a pin leg sample rack.

[0026] Two sides of a top of the base are each provided with a sample rack screw hole, a fixing column is fixed in the sample rack screw hole through a screw, the two fixing columns are located on the left and right sides of the sample rack groove, two sides of the fixing head of the sample feeding rod are connected with the two fixing columns to realize the connection and separation between the sample rack and the sample feeding rod; a top of the fixing column is provided with a circular ring-shaped lateral protrusion for limiting and fixing the fixing head.

[0027] Further, the metal can body, the mobile sealing baffle and the sample feeding rod are made of one of aluminum alloy or stainless steel; the sample rack is made of one of red copper or brass; and the foam heat insulation can body and the sample storage liquid nitrogen pool are made of polystyrene foam.

[0028] The application further provides a use method of the liquid nitrogen snow mud freezing device for sample freezing and storage, which comprises the following steps:

[0029] S1, preparing liquid nitrogen snow mud: placing the foam heat insulation can body with a foam bottom plate at the bottom into a bottom-sealed metal can body, injecting a certain volume of liquid nitrogen into the foam heat insulation can body, fixing and connecting the metal can body flange interface of the metal can body with the sealing cover flange interface of the snow mud can sealing cover through a bolt, inserting the mobile sealing baffle into the gap formed by the two flange interfaces to keep the liquid nitrogen snow mud can body in a closed state, starting the vacuum pump connected with the liquid nitrogen snow mud can body to vacuumize the liquid nitrogen snow mud can body, and converting the liquid nitrogen in the foam heat insulation can body into liquid nitrogen snow mud in a supercooled state, and monitoring the vacuum value in the liquid nitrogen snow mud can body in real time through a vacuum gauge until reaching 1-50 pa;

[0030] S2, loading the sample to be frozen: during the formation of the liquid nitrogen slush, insert the rod body of the sample loading rod into the second circular hole of the detachable top cover of the slush tank sealing cover; fix the fixed head in the screw hole at the bottom end of the rod body; place the sample table with the sample to be frozen fixed on the legs into the square sample table groove of the sample table frame, and fix the sample table frame on the fixed head of the sample loading rod by the fixing column; place the sample loading rod with the sample and the detachable top cover on the cover of the slush tank sealing cover, and adjust the depth of the sample loading rod to avoid the collision of the sample table frame with the movable sealing baffle;

[0031] S3, sample pushing and freezing: after the vacuum value in the liquid nitrogen slush tank reaches the required value, slowly open the air release valve to break the vacuum of the liquid nitrogen slush tank; after the air release is completed, slowly push the movable sealing baffle to remove the sealing isolation between the liquid nitrogen slush tank and the slush tank sealing cover, so as to realize the communication; quickly push the sample loading rod downward to send the sample table frame to the bottom of the foam heat insulation tank, so that it is immersed in the liquid nitrogen slush; rotate the sample loading rod handle to rotate the fixed head out of the fixed column, and then quickly pull out the sample loading rod after separation; pull out the movable sealing baffle to make the liquid nitrogen slush tank return to the closed state, start the vacuum pump to vacuum the liquid nitrogen slush tank, and complete the freezing of the sample in the liquid nitrogen slush, which lasts for 5-10 minutes;

[0032] S4, taking out and storing the frozen sample: after the freezing process is completed, slowly open the air release valve to break the vacuum of the liquid nitrogen slush tank; after the air release is completed, hold the handle of the metal tank body and transfer the liquid nitrogen slush tank to above the sample storage liquid nitrogen pool which stores a certain amount of liquid nitrogen; carefully remove the movable bottom plate at the bottom of the metal tank body, and then pull the drawstring of the foam bottom plate of the foam heat insulation tank to carefully pull out the foam bottom plate; when pulling out, tilt the liquid nitrogen slush tank at a certain angle to prevent the liquid nitrogen from flowing out too quickly; the sample table frame will fall into the sample storage liquid nitrogen pool along with the flowing liquid nitrogen and be stored in the liquid nitrogen for use.

[0033] Compared with the prior art, the present application has the following advantages:

[0034] 1、The present application uses a liquid nitrogen slush freezing device which is convenient to use and small in size, realizes rapid and high-quality supercooled liquid nitrogen slush freezing of the sample, provides a better sample freezing scheme for the existing boiling liquid nitrogen pool scanning electron microscope freezing transmission system, and makes up for the technical defects of low freezing efficiency and easy formation of sample ice crystals; the sample is detached from the bottom of the slush tank after freezing, so that frosting on the surface of the sample during sample transfer is avoided, and the microstructure of the sample is not covered.

[0035] 2、The present application realizes the isolation and communication between the liquid nitrogen slush tank and the sealing cover through the mobile sealing baffle, ensures that the sample waiting in the sealing cover after the liquid nitrogen slush is generated can be quickly inserted into the supercooled liquid nitrogen slush in the lower slush tank, and realizes the rapid and high-quality freezing. Through the design of the sample rack and the fixed head of the sample feeding rod, the quick connection and separation between the sample and the feeding rod are realized. Through the design of the movable bottom of the slush tank body, the sample after the freezing is completed is directly dropped into the sample storage liquid nitrogen pool, so that the surface condensation ice crystals are avoided when the sample is transferred out of the liquid nitrogen slush and contacted with the air.

[0036] Based on the above reasons, the present application can be widely popularized in the field of sample freezing and fixing. BRIEF DESCRIPTION OF DRAWINGS

[0037] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced. Obviously, the drawings in the following description are some embodiments of the present application, and other drawings can also be obtained by those skilled in the art without creative labor.

[0038] Figure 1 It is a structural schematic diagram of the device of the present application.

[0039] Figure 2 It is a three-dimensional appearance diagram of the liquid nitrogen slush tank of the present application.

[0040] Figure 3 It is a sectional view of the liquid nitrogen slush tank of the present application.

[0041] Figure 4 It is a side view of the tank body part of the liquid nitrogen slush tank of the present application.

[0042] Figure 5 It is an appearance diagram of the connection between the fixed head of the sample feeding rod and the sample rack of the present application.

[0043] Figure 6 It is a sectional view of the sample rack loaded with the sample table of the present application.

[0044] Figure 7 It is a schematic diagram of the anti-falling mechanism on the sealing cover of the slush tank of the present application.

[0045] In the figure: 1, liquid nitrogen slush tank body; 2, slush tank sealing cover; 3, mobile sealing baffle; 4, sample feeding rod; 5, sample rack; 6, sample storage liquid nitrogen pool; 7, vacuum pump;

[0046] 11, foam insulation tank; 12, metal tank; 111, foam bottom plate; 121, metal bottom plate; 122, first round hole; 1211, first groove; 1212, metal bottom plate sealing ring; 123, vacuum interface; 124, air release valve; 125, vacuum gauge; 126, metal tank flange interface; 1261, first flange interface groove; 1262, groove; 1263, flange interface sealing ring; 1264, first flange interface screw hole; 127, handle;

[0047] 21, detachable top cover; 22, cover body; 211, second round hole; 212, anti-falling mechanism; 2121, clamping groove; 2122, spring; 2123, resistance push block; 221, sealing cover flange interface; 2211, second flange interface groove; 2212, second flange interface screw hole;

[0048] 31, moving sealing baffle round hole;

[0049] 41, rod body; 42, sample rod handle; 43, fixed head; 44, sample rod screw hole; 431, fixed head screw hole;

[0050] 51, base; 52, sample rack groove; 53, sample rack round hole; 531, nail leg sample table; 54, fixed column; 55, sample rack screw hole. DETAILED DESCRIPTION

[0051] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the drawings and in combination with the embodiments.

[0052] In order to make the purpose, technical scheme and advantages of the embodiments of the present application more clear, the technical scheme of the embodiments of the present application will be described clearly and completely below in combination with the drawings of the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all. The description of the at least one exemplary embodiment is actually only illustrative, but not as any limitation on the present application and its application or use. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0053] It should be noted that the terms used herein are only for describing specific embodiments, and are not intended to limit the exemplary embodiments according to the present application. As used herein, the singular form is intended to include the plural form unless the context clearly indicates otherwise, and it should also be understood that when the terms "comprise" and / or "include" are used in the specification, there is a feature, step, operation, device, component and / or combination thereof.

[0054] The relative arrangement of parts and steps, numerical expressions, and numerical values set forth in the examples herein are not intended to limit the scope of the application unless otherwise specifically stated. It is also to be understood that the drawings are not necessarily to scale as the dimensions of the various parts can have been arbitrarily inflated or deflated for the sake of pictorial clarity. Techniques, methods, and apparatus known to those of ordinary skill in the relevant art can not be discussed in detail but can be assumed by those skilled in the art to be part of a skill within the art. In all examples shown and discussed herein, any specific value is to be interpreted as illustrative only and not as a limitation. Thus, other examples of exemplary embodiments can have different values. It is to be noted that like numbers and letters refer to like parts throughout the several views of the drawings and, as such, no further discussion with regard thereto is needed.

[0055] In the description of the present application, it is to be understood that the orientation or positional relationships indicated by orientation words such as "front, back, upper, lower, left, right", "transverse, vertical, perpendicular, horizontal", and "top, bottom" and the like are generally based on the orientation or positional relationships shown in the drawings, and are merely 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 or be constructed and operated in a particular orientation, and therefore cannot be understood as limiting the scope of protection of the present application: the orientation words "inner, outer" refer to the inner and outer relative to the contour of each component itself.

[0056] For the convenience of description, spatial relative terms such as "over", "above", "upper surface", "upper", and the like can be used herein to describe the spatial positional relationship of one device or feature with respect to other devices or features as shown in the drawings. It should be understood that the spatial relative terms are intended to include different orientations in use or operation in addition to the orientation of the devices described in the drawings. For example, if the devices in the drawings are inverted, the device described as "above" or "over" other devices or structures will be positioned "below" or "under" the other devices or structures. Thus, the exemplary term "above" can include both "above" and "below" orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used herein are interpreted accordingly.

[0057] In addition, it should be noted that the use of the words "first", "second", and the like to describe various components is merely intended to distinguish the respective components from each other, and the words have no special meaning unless otherwise stated, and therefore cannot be understood as limiting the scope of protection of the present application.

[0058] This invention provides a liquid nitrogen slush freezing device and its method for sample freezing and storage. It addresses the problem of low freezing rates and easy ice crystal formation in samples frozen by boiling liquid nitrogen by using a cryo-scanning electron microscope (SEM). The removable bottom design of the liquid nitrogen slush tank allows the frozen sample to fall directly from the liquid nitrogen slush into the sample storage liquid nitrogen pool, preventing contact with air and thus avoiding ice crystal formation on the sample surface. This device can be used in conjunction with commercial SEM cryo-transfer systems, providing users with a convenient and efficient liquid nitrogen slush freezing solution.

[0059] This invention provides the following: Figures 1-7 The illustrated liquid nitrogen slush freezing device for sample freezing and storage includes a liquid nitrogen slush tank body 1, a slush tank sealing cap 2, a movable sealing baffle 3, a sample injection rod 4, a sample stand 5, a liquid nitrogen storage tank 6, and a vacuum pump 7 for evacuating the liquid nitrogen slush tank. The liquid nitrogen slush tank body 1, the slush tank sealing cap 2, and the movable sealing baffle 3 form the main body of the freezing device. The liquid nitrogen slush tank body 1, the slush tank sealing cap 2, and the movable sealing baffle 3 are used together to form a sealed liquid nitrogen slush tank, creating a sealed space inside for preparing liquid nitrogen slush and storing it. The samples are cryogenically fixed. The sample inlet rod 4 pushes the sample stand 5, on which the sample to be frozen is fixed, into the liquid nitrogen slush tank 1 for freezing (i.e., pushing the sample to be frozen on the sample stand 5 into the liquid nitrogen slush tank 1 for freezing). The liquid nitrogen storage tank 6 provides a liquid nitrogen cryogenic preservation environment for samples removed from the bottom of the liquid nitrogen slush tank 1 and holds the frozen samples removed from the tank 1. The vacuum pump 7 is connected to the liquid nitrogen slush tank 1 to create a vacuum environment for preparing liquid nitrogen slush. This invention utilizes liquid nitrogen slush for rapid and efficient cryogenic fixation of water-containing samples, avoiding the formation of ice crystals within the sample, preserving its true microstructure, and ensuring that the sample does not come into contact with air throughout the freezing and storage process, thus preventing surface condensation and ice crystal formation.

[0060] As a preferred embodiment, the liquid nitrogen slush tank body 1 is a cylindrical tank body with double-layer structure, the inner layer is a foam insulation tank body 11, the inner diameter is 30-50mm, the outer diameter is 50-100mm, the height is 80-120mm, and the wall thickness is 10-25mm; the outer layer is a metal tank body 12, the inner diameter is 60-120mm, the outer diameter is 70-136mm, the height is 110-150mm, and the wall thickness is 5-8mm; the tank bottom thickness is 5-8mm; the foam insulation tank body 11 and the metal tank body 12 are provided with a gap, the gap is 5-10mm, and the gap is filled with air; both layers of tank bodies are designed as a movable bottom, wherein the bottom of the inner layer foam insulation tank body 11 is provided with a foam bottom plate 111, and the foam bottom plate 111 can be easily removed. The diameter of the movable bottom foam bottom plate 111 is 30-50.5mm, and the thickness is 3-5mm. The foam insulation tank body 11 is placed by interference fit; the foam bottom plate 111 is provided with a drawstring (not shown in the figure), which is used to draw out the foam bottom plate 111 from the bottom of the foam insulation tank body 11; the bottom of the metal tank body 12 is designed to be detachable, and a first circular hole 122 with a diameter of 45-95mm is opened in the tank bottom, the first circular hole 122 is connected with a metal bottom plate 121, the first circular hole 122 and the metal bottom plate 121 are used by gap fit, the metal bottom plate 121 is a circular metal plate with shoulder design, a first groove 1211 is arranged on the outer circle of the shoulder for placing an annular metal bottom plate sealing ring 1212, the annular metal bottom plate sealing ring 1212 is in close contact with the inner wall of the first circular hole 122, so as to realize the radial sealing of the metal bottom plate 121 and the first circular hole 122 of the metal tank bottom (realize the radial sealing with the bottom of the metal tank body 12); the outer diameter of the metal bottom plate 121 is 60-120mm, the thickness is 5-8mm, the shoulder thickness is 3-5mm, and the shoulder diameter matches the inner diameter of the first circular hole 122 of the bottom of the metal tank body 12.

[0061] As a preferred embodiment, one side of the outer metal tank body 12 of the liquid nitrogen slush tank is designed with an extended vacuum interface 123 for connecting the vacuum pump 7 and the vacuum gauge 125, wherein the vacuum interface 123 is connected with the vacuum pump 7 through a pipeline, and the vacuum gauge 125 is installed on the pipeline. The other side of the outer metal tank body 12 is designed with an extended air release valve 124 for connecting the atmosphere to break the vacuum. The top opening of the metal tank body 12 is designed with a metal tank flange interface 126 for connecting the slush tank sealing cover 2, which is used in cooperation with the slush tank sealing cover 2 and the movable sealing baffle 3 to realize the sealing of the liquid nitrogen slush tank body 1 and realize the closed connection. The thickness of the metal tank flange interface 126 is 5-7mm, and the width of the annular lateral protruding part on both sides of the metal tank flange interface 126 is 10-15mm; the surface of the metal tank flange interface 126 is designed with a groove and a sealing ring for inserting the movable sealing baffle 3 and realizing the vacuum sealing. Specifically, the upper surface of the metal tank flange interface 126 is designed with a rectangular first flange interface groove 1261 penetrating the entire interface plane, which is used for sliding insertion of the movable sealing baffle 3; the depth of the first flange interface groove 1261 is 1.5-2.5mm, the width is 70-135mm, and the outer two sides of the first flange interface groove 1261 are provided with four first flange interface screw holes 1264 for bolt connection and fixation with the slush tank sealing cover 2; the metal tank 12 is designed with a circle of grooves 1262 at 2mm from the inner edge of the top (on the surface of the first flange interface groove 1261) for placing the flange interface sealing ring 1263, which is in close contact with the lower surface of the movable sealing baffle 3 to realize the axial sealing between the movable sealing baffle 3 and the metal tank 12; the outer side of the metal tank 12 is provided with a handle 127 with a length of 80-100mm for holding the tank.

[0062] As a preferred embodiment, the slush can sealing cover 2 is a metal cover, which is composed of a detachable top cover 21 and a lower cover body 22; the diameter of the detachable top cover 21 is 70-136 mm, which is connected with the cover body 22 through shoulder positioning to achieve clearance fit; the center of the detachable top cover 21 is provided with a second circular hole 211 for inserting the sample injection rod 4, which is inserted into the liquid nitrogen slush can body 1 through the second circular hole 211; the diameter of the second circular hole 211 is 5-7 mm; one side of the second circular hole 211 is provided with an anti-falling mechanism 212 to fix the position of the sample injection rod 4, which includes a clamping groove 2121, a spring 2122 and a resistance push block 2123; the clamping groove 2121 is opened at the top of the detachable top cover 21 and communicates with the second circular hole 211; one end of the spring 2122 is fixed in the clamping groove 2121, and the other end of the spring 2122 is fixedly connected with the resistance push block 2123, which slides in the clamping groove 2121 (two fixed blocks can be installed in the clamping groove 2121 through bolts, the spring 2122 and the resistance push block 2123 are placed between the two fixed blocks, and the resistance push block 2123 slides between the two fixed blocks); through the spring 2122 and the resistance push block 2123 placed in the clamping groove 2121, the resistance push block 2123 pushes the sample injection rod 4 under the elastic force of the spring 2122 to prevent it from sliding down under the action of gravity; the height of the cover body 22 is 30-40 mm, the inner diameter is 60-120 mm, the outer diameter is 70-136 mm, the wall thickness is 5-8 mm, and the inner diameter and the outer diameter of the cover body 22 are consistent with the metal can body 12. The bottom of the cover body 22 is designed with a sealing cover flange interface 221 with the same outer diameter and thickness (width and thickness) as the metal can body flange interface 126 of the metal can body 12, which are used together to fix the liquid nitrogen slush can body 1 and the slush can sealing cover 2; the lower surface of the sealing cover flange interface 221 is designed with a rectangular second flange interface groove 2211 penetrating the whole interface plane, which is used for sliding insertion of the movable sealing baffle 3, and the movable sealing baffle 3 is inserted between the second flange interface groove 2211 and the first flange interface groove 1261; the depth of the second flange interface groove 2211 is 1.5-2.5 mm, the width is 70-135 mm, and four second flange interface screw holes 2212 are arranged side by side outside the groove area, which are used for bolt connection with the metal can body flange interface 126 of the metal can body 12, wherein the four second flange interface screw holes 2212 and the four first flange interface screw holes 1264 are connected by bolts respectively.

[0063] As a preferred embodiment, the mobile sealing baffle 3 is a rectangular metal plate, both ends of which are circular arcs, the radii of which are consistent with the circular edges of the metal can body flange interface 126 and the sealing cover flange interface 221; the width of the mobile sealing baffle 3 matches the width of the first flange interface groove 1261 and the second flange interface groove 2211, the length is 140-270 mm, the thickness is 3-5 mm, and one side of the mobile sealing baffle 3 is provided with a mobile sealing baffle circular hole 31 with a diameter consistent with the inner diameter of the metal can body 12 at a distance of 10-15 mm from the arc-shaped edge (from one side of the arc-shaped edge); the mobile sealing baffle 3 is inserted into the gap formed by the combination of the metal can body 12 and the snow mud can sealing cover 2 flange interface, and the switching between the communication and isolation states between the snow mud sealing can body 1 and the snow mud can sealing cover 2 is realized by pulling the mobile sealing baffle 3 to different positions.

[0064] As a preferred embodiment, the sample feeding rod 4 is composed of a rod body 41, a one-bar feeding rod handle 42, and a fixed head 43, and is used for pushing the sample into the liquid nitrogen snow mud can. Specifically, the rod body 41 is a metal circular rod with a diameter of 5-7 mm and a length of 160-200 mm, the top of which is provided with a one-bar feeding rod handle 42, and the bottom of which is provided with a fixed head 43 for fixing the sample rack 5; the fixed head 43 is a detachable metal hook with an S shape, a length of 25-30 mm, and a thickness of 3-5 mm, and a fixed head screw hole 431 is arranged at the center position of the fixed head 43, which is fixed to the feeding rod screw hole 44 at the bottom end of the rod body 41 through a screw, i.e., the fixed head 43 is fixed to the bottom end of the rod body 41 through the fixed head screw hole 431, a screw, and the feeding rod screw hole 44.

[0065] As a preferred embodiment, the main body of the sample rack 5 is a rectangular metal base 51 with a length of 25-35 mm, a width of 15-18 mm, and a height of 25-30 mm, and a square sample rack groove 52 with a length and a width of 15-18 mm is arranged at the middle position of the base 51 and penetrates through the entire base from front to back; the groove depth of the sample rack groove 52 is 20-25 mm, and a sample rack circular hole 53 with a depth of 2-3 mm and a diameter of 3 mm is arranged at the center position of the sample rack groove 52 and is used for placing a pin leg sample rack 531; a fixed column 54 is arranged at the top of each of the left and right sides of the base 51 outside the sample rack groove 52, the fixed column 54 is fixed in the sample rack screw hole 55 through a screw (i.e., the base 5 is fixed through a screw), and is used for connecting with the fixed head 43 of the sample feeding rod 4 and connecting (the S-shaped hooks at both ends of the fixed head 43 are hooked on the two fixed columns 54) to realize the connection and separation between the sample rack 5 and the sample feeding rod 4; the diameter of the fixed column 54 is 3-5 mm, the height is 20-30 mm, the top of the fixed column 54 is provided with a circular ring-shaped lateral protrusion with a width of 2-3 mm and a thickness of 2-3 mm, and is used for limiting and fixing the fixed head 43.

[0066] As a preferred embodiment, the sample storage liquid nitrogen pool 6 is a heat-insulating foam pool, with a length and width of 200-250 mm, a height of 100-150 mm, and a bottom thickness and wall thickness of 20-25 mm.

[0067] As a preferred embodiment, the metal tank body 12, the movable sealing baffle 3, and the sample loading rod 4 are made of one of aluminum alloy and stainless steel; the sample rack 5 is made of one of red copper and brass; and the foam heat-insulating tank body 11 and the sample storage liquid nitrogen pool 6 are made of polystyrene foam.

[0068] The application also provides a use method of the liquid nitrogen slush freezing device for sample freezing and storage, including the following steps.

[0069] a. Preparation of liquid nitrogen slush: place the foam heat-insulating tank body 11 with a bottom-loaded movable foam bottom plate 111 in the bottom-sealed metal tank body 12, inject a certain volume of liquid nitrogen into the foam heat-insulating tank body 11, connect the metal tank body flange interface 126 of the metal tank body 12 and the sealing cover flange interface 221 of the slush tank sealing cover 2 through bolt fixing, insert the movable sealing baffle 3 into the gap formed between the two flange interfaces, so that the liquid nitrogen slush tank body 1 is kept airtight and in a sealed state, start the vacuum pump 7 connected to the liquid nitrogen slush tank body 1, and vacuumize the liquid nitrogen slush tank body 1, so that the liquid nitrogen in the foam heat-insulating tank body 11 is converted into liquid nitrogen slush in a supercooled state; during the process, the vacuum value in the liquid nitrogen slush tank body 1 is monitored in real time through the vacuum gauge 125, until reaching 1-50 pa.

[0070] b. Loading of samples to be frozen: during the waiting period for the formation of liquid nitrogen slush, insert the rod body 41 of the sample loading rod 4 into the second circular hole 211 of the detachable top cover 21 of the slush tank sealing cover 2, and fix the fixing head 43 in the sample loading rod screw hole 44 at the bottom end of the rod body 41 through a screw. Place the sample rack 5 with the sample rack fixing column 54 fixed on the fixing head 43 of the sample loading rod 4 in the square sample rack groove 52 of the sample rack 5, and place the sample loading rod 4 with the sample and the detachable top cover 21 on the cover body 22 of the slush tank sealing cover 2, and adjust the insertion depth of the sample loading rod 4 to avoid the collision between the sample rack 5 and the movable sealing baffle 3.

[0071] c. Sample pushing and freezing: After the vacuum value in the liquid nitrogen slush tank body 1 reaches the required value, slowly open the air release valve 124 to break the vacuum of the liquid nitrogen slush tank; after the air release is completed, slowly push the movable sealing baffle 3 to remove the closure isolation between the liquid nitrogen slush tank body 1 and the slush tank sealing cover 2, and realize communication. Push the sample loading rod 4 downward quickly to send the sample rack 5 to the bottom of the foam heat insulation tank 11, so that it is immersed in the liquid nitrogen slush; rotate the sample loading rod handle 42 to make the fixing head 43 rotate out from the side of the fixing column 54 of the sample rack 5, complete the separation, and then pull out the sample loading rod 4 quickly. Pull out the movable sealing baffle 3 to make the liquid nitrogen slush tank body 1 return to the closed (sealed) state, start the vacuum pump 7 to vacuum the liquid nitrogen slush tank body 1, and complete the freezing fixation of the sample in the liquid nitrogen slush, which lasts for 5-10 minutes;

[0072] d. Freezing sample removal and storage: After the freezing process is completed, slowly open the air release valve 124 to break the vacuum of the liquid nitrogen slush tank body 1; after the air release is completed, hold the handle 127 of the metal tank body 12 to transfer the liquid nitrogen slush tank to above the sample storage liquid nitrogen pool 6 which stores a certain amount of liquid nitrogen; carefully remove the movable metal bottom plate 121 at the bottom of the metal tank body 12, and then pull the drawstring of the movable foam bottom plate 111 of the foam heat insulation tank 11 to carefully pull out the foam bottom plate 111. When pulling out, pay attention to tilt the liquid nitrogen slush tank at a certain angle to prevent the liquid nitrogen from flowing out too quickly; the sample rack 5 will fall into the sample storage liquid nitrogen pool 6 along with the flowing liquid nitrogen and be stored in the liquid nitrogen for use.

[0073] The present application realizes the isolation and communication between the liquid nitrogen slush tank and the sealing cover through the movable sealing baffle, ensures that the sample waiting in the sealing cover after the liquid nitrogen slush is generated can be quickly inserted into the supercooled liquid nitrogen slush in the lower slush tank, and realizes rapid and high-quality freezing. Through the design of the sample rack and the fixing head of the sample loading rod, the rapid connection and separation between the sample and the sample loading rod are realized. Through the design of the movable bottom of the slush tank body, the frozen sample directly falls into the sample storage liquid nitrogen pool, avoiding the contact with air when it is transferred out of the liquid nitrogen slush to form surface condensation ice crystals.

[0074] The method of the present application can realize rapid and high-quality freezing of the sample in the supercooled liquid nitrogen, and ensure that the sample does not contact with air during the whole freezing and storage process, avoiding the formation of surface condensation ice crystals.

[0075] Example 1

[0076] The inner diameter of the inner foam heat insulation tank body 11 is 30 mm, the outer diameter is 50 mm, the height is 80 mm, and the wall thickness is 10 mm; the inner diameter of the outer metal tank body 12 is 60 mm, the outer diameter is 70 mm, the height is 110 mm, the wall thickness is 5 mm, and the tank bottom thickness is 5 mm; a gap is provided between the foam heat insulation tank body 11 and the metal tank body 12, and the gap is 5 mm, and the gap is filled with air; the foam heat insulation tank body 11 is designed as a movable bottom, the diameter of the movable foam bottom plate 111 is 30.5 mm, the thickness is 3 mm, and the movable foam bottom plate 111 is placed in the foam heat insulation tank body 11 through interference fit; the foam bottom plate 111 is provided with a drawstring for drawing out the foam bottom plate 111 from the bottom of the foam heat insulation tank body 11; the bottom of the metal tank body 12 is designed to be detachable, the diameter of the first circular hole 122 of the tank bottom opening is 45 mm, and the metal bottom plate 121 is used through gap fit; the metal bottom plate 121 is a circular metal plate with a shoulder design, the outer diameter is 60 mm, the thickness is 5 mm, the shoulder diameter is 45 mm, the thickness is 3 mm, and a groove is provided on the outer circle of the shoulder for placing the annular metal bottom plate sealing ring 1212 to realize radial sealing with the metal tank body 12; the materials of the components of the foam heat insulation tank body 11 are high-density polystyrene, and the materials of the components of the metal tank body 12 are all aluminum alloy.

[0077] The metal tank body 12 is designed with an extended vacuum interface 123 on one side for connecting the vacuum pump 7 and the vacuum gauge 125, and an extended air release valve 124 on the other side for connecting the atmosphere to break the vacuum; the metal tank body flange interface 126 is designed at the top opening of the metal tank body 12 for use in cooperation with the snow tank sealing cover 2 and the movable sealing baffle 3 to realize the sealing of the liquid nitrogen snow tank body 1, the thickness of the metal tank body flange interface 126 is 5 mm, and the width of the annular lateral protruding part is 10 mm; the upper surface of the metal tank body flange interface 126 is designed with a rectangular first flange interface groove 1261 penetrating the entire interface plane, which is used for sliding insertion of the movable sealing baffle 3; the depth of the first flange interface groove 1261 is 1.5 mm, the width is 75 mm, and the outer two sides of the groove are provided with four first flange interface screw holes 1264 for bolt connection with the snow tank sealing cover 2; the metal tank body 12 is designed with a groove 1262 at a distance of 2 mm from the top inner edge for placing the flange interface sealing ring 1263 to realize the axial sealing between the movable sealing baffle 3 and the metal tank body 12; a handle 127 is provided on the outside of the metal tank body 12, with a length of 80 mm, for convenient holding of the tank body; the flow rate of the vacuum pump 7 is 8 cubic meters per hour, and the limit vacuum degree is 0.5 Pa.

[0078] The sealing cover 2 of the snow slush tank is a metal cover, which is composed of a detachable top cover 21 and a lower cover body 22. The diameter of the detachable top cover 21 is 70 mm, and the detachable top cover 21 is connected to the cover body 22 in a clearance fit through shoulder positioning. A second circular hole 211 is arranged at the center of the top cover 21, and the second circular hole 211 is used for inserting a sample injection rod 4. The diameter of the second circular hole 211 is 5 mm. A drop prevention mechanism 212 is arranged on one side of the second circular hole 211. The drop prevention mechanism 212 is used for pushing the sample injection rod 4 upward by a spring 2122 and a resistance push block 2123 placed in a clamping groove 2121, so as to prevent the sample injection rod 4 from sliding downward under the action of gravity. The height of the cover body 22 is 30 mm, the inner diameter of the cover body 22 is 60 mm, and the outer diameter of the cover body 22 is 70 mm. A sealing cover flange interface 221 is arranged at the bottom of the cover body 22, and the width and thickness of the sealing cover flange interface 221 are consistent with those of a metal tank body flange interface 126 of a metal tank body 12. The sealing cover flange interface 221 is used in cooperation with the metal tank body flange interface 126. A rectangular second flange interface groove 2211 is arranged on the surface of the sealing cover flange interface 221 and penetrates the entire interface plane, and the second flange interface groove 2211 is used for sliding insertion of a movable sealing baffle 3. The depth of the second flange interface groove 2211 is 1.5 mm, and the width of the second flange interface groove 2211 is 75 mm. Four second flange interface screw holes 2212 are arranged side by side outside the groove area, and the sealing cover flange interface 221 is fixedly connected to the metal tank body flange interface 126 through bolt connection. The materials of the components of the sealing cover 2 of the snow slush tank are all aluminum alloy.

[0079] The movable sealing baffle 3 is a metal plate with a shape similar to a rectangle, and the material of the movable sealing baffle 3 is aluminum alloy. The two ends of the movable sealing baffle 3 are circular arc-shaped, and the radii of the two ends of the movable sealing baffle 3 are consistent with the radii of the circular edges of the metal tank body flange interface 126 and the sealing cover flange interface 221. The width of the movable sealing baffle 3 is 75 mm, the length of the movable sealing baffle 3 is 140 mm, and the thickness of the movable sealing baffle 3 is 3 mm. A movable sealing baffle circular hole 31 with a diameter of 60 mm is arranged at a position 10 mm away from the arc-shaped edge on one side of the movable sealing baffle 3. The movable sealing baffle 3 is pulled out to be in different positions, so as to realize switching between the communication and isolation states between the snow slush tank body 1 and the sealing cover 2 of the snow slush tank.

[0080] The rod body 41 of the sample injection rod 4 is a metal circular rod with a diameter of 5 mm and a length of 160 mm. A one-bar-shaped injection rod handle 42 is arranged at the top of the rod body 41 for convenient operation. An S-shaped detachable metal hook is arranged at the bottom of the rod body 41, and the metal hook is used as a fixing head 43 for fixing a sample rack. The length of the fixing head 43 is 25 mm, the thickness of the fixing head 43 is 3 mm, a fixing head screw hole 431 is arranged at the center of the fixing head 43, and the fixing head 43 is fixedly connected to an injection rod screw hole 44 at the bottom end of the rod body 41 through screw connection. The materials of the components of the sample injection rod 4 are all aluminum alloy.

[0081] The rectangular base 51 of the sample rack 5 body part has a length of 25 mm, a width of 15 mm, and a height of 25 mm, and a square sample rack groove 52 with a length of 15 mm and a width of 15 mm is arranged at the middle of the base and penetrates through the whole base, and the sample rack groove 52 has a groove depth of 20 mm, and a sample rack circular hole 53 with a depth of 2 mm and a diameter of 3 mm is arranged at the center of the sample rack groove 52 and is used for placing a nail leg sample rack 531; the base 51 is provided with a fixed column 54 on the left and right sides of the top of the base 51 outside the sample rack groove 52, and the fixed column 54 is fixed in a sample rack screw hole 55 through a screw and is used for cooperating with a fixed head 43 of a sample feeding rod 4 to realize the connection and separation between the sample rack 5 and the sample feeding rod 4; the fixed column 54 has a diameter of 3 mm and a height of 20 mm, and a circular ring-shaped lateral protrusion is arranged at the top of the fixed column 54, and the circular ring has a width of 2 mm and a thickness of 2 mm; the materials of the components of the sample rack 5 are all red copper.

[0082] The sample storage liquid nitrogen pool 6 is a heat insulation foam pool with a length of 200 mm, a width of 200 mm, and a height of 100 mm, and the bottom thickness and the wall thickness are both 20 mm, and the material is high-density polystyrene foam.

[0083] The use method of the device is as follows:

[0084] The foam heat insulation tank body 11 with the movable bottom foam bottom plate 111 arranged at the bottom is placed in the bottom-sealed metal tank body 12, 100 mL of liquid nitrogen is injected into the metal tank body 12, and the metal tank body flange interface 126 of the metal tank body 12 is fixedly connected with the sealing cover flange interface 221 of the snow mud tank sealing cover 2 through a bolt. The movable sealing baffle 3 is inserted into the gap between the metal tank body flange interface 126 and the sealing cover flange interface 221, so that the liquid nitrogen snow mud tank body 1 is kept closed. The vacuum pump 7 connected with the liquid nitrogen snow mud tank body 1 is started to vacuumize the liquid nitrogen snow mud tank body 1, so that the liquid nitrogen in the foam heat insulation tank body 11 is changed into liquid nitrogen snow mud in a supercooled state. During the period, the vacuum value in the liquid nitrogen snow mud tank body 1 is monitored in real time through the vacuum gauge 125 to be about 15 pa.

[0085] During the waiting period for the formation of the liquid nitrogen snow mud, the rod body 41 of the sample feeding rod 4 is inserted into the second circular hole 211 of the detachable top cover 21 of the snow mud tank sealing cover 2, and the fixed head 43 is fixed in the sample rod screw hole 44 at the bottom end of the rod body 41 through a screw. The nail leg sample rack 531 with a sample to be frozen is placed in the square sample rack groove 52 of the sample rack 5, and the sample rack 5 is fixed on the fixed head 43 of the sample feeding rod 4 through the fixed column 54. The sample feeding rod 4 with the sample fixed thereon and the detachable top cover 21 are placed on the cover body 22 of the snow mud tank sealing cover 2, and attention is paid to adjust the depth of the sample feeding rod 4 inserted to avoid the collision between the sample rack 5 and the movable sealing baffle 3.

[0086] After the vacuum value in the liquid nitrogen slush tank body 1 reaches the required value, slowly open the air release valve 124 to break the vacuum of the liquid nitrogen slush tank; after the air release is completed, slowly push in the movable sealing baffle 3 to remove the closure isolation between the liquid nitrogen slush tank body 1 and the slush tank sealing cover 2, and realize communication. Push in the sample loading rod 4 quickly, and send the sample rack 5 to the bottom of the foam heat insulation tank body 11 to immerse it in the liquid nitrogen slush; rotate the sample loading rod handle 42 on the sample loading rod 4 to rotate the fixed head 43 out from the side of the fixed column 54 of the sample rack 5, and quickly pull out the sample loading rod 4 after separation. Pull out the movable sealing baffle 3 to make the liquid nitrogen slush tank body 1 return to the closed state, start the vacuum pump 7 to vacuum the liquid nitrogen slush tank body 1, and complete the freezing fixation of the sample in the liquid nitrogen slush, and this process lasts for 5 minutes.

[0087] After the freezing process is completed, slowly open the air release valve 124 to break the vacuum of the liquid nitrogen slush tank body 1; after the air release is completed, hold the handle 127 on the side of the metal tank body 12 to transfer the liquid nitrogen slush tank to above the sample storage liquid nitrogen pool 6 which stores a certain amount of liquid nitrogen; carefully remove the movable bottom metal plate 121 at the bottom of the metal tank body 12, and then pull the pull rope of the movable foam bottom plate 111 of the foam heat insulation tank body 11 to carefully pull out the foam bottom plate 111. When pulling out, pay attention to tilt the liquid nitrogen slush tank at a certain angle to prevent the liquid nitrogen from flowing out too quickly; the sample rack 5 will fall into the sample storage liquid nitrogen pool 6 along with the flowing liquid nitrogen, and is stored in the liquid nitrogen for use.

[0088] Example 2

[0089] The inner diameter of the inner foam heat insulation tank body 11 is 50 mm, the outer diameter is 80 mm, the height is 120 mm, and the wall thickness is 15 mm; the inner diameter of the outer metal tank body 12 is 100 mm, the outer diameter is 116 mm, the height is 150 mm, the wall thickness is 8 mm, and the tank bottom thickness is 8 mm; a gap is arranged between the foam heat insulation tank body 11 and the metal tank body 12, and the gap is 10 mm, and the gap is filled with air; the foam heat insulation tank body 11 is designed as a movable bottom, the diameter of the movable foam bottom plate 111 is 50.5 mm, and the thickness is 5 mm, which is placed in the foam heat insulation tank body 11 through interference fit; the foam bottom plate 111 is provided with a pull rope for pulling out the foam bottom plate 111 from the bottom of the foam heat insulation tank body 11; the bottom of the metal tank body 12 is designed to be detachable, the diameter of the first circular hole 122 of the tank bottom opening is 75 mm, and the metal bottom plate 121 is used through gap fit; the metal bottom plate 121 is a circular metal plate with a shoulder design, the outer diameter is 110 mm, the thickness is 8 mm, the shoulder diameter is 75 mm, the thickness is 5 mm, and a groove is arranged on the outer circle of the shoulder for placing the annular metal bottom plate sealing ring 1212 to realize radial sealing with the metal tank body 12; the materials of the components of the foam heat insulation tank body 11 are high-density polystyrene, and the materials of the components of the metal tank body 12 are stainless steel.

[0090] The metal tank body 12 is designed with an extended vacuum interface 123 on one side for connecting the vacuum pump 7 and the vacuum gauge 125, and an extended air release valve 124 on the other side for connecting to the atmosphere to break the vacuum; the metal tank body 12 is designed with a metal tank body flange interface 126 at the top opening for cooperating with the snow tank sealing cover 2 and the movable sealing baffle 3 to realize the sealing of the liquid nitrogen snow tank body 1, the thickness of the metal tank body flange interface 126 is 7mm, and the width of the annular lateral protruding part is 15mm; the upper surface of the metal tank body flange interface 126 is designed with a rectangular first flange interface groove 1261 penetrating the entire interface plane for sliding insertion of the movable sealing baffle 3; the depth of the first flange interface groove 1261 is 2.5mm, the width is 135mm, and the outer two sides of the groove area are provided with four first flange interface screw holes 1264 for bolt connection and fixation with the snow tank sealing cover 2; the metal tank body 12 is designed with a groove 1262 at a distance of 2mm from the top inner edge for placing a flange interface sealing ring 1263 to realize the axial sealing between the movable sealing baffle 3 and the metal tank body 12; a handle 127 is provided on the outside of the metal tank body 12 with a length of 100mm for convenient holding of the tank body; the flow rate of the vacuum pump 7 is 8 cubic meters / hour, and the limit vacuum degree is 0.5Pa.

[0091] The snow tank sealing cover 2 is a metal cover composed of a detachable top cover 21 and a lower cover body 22; the diameter of the detachable top cover 21 is 110mm, which is connected with the cover body 22 through shoulder positioning to realize gap cooperation; the center of the top cover 21 is provided with a second circular hole 211 for inserting the sample injection rod 4, and the diameter of the second circular hole 211 is 7mm; one side of the second circular hole 211 is provided with an anti-falling mechanism 212, which pushes the top of the sample injection rod 4 through the spring 2122 and resistance push block 2123 placed in the clamping groove 2121 to prevent it from sliding down under the action of gravity; the height of the cover body 22 is 40mm, the inner diameter is 100mm, and the outer diameter is 110mm, and the bottom is designed with a sealing cover flange interface 221 with the same width and thickness as the metal tank body flange interface 126 of the metal tank body 12, which are matched; the surface of the sealing cover flange interface 221 is designed with a rectangular second flange interface groove 2211 penetrating the entire interface plane for sliding insertion of the movable sealing baffle 3; the depth of the second flange interface groove 2211 is 2.5mm, the width is 135mm, and four second flange interface screw holes 2212 are provided side by side in the groove area for bolt connection and fixation with the metal tank body flange interface 126; the materials of the components of the snow tank sealing cover 2 are all stainless steel.

[0092] The mobile sealing baffle 3 is a metal plate with approximate rectangular shape, made of aluminum alloy, with two arc-shaped ends, the radii of which are consistent with the circular edges of the metal can body flange interface 126 and the sealing cover flange interface 221; the width of the mobile sealing baffle 3 is 135 mm, the length is 240 mm, and the thickness is 5 mm; at a position 15 mm away from the arc-shaped edge on one side of the mobile sealing baffle 3, there is a mobile sealing baffle circular hole 31 with a diameter of 100 mm; by pulling the mobile sealing baffle 3 to different positions, the communication and isolation between the snow mud sealing can body 1 and the snow mud sealing can cover 2 can be switched.

[0093] The rod body 41 of the sample feeding rod 4 is a metal circular rod with a diameter of 7 mm and a length of 200 mm; a one-stroke feeding rod handle 42 is arranged at the top of the rod body 41 for convenient operation; a detachable metal hook in S shape is arranged at the bottom of the rod body 41, which is a fixing head 43 for fixing the sample rack 5, the length of the fixing head 43 is 30 mm, the thickness is 5 mm, and a fixing head screw hole 431 is arranged at the center position of the fixing head 43; the fixing head screw hole 431 can be fixed on the feeding rod screw hole 44 at the bottom end of the rod body 41 through a screw; the materials of the components of the sample feeding rod 4 are all stainless steel.

[0094] The rectangular base 51 of the sample rack 5 has a length of 35 mm, a width of 18 mm, and a height of 30 mm; a square sample rack groove 52 with a length of 18 mm and a width of 18 mm is arranged at the middle position of the base and penetrates through the whole base from front to back; the groove depth of the sample rack groove 52 is 25 mm; a sample rack circular hole 53 with a depth of 3 mm and a diameter of 3 mm is arranged at the center position of the sample rack groove 52, which is used for placing a pin leg sample rack 531; a fixing column 54 is arranged at the top of each of the left and right sides of the base 51 outside the sample rack groove 52, which is fixed in a sample rack screw hole 55 through a screw, and is used for cooperating with the fixing head 43 of the sample feeding rod 4 to realize the connection and separation between the sample rack 5 and the sample feeding rod 4; the diameter of the fixing column 54 is 5 mm, the height is 30 mm, the top of the fixing column 54 is arranged with a circular ring-shaped lateral protrusion with a width of 3 mm and a thickness of 3 mm; the materials of the components of the sample rack 5 are all brass.

[0095] The sample storage liquid nitrogen pool 6 is a heat-insulating foam pool with a length of 250 mm, a width of 250 mm, and a height of 150 mm; the bottom thickness and the wall thickness are both 25 mm; the material of the sample storage liquid nitrogen pool 6 is high-density polystyrene foam.

[0096] The use method of the device of the present application is as follows:

[0097] Put the foam insulation tank 11 with the bottom of the movable bottom foam bottom plate 111 into the bottom sealed metal tank 12, inject 400 mL of liquid nitrogen into it; connect the metal tank flange interface 126 of the metal tank 12 and the sealing cover flange interface 221 of the snow tank sealing cover 2 by bolt fixation. Insert the movable sealing baffle 3 into the gap between the metal tank flange interface 126 and the sealing cover flange interface 221 to keep the liquid nitrogen snow tank body 1 closed. Start the vacuum pump 7 connected to the liquid nitrogen snow tank body 1 to vacuumize the liquid nitrogen snow tank body 1, so that the liquid nitrogen in the foam insulation tank 11 becomes supercooled liquid nitrogen snow; during the process, the vacuum value in the liquid nitrogen snow tank body 1 is monitored in real time by the vacuum gauge 125 to about 30 pa.

[0098] During the waiting period for the formation of liquid nitrogen snow, insert the rod body 41 of the sample loading rod 4 into the second circular hole 211 of the detachable top cover 21 of the snow tank sealing cover 2; fix the fixed head 43 in the sample loading rod screw hole 44 at the bottom end of the rod body 41 by screwing. Place the sample stage 531 with the pin leg sample stage fixed on it into the square sample stage recess 52 of the sample stage holder 5, and fix the sample stage holder 5 on the fixed head 43 of the sample loading rod 4 by the fixed column 54. Place the sample loading rod 4 with the sample fixed on it together with the detachable top cover 21 on the cover body 22 of the snow tank sealing cover 2, and adjust the depth of the sample loading rod 4 inserted to avoid the sample stage holder 5 colliding with the movable sealing baffle 3.

[0099] After the vacuum value in the liquid nitrogen snow tank body 1 reaches the required value, slowly open the air release valve 124 to break the vacuum of the liquid nitrogen snow tank; after the air release is completed, slowly push in the movable sealing baffle 3 to remove the closed isolation between the liquid nitrogen snow tank body 1 and the snow tank sealing cover 2, and realize communication. Push down the sample loading rod 4 quickly to send the sample stage holder 5 to the bottom of the foam insulation tank 11, so that it is immersed in the liquid nitrogen snow; rotate the sample loading rod handle 42 on the sample loading rod 4 to make the fixed head 43 rotate out from the side of the fixed column 54 of the sample stage holder 5, complete the separation, and then quickly pull out the sample loading rod 4. Pull out the movable sealing baffle 3 to make the liquid nitrogen snow tank body 1 return to the closed state, start the vacuum pump 7 to vacuumize the liquid nitrogen snow tank body 1, so that the sample is frozen in the liquid nitrogen snow, and this process lasts for 8 minutes;

[0100] After the freezing process is completed, slowly open the gas release valve 124 to break the vacuum of the liquid nitrogen slush tank body 1; after the gas release is completed, hold the handle 127 on the side of the metal tank body 12 to transfer the liquid nitrogen slush tank to above the sample storage liquid nitrogen pool 6 which stores a certain amount of liquid nitrogen; carefully remove the movable bottom metal plate 121 at the bottom of the metal tank body 12, then pull the drawstring of the movable foam bottom plate 111 of the foam heat insulation tank body 11, carefully draw out the foam bottom plate 111, and pay attention to tilt the liquid nitrogen slush tank at a certain angle when drawing out to prevent the liquid nitrogen from flowing out too quickly; the sample rack 5 will fall into the sample storage liquid nitrogen pool 6 along with the outflowing liquid nitrogen and be stored in the liquid nitrogen for later use.

[0101] Finally, it should be noted that: the above embodiments are only used to illustrate the technical solutions of the present application, and not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: it can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present application.

Claims

1. A liquid nitrogen slush freezing device for sample freezing and storage, characterized in that, include: The liquid nitrogen slush tank body (1), slush tank sealing cap (2), movable sealing baffle (3), sample injection rod (4), sample stand (5), sample storage liquid nitrogen pool (6) and vacuum pump (7) are provided. The slush tank sealing cap (2) is sealed to the top of the liquid nitrogen slush tank body (1). The movable sealing baffle (3) is sealed between the liquid nitrogen slush tank body (1) and the slush tank sealing cap (2). The liquid nitrogen slush tank body (1), slush tank sealing cap (2) and movable sealing baffle (3) constitute a liquid nitrogen slush tank with a sealed internal space. The liquid nitrogen slush tank (1) is a cylindrical tank with an inner and outer double-layer structure, including an inner foam insulation tank (11) and an outer metal tank (12). The foam insulation tank (11) is placed inside the metal tank (12) and has a removable bottom. The bottom of the metal tank (12) is detachable. The sample stand (5) is connected below the sample injection rod (4). The sample injection rod (4) is inserted into the liquid nitrogen slush tank (1) through the slush tank sealing cover (2) to push the sample stand (5) with the sample to be frozen into the liquid nitrogen slush tank (1) for freezing. The vacuum pump (7) is connected to the liquid nitrogen slush tank (1) and is used to evacuate the inside of the liquid nitrogen slush tank (1); the sample storage liquid nitrogen pool (6) is a heat-insulating foam pool used to hold frozen samples that have been removed from the bottom of the liquid nitrogen slush tank (1) and to provide a liquid nitrogen cryopreservation environment for the frozen samples.

2. The liquid nitrogen slush freezing device for sample freezing and storage according to claim 1, characterized in that, There is a gap between the outer wall of the foam insulation tank (11) and the inner wall of the metal tank (12), and the gap is filled with air; The bottom of the foam insulation tank (11) is provided with a removable foam bottom plate (111), and the foam bottom plate (111) is placed with the foam insulation tank (11) by an interference fit; the foam bottom plate (111) is connected to a drawstring for pulling the foam bottom plate (111) out from the bottom of the foam insulation tank (11). The outer wall of the metal can (12) is provided with a protruding vacuum port (123) on one side. The vacuum port (123) is connected to the vacuum pump (7) through a pipeline. A vacuum gauge (125) is installed on the pipeline. The outer wall of the metal can (12) is provided with a protruding vent valve (124) for connecting to the atmosphere and breaking the vacuum. The outer side of the metal can (12) is provided with a handle (127) for holding the can.

3. The liquid nitrogen slush freezing device for sample freezing and storage according to claim 1, characterized in that, The bottom of the metal can (12) has a first circular hole (122), and a metal base plate (121) is connected in the first circular hole (122). The metal base plate (121) is a circular metal plate with a shoulder design. The outer ring of the shoulder is provided with a first groove (1211). An annular metal base plate sealing ring (1212) is placed in the first groove (1211). The metal base plate sealing ring (1212) is in close contact with the inner wall of the first circular hole (122) to achieve radial sealing between the metal base plate (121) and the bottom of the metal can (12).

4. The liquid nitrogen slush freezing device for sample freezing and storage according to claim 1, characterized in that, The metal tank (12) is provided with a metal tank flange interface (126) at the top opening, which is used in conjunction with the slush tank sealing cover (2) and the movable sealing baffle (3) to achieve the sealing of the liquid nitrogen slush tank (1); The upper surface of the metal tank flange interface (126) is provided with a first flange interface groove (1261) that runs through the entire interface plane, for sliding insertion of the movable sealing baffle (3); the first flange interface groove (1261) is provided with annular lateral protrusions on both sides, and the annular lateral protrusions are provided with a plurality of first flange interface screw holes (1264) for connecting and fixing with the snow can sealing cover (2) by bolts; The surface of the first flange interface groove (1261) has a groove (1262), and a flange interface sealing ring (1263) is placed in the groove (1262). The flange interface sealing ring (1263) is in close contact with the lower surface of the movable sealing baffle (3) to achieve axial sealing between the movable sealing baffle (3) and the metal tank (12).

5. The liquid nitrogen slush freezing device for sample freezing and storage according to claim 1, characterized in that, The slush can sealing cap (2) is a metal cap, consisting of a detachable top cap (21) and a lower cap body (22). The detachable top cap (21) has a shoulder, which is used to position and connect with the cap body (22). The removable top cover (21) has a second circular hole (211) in the center for inserting the sample injection rod (4). An anti-drop mechanism (212) is provided on one side of the second circular hole (211). The anti-drop mechanism (212) includes a slot (2121), a spring (2122), and a resistance push block (2123). The slot (2121) is opened on the top of the removable top cover (21). One end of the spring (2122) is fixed in the slot (2121), and the other end of the spring (2122) is fixedly connected to the resistance push block (2123). The resistance push block (2123) slides in the slot (2121). Under the elastic force of the spring (2122), the resistance push block (2123) pushes the sample injection rod (4) to prevent the sample injection rod (4) from sliding down under the action of gravity. The bottom of the cover (22) is provided with a sealing cover flange interface (221), which is connected to the metal tank flange interface (126) of the metal tank (12) to realize the fixed connection between the liquid nitrogen slush tank body (1) and the slush tank sealing cover (2). The lower surface of the sealing cover flange interface (221) is provided with a second flange interface groove (2211) that runs through the entire interface plane, for sliding insertion of the movable sealing baffle (3); The second flange interface groove (2211) has annular lateral protrusions on both sides, and the annular lateral protrusions have multiple second flange interface screw holes (2212) for bolt connection and fixation with the metal tank flange interface (126) of the metal tank (12).

6. The liquid nitrogen slush freezing device for sample freezing and storage according to claim 1, characterized in that, The movable sealing baffle (3) is a metal plate with rounded ends. The curvature of the rounded ends matches the circular edges of the metal tank flange interface (126) and the sealing cover flange interface (221) of the metal tank (12). The width of the movable sealing baffle (3) matches the width of the first flange interface groove (1261) of the metal tank flange interface (126). The movable sealing baffle (3) has a circular hole (31) on one side with a diameter consistent with the inner diameter of the metal tank (12). By pulling the movable sealing baffle (3), the circular hole (31) can be moved to different positions, thereby switching between the connected and isolated states between the liquid nitrogen snow mud tank (1) and the sealing cover (2).

7. The liquid nitrogen slush freezing device for sample freezing and storage according to claim 1, characterized in that, The sample injection rod (4) includes a rod body (41), which is a metal round rod. The top of the rod body (41) is provided with a straight injection rod handle (42), and the bottom is provided with a fixing head (43) for fixing the sample stage (5). The fixing head (43) is an S-shaped detachable metal hook. The center of the fixing head (43) is provided with a fixing head screw hole (431), and the bottom of the rod body (41) is provided with an injection rod screw hole (44). The fixing head (43) is fixed to the bottom of the rod body (41) through the fixing head screw hole (431), screws, and the injection rod screw hole (44).

8. The liquid nitrogen slush freezing device for sample freezing and storage according to claim 1, characterized in that, The main body of the sample stage (5) is a rectangular metal base (51). A square sample stage groove (52) that runs through the entire base (51) is provided in the middle of the base (51). A sample stage round hole (53) is opened in the center of the sample stage groove (52) for placing the nail leg sample stage (531). The base (51) has sample stage screw holes (55) on both sides of its top. The sample stage screw holes (55) are fixed with screws and fixing posts (54). The two fixing posts (54) are located on the left and right sides of the sample stage groove (52). The two sides of the fixing head (43) of the sample injection rod (4) are connected with the two fixing posts (54) to realize the connection and separation between the sample stage (5) and the sample injection rod (4). The top of the fixing post (54) is provided with a circular lateral protrusion for limiting and fixing the fixing head (43).

9. The liquid nitrogen slush freezing device for sample freezing and storage according to claim 1, characterized in that, The metal tank (12), the movable sealing baffle (3), and the sample injection rod (4) are all made of aluminum alloy or stainless steel; the sample stand (5) is made of copper or brass; and the foam insulation tank (11) and the sample storage liquid nitrogen pool (6) are made of polystyrene foam.

10. A method of using the liquid nitrogen slush freezing device for sample freezing and storage as described in any one of claims 1-9, characterized in that, Includes the following steps: S1. Preparation of liquid nitrogen slush: Place the foam-insulated tank (11) with the bottom plate (111) inside the sealed metal tank (12), and inject a certain volume of liquid nitrogen into the foam-insulated tank (11); fix the metal tank flange interface (126) of the metal tank (12) to the sealing cover flange interface (221) of the slush tank sealing cover (2) with bolts; insert a movable sealing baffle (3) into the gap formed by the two flange interfaces to keep the liquid nitrogen slush tank (1) sealed; start the vacuum pump (7) connected to the liquid nitrogen slush tank (1) to evacuate the liquid nitrogen slush tank (1) so that the liquid nitrogen in the foam-insulated tank (11) is converted into supercooled liquid nitrogen slush; during this period, monitor the vacuum value in the liquid nitrogen slush tank (1) in real time with a vacuum gauge (125) until it reaches 1-50 Pa; S2. Loading the sample to be frozen: While waiting for the liquid nitrogen slush to form, insert the rod body (41) of the sample injection rod (4) into the second round hole (211) of the removable top cover (21) of the slush tank sealing cover (2); fix the fixing head (43) in the injection rod screw hole (44) at the bottom of the rod body (41) with screws; place the nail leg sample stage (531) with the sample to be frozen fixed in the square sample stage groove (52) of the sample stage (5); fix the sample stage (5) to the fixing head (43) of the sample injection rod (4) with fixing post (54); place the sample injection rod (4) with the sample fixed together with the removable top cover (21) on the cover body (22) of the slush tank sealing cover (2), and adjust the insertion depth of the sample injection rod (4) to avoid the sample stage (5) from colliding with the moving sealing baffle (3); S3. Sample insertion and freezing: After the vacuum value inside the liquid nitrogen snow tank (1) reaches the required level, slowly open the vent valve (124) to break the vacuum in the liquid nitrogen snow tank (1); after the venting is completed, slowly push in the movable sealing baffle (3) to release the seal between the liquid nitrogen snow tank (1) and the snow tank sealing cover (2) and achieve communication; quickly push down the sample injection rod (4) to send the sample platform (5) to the bottom of the foam insulation tank (11) so that it is immersed in the liquid nitrogen snow; rotate the injection rod handle (42) so that the fixing head (43) rotates out from the side of the fixing column (54) and quickly pull out the sample injection rod (4) after separation; pull out the movable sealing baffle (3) so that the liquid nitrogen snow tank (1) is closed again, start the vacuum pump (7) to evacuate the liquid nitrogen snow tank (1) so that the sample is frozen and fixed in the liquid nitrogen snow. This process lasts for 5-10 minutes. S4. Removal and storage of frozen samples: After the freezing process is completed, slowly open the vent valve (124) to break the vacuum in the liquid nitrogen slush tank (1); after the venting is completed, hold the handle (127) of the metal tank (12) and transfer the liquid nitrogen slush tank to the sample storage liquid nitrogen pool (6) which contains a certain amount of liquid nitrogen; carefully remove the removable bottom metal plate (121) at the bottom of the metal tank (12), and then pull the drawstring of the foam bottom plate (111) of the foam insulation tank (11) to carefully pull out the foam bottom plate (111). When pulling out, tilt the liquid nitrogen slush tank at a certain angle to prevent the liquid nitrogen from flowing out too quickly; the sample stand (5) will fall into the sample storage liquid nitrogen pool (6) with the flowing liquid nitrogen and be stored in liquid nitrogen for later use.

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