Sample handling device, system and method for suspended containerless processing technology

Abstract

This application relates to the field of containerless suspension processing, specifically providing a sampling device, system, and method for containerless suspension processing technology. The sampling device includes a first gripper and a second gripper, symmetrically arranged and both bent towards the center. Each gripper has two teeth. The first and second grippers are close to each other in a closed state, and also open, far apart from each other. This sampling system is small in size, suitable for moving samples within a suspension chamber, and offers high precision. It can be used for gripping and placing samples within a suspension chamber. Multiple sample materials can be processed in a containerless suspension process after a single vacuuming and gas atmosphere replacement step. This significantly reduces the time cost of containerless suspension processing technology and improves its efficiency.

Description

Technical Field

[0001] This application relates to the field of containerless suspension processing technology, and more specifically, to a sampling device, system, and method for containerless suspension processing technology. Background Technology

[0002] Containerless suspension technology is a key technology that simulates the space environment with characteristics such as microgravity, ultra-high vacuum, containerlessness, and strong radiation on the ground through external physical fields. It is also an important means to solve the problems of high cost, low number of experiments, and limited opportunities in conducting materials research using space experimental systems such as space shuttles, spacecraft, space stations, and on-orbit satellites.

[0003] Containerless levitation technology can be categorized into electromagnetic levitation, electrostatic levitation, pneumatic levitation, and acoustic levitation, depending on the physical field used. Primarily, within a sealed chamber with an ultra-high vacuum or inert gas atmosphere, the forces generated by physical fields such as electromagnetic fields, electrostatic fields, gas flow fields, and acoustic fields counteract the material's gravity, placing the material in a suspended, containerless state. This allows for processes such as melting, solidification, and thermophysical property measurement, achieving the goals of researching and preparing new materials, exploring their thermophysical properties, and expanding their application areas and scope.

[0004] Generally, containerless suspension processing of materials requires an ultra-high vacuum environment or an inert gas atmosphere with ultra-low oxygen content. The sample processing typically involves vacuuming, gas atmosphere replacement, sample suspension, and sample treatment. Vacuuming and gas atmosphere replacement account for two-thirds of the containerless suspension processing time. For example, it usually takes 3-4 hours to reach a 10⁻⁶ ppm in a 40-50L sealed chamber. -5 A high vacuum of 10 Pa can be achieved in about 14-15 hours. -9 The ultra-high vacuum of Pa; under high vacuum or ultra-high vacuum conditions, gas atmosphere replacement takes 1-2 hours; overall, the time cost of suspending a single sample without a container is nearly 20-22 hours. Suspending only one sample under vacuum and a specific atmosphere leads to a large time cost; therefore, it is necessary to realize the storage, recovery, and movement of samples inside the chamber, which requires the installation of a sample pick-and-place system inside the chamber, in which the sample pick-and-place device precisely moves the sample.

[0005] Existing containerless suspension processing devices are still in the early stages of exploration for the delivery and recovery of batch samples. Currently, manual sample handling is the primary method, especially involving pneumatic suspension containerless processing technology. A Chinese patent application titled "A Device and Method for Material Solidification Experiments in Simulated Microgravity Environments," with publication number CN104569033A, discloses a device for simulating material solidification experiments in microgravity environments. This device proposes a containerless microgravity processing technology using electrostatic suspension combined with a short drop tube. Sample recovery is achieved by the sample falling into a recovery tray located at the bottom of a vacuum chamber, and only one sample can be processed per experiment. An invention patent entitled "An Automatic Sample Changing Mechanism," with publication number CN113353632B, discloses an automatic sample changing mechanism. This device is installed within the vacuum chamber of a neutron scattering electrostatic levitation system. Through upper and lower sample changing components (the sample tray employs a porous rotary structure) connected by a sample drop conduit, and a sample recovery mechanism below the lower sample changing component, it achieves automatic replacement and recovery of multiple samples within the vacuum chamber. However, this device requires a large installation space, especially in the height direction, significantly expanding the size of the vacuum chamber and increasing the cost of vacuuming. Furthermore, the sample changing mechanism obstructs the area around the suspended sample, limiting its application in containerless processing systems such as laser-heated electrostatic levitation, electromagnetic levitation, and pneumatic levitation, as well as the use of sensors to measure the thermophysical properties of samples such as density, viscosity, and surface tension. In particular, the sample changing mechanism interferes with the nozzle flow field of the pneumatic levitation system.

[0006] In summary, existing sampling devices or systems are not suitable for use in containerless suspension processing technology due to their large size, interference with the flow field, and impact on detection and suspension. Summary of the Invention

[0007] The purpose of this invention is to address the shortcomings of the prior art by providing a sampling device, system, and method for containerless suspension processing technology, thereby solving the problem that existing sampling devices or systems are unsuitable for use in containerless suspension processing technology due to their large size, interference with the flow field, and impact on detection and suspension.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0009] This application provides a sampling device, system, and method for containerless suspension processing technology. The sampling device for containerless suspension processing technology includes a first gripper and a second gripper, which are symmetrically arranged and both curved towards the center. Each gripper has two teeth with a gap between them. The first and second grippers are close together in a closed state, and also open together when they are far apart. In the closed state, the tips of the teeth are positioned on a spherical surface.

[0010] A sample handling system for containerless suspension processing technology includes a support component, on which a first sample storage device, a second sample storage device, and a sample transfer device are fixedly mounted. The first sample storage device is used to store the sample to be suspended, the second sample storage device is used to store the suspended sample, and the sample transfer device is used to move the sample. The sample transfer device includes a vertical motion mechanism fixedly mounted on the support component, a rotary motion mechanism fixedly connected to the vertical motion mechanism, and a horizontal motion mechanism fixedly connected to the rotary motion mechanism.

[0011] Furthermore, the sample transfer device also includes a transmission mechanism fixedly connected to the horizontal motion mechanism, and the transmission mechanism is fixedly connected to the gripping mechanism. The transmission mechanism is used to control the state of the gripping mechanism.

[0012] Furthermore, the gripping mechanism includes a first connecting rod and a second connecting rod fixedly connected to the transmission mechanism. One end of the first connecting rod and the second connecting rod are connected to the transmission mechanism, and the other end of the first connecting rod and the second connecting rod are connected to the aforementioned sampling device. The first connecting rod is fixedly connected to the first gripper head, and the second connecting rod is fixedly connected to the second gripper head.

[0013] Furthermore, the vertical motion mechanism includes a second motor and a first linear bearing fixedly connected to the support component. The second motor is a through-type hollow shaft stepper motor, and a second lead screw passes through the second motor, enabling the second lead screw to move in the vertical direction. A first optical axis passes through the first linear bearing, and the first optical axis and the first linear bearing are used for limiting.

[0014] Furthermore, the rotary motion mechanism includes a motor fixing flange fixedly connected to the top of the second lead screw, a third motor fixedly mounted on the motor fixing flange, the third motor being a stepper motor with a reduction gearbox, the motor shaft of the third motor being vertical, and a rotating platform fixedly mounted on the motor shaft of the third motor, the rotating platform rotating with the rotation of the motor shaft of the third motor.

[0015] Furthermore, the horizontal motion mechanism includes a bearing-motor fixing component fixedly connected to the upper side of the rotating platform. A third lead screw and a third optical shaft are provided through the bearing-motor fixing component. The third lead screw passes through a fourth motor. The third optical shaft is set on the bearing-motor fixing component through a second linear bearing. The third lead screw and the third optical shaft are also fixed to the optical shaft-lead screw fixing component. The optical shaft-lead screw fixing component is fixedly set at the ends of the third lead screw and the third optical shaft.

[0016] Furthermore, the transmission mechanism includes a fixed housing that is fixedly connected to the optical axis-lead screw fixing component. A fifth motor is fixedly installed on the side wall of the fixed housing. The motor shaft of the fifth motor is coaxially and fixedly connected to the motor shaft gear. The motor shaft gear meshes with the forward and reverse lead screw gear. The forward and reverse lead screw gear is coaxially and fixedly connected to the fourth lead screw. The fourth lead screw passes through the side wall of the fixed housing. The fourth optical axis is parallel to the fourth lead screw and is set at the same height. The fourth optical axis passes through the side wall of the fixed housing. The two ends of the fourth optical axis and the fourth lead screw are provided with gripper connecting slides. The gripper connecting slides are located on the outside of the fixed housing.

[0017] Furthermore, the first sample storage device includes a first movable bracket that is detachably and fixedly connected to the support component. A first motor is fixedly installed on the lower side of the first movable bracket. A first lead screw passes through the first motor and the first movable bracket. A piston is fixedly installed at the top of the first lead screw, and a first sample storage cylinder is fixedly installed on the side of the first lead screw.

[0018] This application also proposes a sampling method for containerless suspension processing technology, which includes the following steps:

[0019] S1, load multiple samples to be suspended into the first sample storage cylinder in sequence, and close the vacuum chamber;

[0020] S2, evacuation of the vacuum chamber and replacement of the gas atmosphere;

[0021] S3. After the suspension system is working stably, the sample in the first sample storage cylinder is moved to the top of the pneumatic suspension nozzle using the above-mentioned sampling device, and the suspended sample is placed in the gap between the first gripper and the second gripper.

[0022] S4. Gradually move the sampling device vertically downward, so that the force of the gas sprayed from the nozzle on the suspended sample gradually increases, and the elastic force of the first gripper and the second gripper on the sample gradually decreases. When it reaches zero, wait for the suspended sample to be in a suspended state. After suspension, remove the sampling device to the periphery of the pneumatic suspension flow field.

[0023] S5, Containerless suspension treatment experiments including melting, thermophysical property determination, solidification nucleation core placement and rapid solidification during the stable suspension process of the sample;

[0024] S6, suspension ends, control the sampling device to pick up the suspended sample after the experiment is completed directly above the pneumatic suspension nozzle, and move it to the second sample storage cylinder;

[0025] S7. Repeat steps S3-S6 until all samples have completed the containerless suspension treatment experiment.

[0026] S8, open the vacuum chamber, take out the second sample storage cylinder, take out all the suspended samples, and the experiment ends.

[0027] Compared with existing technologies, the beneficial effects of this invention are as follows: The sampling system of this application is small in size and has high moving precision, enabling it to grip and place samples inside the suspension chamber. It allows for the containerless suspension processing of multiple sample materials after a single vacuuming and gas atmosphere replacement process. This significantly reduces the time cost of containerless suspension processing technology and improves its efficiency. Furthermore, the sampling system is independent of the suspension system, provides unobstructed views of the suspended sample, and is compatible with multiple containerless suspension processing systems such as electrostatic suspension and electromagnetic suspension.

[0028] Meanwhile, in the sampling device, system, and method of this application, a gripper is used to assist in sample suspension. During sampling, the sample is placed at a higher position in the airflow. The airflow flows through the gripper, generating an air film that exerts a force on the sample. The gripper supports the sample. As the gripper is gradually moved downward, the force exerted by the airflow on the sample gradually increases, while the supporting effect of the gripper on the sample gradually decreases. When it becomes zero, the sample is stably suspended inside the gripper structure. Finally, the gripper is removed, and the sample remains stably suspended. The gripper of the sampling device ensures that the sampling device does not interfere with the flow field inside the chamber, resulting in more stable sample suspension. This application makes the sample suspension process more stable. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of a first sample storage device in a sampling system for containerless suspension processing technology provided by the present invention;

[0030] Figure 2 This is a schematic diagram of a second sample storage device in a sampling system for containerless suspension processing technology provided by the present invention;

[0031] Figure 3 This is a schematic diagram of a sampling system for containerless suspension processing technology provided by the present invention;

[0032] Figure 4 A schematic diagram of a rotary motion mechanism in a sampling system for containerless suspension processing technology provided by the present invention;

[0033] Figure 5This is a schematic diagram of the transmission mechanism and gripping mechanism in a sampling system for containerless suspension processing technology provided by the present invention.

[0034] Icons: 1-Sampling device; 11-Vertical motion mechanism; 111-Second motor; 112-Second lead screw; 113-First linear bearing; 114-First optical axis; 12-Rotary motion mechanism; 121-Third motor; 122-Motor mounting flange; 123-Rotating platform; 13-Horizontal motion mechanism; 131-Fourth motor; 132-Third lead screw; 133-Third optical axis; 134-Second linear bearing; 135-Bearing-motor fixing component; 136-Optical axis-lead screw fixing component; 14-Transmission mechanism; 141-Fixed housing; 14 2-Fifth motor; 143-Motor shaft gear; 144-Forward and reverse lead screw gear; 145-Fourth lead screw; 146-Fourth optical axis; 147-Gripper connecting slide; 15-Grip mechanism; 151-First connecting rod; 152-First gripper head; 153-Second connecting rod; 154-Second gripper head; 2-First sample storage device; 21-First motor; 22-First lead screw; 23-First movable support; 24-First sample storage cylinder; 25-Piston; 3-Second sample storage device; 31-Second movable support; 32-Second sample storage cylinder; 4-Supporting component. Detailed Implementation

[0035] To make the implementation process of this invention clearer, a detailed description will be provided below in conjunction with the accompanying drawings.

[0036] This invention provides a sampling system for containerless suspension processing technology. The system includes a sample transfer device 1, a first sample storage device 2, a second sample storage device 3, and a support component 4. The support component 4 supports the sample transfer device 1, the first sample storage device 2, and the second sample storage device 3. The sample transfer device 1, the first sample storage device 2, and the second sample storage device 3 are fixed to the support component 4, which is fixed inside a suspension device. The suspension device can be a pneumatic suspension device, electromagnetic suspension, electrostatic suspension, acoustic suspension, etc., enabling containerless suspension processing technology. The support component 4 can be fixed to the bottom wall or the side wall of the suspension device. This embodiment specifically describes a sampling system using pneumatic suspension technology because, compared to electromagnetic suspension, electrostatic suspension, acoustic suspension, and other containerless suspension processing technologies, the dynamic effect of the gas flow field and the requirements for suspension stability during pneumatic suspension make sample movement, recovery, and storage more difficult. Therefore, this embodiment chooses pneumatic suspension for specific description. This is not a limitation on the sampling system of this application, but merely an example of a specific structure.

[0037] The first sample storage device 2 is used to store samples to be suspended, and the second sample storage device 3 is used to store suspended samples. Before suspension, the sample transfer device 1 is used to transfer the sample from the first sample storage device 2 to the suspension position. After suspension, the sample transfer device 1 is used to transfer the suspended sample to the second sample storage device 3. Each sample in the first sample storage device 2 is suspended sequentially, and the suspended sample is stored in the second sample storage device 3. After all the samples to be suspended in the first sample storage device 2 have been suspended, all samples in the second sample storage device 3 are taken out at once. The order of the samples in the second sample storage device 3 corresponds to the order of the samples in the first sample storage device 2. The sample on the lower left side of the second sample storage device 3 corresponds to the sample on the uppermost side of the first sample storage device 2. In this way, the order of the samples can be identified, and the position of the corresponding sample can be clearly determined.

[0038] The supporting component 4 consists of a plate-like structure and connecting columns. The cross-sectional shape of the plate-like structure can be rectangular, circular, hexagonal, etc., and the specific shape is related to the shape of the suspension device, generally the same as the cross-sectional shape of the suspension device chamber. The thickness of the plate-like structure is 3mm-1cm. The material is a hard material such as stainless steel. The plate-like structure is provided with small holes for suspending samples or suspension nozzles to pass through, and the size of the small holes is greater than or equal to the outer diameter of the suspension device. Connecting columns connecting to the inner wall of the suspension chamber are provided on the lower or side of the plate-like structure. Preferably, the connecting columns are provided on the lower side of the plate-like structure, which makes the fixation more stable. Preferably, three or more connecting columns are symmetrically arranged around the aforementioned through holes. The connecting columns can be fixed to the plate-like structure by threads, screw holes, or welding. The length and diameter of the multiple connecting columns are generally equal, so that the weight borne by each connecting column is equal, and the support is more stable. On the upper side of the plate-like structure, that is, the side away from the connecting columns, the first sample storage device 2, the second sample storage device 3, and the sample transfer device 1 are fixedly arranged. The first sample storage device 2 and the second sample storage device 3 are fixedly installed on both sides of the suspended small hole on the plate-shaped structure.

[0039] The pneumatically levitated nozzle is coaxially screwed to the through-hole of the plate-like structure. The diameter of the through-hole in the plate-like structure is greater than or equal to the outer diameter of the air inlet of the pneumatically levitated nozzle, ensuring that the bottom of the nozzle can pass through the through-hole in the plate-like structure. It should be noted that the pneumatically levitated nozzle can be replaced with an electromagnetic levitation coil, an electrostatic levitation generator, or an acoustic levitation generator to achieve the application of the sampling system in electrostatic levitation, electromagnetic levitation, and acoustic levitation.

[0040] The first sample storage device 2 is fixedly mounted on a plate-like structure. It can be fixed by providing through holes in the plate-like structure and fixing it at the through holes, or by using a bracket to fix it to the edge of the plate-like structure. This embodiment uses a bracket-based fixing method as an example. Specifically, as follows... Figure 1As shown, the first sample storage device 2 includes a first motor 21, a first lead screw 22, a first movable support 23, a first sample storage cylinder 24, and a piston 25. The first movable support 23 fixes the first sample storage cylinder 24 and the first motor 21 to the edge of the plate-like structure. The first motor 21 is fixed to the lower part of the first movable support 23, which can be achieved by screwing. The first sample storage cylinder 24 is fixedly screwed to the upper part of the first movable support 23. A slot connection structure is provided on the side of the first movable support 23 for connecting with the plate-like structure. The width of the slot is equal to the thickness of the plate-like structure. The main function of this design is to allow for flexible installation of the first sample storage device 2 on the plate-like structure. One or more devices can be installed depending on the type and size of the experimental samples, and the position between the device and the sample transfer device 1 can be flexibly adjusted.

[0041] The first sample storage cylinder 24 is a tubular structure with an open top and a small hole at the bottom for the first lead screw 22 of the first motor 21 to pass through. Preferably, the inner diameter of the first sample storage cylinder 24 is 1.6 times the diameter of the suspended sample. For example, if the diameter of the suspended sample is 5 mm, the inner diameter of the first sample storage cylinder 24 is 8 mm. The first sample storage cylinder 24 can load and unload samples with a size of 5 mm to 8 mm. A vertical through groove with a width of 1 / 2 the diameter of the suspended sample is opened from the bottom of the side wall of the first sample storage cylinder 24 to the top of the first sample storage cylinder 24 at a distance of 10-15 mm. The piston 25 serves three purposes: first, it facilitates observation of the quantity and order of samples to be suspended inside; second, it limits the piston 25, preventing it from rotating due to the first lead screw 22. When moving up and down, the protrusion on the side of the piston 25 is confined within the through groove, moving up and down with the first lead screw 22 to prevent rotational movement and ensure vertical displacement; third, it prevents the first lead screw 22 from pulling the piston 25 out of the bottom of the first sample storage cylinder 24. Simultaneously, it facilitates observation of the samples inside the first sample storage cylinder 24 from the groove opening, clarifying the sample delivery order. The diameter of the piston 25 is the same as the inner diameter of the first sample storage cylinder 24, and its outer wall is designed with a boss structure that matches the groove opening size of the first sample storage cylinder 24. The boss inserts into the groove opening to limit the piston 25.

[0042] The first motor 21 is preferably a miniature through-type stepper motor. The first lead screw 22 of the first motor 21 passes through the first motor 21. The outer surface of the first lead screw 22 has threads. When the first motor 21 is working, the rotation of the motor causes the first lead screw 22 to move up and down, achieving the function of a push rod. This saves space in the horizontal direction of the device, making the device smaller and facilitating the control of the vertical position of the gripper in the suspension chamber. Preferably, the diameter of the motor portion of the first motor 21 is 25mm, and the diameter of the first lead screw 22 is 3.5mm. The first lead screw 22 of the first motor 21 is coaxially arranged with the first sample storage cylinder 24, passing through the first movable bracket 23 and the first sample storage cylinder 24. The piston 25 is screwed and fixed to the top of the first lead screw 22 of the first motor 21. The first movable bracket 23, the first sample storage cylinder 24, and the piston 25 are made of a hard, lightweight material, such as 7075 series aluminum alloy, which ensures lightweight while possessing good wear resistance, rigidity, and machinability. Multiple samples are loaded into the first sample storage cylinder 24. The first motor 21 causes the first lead screw 22 to move upward, and the piston 25 moves upward inside the first sample storage cylinder 24, pushing the sample to be suspended to the upper port of the first sample storage cylinder 24, so that it can be picked up by the sample transfer device 1. This greatly optimizes the sample delivery structure design, achieving the sample delivery function with the fewest possible parts, reducing manufacturing costs and saving installation and usage space, thus making the system smaller in size and suitable for operation in confined suspension chambers.

[0043] The second sample storage device 3 is used to recover the suspended samples. After the experiment, the suspension chamber is removed, allowing for the sequential storage of prepared and tested suspended samples according to the experimental order. The second sample storage device 3 includes a second movable support 31 and a second sample storage cylinder 32, as shown below. Figure 2 As shown. The second movable support 31 and the second sample storage cylinder 32 are made of hard and lightweight materials, such as 7075 series aluminum alloy. The shape and diameter of the second sample storage cylinder 32 are the same as those of the first sample storage cylinder 24. Specifically, the inner diameter is 1.6 times the diameter of the suspended sample. For example, if the diameter of the suspended sample is 5 mm, the inner diameter of the sample storage cylinder is 8 mm. Therefore, the second sample storage cylinder 32 can store samples with a size of 5 mm to 8 mm.

[0044] A slot with a width of half the diameter of the minimum suspended sample is formed on the side wall of the second sample storage cylinder 32. This slot allows for sample observation during storage and unloading, preventing confusion in sample order. The second sample storage cylinder 32 is screwed onto the second movable support 31 via a flange interface. The second movable support 31 has the same shape and structure as the first movable support 23. The second sample storage cylinder 32 is fixed to the plate-like structure via the second movable support 31, and can be fixed on the same side of the plate-like structure as the first movable support 23, or on the opposite side.

[0045] The sample transfer device 1 includes a first motion mechanism and a clamping mechanism. The first motion mechanism includes a vertical motion mechanism 11, a rotary motion mechanism 12, and a horizontal motion mechanism 13. The clamping mechanism includes a transmission mechanism 14 and a gripping mechanism 15, such as... Figure 3 As shown. Specifically, the sample transfer device 1 is fixedly mounted on the plate-like structure. In order to reduce the impact on the suspension process at the middle position, the sample transfer device 1 is fixedly mounted on the edge of the plate-like structure. The gripping mechanism 15 is used to grip and release samples. The opening and closing of the gripping mechanism 15 is controlled by the transmission mechanism 14. The transmission mechanism 14 is fixedly installed at the free end of the third lead screw 132 of the horizontal motion mechanism 13. Under the action of the fourth motor 131, the free end of the third lead screw 132 can move in the horizontal direction. The bearing-motor fixing part 135 in the horizontal motion mechanism 13 is fixedly installed on the rotating platform 123 of the rotary motion mechanism 12. In the rotary motion mechanism 12, the third motor 121 can make the rotating platform 123 rotate, thereby controlling the angle of movement of the gripping mechanism 15 in the horizontal plane. The cooperation between the rotary motion mechanism 12 and the horizontal motion mechanism 13 can enable the gripping mechanism 15 to reach any position in the plane within the range of measurement. The rotary motion mechanism 12 is fixed at the free end of the second lead screw 112 in the vertical motion mechanism 11. The free end of the second lead screw 112 can move in the vertical direction under the action of the second motor 111. The vertical motion mechanism 11 is fixedly installed on the plate structure. The vertical motion mechanism 11 controls the vertical movement of the gripping mechanism 15, the rotary motion mechanism 12 controls the forward direction of the gripping mechanism 15 in the horizontal plane, and the horizontal motion mechanism 13 controls the radial movement of the gripping mechanism 15 in the plane. Under the action of the vertical motion mechanism 11, the rotary motion mechanism 12, and the horizontal motion mechanism 13, the gripping mechanism 15 can move between the first sample storage device 2, the second sample storage device 3, and the suspension position to realize sample transfer. The transmission mechanism 14 controls the opening and closing of the gripping mechanism 15, that is, controls the gripping mechanism 15 to pick up and put down the sample. Detailed descriptions of each part are as follows:

[0046] The vertical motion mechanism 11 includes a second motor 111, a second lead screw 112, a first linear bearing 113, and a first optical shaft 114. The second motor 111 is a through-type hollow shaft motor. The second lead screw 112 passes through the second motor 111, and its surface is threaded. Under the action of the motor, the second lead screw 112 can move vertically up and down; this saves space by converting rotation into vertical motion. The motor portion of the second motor 111 is fixed to the lower side of the edge of the plate-like structure, which can be fixed with screws or other methods. The second lead screw 112 passes through the first through hole and extends upwards towards the plate-like structure, with its upper end being a free end. The center of the second through hole is located at a point where the center of the first through hole is the center of a circle, the radius of the flange of the first linear bearing 113 is the radius of the cross-sectional width of the second motor 111, and so on. This maximizes space efficiency, as the space within the suspension chamber is limited. The first linear bearing 113 is fixed to the upper side of the plate-like structure at the second through hole via a flange bolt connection. The distance between the central axis of the first linear bearing 113 and the central axis of the second lead screw 112 is the sum of the radius of the flange of the first linear bearing 113 and the width of the cross-sectional plate of the second motor 111. A first optical shaft 114 is fitted into the shaft hole of the first linear bearing 113. The lengths of the second lead screw 112 and the first optical shaft 114 are at least 1.2 times the effective stroke of the vertical motion mechanism 11. The effective stroke of the vertical motion mechanism 11 is greater than or equal to the product of the number of suspended samples stored and the sample diameter. For example, when the suspended sample is 5 mm and the storage quantity is 15, the effective stroke is at least 75 mm. The specific dimensions of the second motor 111, the second lead screw 112, the first linear bearing 113, and the first optical shaft 114 are not limited. Considering production costs, the dimensions of the second motor 111, the second lead screw 112, the first linear bearing 113, and the first optical shaft 114 are selected from existing standard parts on the market. The second motor 111 is a through-type hollow shaft stepper motor with a shaft diameter of 4mm (lead screw diameter), and a length, width, and height of 28mm, 28mm, and 44mm, respectively. Its advantage is its compact size. The lead screw 10 can pass through the motor shaft, eliminating the extra space occupied by the motor compared with ordinary motors, and greatly reducing the size of the sampling system. The first linear bearing 113 and the first optical shaft 114 limit the horizontal displacement and ensure the stability and flow field of the vertical movement. Their shaft diameter is the same as that of the second lead screw 112.

[0047] The rotary motion mechanism 12 includes a third motor 121, a motor mounting flange 122, and a rotating platform 123, as follows: Figure 3 and Figure 4As shown. The third motor 121 is a stepper motor with a reduction gearbox. Its dimensions are 4mm shaft diameter, and its length, width, and height are 89mm, 28mm, and 28mm respectively. Its function is to increase the axial rotational torque through the reduction gearbox, thereby improving the motor's load capacity and rotational accuracy, and thus enhancing the precision of the gripper's movement. The third motor 121 is horizontally fitted onto the motor mounting flange 122 and secured to the top of the motor mounting flange 122 by screws. The upper side of the motor mounting flange 122 has an opening for connecting the rotating platform 123, and the bottom of the motor mounting flange 122 is used to connect the upper end of the second lead screw 112 and the first optical shaft 114, serving to transmit vertical movement. Both the second lead screw 112 and the first optical shaft 114 are screwed to the bottom of the motor mounting flange 122. The first optical shaft 114 is connected at the end, and the second lead screw 112 is connected in the middle. The central axis of the second lead screw 112 is collinear with the motor shaft of the third motor 121, making the transmission of vertical motion more accurate and the torque zero during rotation, thus making the structure more stable. The rotating platform 123 is axially fitted and fixed to the motor shaft of the third motor 121. The rotating platform 123 is provided with a groove along the horizontal plane for fixing the horizontal motion mechanism 13 and transmitting rotation to the horizontal motion mechanism 13.

[0048] The horizontal motion mechanism 13 includes a fourth motor 131, a third lead screw 132, a third optical axis 133, a second linear bearing 134, a bearing-motor fixing component 135, and an optical axis-lead screw fixing component 136. The bearing-motor fixing component 135 and the optical axis-lead screw fixing component 136 are two rectangular plates, each with corresponding through holes through which the third lead screw 132 and the third optical axis 133 pass. The bearing-motor fixing component 135 is vertically positioned, meaning the larger surface area is vertical. The lower side of the bearing-motor fixing component 135 is fixedly mounted in a groove on the upper surface of the rotating platform 123 of the rotary motion mechanism 12. The lower end of the bearing-motor fixing component 135 is inserted into the groove of the rotating platform 123 and fixed radially by screws. When the rotating platform 123 rotates, the bearing-motor fixing component 135 rotates with it. The bearing-motor fixing component 135 has two through holes along the vertical direction, with the line connecting the centers of the two through holes pointing in the vertical direction.

[0049] A fourth motor 131 is installed at a through hole near the rotating platform 123. The fourth motor 131 is fixedly connected to the bearing-motor fixing component 135. A third lead screw 132 passes through the through hole and is driven by the fourth motor 131 to move the third lead screw 132 forward or backward in the horizontal direction. The free end of the third lead screw 132 faces the suspension device. A second linear bearing 134 is fixed at a through hole away from the rotating platform 123. A third optical axis 133 passes through the through hole and the second linear bearing 134. The optical axis-lead screw fixing component 136 is arranged parallel to the bearing-motor fixing component 135. The optical axis-lead screw fixing component 136 fixes the free ends of the third lead screw 132 and the third optical axis 133 together by screws and limits their movement together with the bearing-motor fixing component 135, ensuring the radial parallel structure of the third lead screw 132 and the third optical axis 133, and improving the stability and smoothness of the horizontal radial movement. The effective stroke of the horizontal motion mechanism 13 is at least 10 times the diameter of the suspended ball to ensure sufficient radial movement space. The structure and transmission components of the horizontal motion mechanism 13 can be the same as or different from those of the vertical motion mechanism 11. Preferably, the fourth motor 131 is the same as the second motor 111, the third lead screw 132 is the same as the second lead screw 112, the third optical axis 133 is the same as the first optical axis 114, and the second linear bearing 134 is the same as the first linear bearing 113. This reduces production and manufacturing costs and improves the consistency and portability of radial and vertical motion control.

[0050] The transmission mechanism 14 is used to control the opening and closing of the gripping mechanism 15, that is, to control the distance between the first gripper head 152 and the second gripper head 154 in the gripping mechanism 15. The transmission mechanism 14 includes a fixed housing 141, a fifth motor 142, a motor shaft gear 143, a forward and reverse lead screw gear 144, a fourth lead screw 145, a fourth optical shaft 146, and gripper connecting slides 147. Two gripper connecting slides 147 are provided, and the two gripper connecting slides 147 are identical in size and shape. The gripping mechanism 15 includes a first connecting rod 151, a first gripper head 152, a second connecting rod 153, and a second gripper head 154; as shown... Figure 5As shown. The rear wall of the fixed housing 141 is fixedly connected to the optical axis-lead screw fixing component 136 near the third lead screw 132. The third lead screw 132 is the free end for force transmission. In this way, the vertical movement, rotational movement, and horizontal movement of the sample transfer device 1 can be transmitted to the transmission mechanism 14, thereby changing the spatial position of the gripping mechanism 15. A fifth motor 142 is fixedly installed on the side wall of the fixed housing 141 near the sample transfer device 1. It can be screwed. The motor shaft of the fifth motor 142 passes through the side wall of the fixed housing 141 and enters the interior of the fixed housing 141. A motor shaft gear 143 is fixedly sleeved on the motor shaft of the fifth motor 142. The motor shaft gear 143 converts the rotation of the motor shaft into the rotation of the motor shaft gear 143. The forward and reverse lead screw gear 144 meshes with the motor shaft gear 143, transmitting the rotation of the motor shaft gear 143 to the forward and reverse lead screw gear 144.

[0051] A forward / reverse lead screw gear 144 is fixedly sleeved in the middle of the fourth lead screw 145, which passes through two corresponding through holes in the side wall of the fixed housing 141. The two ends of the fourth lead screw 145 are left-hand and right-hand external threads, respectively. Their function is to ensure that when the fourth lead screw 145 rotates, it drives the jaw connecting slide 147 screwed to it, resulting in two motion trajectories: opening and closing. This causes the distance between the first gripper 152 and the second gripper 154 to change, thus realizing the function of releasing and gripping samples. The length of the left-hand and right-hand threads is five times the width of the jaw connecting slide 147 (the length of the narrower side), ensuring that the jaw connecting slide 147 has sufficient opening and closing displacement. The width of the jaw connecting slide 147 should be twice the diameter of the suspended sample (for example, if the suspended sample diameter is 5mm, the width of the jaw connecting slide 147 should be 10mm). A width that is too large will increase the weight of the gripper system, while a width that is too small will cause instability and shaking when transporting samples. The fourth lead screw 145 is fixed to the outer side wall of the fixed housing 141 by means of a bearing connection. Its main function is to limit the axial displacement of the fourth lead screw 145 and reduce the frictional force of axial rotation. The fourth optical shaft 146 also passes through two other corresponding through holes in the side wall of the fixed housing 141. The fourth optical shaft 146 is located on the side of the fourth lead screw 145 away from the motor shaft gear 143.

[0052] The fourth optical axis 146 and the fourth lead screw 145 have the same central axis height and are parallel to each other. The axial distance between the fourth optical axis 146 and the fourth lead screw 145 is 5mm larger than the radius of the forward and reverse lead screw gear 144, ensuring the operational stability, structural compactness, and weight reduction of the gripper system. The fourth optical axis 146 and the fourth lead screw 145 are connected in the same way, fixed to the side wall of the fixed housing 141 by bearing connection. The main function of the fourth optical axis 146 is to limit the rotational movement of the gripper connecting slide 147 around its axis and ensure its smooth axial displacement. Two gripper connecting slides 147 are provided, respectively located on the outer side of opposite side walls of the fixed housing 141, serving to connect the two ends of the fourth optical axis 146 and the fourth lead screw 145 and to limit their movement. The two gripper connecting slides 147 have the same shape and size. The gripper connecting slide 147 is a cuboid with two through holes in the middle. The narrower side is parallel to the central axis of the fourth optical axis 146 and the fourth lead screw 145. The position and spacing of the two through holes correspond to the spacing between the fourth optical axis 146 and the fourth lead screw 145.

[0053] On the end face of the gripper connecting slide 147 on one side of the fourth optical axis 146, a first connecting rod 151 and a second connecting rod 153 are fixedly installed respectively. The first connecting rod 151 and the second connecting rod 153 are symmetrically arranged, and the distance between them decreases from the end near the gripper connecting slide 147 to the end away from the gripper connecting slide 147. Figure 5The stepped shape shown can also be a straight line or other shapes. The first gripper 152 and the second gripper 154 constitute the sampling device. The first gripper 152 is fixedly installed at the free end of the first connecting rod 151, and the second gripper 154 is fixedly installed at the free end of the second connecting rod 153. The first gripper 152 and the second gripper 154 are symmetrically arranged and both bend towards the middle. When the first gripper 152 and the second gripper 154 approach each other, the gripper closes; when the first gripper 152 and the second gripper 154 move away from each other, the gripper opens. Specifically, both the first gripper 152 and the second gripper 154 are equipped with two claws, with a gap between them. The gap between the claws must be smaller than the diameter of the smallest suspended sample (e.g., the smallest suspended sample diameter in pneumatic suspension is 2 mm), and can be 1.5-1.8 mm. The width and radius of curvature of the claws are comparable to the radius of the smallest suspended sample. In particular, when the tips of the two claws are in contact, a circular hole (approximately 1.5-1.8 mm) smaller than the smallest size of the suspended sample must be formed at the center to support the sample without obstructing the upward airflow from the nozzle. The shape of each claw can be the same or different. The part of the claw closer to the center is the tip, and the part farther from the center is the rear end. From the front end to the rear end, the diameter of the claw increases, and the gap between the claws gradually narrows, causing the airflow velocity to gradually increase. Thus, the airflow has the greatest supporting force on the sample at the middle position between the claws. The support points are symmetrical, canceling each other out in the horizontal direction, and the resultant force is in the vertical direction, offsetting the weight of the sample. When in the closed state, the tips of the claws are distributed on the spherical surface, preferably on a circle within a plane, allowing the claws to smoothly grip spherical samples. This firstly accommodates various suspended samples larger than 2 mm in size; secondly, the shape and aperture design of the claws guide the airflow from the suspension nozzle, enabling the suspended sample to be placed in the center of the airflow for suspension after the nozzle airflow has stabilized, and to be retrieved from the stabilized airflow; finally, if the sample falls into the conical opening of the nozzle, the claw-type mechanism can remove the sample from the conical opening.

[0054] The fifth motor 142, motor shaft gear 143, and forward / reverse lead screw gear 144 can be standard parts. The fifth motor 142 is a miniature stepper motor with length, width, and height dimensions of 20mm, 20mm, and 24mm respectively, and a shaft diameter of 4mm. The motor shaft gear 143 and the forward / reverse lead screw gear 144 are copper mold gears with a shaft hole diameter of 4mm (matching the diameter dimensions of the motor shaft and the fourth lead screw 145, respectively), and the material can be brass. The number of teeth on the motor shaft gear 143 and the forward / reverse lead screw gear 144 can be the same or different, depending on the load. When the load is small, the number of teeth on both gears is the same; when the load is large, increasing the tooth ratio of the forward / reverse lead screw gear 144 to the motor shaft gear 143 can improve the load capacity. The main function of the transmission mechanism 14 is that the rotational motion of the fifth motor 142 is transmitted sequentially through the motor shaft gear 143, the forward and reverse lead screw gear 144, the fourth lead screw 145, the fourth optical shaft 146, and the gripper connecting slide 147 to the first gripper 152 and the second gripper 154, so as to realize the approach and distance of the first gripper 152 and the second gripper 154, that is, to realize the opening and closing, and then the sample is picked up and put down.

[0055] The sampling system described in this application is small in size, requiring only 213-71-233 mm in length, width, and height, or even smaller. Its compact size and simplified structure allow for sample loading and unloading within a closed chamber without expanding the vacuum chamber's dimensions. This significantly optimizes the process flow of containerless suspension systems, reducing sample preparation and testing time and costs. To achieve further functionality and improve space utilization within the suspension chamber, a second motion mechanism can be fixed to the side of the plate-like structure of the supporting component 4. Similar to the first motion mechanism, this second motion mechanism enables precise movement of the probe end. The probe end can be equipped with a thermocouple temperature sensor to achieve dynamic multi-point temperature measurement of the suspended sample within the closed chamber. Figure 3 As shown, it can also be configured as a nucleation rod, cooling rod, magnetic field generator, etc., to perform operations such as solidification nucleation core placement, cooling, and external magnetic field application on suspended samples, achieving multi-functionality. Furthermore, for example, after incorporating the function of dynamic temperature measurement using an external heating coupler, the overall system space dimensions of the microrobot are 396 × 196 × 282 mm (length × width × height), with only a slight increase in the size of the vacuum chamber, fully demonstrating the compact, flexible, and multifunctional characteristics of this invention.

[0056] In use, multiple samples to be suspended are sequentially loaded into the first sample storage cylinder 24, and the vacuum chamber is closed. Depending on the experimental objective, the vacuum chamber is evacuated and the gas atmosphere is replaced, with a total duration of approximately 3-22 hours, depending on the vacuum requirements of the suspended samples. Under the action of the first motor 21, the piston 25 transports the sample to the upper end of the first sample storage cylinder 24. Through the cooperation of the vertical motion mechanism 11, the rotary motion mechanism 12, and the horizontal motion mechanism 13, the gripping mechanism 15 is moved to the vicinity of the sample to be suspended. Under the action of the transmission mechanism 14, the gripping mechanism 15 is opened and its position is precisely moved so that when the gripper is closed, it can just grasp the sample to be suspended at the upper end of the first sample storage cylinder 24. After the position is moved, under the action of the transmission mechanism 14, the gripping mechanism 15 is closed, keeping the gripper 15 closed, and the sample is moved to the top of the pneumatic suspension nozzle (the target position for suspension). The sample is suspended through the pneumatic suspension nozzle, and the gripper mechanism is withdrawn to the periphery of the pneumatic suspension flow field. Simultaneously, the next sample to be suspended moves to the upper end of the first sample storage cylinder 24 under the action of piston 25, awaiting sampling. During the stable suspension process, experiments involving melting, thermophysical property determination, solidification nucleation, and rapid solidification are performed. After completion, the gripping mechanism 15 is moved and controlled to grasp the suspended sample and place it into the second sample storage cylinder 32. Once all samples are suspended, they are removed from the chamber together. This system can accurately pick up, place, and move samples within a confined suspension chamber, eliminating the need for individual vacuuming of each sample and significantly saving time. The automatic sample material replacement (including sample placement, sample recovery, and storage) during the containerless suspension experiment after vacuuming and atmosphere replacement procedures solves the problem of low efficiency in containerless suspension experiments.

[0057] This application also provides a sampling method for containerless suspension processing technology, the method comprising the following steps:

[0058] S1, multiple samples to be suspended are sequentially loaded into the first sample storage cylinder 24, and the vacuum chamber is closed.

[0059] S2 involves evacuating the vacuum chamber and replacing the gas atmosphere. The specific duration depends on the vacuum requirements of the suspended sample, ranging from 3 to 22 hours.

[0060] S3, after the suspension system is working stably, the sample in the first sample storage cylinder 24 is moved directly above the pneumatic suspension nozzle using the above-mentioned sampling device, until the suspended sample is in the gap between the first gripper and the second gripper. The sampling device consists of the first gripper 152 and the second gripper 154. The position of the sampling device is controlled by the above-mentioned vertical motion mechanism 11, rotary motion mechanism 12, and horizontal motion mechanism 13, and the opening and closing of the sampling device is controlled by the transmission mechanism 14.

[0061] S4. Gradually move the sampling device vertically downwards, causing the force of the gas ejected from the nozzle on the suspended sample to gradually increase. The elastic force on the sample at the contact point of the first gripper 152 and the second gripper 154 gradually decreases until it reaches zero, at which point the suspended sample is in a suspended state. After suspension, remove the sampling device to the periphery of the pneumatic suspension flow field. The sampling device can support the sample while not obstructing the upward airflow from the nozzle. This allows it to handle various suspended samples larger than 2mm. Furthermore, the shape and orifice design of the grippers guide the airflow from the suspension nozzle, enabling the suspended sample to be placed in the center of the airflow for suspension after the nozzle airflow has stabilized.

[0062] S5 involves containerless suspension treatment experiments, including melting, thermophysical property determination, solidification nucleation core placement, and rapid solidification, during the stable suspension process of the sample.

[0063] S6, suspension ends. The sampling device is controlled to pick up the suspended sample directly above the pneumatic suspension nozzle after the experiment and move it to the second sample storage cylinder 32. The sample is picked up from the stable suspended airflow. If the sample falls into the conical opening of the nozzle, the sampling device can remove the sample from the conical opening.

[0064] S7. Repeat steps S3-S6 until all samples have completed the containerless suspension treatment experiment.

[0065] S8, open the suspension chamber, take out the second sample storage cylinder 32, take out all the suspended samples, and the experiment ends.

[0066] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A sampling system for containerless suspension processing technology, the system comprising a support component, characterized in that, The supporting component is fixedly equipped with a first sample storage device, a second sample storage device, and a sample transfer device. The first sample storage device is used to store the sample to be suspended, the second sample storage device is used to store the suspended sample, and the sample transfer device is used to move the sample. The sample transfer device includes a vertical motion mechanism fixedly mounted on the supporting component, a rotary motion mechanism fixedly connected to the vertical motion mechanism, and a horizontal motion mechanism fixedly connected to the rotary motion mechanism. The sample transfer device also includes a transmission mechanism fixedly connected to the horizontal motion mechanism. The transmission mechanism is fixedly connected to a gripping mechanism and is used to control the state of the gripping mechanism. The gripping mechanism includes a first connecting rod and a second connecting rod fixedly connected to the transmission mechanism. One end of the first connecting rod and the second connecting rod is connected to the transmission mechanism, and the other end of the first connecting rod and the second connecting rod is connected to the sample taking and placing device. The first connecting rod is fixedly connected to a first gripping head, and the second connecting rod is fixedly connected to a second gripping head. The sampling device includes a first gripper and a second gripper, which are symmetrically arranged and both curved towards the center. Each gripper has two teeth with a gap between them. When the grippers are close to each other and in a closed state, they are also far apart and in an open state. When in the closed state, the tips of the teeth are positioned on the spherical surface. The system is used to pick up and place pneumatically suspended spherical samples. The gap is smaller than the diameter of the smallest suspended sample. When the tips of the first and second grippers are closed, a circular hole smaller than the diameter of the smallest suspended sample is formed in the center. While supporting the sample, it does not obstruct the airflow from the nozzle from bottom to top. The airflow flows through the gap, generating an air film that exerts a force on the sample. From the middle to the edge, the gap narrows, and the airflow speed gradually increases. The airflow exerts the greatest supporting force on the sample at the middle position between the grippers. The support points are symmetrical, and the horizontal forces cancel each other out. The resultant force is along the vertical direction, canceling out the weight of the sample and achieving suspension.

2. The sampling system for containerless suspension processing technology according to claim 1, characterized in that, The vertical motion mechanism includes a second motor and a first linear bearing fixedly connected to the support component. The second motor is a through-type hollow shaft stepper motor, and a second lead screw passes through the second motor. The second motor enables the second lead screw to move in the vertical direction. A first optical axis passes through the first linear bearing, and the first optical axis and the first linear bearing are used for limiting.

3. The sampling system for containerless suspension processing technology according to claim 2, characterized in that, The rotary motion mechanism includes a motor fixing flange fixedly connected to the top end of the second lead screw. A third motor is fixedly mounted on the motor fixing flange. The third motor is a stepper motor with a reduction gearbox. The motor shaft of the third motor is vertical. A rotating platform is fixedly mounted on the motor shaft of the third motor. The rotating platform rotates with the rotation of the motor shaft of the third motor.

4. The sampling system for containerless suspension processing technology according to claim 3, characterized in that, The horizontal motion mechanism includes a bearing-motor fixing component fixedly connected to the upper side of the rotating platform. A third lead screw and a third optical axis are provided through the bearing-motor fixing component. The third lead screw passes through a fourth motor. The third optical axis is set on the bearing-motor fixing component through a second linear bearing. The third lead screw and the third optical axis are also fixed to the optical axis-lead screw fixing component. The optical axis-lead screw fixing component is fixedly set at the ends of the third lead screw and the third optical axis.

5. The sampling system for containerless suspension processing technology according to claim 4, characterized in that, The transmission mechanism includes a fixed housing fixedly connected to the optical axis-lead screw fixing component. A fifth motor is fixedly installed on the side wall of the fixed housing. The motor shaft of the fifth motor is coaxially fixedly connected to the motor shaft gear. The motor shaft gear meshes with the forward and reverse lead screw gear. The forward and reverse lead screw gear is coaxially fixedly connected to the fourth lead screw. The fourth lead screw passes through the side wall of the fixed housing. The fourth optical axis is parallel to and at the same height as the fourth lead screw. The fourth optical axis passes through the side wall of the fixed housing. Both ends of the fourth optical axis and the fourth lead screw are provided with gripper connecting slides. The gripper connecting slides are located on the outside of the fixed housing.

6. The sampling system for containerless suspension processing technology according to claim 5, characterized in that, The first sample storage device includes a first movable bracket that is detachably and fixedly connected to the support component. A first motor is fixedly installed on the lower side of the first movable bracket. A first lead screw passes through the first motor and the first movable bracket. A piston is fixedly installed at the top of the first lead screw. A first sample storage cylinder is fixedly installed on the side of the first lead screw.

7. A sampling method for containerless suspension processing technology, characterized in that, The method includes the following steps: S1, load multiple samples to be suspended into the first sample storage cylinder in sequence, and close the vacuum chamber; S2, evacuation of the vacuum chamber and replacement of the gas atmosphere; S3, after the suspension system is working stably, the sample in the first sample storage cylinder is moved to the top of the pneumatic suspension nozzle using the sampling device as described in claim 1, and the suspended sample is placed in the gap between the first gripper head and the second gripper head. S4. Gradually move the sampling device vertically downward, so that the force of the gas sprayed from the nozzle on the suspended sample gradually increases, and the elastic force of the first gripper and the second gripper on the sample gradually decreases. When it reaches zero, wait for the suspended sample to be in a suspended state. After suspension, remove the sampling device to the periphery of the pneumatic suspension flow field. S5, a containerless suspension treatment experiment that involves melting, thermophysical property determination, solidification nucleation core placement and rapid solidification during the stable suspension process of the sample. S6, suspension ends, control the sampling device to pick up the suspended sample after the experiment is completed directly above the pneumatic suspension nozzle, and move it to the second sample storage cylinder; S7. Repeat steps S3-S6 until all samples have completed the containerless suspension treatment experiment. S8, open the vacuum chamber, take out the second sample storage cylinder, take out all the suspended samples, and the experiment ends.

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