Device and method for testing flying liquid drop contact position

Abstract

The invention discloses a device for testing the contact position of a flying liquid drop, and the device comprises a signal generator which is connected with a power amplifier; the ultrasonic transducer is connected with the signal generator; the coupling liquid pool is arranged above the ultrasonic transducer, and a source liquid pool is arranged above the coupling liquid pool; the liquid drop collecting substrate is arranged above the source liquid pool; the high-speed camera is arranged above one side of the source liquid pool; and the upper computer is in communication connection with the high-speed camera. According to the device for testing the flying liquid drop contact position, through the combination of the high-speed camera and the upper computer, the flying liquid drop contact position can be simply and effectively detected.

Description

Technical Field

[0001] The invention relates to the technical field of ultrasonic liquid transfer, and in particular to a device and a method for testing the contact position of a flying droplet. Background Art

[0002] Acoustic Droplet Ejection (ADE) technology has made significant progress in recent years. If ultrasonic pipetting technology is to be applied in the fields of biotechnology, drug development and in vitro diagnostics, the required liquid volume will be reduced from milliliters and microliters to nanoliters or picoliters of droplets.

[0003] During ultrasonic pipetting, when a droplet is stimulated to move upward from the liquid surface, in most cases it does not move vertically upward with uniform deceleration, but has a certain deflection from the vertical direction. Therefore, when the droplet continues to fly until it contacts the droplet collection substrate above, it is necessary to confirm whether the contact position of the droplet is within the target range.

[0004] The volume of moving droplets is usually in the nanoliter or even picoliter range. The volume of moving droplets is too small and the flying speed of droplets is too fast, so it is difficult to directly confirm whether the droplets are in contact with the bottom of the target hole of the upper droplet collection substrate. Since the volume of droplets is too small, even if the bottom of the target hole of the collection substrate is directly observed, it is difficult to determine by naked eye whether the droplets are in contact with the target position. Summary of the invention

[0005] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a device and a testing method for testing the contact position of a flying droplet, which can determine the motion trajectory of a flying droplet and be used to test and calibrate the contact position of a flying droplet and a porous plate in an ultrasonic pipetting system.

[0006] To achieve the above object, the present invention provides the following technical solution: a device for testing the contact position of a flying droplet, comprising:

[0007] A signal generator, which is connected to a power amplifier and is used to generate a sinusoidal pulse signal and then output it after being amplified by the power amplifier;

[0008] The ultrasonic transducer is connected to the signal generator and is used to receive the output sinusoidal pulse signal and convert the sinusoidal pulse electrical signal into high-frequency ultrasonic wave for output;

[0009] A coupling liquid pool is arranged above the ultrasonic transducer, and a source liquid pool is arranged above the coupling liquid pool. The high-frequency ultrasonic wave output by the ultrasonic transducer passes through the coupling liquid pool and the source liquid pool and is focused on the liquid surface of the source liquid pool, thereby exciting the droplets to fly into the air.

[0010] A droplet collecting substrate is disposed above the source liquid pool to collect the excited droplets;

[0011] A high-speed camera is arranged above one side of the source liquid pool, and a parallel light source is arranged above the other side of the source liquid pool to supplement light for the flying droplets and then collect images through the high-speed camera;

[0012] The host computer is connected to the high-speed camera for receiving images taken by the high-speed camera, filtering the images to obtain images containing droplets, performing graphic preprocessing on the droplet images, identifying the center of mass of the droplets, calculating the flight trajectory equation of the droplets, and then calculating the droplet contact position based on the calculated droplet flight trajectory equation.

[0013] As a further improvement of the present invention, two high-speed cameras and two parallel light sources are provided, and the two high-speed cameras and the two parallel light sources are arranged opposite to each other, respectively facing the X-axis and Y-axis directions of the central axis of the ultrasonic transducer, and the flying droplets are arranged between the high-speed camera and the parallel light source to form a "main view + left view" droplet shooting.

[0014] As a further improvement of the present invention, the droplet flight trajectory equation calculated by the host computer is as follows:

[0015]

[0016] Among them, k represents the linear relationship between y and x, that is, the motion of the droplet in the xy plane is uniform, and v z0 represents the initial velocity of the droplet in the Z direction when it just leaves the liquid surface, v x represents the velocity of the droplet in the X direction, and g is the gravitational acceleration. As a further improvement of the present invention, k is calculated by the following formula:

[0017]

[0018] Among them, v x represents the velocity of the droplet in the X direction, v y Indicates the velocity of the droplet in the Y direction.

[0019] As a further improvement of the present invention, the v x Calculated according to the following formula:

[0020]

[0021] Where T is the interval between the previous frame and the next frame of the droplet image taken continuously by the high-speed camera, △ xi is the distance in the X direction between the centroids of two adjacent continuous droplet images taken in the Y direction by a high-speed camera.

[0022] As a further improvement of the present invention, the v z0 According to the following formula:

[0023]

[0024] Wherein, h0 is the distance between the central axis of the high-speed camera lens and the surface of the source liquid pool in the Z direction; v z The average velocity of the droplet in the Z direction captured by a high-speed camera.

[0025] As a further improvement of the present invention, the v z According to the following formula:

[0026]

[0027] Among them, △ zi It is the distance in the Z direction between the centroids of two adjacent continuous droplet images taken in the Z direction by a high-speed camera.

[0028] As a further improvement of the present invention, the host computer also calculates the final coordinate position of the droplet on the collection substrate through the following simultaneous equations:

[0029]

[0030] Wherein, H is the distance between the surface of the source liquid pool and the bottom of the droplet collection substrate in the Z direction.

[0031] Another aspect of the present invention provides a testing method, comprising the following steps:

[0032] Step 1: Establish an xyz coordinate system, adjust the positions of the two high-speed cameras, place the two high-speed cameras at the same height and face the X and Y directions of the central axis of the ultrasonic transducer respectively, form a "main view + left view" droplet shooting experimental environment, and face the two parallel light sources to the two high-speed cameras;

[0033] Step 2: Turn on the signal generator, the power amplifier and the ultrasonic transducer to continuously excite the droplets in the source liquid pool, then adjust the magnification and focal length of the high-speed camera to make the magnification and focal length of the two high-speed cameras consistent, adjust the parallel light source to a suitable brightness, obtain a clear image of the flying droplets in the field of view, and shoot the image;

[0034] Step three, preprocess the droplet image in the X and Y directions to obtain the droplet contour curve, determine the center of mass of the droplet, obtain a droplet center of mass map, and then determine the droplet flight trajectory equation based on the droplet center of mass coordinate position, and calculate the contact position between the droplet and the droplet collection substrate.

[0035] The beneficial effects of the present invention are as follows: two high-speed cameras are used to capture images of flying droplets in ultrasonic pipetting in the X and Y directions; the droplet contour is identified, the position of the droplet center of mass is obtained, and the equation of the droplet flight trajectory curve is obtained by fitting; the droplet flight trajectory curve is used to obtain the contact position of the droplet continuing to fly to the droplet collection substrate above; the testing method is simpler and more convenient, and the equipment cost is low and the testing accuracy is high. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 is a schematic diagram of a device for testing the contact position of a flying droplet according to an embodiment of the present application;

[0037] Figure 2 is a schematic diagram of a droplet photographed in the X and Y directions according to an embodiment of the present application;

[0038] Figure 3 is a schematic diagram of determining the centroid of a droplet according to an embodiment of the present application;

[0039] Figure 4 is a schematic diagram of the distance between two adjacent pictures on the x and y axes in an embodiment of the present application;

[0040] Figure 5 Schematic diagram of the distance between the central axis of the high-speed camera lens, the surface of the source liquid pool and the droplet collection substrate in the Z direction according to an embodiment of the present application;

[0041] Figure 6 is a schematic diagram of the distance between two adjacent images on the Z axis in an embodiment of the present application;

[0042] Figure 7 It is a schematic diagram of the contact position between the droplets and the collecting substrate in an embodiment of the present application. DETAILED DESCRIPTION

[0043] The present invention will be further described below in detail with reference to the embodiments shown in the accompanying drawings.

[0044] Reference Figure 1 As shown, a device for testing the contact position of a flying droplet in this embodiment includes: an ultrasonic pipetting module, a droplet observation module and a droplet image processing module.

[0045] The ultrasonic liquid transfer module is used to stimulate and generate micro-droplets moving upward, and includes a signal generator 1, a power amplifier 2, an ultrasonic transducer 3, a coupling liquid pool 4, a source liquid pool 5 and a droplet collection substrate 9;

[0046] The droplet observation module is used to capture images of flying droplets, and includes two high-speed cameras 6 and two parallel light sources 7;

[0047] The droplet image processing module is used to pre-process the flying droplet image and fit the motion trajectory curve of the droplet, including a host computer 8 and a software program preset in the host computer;

[0048] Furthermore, the ultrasonic pipetting module generates a sinusoidal pulse signal through a signal generator 1, and then amplifies the sinusoidal pulse signal through a power amplifier 2 and transmits it to an ultrasonic transducer 3. The ultrasonic transducer 3 converts the amplified electrical signal into a high-frequency ultrasonic wave. The high-frequency ultrasonic wave passes through a coupling liquid pool 4 and a source liquid pool 5 and is focused on the liquid surface of the source liquid pool, converting the sound energy into kinetic energy of droplets on the liquid surface, and exciting the droplets to fly into the air until they come into contact with the droplet collection substrate 9 and are collected.

[0049] Furthermore, the droplet observation device is provided with two high-speed cameras 6 in the X and Y directions. When the ultrasonic pipetting module excites the droplets into the air, the two high-speed cameras 6 take clear and complete images of the droplets with the help of two parallel light sources 7 facing each other and save them to the host computer 8.

[0050] Furthermore, the host computer 8 receives the images taken by the high-speed camera 6, and screens the images containing the droplets, performs graphic preprocessing on the droplet images, identifies the center of mass of the droplets, and calculates the flight trajectory of the droplets.

[0051] Based on the above device structure, this embodiment further provides a testing method, which is as follows:

[0052] Establish an xyz coordinate system, adjust the positions of the two high-speed cameras 6, adjust the two high-speed cameras 6 to be at the same height and face the X and Y directions of the central axis of the ultrasonic transducer 3 respectively, form a "main view + left view" droplet shooting experimental environment, and place two parallel light sources 7 facing the two high-speed cameras 6;

[0053] Turn on the ultrasonic pipetting module to continuously excite the droplets in the source liquid pool 5, adjust the magnification and focal length of the high-speed camera 6 to make the magnification and focal length of the two high-speed cameras 6 consistent, adjust the parallel light source 7 to a suitable brightness to obtain a clear image of the flying droplets in the field of view, and shoot the image.

[0054] The images containing droplets are obtained by filtering through the droplet image processing module, such as Figure 2 The image of the droplet in the X and Y directions is shown, and the image preprocessing is performed on the droplet image to obtain the droplet contour curve and determine the center of mass of the droplet, as shown in FIG. Figure 3 The droplet centroid diagram shown is used to determine the droplet flight trajectory equation based on the droplet centroid coordinate position, and calculate the contact position between the droplet and the droplet collection substrate 9.

[0055] The above flight trajectory equation is as follows:

[0056] The droplet is regarded as a constant deceleration motion in the Z direction and a constant velocity motion in the X and Y directions, and the droplet trajectory equation is defined as:

[0057]

[0058] Among them, k represents the linear relationship between y and x, that is, the movement of the droplet in the xy plane is uniform; further calculate k in the above trajectory equation:

[0059]

[0060] v z0 v represents the initial velocity of the droplet in the Z direction when it just leaves the liquid surface; x represents the velocity of the droplet in the x direction; v y represents the velocity of the droplet in the y direction; g is the acceleration due to gravity, which is 9.8 m / s 2 .

[0061] Then calculate v x , according to the following formula:

[0062]

[0063] Where T is the interval between the previous frame and the next frame of the droplet image continuously captured by the high-speed camera.

[0064] like Figure 4 As shown, xi is the distance in the X direction between the centroids of two adjacent continuous droplet images taken by the high-speed camera in the Y direction, such as Figure 4 The distance between the centroids of two consecutive droplet images in the X direction is shown;

[0065] Furthermore, the v y According to the following formula:

[0066]

[0067] Among them, △ yi is the distance in the Y direction between the centroids of two adjacent continuous droplet images taken by a high-speed camera in the X direction;

[0068] Furthermore, the v z0 According to the following formula:

[0069]

[0070] Among them, Figure 5 As shown, h0 is the distance between the central axis of the high-speed camera lens and the surface of the source liquid pool 5 in the Z direction;

[0071] v z is the average velocity of the droplet in the z direction captured by a high-speed camera;

[0072] The v z According to the following formula:

[0073]

[0074] Among them, Figure 6 As shown, zi is the distance in the Z direction between the centroids of two adjacent continuous droplet images taken in the Z direction by a high-speed camera;

[0075] like Figure 7 As shown, when the flight trajectory equation of the droplet is determined, the final coordinate position of the droplet on the collection substrate 9 can be calculated according to the following simultaneous equations:

[0076]

[0077] Wherein, H is the distance between the surface of the source liquid pool 5 and the bottom of the droplet collecting substrate 9 in the Z direction.

[0078] This embodiment provides the following example

[0079] Sterile double distilled water was used as the solution of the coupling liquid pool 4 and the source liquid pool 5. The position and focal length of the high-speed camera 6 were adjusted so that the distance between the camera 6 and the surface of the source liquid pool 5 in the Z direction was h0=1.5 cm, and the distance between the surface of the source liquid pool 5 and the bottom of the droplet collection substrate 9 in the Z direction was H=6 cm. The aperture of the droplet collection substrate 9 used was 11.3 mm. The voltage amplitude and frequency of the electrical signal of the signal generator 1 were adjusted, and the power of the power amplifier 2 was adjusted so that the ultrasonic transducer 3 could continuously and stably excite the droplets. The high-speed camera 6 and the host computer 8 were turned on to conduct experiments. A group of droplet contact positions were obtained under the continuous pipetting experiment under the condition of unchanged input conditions. The results are shown in Table 1:

[0080] Table 1 records the coordinates of a group of contact points between the droplets and the collecting substrate 9

[0081]

[0082] In summary, the device for testing the contact position of flying droplets in this embodiment adopts the method of first establishing a coordinate system and then using the flight trajectory equation to calculate the contact position. The contact position can be simply and quickly calculated by integrating the distance between the surface of the source liquid pool 5 and the bottom of the droplet collection substrate 9 in the Z direction.

[0083] The above is only a preferred embodiment of the present invention, and the protection scope of the present invention is not limited to the above embodiments. All technical solutions under the concept of the present invention belong to the protection scope of the present invention. It should be pointed out that for ordinary technicians in this technical field, some improvements and modifications without departing from the principle of the present invention should also be regarded as the protection scope of the present invention.

Claims

1. A device for testing the contact position of a flying droplet, characterized in that: include: A signal generator (1), the signal generator (1) is connected to a power amplifier (2), and is used to generate a sinusoidal pulse signal, which is then amplified by the power amplifier (2) and then output; The ultrasonic transducer (3) is connected to the signal generator (1) and is used to receive the output sinusoidal pulse signal and convert the sinusoidal pulse electrical signal into high-frequency ultrasonic waves for output; A coupling liquid pool (4) is arranged above the ultrasonic transducer (3); a source liquid pool (5) is arranged above the coupling liquid pool (4); high-frequency ultrasonic waves output by the ultrasonic transducer (3) pass through the coupling liquid pool (4) and the source liquid pool (5) and are focused on the liquid surface of the source liquid pool (5), thereby exciting liquid droplets to fly into the air; A droplet collecting substrate (9) is disposed above the source liquid pool (5) to collect the excited droplets; A high-speed camera (6) is arranged above one side of the source liquid pool (5), and a parallel light source (7) is arranged above the other side of the source liquid pool (5) to supplement light for the flying droplets and then collect images through the high-speed camera (6); The host computer (8) is connected to the high-speed camera (6) for receiving images captured by the high-speed camera (6), screening the images to obtain images containing droplets, performing graphic preprocessing on the droplet images, identifying the center of mass of the droplets, calculating the flight trajectory equation of the droplets, and then calculating the droplet contact position based on the calculated droplet flight trajectory equation.

2. The device for testing the contact position of a flying droplet according to claim 1, characterized in that: Two high-speed cameras (6) and two parallel light sources (7) are provided. The two high-speed cameras (6) and the two parallel light sources (7) are arranged opposite to each other, facing the X-axis and Y-axis directions of the central axis of the ultrasonic transducer (3), respectively. The flying droplets are arranged between the high-speed cameras (6) and the parallel light sources (7) to form a "main view + left view" droplet shooting.

3. The device for testing the contact position of a flying droplet according to claim 2, characterized in that: The droplet flight trajectory equation calculated by the host computer (8) is as follows: Among them, k represents the linear relationship between y and x, that is, the motion of the droplet in the xy plane is uniform, and v z0 represents the initial velocity of the droplet in the Z direction when it just leaves the liquid surface, v x represents the velocity of the droplet in the X direction, and g is the gravitational acceleration.

4. The device for testing the contact position of a flying droplet according to claim 3, characterized in that: The k is calculated by the following formula: Among them, v x represents the velocity of the droplet in the X direction, v y Indicates the velocity of the droplet in the Y direction.

5. The device for testing the contact position of a flying droplet according to claim 4, characterized in that: The v x Calculated according to the following formula: Where T is the interval between the previous frame and the next frame of the droplet image taken continuously by the high-speed camera, △ xi is the distance in the X direction between the centroids of two adjacent continuous droplet images taken in the Y direction by a high-speed camera.

6. The device for testing the contact position of a flying droplet according to claim 5, characterized in that: The v z0 According to the following formula: Wherein, h0 is the distance between the central axis of the high-speed camera lens and the surface of the source liquid pool in the Z direction; v z The average velocity of the droplet in the Z direction captured by a high-speed camera.

7. The device for testing the contact position of a flying droplet according to claim 6, characterized in that: The v z According to the following formula: Among them, △ zi It is the distance in the Z direction between the centroids of two adjacent continuous droplet images taken in the Z direction by a high-speed camera.

8. The device for testing the contact position of a flying droplet according to claim 7, characterized in that: The host computer (8) also calculates the final coordinate position of the droplet on the collection substrate through the following simultaneous equations: Wherein, H is the distance between the surface of the source liquid pool (5) and the bottom of the droplet collection substrate (9) in the Z direction.

9. A method for testing the contact position of a flying droplet using the device of claims 1 to 8, characterized in that: The steps include: Step 1, establish an xyz coordinate system, adjust the positions of the two high-speed cameras (6), place the two high-speed cameras (6) at the same height and face the X and Y directions of the central axis of the ultrasonic transducer (3) respectively, form a "main view + left view" droplet shooting experimental environment, and place two parallel light sources (7) facing the two high-speed cameras (6); Step 2: Turn on the signal generator (1), the power amplifier (2) and the ultrasonic transducer (3) to continuously excite the droplets in the source liquid pool (5), then adjust the magnification and focal length of the high-speed camera (6) to make the magnification and focal length of the two high-speed cameras (6) consistent, adjust the parallel light source (7) to a suitable brightness, obtain a clear image of the flying droplets in the field of view, and shoot the image; Step three, preprocess the droplet image in the X and Y directions to obtain the droplet contour curve, determine the center of mass of the droplet, obtain a droplet center of mass map, and then determine the droplet flight trajectory equation based on the droplet center of mass coordinate position, and calculate the contact position between the droplet and the droplet collection substrate.

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