CN114371124A - Droplet adhesive force detecting system based on micro-cantilever beam - Google Patents

Abstract

The invention relates to a micro-cantilever beam-based liquid drop adhesion detection system, which specifically comprises a laser, a micro-cantilever beam, a micro-beam clamping table, a micro-liquid drop injector, an injector support, a photoelectric detector, a micro-camera, a camera support, a data acquisition card, a computer and the like, wherein the front end of the micro-cantilever beam is forwards suspended to form a free end, the bottom of the micro-sample injector is provided with an injector hydrophilic liquid hole, the injector hydrophilic liquid hole longitudinally moves under the clamping of the sample injector support so as to control the liquid drop to move up and down on the surface of the micro-cantilever beam, the tip of the micro-cantilever beam is irradiated by a laser beam, the adsorption-desorption process of the liquid drop on the surface of the micro-cantilever beam is detected, the adsorption-desorption mechanical curve of the liquid drop on the solid surface is obtained, and the longitudinal adhesion between the liquid drop and the surface of the micro-cantilever beam can be simply and accurately obtained.

Description

A droplet adhesion detection system based on microcantilever

technical field

The invention relates to the detection of droplet adhesion, and more particularly to a liquid droplet adhesion detection system at a solid-liquid interface.

Background technique

The adhesion between the solid-liquid interface is a key factor affecting the dynamic performance of the liquid phase on the solid surface. The detection of interfacial adhesion has received extensive attention in both theoretical research and practical applications, and is a key breakthrough point for lyophobic surfaces to move towards practical applications. . The traditional measurement of droplet adhesion is to use airflows of different intensities to blow off the droplets on the substrate, so as to obtain the minimum airflow intensity that can blow the droplets off, and then calculate the size of the droplet adhesion; here During a measurement, part of the airflow that reaches the substrate first changes its direction and then acts on the droplet, thus interfering with the measurement.

In the patent document with publication number CN211825620, a liquid droplet adhesion measurement device is disclosed, which is to place a substrate to be measured and a measurement component on the table top of a workbench. The measurement component has an adsorption surface and the adsorption surface faces the substrate. The measurement component can be Movement relative to the substrate is used to adsorb droplets on the substrate at different angles and/or distances and read the adsorption force of the measurement component; however, this detection method is to drive the measurement component through a magnet controlled slider. Large-scale substrates The sensitivity of the adsorbed droplets cannot meet the requirements, which greatly limits the detection accuracy.

SUMMARY OF THE INVENTION

In order to avoid the above-mentioned shortcomings of the prior art, the present invention provides a droplet adhesion detection system based on a micro-cantilever beam, so as to realize high-sensitivity detection of the droplet adhesion.

A micro-cantilever-based droplet adhesion detection system of the present invention is characterized by comprising: a micro-cantilever-based droplet adhesion detection system, which is characterized by comprising:

The micro-cantilever beam, its tail is clamped by the micro-beam clamping table, and the front end is horizontally overhanging as a free end;

a laser, which emits a laser beam and irradiates the free end of the micro-cantilever beam from bottom to top along a direction at an angle of 45° with the micro-cantilever beam, and generates a reflected beam at the free end of the micro-cantilever beam;

The micro-sampler is arranged above the free end of the micro-cantilever beam by using a sample-injector bracket, the sample-injector bracket can drive the micro-injector to move vertically up and down, and the bottom of the micro-injector is a syringe liquid hole. The sample liquid stored in the injector can be pushed into the liquid hole of the syringe by the syringe and kept as droplets hanging on the liquid hole of the syringe;

a microscopic camera, which is fixed and supported above the microcantilever by the camera bracket, and is used to capture and obtain images of the adhesion-desorption process of the droplet and the microcantilever;

The photodetector is arranged in the reflection circuit of the reflected light, and is used to receive the reflected light, and the data acquisition card transmits the collected output signal of the photodetector to the computer for signal processing, so as to realize the droplet adhesion detection.

The droplet in the liquid hole of the micro-sampler is not in contact with the micro-beam in the initial state, and the light spot of the laser beam emitted by the laser after being reflected by the micro-cantilever beam coincides with the center position of the detector;

First, control the injector bracket to move the micro-injector downward until the droplet hanging in the liquid hole of the syringe contacts the upper surface of the free end of the micro-cantilever beam, the micro-cantilever beam shifts downward, and the spot position changes;

Adjust the injector bracket again, drag the droplet upwards, make the microbeam return to the parallel state, and the light spot coincides with the center of the detector again;

Finally, the injector bracket is controlled to move the micro injector upward, and the drop drives the free end of the micro cantilever to move upward until the drop is separated from the surface of the micro cantilever; The offset of the beam.

The photodetector is a four-quadrant detector, and the photosensitive target surface of the photodetector is a circular surface with O point as the center point and R as the radius; the light spot is O'(x ₀ , y ₀ ) as the center point, A circular face with a radius of r;

Characterize the current intensities of the I, II, III and IV quadrants detected by the photodetector with I _A , I _B , I _C and I _D in a one-to-one correspondence;

When the position of the light spot on the photodetector changes, the output current intensity of each quadrant of the detector changes. According to the change of the photocurrent generated by the light spot, the relative offset of the light spot on the photosensitive surface is calculated by the following formula (1), and is calculated by Formula (2) calculates the bending deflection ΔZ of the micro-cantilever beam:

in:

K _x is the detection sensitivity of the detector in the X-axis direction;

K _y is the detection sensitivity of the detector in the Y-axis direction;

ΔS is the linear offset of the spot center point relative to the photosensitive target surface O;

l is the distance from the contact center point of the droplet and the micro-cantilever to the fixed end of the micro-cantilever;

L is the distance from the free end of the micro-cantilever beam to the photosensitive target surface of the photodetector after the laser beam is reflected by the micro-cantilever beam;

Then, the droplet adhesion force F is: F=kΔZ

where k is the spring constant of the microcantilever.

The micro-cantilever-based droplet adhesion detection system of the present invention is also characterized in that: the syringe liquid hole of the micro-injector (4) is a flat head, and is treated with hydrophilicity to enhance the droplet and liquid Adhesion between pores.

The micro-cantilever-based droplet adhesion detection system of the present invention is also characterized in that: the capacity of the micro-injector is 10 μL, the diameter of the liquid hole of the syringe is 0.05 mm; the output laser wavelength of the laser is 632 nm -780nm semiconductor laser.

A droplet adhesion detection system based on a micro-cantilever beam of the present invention is also characterized in that: the photodetector (6) is a position-sensitive sensor PSD.

The micro-cantilever beam-based droplet adhesion detection system of the present invention is also characterized in that the micro-cantilever beam is a rectangular single beam, the beam length is 500 μm, the width is 9 μm, and the thickness is 1 μm.

Compared with the prior art, the beneficial effects of the present invention are reflected in:

1. In the present invention, the laser irradiates the free end of the micro-cantilever beam, which can realize the accurate detection of the surface stress change process on the micro-nano scale, accurately detect the adhesion of the droplet on the solid surface, and obtain the droplet more simply and reliably. The adhesion between the substrate and the substrate, the response speed is faster and the sensitivity is higher;

2. The optical path in the present invention has a simple structure and is easy to build. Through computer information processing and display of measurement results, the dynamic desorption curve of droplets on the solid surface can be obtained more intuitively and vividly;

3. According to the specific application of the present invention, the micro-cantilever beam can be enlarged and displayed by using a micro-camera, the surface of the micro-cantilever beam can be modified, and it is easy to obtain the correlation between the different microstructures of the solid surface and the adhesion of the surface droplets, which is for building, Manipulating the lyophobic surface provides orientation.

Description of drawings

Fig. 1 is the structural schematic diagram of the detection system of the present invention;

Fig. 2 is the deflection schematic diagram of the micro-cantilever beam in the detection system of the present invention;

Fig. 3 is the photoelectric detection principle process diagram in the detection system of the present invention;

Fig. 4 is the LabVIEW data visualization display operation page in the detection system of the present invention;

Fig. 5 is the desorption curve of the droplet on the surface of the micro-cantilever in the detection system of the present invention;

Labels in the figure: 1 laser, 2 micro-cantilever beam, 3 micro-beam clamping table, 4 micro sampler, 5 sampler bracket, 6 photodetector, 7 microscope camera, 8 camera bracket, 9 data acquisition card, 10 Computers.

Detailed ways

The patent of the present invention will be described in detail below in conjunction with the accompanying drawings, so that the skilled person can understand

Example 1

As shown in Figure 1, a micro-cantilever-based droplet adhesion detection system is characterized in that it includes:

a micro-cantilever beam (2), the tail of which is clamped by the micro-beam clamping table (3), and the front end is horizontally cantilevered as a free end;

A laser (1) that emits a laser beam along a direction at an angle of 45° to the micro-cantilever beam (2) from bottom to top and irradiates the free end of the micro-cantilever beam (2), and generates a laser beam at the free end of the micro-cantilever beam (2) reflected beam;

A micro-sampler (4), which is arranged above the free end of the micro-cantilever beam (2) using a sample-injector bracket (5), the sample-injector bracket (5) capable of driving the micro-injector (4) vertically Move down, the bottom of the micro-injector (4) is the liquid hole of the syringe, the sample liquid stored in the micro-injector (4) can be pushed into the liquid hole of the syringe by the syringe and kept as droplets hanging on the liquid hole of the syringe ;

a microscopic camera (7), fixed and supported above the micro-cantilever beam (2) by a camera-head bracket (8), for capturing images of the adhesion-desorption process of the droplet and the micro-cantilever beam;

A photodetector (6), arranged in the reflection circuit of the reflected light, is used for receiving the reflected light, and the data acquisition card (9) transmits the acquired output signal of the photodetector (6) to the computer (10) Perform signal processing to detect droplet adhesion.

The droplets in the liquid holes of the micro-injector (4) are not in contact with the microbeam (2) in the initial state, and the light spot after the laser beam emitted by the laser (1) is reflected by the microcantilever beam and the detector (6). The center position coincides;

First, control the injector bracket (5) to move the micro injector (4) downward until the droplet suspended in the liquid hole of the syringe contacts the upper surface of the free end of the micro-cantilever beam, and the micro-cantilever beam is deflected downward , the spot position changes;

Adjust the injector bracket (5) again, drag the droplet upwards to make the microbeam return to a parallel state, and the light spot coincides with the center of the detector again;

Finally, the injector bracket (5) is controlled to move the micro injector (4) upward, and the droplet drives the free end of the micro-cantilever beam to move upward until the droplet is detached from the surface of the micro-cantilever beam; use the data acquisition card (9 ) collect the offset of the microbeam during the upward movement of the droplet.

The photodetector (6) is a four-quadrant detector, and the photosensitive target surface of the photodetector (6) is a circular surface with point O as the center point and R as the radius; the light spot is O'(x ₀ , y ₀ ) as the center point and r as the radius;

Characterize the current intensities of the I, II, III and IV quadrants detected by the photodetector (6) in one-to-one correspondence with I _A , I _B , I _C and I _D ;

When the position of the light spot on the photodetector changes, the output current intensity of each quadrant of the detector changes. According to the change of the photocurrent generated by the light spot, the relative offset of the light spot on the photosensitive surface is calculated by the following formula (1), and is calculated by Formula (2) calculates the bending deflection ΔZ of the micro-cantilever beam:

in:

K _x is the detection sensitivity of the detector in the X-axis direction;

K _y is the detection sensitivity of the detector in the Y-axis direction;

ΔS is the linear offset of the spot center point relative to the photosensitive target surface O;

l is the distance from the contact center point of the droplet and the micro-cantilever to the fixed end of the micro-cantilever;

L is the distance from the free end of the micro-cantilever beam to the photosensitive target surface of the photodetector after the laser beam is reflected by the micro-cantilever beam;

Then, the droplet adhesion force F is: F=kΔZ

where k is the spring constant of the microcantilever.

Example 2

The use steps of a micro-cantilever-based droplet adhesion detection system are as follows:

Use the microinjector (4) to slowly extrude 0.4 μL of water droplets, keep the droplets from the needle of the microinjector (4) without dripping, and the distance from the photosensitive target surface of the photodetector (6) to the free end of the microcantilever (2) 3.7cm, fine-tune the injector holder (5), after the water droplet contacts the surface of the micro-cantilever (2), then move down 20μm to make the water droplet fully contact the surface of the micro-cantilever (2) without damaging the surface of the water droplet Tension, the distance between the center point of the contact between the water droplet and the micro-cantilever beam (2) and the fixed end of the micro-cantilever beam (2) is 450 μm, and fine-tune the injector bracket (5) in the reverse direction, so that the needle of the micro injector (4) drives the water drop slowly. Detach the surface of the micro-cantilever beam (2), and display the deflection displacement of the micro-cantilever beam (2) in real time on the Lab VIEW program at the computer (10) end through the data acquisition card (9). In an instant, the bending degree of the micro-cantilever beam (2) reaches a threshold value, and the adhesion force of the water droplet on the surface of the micro-cantilever beam (2) is calculated by the formula, and the mechanical curve of the desorption of the droplet on the surface of the micro-cantilever beam is obtained.

The present invention is described through specific implementation processes, but these are not intended to limit the present invention. Without departing from the spirit of the present invention, various changes and modifications made to the technical solutions of the present invention by those skilled in the art shall fall within the scope of the present invention. Within the scope of protection determined by the claims of the present invention.

Claims (7)

1. a droplet adhesion detection system based on micro-cantilever is characterized in that comprising: a micro-cantilever beam (2), the tail of which is clamped by the micro-beam clamping table (3), and the front end is horizontally cantilevered as a free end; A laser (1) that emits a laser beam along a direction at an angle of 45° to the micro-cantilever beam (2) from bottom to top and irradiates the free end of the micro-cantilever beam (2), and generates a laser beam at the free end of the micro-cantilever beam (2) reflected beam; A micro-sampler (4), which is arranged above the free end of the micro-cantilever beam (2) using a sample-injector bracket (5), the sample-injector bracket (5) capable of driving the micro-injector (4) vertically Move down, the bottom of the micro-injector (4) is the liquid hole of the syringe, the sample liquid stored in the micro-injector (4) can be pushed into the liquid hole of the syringe by the syringe and kept as droplets hanging on the liquid hole of the syringe ; a microscopic camera (7), fixed and supported above the micro-cantilever beam (2) by a camera-head bracket (8), for capturing images of the adhesion-desorption process of the droplet and the micro-cantilever beam; A photodetector (6), arranged in the reflection circuit of the reflected light, is used for receiving the reflected light, and the data acquisition card (9) transmits the acquired output signal of the photodetector (6) to the computer (10) Perform signal processing to realize the detection of droplet adhesion. 2. The droplet adhesion detection system based on micro-cantilever beam according to claim 1, is characterized in that: The droplets in the liquid holes of the micro-injector (4) are not in contact with the microbeam (2) in the initial state, and the light spot after the laser beam emitted by the laser (1) is reflected by the microcantilever beam and the detector (6). The center position coincides; First, control the injector bracket (5) to move the micro injector (4) downward until the droplet suspended in the liquid hole of the syringe contacts the upper surface of the free end of the micro-cantilever beam, and the micro-cantilever beam is deflected downward , the spot position changes; Adjust the injector bracket (5) again, drag the droplet upwards to make the microbeam return to a parallel state, and the light spot coincides with the center of the detector again; Finally, the injector bracket (5) is controlled to move the micro injector (4) upward, and the droplet drives the free end of the micro-cantilever beam to move upward until the droplet is detached from the surface of the micro-cantilever beam; use the data acquisition card (9 ) collect the offset of the microbeam during the upward movement of the droplet. 3. The droplet adhesion detection system based on micro-cantilever beam according to claim 1, is characterized in that: The photodetector (6) is a four-quadrant detector, and the photosensitive target surface of the photodetector (6) is a circular surface with point O as the center point and R as the radius; the light spot is O'(x ₀ , y ₀ ) as the center point and r as the radius; Characterize the current intensities of the I, II, III and IV quadrants detected by the photodetector (6) in one-to-one correspondence with I _A , I _B , I _C and I _D ; When the position of the light spot on the photodetector changes, the output current intensity of each quadrant of the detector changes. According to the photocurrent change generated by the light spot, the relative offset of the light spot on the photosensitive surface is calculated by the following formula (1). Formula (2) calculates the bending deflection ΔZ of the micro-cantilever beam:

in: K _x is the detection sensitivity of the detector in the X-axis direction; K _y is the detection sensitivity of the detector in the Y-axis direction; ΔS is the linear offset of the spot center point relative to the photosensitive target surface O; l is the distance from the contact center point of the droplet and the micro-cantilever to the fixed end of the micro-cantilever; L is the distance from the free end of the micro-cantilever beam to the photosensitive target surface of the photodetector after the laser beam is reflected by the micro-cantilever beam; Then, the droplet adhesion force F is: F=kΔZ where k is the spring constant of the microcantilever. 4. The micro-cantilever-based droplet adhesion detection system according to claim 1, wherein the syringe liquid hole of the micro-sampler (4) is a flat head, and is treated with hydrophilicity to enhance the Adhesion between the droplet and the liquid hole. 5. The micro-cantilever-based droplet adhesion detection system according to claim 1, characterized in that: the capacity of the micro-injector is 10 μL, and the diameter of the liquid hole of the syringe is 0.05 mm; the laser is an output A semiconductor laser with a laser wavelength of 632nm-780nm. 6. The micro-cantilever-based droplet adhesion detection system according to claim 1, wherein the photodetector (6) is a position sensitive sensor PSD. 7 . The droplet adhesion detection system based on the micro-cantilever beam according to claim 1 , wherein the micro-cantilever beam is a rectangular single beam, the beam length is 500 μm, the width is 9 μm, and the thickness is 1 μm. 8 .

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