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CN113687106A - Extremely-low flow velocity measuring device and method based on atomic force microscope - Google Patents

Extremely-low flow velocity measuring device and method based on atomic force microscope Download PDF

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CN113687106A
CN113687106A CN202110891649.7A CN202110891649A CN113687106A CN 113687106 A CN113687106 A CN 113687106A CN 202110891649 A CN202110891649 A CN 202110891649A CN 113687106 A CN113687106 A CN 113687106A
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fluid
atomic force
force microscope
flow velocity
low flow
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刘志坚
于巽飞
吴天泽
孟美琳
隋卓航
潘新祥
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Dalian Maritime University
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Dalian Maritime University
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01Q—SCANNING-PROBE TECHNIQUES OR APPARATUS; APPLICATIONS OF SCANNING-PROBE TECHNIQUES, e.g. SCANNING PROBE MICROSCOPY [SPM]
    • G01Q60/00—Particular types of SPM [Scanning Probe Microscopy] or microscopes; Essential components thereof
    • G01Q60/24—AFM [Atomic Force Microscopy] or apparatus therefor, e.g. AFM probes
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01B—MEASURING LENGTH, THICKNESS OR SIMILAR LINEAR DIMENSIONS; MEASURING ANGLES; MEASURING AREAS; MEASURING IRREGULARITIES OF SURFACES OR CONTOURS
    • G01B11/00—Measuring arrangements characterised by the use of optical techniques
    • G01B11/16—Measuring arrangements characterised by the use of optical techniques for measuring the deformation in a solid, e.g. optical strain gauge
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01P—MEASURING LINEAR OR ANGULAR SPEED, ACCELERATION, DECELERATION, OR SHOCK; INDICATING PRESENCE, ABSENCE, OR DIRECTION, OF MOVEMENT
    • G01P5/00—Measuring speed of fluids, e.g. of air stream; Measuring speed of bodies relative to fluids, e.g. of ship, of aircraft

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  • Nuclear Medicine, Radiotherapy & Molecular Imaging (AREA)
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Abstract

本发明提供一种基于原子力显微镜的极低流速测量装置和方法。本发明包括原子力显微镜、激光发射器、四象限光电探测器和流动装置，流动装置用于模拟极低流速液体的流动，原子力显微镜的长臂探针能够接触流体以测量流体速度，激光发射器用于发射激光，四象限光电探测器用于检测经悬臂梁反射后的激光。本发明利用原子力显微的长臂探针，将探针伸入到流体内部，从而受到流动的阻力，带动悬臂产生扭转变形，扭转变形被四象限光电探测器记录下，实现了对极低流速流体速度的测量。此方法能通过感受流体的微弱作用力来测量极低流速流体的流速，不会对被测流体的波动产生较大的影响，可以在几乎不影响流体流动的情况下达到非常高的灵敏度。

Figure 202110891649

The invention provides an extremely low flow rate measurement device and method based on an atomic force microscope. The invention includes an atomic force microscope, a laser emitter, a four-quadrant photodetector and a flow device, the flow device is used to simulate the flow of a liquid with a very low flow rate, the long-arm probe of the atomic force microscope can contact the fluid to measure the fluid velocity, and the laser emitter is used for The laser light is emitted, and the four-quadrant photodetector is used to detect the laser light reflected by the cantilever beam. The invention uses the long-arm probe of the atomic force microscope to extend the probe into the fluid, so as to be resisted by the flow, it drives the cantilever to produce torsional deformation. Measurement of fluid velocity. This method can measure the flow rate of very low flow rate fluids by sensing the weak force of the fluid, and will not have a great impact on the fluctuation of the measured fluid, and can achieve very high sensitivity without affecting the fluid flow.

Figure 202110891649

Description

Extremely-low flow velocity measuring device and method based on atomic force microscope
Technical Field
The invention relates to the technical field of atomic force microscope application, in particular to an extremely low flow velocity measuring device and method based on an atomic force microscope.
Background
An Atomic Force Microscope (AFM) is an optical instrument that can obtain microscopic three-dimensional topography of a material surface by scanning the surface of a sample. In the detection process, one end of the probe cantilever is fixed, the other end decorated with the needle tip is close to the sample, the cantilever is influenced by the acting force between the needle tip and the sample to generate deformation or change of a motion state, and the changes are measured and recorded by an optical method. In recent years, with the continuous and intensive research, the atomic force microscope has been developed from the traditional surface three-dimensional topography observation instrument to a measurement device with weak force between a sample and a probe. For example, the change of the surface hydration force of the liquid is monitored by an atomic force microscope, and the viscosity of the solution is detected.
The traditional flow velocity measuring methods mainly comprise a flow method, a buoy method, a color tracing method and the like, and the methods can effectively measure the flow velocity of the fluid in the conventional state. However, for some extremely low flow rates of fluid, such as the flow rate of blood in a human blood vessel and the flow rate of medical fluid in a hospital infusion tube, the conventional measurement method is difficult to accurately and simply measure, and can generate large fluctuation of the flow of the fluid. The length of the long-arm probe of the atomic force microscope is dozens of microns, but the curvature radius of the tip end of the probe is only dozens of microns, so that the flow velocity of the fluid with extremely low flow velocity can be measured by sensing the weak acting force of the fluid, the fluctuation of the measured fluid cannot be greatly influenced, and the probe tip is very sensitive to the tiny acting force among fluid molecules, so that the very high sensitivity can be achieved under the condition of hardly influencing the flow of the fluid.
Disclosure of Invention
In view of the above-mentioned technical problems, an atomic force microscope-based extremely low flow velocity measurement apparatus and method are provided. The technical means adopted by the invention are as follows:
an atomic force microscope-based extremely low flow velocity measurement device comprising: the flow device is used for simulating the flow of liquid with extremely low flow velocity, a long-arm probe of the atomic force microscope can be in contact with the fluid to measure the fluid velocity, the laser emitter is used for emitting laser, the laser emitter is arranged above a measurement cantilever beam arm, and the four-quadrant photodetector is used for detecting the laser reflected by the cantilever beam.
The invention also discloses an extremely low flow velocity measuring method of the extremely low flow velocity measuring device based on the atomic force microscope, which comprises the following steps:
step 1, inserting a long-arm probe to measure torsional force: after a laser transmitter and a four-quadrant photoelectric detector are installed, a long-arm probe of an atomic force microscope is extended into a fluid, the deformation degree of a cantilever arm is converted into an electric signal by an optical method, and torsional force data is acquired;
step 2, calibrating the corresponding relation between the force and the speed: under the condition that the depth of the liquid inserted in the step 1 is kept to be the same, different torsional forces correspond to different speeds, and the torsional force is calibrated by adjusting the flow rate of the flow device and measuring the obtained torsional force data;
and step 3, carrying out speed measurement: under the condition that the depth of the liquid inserted in the step 1 is kept the same, the magnitude of the torsional force is measured, and the speed is determined through the corresponding relation between the force and the speed calibrated in the step 2.
Further, in the step 2, the flow velocity of the fluid is adjusted by adjusting the height of the water tank of the flow device, the torsional force is measured by the voltage collected by the photoelectric sensor, the relation between the force and the velocity is the relation between the voltage and the height of the water tank, and the corresponding relation between the voltage and the height of the water tank is measured through experiments.
The invention utilizes the long-arm probe of the atomic force microscope to extend the probe into the fluid, thereby the cantilever is driven to generate torsional deformation by the flowing resistance, the torsional deformation is recorded by the four-quadrant photoelectric detector, and the measurement of the speed of the fluid with extremely low flow velocity is realized. The method can measure the flow velocity of the fluid with extremely low flow velocity by sensing the weak acting force of the fluid, can not generate larger influence on the fluctuation of the measured fluid, and can achieve very high sensitivity under the condition of hardly influencing the flow of the fluid because the needle tip is very sensitive to the tiny acting force among fluid molecules.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
FIG. 1 is a diagram of an experimental apparatus for measuring a very low flow rate based on an atomic force microscope.
FIG. 2 is an experimental schematic diagram of a very low flow velocity measurement method based on an atomic force microscope.
Fig. 3 is an experimental overview of the extremely low flow rate measurement method based on the atomic force microscope of the present invention.
Fig. 4 is a diagram of the correspondence between the experimental voltage and the height of the water tank in the extremely low flow rate measurement method based on the atomic force microscope.
FIG. 5 is a graph of experimental voltage measurement data variation of the atomic force microscope-based extremely low flow rate measurement method of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
As shown in fig. 1 to 3, an embodiment of the present invention discloses an atomic force microscope-based extremely low flow velocity measurement apparatus, including: the device comprises an atomic force microscope, a laser emitter, a four-quadrant photoelectric detector (PSD) and a flowing device, wherein the flowing device is used for simulating the flowing of liquid with extremely low flow velocity, a long-arm probe of the atomic force microscope can be in contact with the fluid to measure the fluid velocity, the laser emitter is used for emitting laser, the laser emitter is arranged above a measurement cantilever beam arm, the four-quadrant photoelectric detector is used for detecting the laser reflected by the cantilever beam, and signals of four quadrants are directly acquired by the system.
When the needle tip extends into the liquid, the cantilever beam is deformed by the acting force generated by the flowing of the liquid, and the size of the deformation is measured by an optical method; if a force is applied to the needle tip in the horizontal direction, the cantilever beam will deform in the horizontal direction; if a force is applied to the tip in a vertical direction, the cantilever beam will deform in height. The measuring method only aims at measuring the flow velocity of liquid in the pipe, so that the deformation of the cantilever in the horizontal direction is only considered.
The laser emitter irradiates a laser beam on the cantilever beam, and the laser beam is reflected by the cantilever beam and then received by a four-quadrant Photodetector (PSD). Assuming the cantilever beam is undeformed, the spot hits the center point on the PSD. When the cantilever beam is deformed under stress, the position of a light spot on the PSD deviates from the central point, and the PSD converts the deviation of the light spot into an electric signal, so that the force signal is converted into the electric signal.
In addition, the sensitivity of the measurement may vary depending on the depth of insertion of the measurement probe, and the sensitivity may be adjusted by adjusting the depth of insertion of the probe into the liquid as the insertion depth increases. In order to ensure that the measured experimental data are accurate during the experiment, the depth of the probe inserted into the liquid is required to be the same in the same experiment.
Based on the above, the specific method for measuring the extremely low flow rate comprises the following steps:
step 1, inserting a long-arm probe to measure torsional force: after a laser transmitter and a four-quadrant photoelectric detector are installed, a long-arm probe of an atomic force microscope is stretched into fluid, the probe can be subjected to acting force generated by liquid flow, so that a cantilever beam is deformed, the deformation degree of the cantilever beam arm is converted into an electric signal by an optical method, and torsional force data is acquired; the cantilever is twisted and deformed by the flowing resistance, and the twisted deformation is recorded by a four-quadrant laser detector, so that the measurement of the speed of the extremely low-flow-speed fluid is realized. In this process, the sensitivity of the measurement can be adjusted by adjusting the depth of insertion of the probe into the liquid, the deeper the insertion, the greater the sensitivity.
Step 2, calibrating the corresponding relation between the force and the speed: under the condition that the depth of the liquid inserted in the step 1 is kept to be the same, different torsional forces correspond to different speeds, and the torsional force is calibrated by adjusting the flow rate of the flow device and measuring the obtained torsional force data; the flow velocity of the fluid is adjusted by adjusting the height of the water tank of the flow device, the torsional force is measured by the voltage collected by the photoelectric sensor, the relation between the force and the velocity is the relation between the voltage and the height of the water tank, and as shown in fig. 4, the corresponding relation between the voltage and the height of the water tank is measured by experiments. In the embodiment, in the measuring process, the signal feedback system in the vertical direction is closed, so that the AFM does not send an instruction for changing the height of the probe, and the depth of the inserted liquid can be ensured to be the same; on the other hand, as can be seen from the height map (vertical direction) obtained during the measurement, the height variation range of the tip is very small (within a few nanometers) throughout the measurement process
And step 3, carrying out speed measurement: under the condition that the depth of the inserted liquid in the step 1 is kept the same, the magnitude of the torsional force is measured, under the condition that the depth of the inserted liquid is the same, different torsional forces correspond to different speeds, and then the speed can be determined through the corresponding relation between the force and the speed calibrated in the step 2. The experiment measures the change condition of the process voltage of the height difference from 0mm to 2mm (as shown in figure 5), and the fact proves that the method not only can measure the speed of the fluid with extremely low flow rate, but also has extremely high sensitivity, and can accurately reflect the change condition of the fluid flow rate in the change process of the speed.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (3)

1.一种基于原子力显微镜的极低流速测量装置，其特征在于，包括原子力显微镜、激光发射器、四象限光电探测器和流动装置，所述流动装置用于模拟极低流速液体的流动，所述原子力显微镜的长臂探针能够接触流体以测量流体速度，所述激光发射器用于发射激光，所述四象限光电探测器用于检测经悬臂梁反射后的激光。1. a very low flow velocity measuring device based on atomic force microscope, is characterized in that, comprises atomic force microscope, laser transmitter, four-quadrant photodetector and flow device, and described flow device is used for simulating the flow of very low flow velocity liquid, so The long-arm probe of the atomic force microscope can contact the fluid to measure the fluid velocity, the laser transmitter is used to emit laser light, and the four-quadrant photodetector is used to detect the laser light reflected by the cantilever beam. 2.一种权利要求1所述的基于原子力显微镜的极低流速测量装置的极低流速测量方法，其特征在于，括如下步骤：2. the extremely low flow velocity measuring method of the extremely low flow velocity measuring device based on atomic force microscope according to claim 1, is characterized in that, comprises the steps: 步骤1、插入长臂探针测扭转力：安装好激光发射器和四象限光电探测器后，将原子力显微镜的长臂探针伸入到流体内部，利用光学的方法将悬梁臂的形变程度转化为电信号，获取扭转力数据；Step 1. Insert the long-arm probe to measure the torsional force: After installing the laser emitter and the four-quadrant photodetector, insert the long-arm probe of the atomic force microscope into the fluid, and use the optical method to convert the deformation degree of the cantilever arm It is an electrical signal to obtain torsional force data; 步骤2、标定力与速度的对应关系：在保持步骤1插入液体深度相同的情况下，不同扭转力对应不同的速度，通过调节流动装置的流速和测量得到的扭转力数据标定扭转力；Step 2. Corresponding relationship between calibration force and speed: Under the condition that the depth of the liquid inserted in step 1 is kept the same, different torsional forces correspond to different speeds, and the torsional force is calibrated by adjusting the flow rate of the flow device and the measured torsional force data; 步骤3、进行速度测量：在保持步骤1插入液体深度相同的情况下，测量出扭转力的大小，通过步骤2所标定的力与速度的对应关系来确定速度。Step 3. Carry out speed measurement: Under the condition that the depth of the liquid inserted in step 1 is kept the same, the magnitude of the torsional force is measured, and the speed is determined by the corresponding relationship between the force and the speed calibrated in step 2. 3.根据权利要求2所述的基于原子力显微镜的极低流速测量装置的极低流速测量方法，其特征在于，所述步骤2中，流体的流速通过调节流动装置水箱的高度来调节，扭转力通过光电传感器收集到的电压来测量，力与速度的关系即为电压与水箱高度的关系，实验测得电压与水箱高度的对应关系。3. the extremely low flow velocity measuring method based on the extremely low flow velocity measuring device of atomic force microscope according to claim 2, is characterized in that, in described step 2, the flow velocity of fluid is adjusted by adjusting the height of the flow device water tank, and the torsional force is adjusted. Measured by the voltage collected by the photoelectric sensor, the relationship between the force and the speed is the relationship between the voltage and the height of the water tank, and the corresponding relationship between the voltage and the height of the water tank is measured experimentally.
CN202110891649.7A 2021-08-04 2021-08-04 Extremely-low flow velocity measuring device and method based on atomic force microscope Pending CN113687106A (en)

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