Dynamic and static optical measurement system and method for interfacial forces at the micron scale

Abstract

The application discloses a kind of microscale interfacial force dynamic and static optical measurement system and its measurement method, the system includes micron probe module, collimating light path module, signal conditioning circuit, host computer acquisition processing module and high-precision displacement driving module, the probe tip of the system is in micron level, adopts a kind of contact resonant probe measurement structure, utilizes the optical measurement method of optical lever principle, can accurately measure the interfacial force piezoelectric signal between probe tip and the surface to be measured, obtains the interfacial force voltage-displacement curve under microscale, to realize the measurement, analysis and research to interfacial microscopic interaction force under microscale. Overall system has the advantages of high sensitivity, good working stability and relatively low cost.

Description

Technical Field

[0001] This invention relates to micro-nano measurement and interfacial micro-interaction forces, specifically a dynamic and static optical measurement system and method for studying interfacial forces at the micrometer scale based on a contact resonant micrometer probe. Background Technology

[0002] With the development of science and technology, micro- and nano-precision detection technology has become a hot field in current scientific research, greatly promoting the fabrication of novel structures and the development of new materials at the micro- and nano-scale. To achieve precise measurement of micro- and nano-sized structures, measurement systems based on various microprobes and sensing principles have been developed, enabling nanometer-level precision measurements. Research shows that when the scale of micro- and nano-probes reaches the micrometer or nanometer scale, the interfacial micro-interaction forces between the probe and the measured surface have a significant impact on the probe. At this point, the interaction between the probe tip and the measured surface is mainly influenced by interfacial effects, rather than gravity or attraction. This makes the interfacial effects between microstructures increasingly important in scientific research.

[0003] In the field of microscopic interaction forces, the theory of interfacial forces has been continuously developed and improved. The explanation now widely accepted by scholars is that interfacial forces originate from the mutual attraction or repulsion between two critically contacting surfaces. Therefore, when a microprobe tip is about to contact the surface of a microdevice, the influence of the interfacial forces between the probe tip and the measured surface cannot be ignored. These forces include capillary forces caused by surface tension, van der Waals forces, Casimir forces, and so on. As the approach distance between the microprobe tip and the measured surface changes, the magnitude, components, and contribution degree of each component of these forces vary, and their influence is much greater than that of gravity. This has a significant impact on the measurement accuracy and reliability of the probe, often leading to problems such as false triggering, unstable triggering, decreased scanning accuracy, and decreased repeatability in the microprobe system.

[0004] Currently, most studies on interfacial micro-interaction forces rely on atomic force microscopy (AFM), where the probe tip curvature radius is generally on the nanometer scale, and the magnitude of the interfacial micro-interaction forces ranges from nN to pN. However, the magnitude and range of interfacial forces at the micrometer scale differ significantly from those at the nanometer scale, and there are few research reports, both domestically and internationally, on the interfacial force characteristics at the critical contact between micrometer-scale probe tips and sample surfaces. Furthermore, considering the different operating modes of AFM (contact mode, non-contact mode, and tapping mode), a good measurement system must be capable of both dynamic and static measurements. Therefore, developing a dynamic and static optical measurement system for interfacial forces at the micrometer scale is both reasonable and necessary. Summary of the Invention

[0005] To address the shortcomings of the existing technologies, this invention proposes a dynamic and static optical measurement system and method for interfacial forces at the micrometer scale. The aim is to achieve the measurement of the interfacial micro-interaction forces when a micrometer-scale probe is in critical contact with the surface being measured, to plot the interfacial force-voltage-separation displacement curve, and to further complete the study of the characteristics of interfacial micro-interaction forces at the micrometer scale.

[0006] The present invention adopts the following technical solution to solve the technical problem:

[0007] The present invention provides a dynamic and static optical measurement system for interfacial forces at the micrometer scale, which includes: a micrometer probe module, a collimating optical path module, a signal conditioning circuit, a host computer acquisition and processing module, and a high-precision displacement driving module.

[0008] The micron probe module includes: a probe head, a flexible spring, a reflector, a 3D-printed probe holder, a PI piezoelectric ceramic ring, and a signal generator;

[0009] The probe head is perpendicularly connected to the center of the flexible spring via metal adhesive; a reflector is positioned above the center of the flexible spring; four small holes are etched on the flexible spring and fixed to the outer ring at the lower end of the 3D printed probe bracket by screws and nuts; the lower end of the 3D printed probe bracket has a uniform four-sided hollow structure to allow the collimated laser beam to enter and exit at an oblique direction; the PI piezoelectric ceramic ring is embedded and fixed at the upper end of the 3D printed probe bracket and is provided with a sinusoidal excitation signal by the signal generator;

[0010] The collimated optical path module includes: a single-wavelength pump laser, three K9 biconvex lenses, and a four-quadrant photodetector;

[0011] The single-wavelength pump laser is coaxially fixed to one side of the 3D printed probe bracket with the first K9 biconvex lens; the second K9 biconvex lens and the third K9 biconvex lens are coaxially fixed to the other side of the 3D printed probe bracket with the four-quadrant photodetector.

[0012] The input terminal of the signal conditioning circuit is connected to the output terminal of the four-quadrant photodetector.

[0013] The host computer data acquisition and processing module includes: a data acquisition card and a computer;

[0014] The signal conditioning circuit is connected to the computer via the data acquisition card;

[0015] The high-precision displacement drive module includes: a piezoelectric ceramic actuator, a PZT piezoelectric ceramic stage, and a three-dimensional precision micro-motion stage;

[0016] The PZT piezoelectric ceramic stage is fixedly connected to the three-dimensional precision micro-motion stage;

[0017] The PZT piezoelectric ceramic stage is provided with a test surface, and the test surface is directly below the test surface.

[0018] The PZT piezoelectric ceramic stage is connected to the piezoelectric ceramic actuator; the input terminal of the piezoelectric ceramic actuator is connected to the computer.

[0019] The signal generator provides a sinusoidal excitation signal to the PI piezoelectric ceramic ring to make it vibrate, thereby causing the flexible spring to drive the probe head to make a resonant motion, and generating interfacial micro-interaction forces as it approaches the surface being measured.

[0020] The laser beam emitted by the single-wavelength pump laser is focused by the first K9 biconvex lens, reflected by the reflector above the center of the flexible reed, and then parallelized by the second K9 biconvex lens. After being transmitted through the third K9 biconvex lens, the parallel laser beam is focused on the four-quadrant photodetector to form a laser spot and outputs a corresponding optical power voltage signal. The optical power voltage signal changes with the position of the laser spot on the four-quadrant photodetector and is related to the resonant motion of the flexible reed.

[0021] The signal conditioning circuit preprocesses the optical power voltage signal and then sends it to the computer through the data acquisition card to obtain the relationship between the optical power voltage signal and the interface micro-interaction force, thereby realizing the dynamic measurement of the interface micro-interaction force.

[0022] The present invention provides a method for measuring the dynamic and static interface forces at the micrometer scale, characterized in that it is applied to the measurement system described in claim 1 and is performed according to the following steps:

[0023] Step 1: Adjust the probe head to align with the surface to be measured on the PZT piezoelectric ceramic stage; turn on the single-wavelength pump laser and adjust it to output the required optical power; adjust the collimation optical path module so that the laser beam is focused onto the center of the four-quadrant photodetector after being reflected by the mirror above the center of the flexible reed.

[0024] Step 2: Keep the micron probe module stationary and adjust the three-dimensional precision micro-motion stage according to the micron-level feed amount so that the surface to be measured gradually approaches the probe microsphere at the end of the probe head. When the distance between the two enters the range of action of the micro-interface force, stop adjusting the three-dimensional precision micro-motion stage.

[0025] Step 3: Turn on the signal generator to output the required sinusoidal excitation signal, so that the flexible reed moves the probe head in a regular resonant motion, and the measurement system performs dynamic measurement; if the signal generator is turned off and no sinusoidal excitation signal is provided, the measurement system performs static measurement.

[0026] Step 4: Using the computer to control the piezoelectric ceramic driver to continuously output a voltage signal, the PZT piezoelectric ceramic stage is driven to move at a nanometer-level feed rate according to the required step distance and step time interval, so that the surface under test gradually approaches the probe microsphere at the end of the probe head to complete the approach to contact process; at this time, the optical power voltage signal output by the four-quadrant photodetector also changes continuously, and the data acquisition card then synchronously acquires and transmits the data signal processed by the signal conditioning circuit to the computer;

[0027] Step 5: After the computer performs Fast Fourier Transform (FFT) and mean filtering on the acquired data signal, it obtains the amplitude, frequency and phase information of the resonant signal, thereby determining the area of ​​action of the interfacial micro-interaction force between the probe microsphere at the probe tip and the measured surface, so as to establish the interfacial force-separation displacement curve.

[0028] Compared with existing technologies, the beneficial effects of this invention are reflected in:

[0029] 1. The present invention employs a contact resonant probe measurement structure, which can provide an excitation signal to dynamically measure the interfacial micro-interaction force when the micrometer probe and the measured surface are in critical contact, greatly reducing the influence of various static and quasi-static interferences, such as zero drift and temperature drift; at the same time, the system structure can also turn off the excitation signal for static measurement. By comparing and analyzing the dynamic and static measurement data, the study on the characteristics of interfacial micro-interaction force is further improved.

[0030] 2. The microspheres at the probe tip in this invention have a micrometer-scale characteristic size, unlike the probe tips of most instruments such as atomic force microscopes (AFM), which are at the nanometer scale. At this scale, the magnitude and range of the interfacial micro-interaction forces are significantly different from those at the nanometer scale. Therefore, this invention is of great significance for studying the interfacial force characteristics between the probe tip and the measured surface at the micrometer scale.

[0031] 3. The main body of this invention adopts an optical measurement system and its measurement method based on the principle of optical lever. It has the advantages of high sensitivity and fast response speed in measuring weak interfacial micro-interaction forces. At the same time, due to the use of optical measurement method, the overall system is greatly reduced in sensitivity to electrical noise and has strong anti-electromagnetic interference capability.

[0032] 4. In the contact resonant probe structure of the present invention, the flexible spring is made of beryllium bronze material and is manufactured by optical imaging and chemical etching methods. It has the advantages of small shape error, good formability, high elastic strength, good stability and not easy to deform, which can significantly improve the measurement accuracy and precision of the interfacial force optical measurement system at the micrometer scale. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the measurement system structure of the present invention;

[0034] Figure 2 This is a graph showing the output noise test results of the measurement system of this invention;

[0035] Figure 3 This is a graph showing the output voltage results of the dynamic test of interfacial forces according to the present invention.

[0036] Figure 4 This is a graph showing the output voltage results of the static test of the interfacial force in this invention.

[0037] The following components are labeled in the diagram: 1. Probe head; 2. Flexible reed; 3. 3D printed probe holder; 4. PI piezoelectric ceramic ring; 5. Signal generator; 6. Single-wavelength pump laser; 7. First K9 biconvex lens; 8. Second K9 biconvex lens; 9. Third K9 biconvex lens; 10. Four-quadrant photodetector; 11. Signal conditioning circuit; 12. Data acquisition card; 13. Computer; 14. Piezoelectric ceramic driver; 15. PZT piezoelectric ceramic stage; 16. Three-dimensional precision micro-motion stage. Detailed Implementation

[0038] In this embodiment, to measure the interfacial micro-interaction forces when a micrometer-scale probe is in critical contact with the surface being measured, a dynamic and static optical measurement system for interfacial forces at the micrometer scale is proposed. Employing an optical measurement method based on the optical lever principle, the system significantly improves measurement accuracy and exhibits low sensitivity to electrical noise. It also possesses outstanding characteristics such as high sensitivity and fast response speed, providing valuable guidance and technical support for the design of novel micro / nano probe measurement systems and addressing issues such as false triggering, unstable triggering, and poor scanning accuracy in microprobe systems. Figure 1 As shown, the measurement system includes a micrometer probe module, a collimating optical path module, a signal conditioning circuit 11, a host computer acquisition and processing module, and a high-precision displacement drive module.

[0039] The micrometer probe module includes a probe head 1, a flexible spring 2, a reflector, a 3D printed probe support 3, a PI piezoelectric ceramic ring 4, and a signal generator 5;

[0040] The probe head 1 is perpendicularly connected to the center of the flexible spring 2 via metal glue; a reflector is set above the center of the flexible spring 2 for light reflection; the flexible spring 2 is processed by optical imaging and chemical etching methods, and four small holes are etched on its outer ring. It is fixed to the lower outer ring of the 3D printed probe bracket 3 by screws and nuts. The lower end of the 3D printed probe bracket 3 has a uniform four-sided hollow structure so that the collimated laser light can enter and exit at an oblique direction; the PI piezoelectric ceramic ring 4 is embedded and fixed at the upper end of the 3D printed probe bracket 3, and a sinusoidal excitation signal is provided by the signal generator 5, so that the probe head 1 follows the flexible spring 2 to perform regular resonant motion, realizing the dynamic measurement of the micro-interface interaction force. In this embodiment, the microsphere at the tip of the probe head 1 has a diameter of 100 μm; the flexible spring 2 has a thickness of 0.1 mm, and its surface shape adopts a centrally symmetrical four-chord structure design; the amplitude of the sinusoidal excitation signal output by the signal generator is selected in the range of 0.5 to 1 V. If it is too high, the output voltage of the high signal-to-noise ratio circuit module will exceed the threshold range; if it is too low, it will be greatly affected by noise, and it will be difficult to observe the change of the final output voltage signal; the frequency setting is determined during experimental debugging. The resonant frequency of different reed structures is different. During the experiment, it is necessary to ensure that the reed vibrates at the resonant frequency, at which time the voltage change phenomenon is more obvious.

[0041] The collimated optical path module includes: a single-wavelength pump laser 6, three K9 biconvex lenses, and a four-quadrant photodetector 10;

[0042] A single-wavelength pump laser is coaxially fixed to one side of the 3D-printed probe holder 3 along with the first K9 biconvex lens 7; the second K9 biconvex lens 8 and the third K9 biconvex lens 9 are coaxially fixed to the other side of the 3D-printed probe holder 3 along with the quadrant photodetector 10. In this embodiment, the wavelength of the single-wavelength pump laser is selected as 633nm, which is within the visible light wavelength range, facilitating alignment and adjustment of the straight optical path during experiments. The output laser power of the single-wavelength pump laser is in the range of 1-20mW, and can be selected and set according to experimental requirements. The focal lengths of the first K9 biconvex lens 7 and the second K9 biconvex lens 8 are 75mm, and the focal length of the third K9 biconvex lens 9 is 50.4mm. The larger focal lengths of the first two lenses are intended to reserve sufficient space to prevent collisions with the 3D-printed probe holder 3. The photosensitive area of ​​the quadrant photodetector 10 is 1.22mm². 2 The photosensitive gap is 24um and is mainly composed of four photodiodes with the same area and photoelectric characteristics distributed in four quadrants. As the position of the light spot hitting it changes, the light intensity and signal output received in each quadrant will also change.

[0043] The input terminal of the signal conditioning circuit 11 is connected to the output terminal of the four-quadrant photodetector 10, and it processes the output current signals of the four photodiodes after performing current-to-voltage conversion.

[0044]

[0045]

[0046] In equation (1), V x V is the output voltage signal of the four-quadrant photodetector 10 in the X direction, where V is the output voltage signal in equation (2). y V1, V2, V3, and V4 are the output voltage signals of the four-quadrant photodetector 10 in the Y direction, and V1, V2, V3, and V4 are the voltage signals of the four photodiodes.

[0047] Subsequently, the signal conditioning circuit 11 amplifies and filters the voltage signals in the X and Y directions to reduce the influence of external environmental noise, thereby improving the measurement sensitivity of the overall system and improving the signal-to-noise ratio.

[0048] The host computer data acquisition and processing module includes: a data acquisition card 12 and a computer 13; the data acquisition card 12 is a USB6120 (16bit, 250KS / s), and the signal conditioning circuit 11 is connected to the computer 13 through the data acquisition card 12.

[0049] The high-precision displacement drive module includes: a piezoelectric ceramic actuator 14, a PZT piezoelectric ceramic stage 15, and a three-dimensional precision micro-motion stage 16;

[0050] A PZT piezoelectric ceramic stage 15 is fixedly connected to a three-dimensional precision micro-motion stage 16; a test surface is provided on the PZT piezoelectric ceramic stage 15, and the test surface is directly below the test surface; the PZT piezoelectric ceramic stage 15 is connected to a piezoelectric ceramic actuator 14; the input terminal of the piezoelectric ceramic actuator 14 is connected to a computer 13; in this embodiment, the PZT piezoelectric ceramic stage can perform vertical nanometer-level displacement, with a closed-loop stroke of 50 μm and a resolution of 0.03 nm.

[0051] The signal generator 5 provides a sinusoidal excitation signal to the PI piezoelectric ceramic ring 4 to make it vibrate, thereby causing the flexible spring 2 to drive the probe head 1 to make a resonant motion, and generating interfacial micro-interaction force as it approaches the surface to be measured.

[0052] The laser beam emitted by the single-wavelength pump laser 6 is focused by the first K9 biconvex lens 7, and after being reflected by the reflector above the center of the flexible reed 2, the reflected divergent laser beam is parallelized by the second K9 biconvex lens 8, and then focused by the third K9 biconvex lens 9 to hit the four-quadrant photodetector 10 to form a laser spot, and outputs a corresponding optical power voltage signal. The optical power voltage signal changes with the position of the laser spot on the four-quadrant photodetector 10 and is related to the resonant motion of the flexible reed 2.

[0053] The signal conditioning circuit 11 preprocesses the optical power voltage signal and sends it to the computer 13 through the data acquisition card 12, thereby obtaining the relationship between the optical power voltage signal and the interface micro-interaction force, and realizing the dynamic measurement of the interface micro-interaction force.

[0054] In this embodiment, a method for measuring the dynamic and static forces at the micrometer scale is performed according to the following steps:

[0055] Step 1: Adjust the probe head 1 to align it with the surface to be measured on the PZT piezoelectric ceramic stage 15; turn on the single-wavelength pump laser 6 and adjust it to output the required optical power; adjust the collimation optical path module so that the laser beam is focused onto the center of the four-quadrant photodetector 10 after being reflected by the mirror above the center of the flexible reed 2.

[0056] Step 2: Keep the micron probe module fixed and adjust the three-dimensional precision micro-motion stage 16 according to the micron-level feed amount so that the surface to be measured gradually approaches the probe microsphere at the end of the probe head 1. When the distance between the two enters the range of action of the micro interface force, stop adjusting the three-dimensional precision micro-motion stage 16.

[0057] Step 3: Turn on the signal generator 5 to output the required sinusoidal excitation signal, so that the flexible reed 2 drives the probe head 1 to make regular resonant motion. At this time, the measurement system performs dynamic measurement. If the signal generator 5 is turned off and no sinusoidal excitation signal is provided, the measurement system performs static measurement.

[0058] Step 4: Using computer 13 to control piezoelectric ceramic driver 14 to continuously output voltage signal, drive PZT piezoelectric ceramic stage 15 to move at nanometer-level feed according to the required step distance and step time interval, so that the surface under test gradually approaches the probe microsphere at the end of probe probe head 1, completing the approach to contact process; at this time, the optical power voltage signal output by four-quadrant photodetector 10 also continuously changes, and data acquisition card 10 then synchronously acquires and transmits the data signal processed by signal conditioning circuit 11 to computer 13;

[0059] Step 4: After the computer 13 performs Fast Fourier Transform (FFT) and mean filtering on the acquired data signal, it obtains the amplitude, frequency and phase information of the resonant signal, thereby determining the area of ​​action of the interfacial micro-interaction force between the probe microsphere at the end of the probe probe 1 and the measured surface, so as to establish the interfacial force-voltage-separation displacement curve.

[0060] In this embodiment, the noise level of an interfacial force optical measurement system based on a contact resonant probe at the micrometer scale was tested and analyzed. The single-wavelength pump laser power was turned on, and the output power was set to 5mW. The collimation optical path module was adjusted so that the laser beam, after being reflected by a mirror above the center of the flexible reed, was focused onto the center of the four-quadrant photodetector. The output signal of the high signal-to-noise ratio circuit module was acquired by a data acquisition card and transmitted to a computer. The signal was collected and processed using LabVIEW. Figure 2 This is a graph showing the noise test results from the measurement system output. These data represent the AC component of the output voltage; the DC component is only related to the position of the light spot on the four-quadrant photodetector. The data acquisition card samples at 10kHz to improve resolution. In this experiment, room lighting and other CNC controllers were turned off to reduce interference from ambient light and instrument vibration. Figure 2 As shown, 800 noise measurement sequences were recorded, with the maximum output noise voltage not exceeding 30mV, the mean noise voltage being 6.98mV, and the standard deviation being 4.60mV. This indicates that the overall system has high resolution and the measurement results are highly reliable.

[0061] In this embodiment, the measurement system is used to dynamically measure the interfacial micro-interaction forces, analyzing the changes in interfacial forces between the probe microsphere and the tested surface during approach, contact, and compression. In the experiment, the three-dimensional precision micro-motion stage is adjusted to gradually bring the tested surface closer to the probe tip microsphere, stopping when the distance between them approaches the range of interfacial force action. A 500mV sinusoidal excitation signal is output from the signal generator, with a frequency set to 74.0Hz, determined by the resonant frequency of the flexible reed itself. The PZT piezoelectric ceramic stage is driven by computer control to gradually bring the tested surface closer to the probe microsphere, completing the approach, contact, and compression process. Afterward, a retraction motion is performed within the same displacement range, comparing the change trend of the output voltage amplitude of the flexible reed's resonant motion with displacement during the initial and retraction processes. In this experiment, the PZT piezoelectric ceramic stage operated in closed-loop mode with a full-range working range of 50 μm. The step distance was set to 50 nm, and the step time interval was 0.5 s. The corresponding displacement-voltage signals were acquired using LabVIEW. Here, the resonant amplitude voltage without interfacial micro-interaction forces was considered as the critical contact point, i.e., the relative distance zero point. Figure 3 This is a graph showing the output voltage results of the dynamic test of interfacial forces. (Example:) Figure 3As shown, during the process, when the measured surface gradually approaches but has not yet contacted the probe microsphere, the flexible reed is not affected by the micro-interface interaction force, and the amplitude voltage remains basically unchanged, fluctuating around 0.54V. When the relative distance between the measured surface and the probe microsphere approaches 3.9µm, the measured surface and the probe microsphere attract each other due to the micro-interface interaction force, and the amplitude of the flexible reed's resonant motion voltage suddenly increases, jumping from 0.54V to around 0.80V, with a sudden change of about 0.26V. At this time, the measured surface and the probe microsphere come into contact at the point of maximum resonant motion of the flexible reed, and the probe makes a point-contact motion. The PZT piezoelectric ceramic stage drives the measured surface to continue approaching the probe microsphere. Due to the spatial size limitation, the resonant amplitude of the flexible reed decreases. At the zero relative distance point, the flexible reed can still resonate normally. After passing the zero relative distance point, the normal resonant motion of the flexible reed is restricted, and the resonant amplitude voltage continues to decrease, falling below 0.54V. At this time, the probe head is in a compressed state. During the retreat process, as the probe head transitions from a compressed state to the stage influenced by microscopic interfacial interactions, the resonant amplitude voltage continuously increases, reaching a maximum amplitude of 1.38V at a relative distance of approximately 12.5µm. At this point, the interfacial force between the measured surface and the probe microsphere reaches its limit, ceasing point-to-point contact. The flexible reed detaches from the attraction and begins normal resonant motion, with the resonant amplitude voltage gradually recovering to around 0.54V, a sudden change of approximately 0.84V. Compared to the initial stage, the relative distance range affected by interfacial forces during the flexible reed's resonant motion is larger, and the critical voltage change is also larger. The overall trend of the interfacial microscopic interactions is consistent with the results of atomic force microscopy (AFM) measurements.

[0062] In this embodiment, the measurement system is used to perform static measurements of the interfacial micro-interaction forces, which can be compared with dynamic measurement results to further improve the study of the characteristics of the interfacial micro-interaction forces. The signal generator is turned off, the sinusoidal excitation signal is removed, and the measurement process is repeated according to the dynamic testing steps. Figure 4 The graph shows the output voltage results of the static test of interfacial forces. In this experiment, the flexible reed does not undergo resonant motion, and the output voltage value is the DC signal of the four-quadrant photodetector, reflecting only the positional change of the laser spot on the four-quadrant photodetector. Figure 4 As shown, when unaffected by microscopic interfacial interaction forces, the voltage value remains essentially constant at around 0.32V, and the overall trend of the progress and regression is basically consistent with the dynamic measurement results. However, compared to dynamic measurements, the static measurement output voltage value changes less, with the regression critical voltage jump around 30mV, and the interfacial force voltage amplitude does not change much with relative distance.

[0063] In summary, this dynamic and static optical measurement system and method for interfacial forces at the micrometer scale can accurately obtain the interfacial force and voltage signals between the probe tip and the measured surface, establish the interfacial force-voltage-separation displacement curve at the micrometer scale, and conduct dynamic and static measurement experiments for comparative analysis. This enables the measurement, analysis, and characterization of interfacial micro-interaction forces, and has certain guiding significance.

Claims

1. A dynamic and static optical measurement system for interfacial forces at the micrometer scale, characterized in that, include: Micrometer probe module, collimation optical path module, signal conditioning circuit (11), host computer acquisition and processing module and high-precision displacement drive module; The micron probe module includes: a probe head (1), a flexible spring (2), a reflector, a 3D printed probe bracket (3), a PI piezoelectric ceramic ring (4), and a signal generator (5); The probe head (1) is vertically connected to the center of the flexible spring (2) through metal glue; the microsphere at the top of the probe head (1) has a diameter of 100 μm; the flexible spring (2) has a thickness of 0.1 mm and its surface shape adopts a centrally symmetrical four-chord structure design; a reflector is set above the center of the flexible spring (2); four small holes are etched on the flexible spring (2) and fixed to the outer ring at the lower end of the 3D printed probe bracket (3) by screws and nuts; the lower end of the 3D printed probe bracket (3) has a uniform four-sided hollow structure so that the collimated laser light can enter and exit at an oblique direction; the PI piezoelectric ceramic ring (4) is embedded and fixed at the upper end of the 3D printed probe bracket (3) and is provided with a sinusoidal excitation signal by the signal generator (5); The collimated optical path module includes: a single-wavelength pump laser (6), three K9 biconvex lenses, and a four-quadrant photodetector (10); The single-wavelength pump laser (6) and the first K9 biconvex lens (7) are coaxially fixed on one side of the 3D printed probe bracket (3); the second K9 biconvex lens (8) and the third K9 biconvex lens (9) are coaxially fixed on the other side of the 3D printed probe bracket (3) with the four-quadrant photodetector (10). The input terminal of the signal conditioning circuit (11) is connected to the output terminal of the four-quadrant photodetector (10); The host computer acquisition and processing module includes: a data acquisition card (12) and a computer (13); The signal conditioning circuit (11) is connected to the computer (13) through the data acquisition card (12); The high-precision displacement drive module includes: a piezoelectric ceramic actuator (14), a PZT piezoelectric ceramic stage (15), and a three-dimensional precision micro-motion stage (16); The PZT piezoelectric ceramic stage (15) is fixedly connected to the three-dimensional precision micro-motion stage (16); The PZT piezoelectric ceramic stage (15) is provided with a test surface, and the test surface is directly below the probe head (1); The PZT piezoelectric ceramic stage (15) is connected to the piezoelectric ceramic driver (14); the input terminal of the piezoelectric ceramic driver (14) is connected to the computer (13); The signal generator (5) provides a sinusoidal excitation signal to the PI piezoelectric ceramic ring (4) to make it vibrate, thereby causing the flexible spring (2) to drive the probe head (1) to make a resonant motion, and generating interfacial micro-interaction force as it approaches the surface to be measured; The laser beam emitted by the single-wavelength pump laser (6) is focused by the first K9 biconvex lens (7), and reflected by the reflector above the center of the flexible reed (2). The reflected divergent laser beam is then parallelized by the second K9 biconvex lens (8), and after being transmitted by the third K9 biconvex lens (9), the parallel laser beam is focused on the four-quadrant photodetector (10) to form a laser spot and output a corresponding optical power voltage signal. The optical power voltage signal changes with the position of the laser spot on the four-quadrant photodetector (10) and is related to the resonant motion of the flexible reed (2). The signal conditioning circuit (11) preprocesses the optical power voltage signal and sends it to the computer (13) through the data acquisition card (12) to obtain the relationship between the optical power voltage signal and the interface micro-interaction force, thereby realizing the dynamic measurement of the interface micro-interaction force.

2. A method for measuring the dynamic and static forces at the micrometer scale, characterized in that, The measurement is performed using the measurement system as described in claim 1, and is carried out according to the following steps: Step 1: Adjust the probe head (1) to align it with the surface to be measured on the PZT piezoelectric ceramic stage (15); turn on the single-wavelength pump laser (6) and adjust it to output the required optical power; adjust the collimation optical path module so that the laser beam is focused onto the center of the four-quadrant photodetector (10) after being reflected by the mirror above the center of the flexible reed (2); Step 2: Keep the micron probe module still and adjust the three-dimensional precision micro-motion stage (16) according to the micron-level feed amount so that the surface to be measured gradually approaches the probe microsphere at the end of the probe head (1). When the distance between the two enters the range of action of the micro interface force, stop adjusting the three-dimensional precision micro-motion stage (16). Step 3: Turn on the signal generator (5) to output the required sinusoidal excitation signal, so that the flexible reed (2) drives the probe head (1) to make regular resonant motion, and the measurement system performs dynamic measurement; if the signal generator (5) is turned off and no sinusoidal excitation signal is provided, the measurement system performs static measurement. Step 4: Using the computer (13), control the piezoelectric ceramic driver (14) to continuously output a voltage signal, drive the PZT piezoelectric ceramic stage (15) to move at a nanometer-level feed rate according to the required step distance and step time interval, so that the surface under test gradually approaches the probe microsphere at the end of the probe probe head (1) to complete the process of approaching to contact; at this time, the optical power voltage signal output by the four-quadrant photodetector (10) also continuously changes, and the data acquisition card (12) then synchronously acquires and transmits the data signal processed by the signal conditioning circuit (11) to the computer (13); Step 5: The computer (13) performs Fast Fourier Transform (FFT) and mean filtering on the collected data signals to obtain the amplitude, frequency and phase information of the resonant signal, thereby determining the action area of ​​the interfacial micro-interaction force between the probe microsphere at the end of the probe head (1) and the measured surface, so as to establish the interfacial force-separation displacement curve.

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