Device and method for macroscopic droplet friction force test

Abstract

The invention discloses a device and a method for macroscopic liquid drop friction force testing, which are used for measuring friction force between a to-be-tested liquid drop arranged on a to-be-tested plate and the to-be-tested plate, and the device comprises a probe, a stress application sheet, a laser sensor and a testing platform, the probe is a strip-shaped sheet, one side surface is a mirror surface, the probe is vertically arranged, the upper end is fixed with the outside, and the lower end is fixedly connected with the center of the upper end surface of the stress application sheet; the stress application sheet is used for dragging the to-be-tested liquid drop to move on the to-be-tested plate; the test platform is used for adjusting the position of the to-be-tested plate. According to the invention, the micro deformation of the probe is amplified through the optical lever principle, the laser irradiates the mirror surface of the probe at a certain deflection angle, the reflected laser is sensed by the laser receiver, and the position of the reflected laser is recorded, so that even if the probe generates micro deformation, the position of the reflected laser can be obviously changed; the friction force of the macroscopic liquid drop friction force is represented through the position change of the reflected laser, the operation is simple, and the detection result is accurate.

Description

Technical Field

[0001] The present invention relates to the field of material physical property detection, and in particular to a device and method for testing the friction force of macroscopic droplets. Background Art

[0002] The motion of liquid droplets on solid surfaces is a ubiquitous phenomenon in nature and plays a key role in numerous technological applications, including microfluidics, printing, condensation, and water harvesting. During liquid motion, the relative motion between the liquid and the solid surface generates friction between the droplet and the solid. This friction can reflect the transport properties of liquids on solid surfaces and can also help us understand how different solid surface properties regulate droplet friction.

[0003] Among related technologies, the droplet probe technology based on atomic force microscopy can accurately measure the friction of micron-sized droplets. However, for the friction of millimeter-sized droplets, only relatively rough measurements can be performed based on the inclined plate method, and it is impossible to monitor the changes in friction of droplets in real time when they move on solid surfaces.

[0004] Since the mechanical mechanisms of micron-sized droplets are different from those of millimeter-sized droplets, in order to deeply understand the motion mechanism of macroscopic droplets, it is necessary to develop a device and method for real-time detection of the friction force of macroscopic droplets. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to provide a device and method for macroscopic droplet friction testing in response to the defects involved in the background technology.

[0006] The present invention adopts the following technical solutions to solve the above technical problems: A device for macroscopic droplet friction testing, for measuring the friction between a droplet placed on a test plate and the test plate, wherein the droplet is any one of aqueous droplets, oily droplets, and ionic liquid droplets, and comprises a probe, a force-applying sheet, a laser sensor, and a test platform; The probe is a long thin sheet with a mirror surface on one side and an elastic modulus ranging from 100 to 5000 μN / mm. The probe is vertically arranged with its upper end fixedly connected to the outside world. The force-applying sheet is a rectangular sheet with an elastic modulus greater than 5000 μN / mm. The center of its upper end face is vertically fixed to the lower end of the probe, and the contact angle between the lower end face and the droplet to be tested is less than or equal to 60°, and is used to drag the droplet to be tested to move on the test plate; The test platform is used to carry the test board and the test droplets on the test board, and can drive the test board to move vertically or horizontally; The laser sensor includes a laser transmitter and a laser receiver. The laser transmitter is used to transmit laser light toward the mirror surface of the probe; the laser receiver is used to receive laser light reflected by the mirror surface of the probe and record position information of the reflected laser light.

[0007] As a further optimization solution of the device for macroscopic droplet friction testing of the present invention, the thickness of the probe is less than or equal to 100 μm.

[0008] As a further optimization solution of the device for macroscopic droplet friction testing of the present invention, the probe adopts a polished silicon wafer or a glass capillary coated with gold / silver / lead.

[0009] As a further optimization solution of the device for macro-droplet friction testing of the present invention, the force-applying thin sheet is any one of a quartz glass thin sheet, a mica thin sheet, and an aluminum oxide thin sheet.

[0010] As a further optimization solution of the device for macroscopic droplet friction testing of the present invention, the force-increasing sheet is fixedly connected to the probe by an epoxy adhesive.

[0011] The present invention amplifies the tiny deformation of the probe through the principle of optical lever. The laser is irradiated on the mirror surface of the probe at a certain angle. The reflected laser is sensed by the laser receiver and its position is recorded. In this way, even if the probe produces a tiny deformation, the position of the reflected laser can change significantly.

[0012] The present invention also discloses a method for measuring the device for macroscopic droplet friction testing, comprising the following steps: Step 1) Adjust the position of the laser emitter on the mirror surface of the probe, and use the laser receiver to record the position voltage signal of the reflected laser, which is used as the initial voltage signal; Step 2) Take N samples of known friction force, where N is a preset sample quantity threshold. The sample includes a test droplet and a test plate. For each sample: In step 2.1, place the sample on the test platform and adjust the position of the test droplet through the test platform so that it contacts the lower end surface of the force-adding sheet; In step 2.2, the test platform drives the test plate to move horizontally at a constant speed in a direction perpendicular to the probe mirror, causing the test droplet and the test plate to move relative to each other. At this time, the probe mirror bends, and a laser receiver is used to record the position voltage signal of the reflected laser during movement; Step 2.3) Subtract the initial voltage signal from the position voltage signal of the reflected laser during movement to obtain the displacement voltage signal; Step 3) Fit the friction force and the corresponding displacement voltage signal of N samples to obtain the relationship between the friction force and the displacement voltage signal; Step 4) Place the droplet to be tested and the plate to be tested on the test platform, and adjust the position of the droplet to be tested through the test platform so that it contacts the lower end surface of the force-applying sheet; Step 5) The test platform drives the test board to move horizontally at a constant speed in a direction perpendicular to the probe mirror, so that the test droplet and the test board move relative to each other. At this time, the probe mirror bends, and a laser receiver is used to record the position voltage signal of the reflected laser during the movement; Step 6), subtracting the initial voltage signal from the position voltage signal of the reflected laser when the droplet to be measured and the plate to be measured move, to obtain the displacement voltage signal of the droplet to be measured and the plate to be measured; Step 7) Substitute the displacement voltage signals of the test droplet and the test plate into the relationship between the friction force and the displacement voltage signal to obtain the friction force corresponding to the displacement voltage signals of the test droplet and the test plate, that is, the friction force between the test droplet and the test plate.

[0013] Compared with the prior art, the present invention adopts the above technical solution and has the following technical effects: 1. This invention fills the gap in methods for accurately measuring the friction of macroscopic droplets. Based on the principle of optical levers, by adjusting the elastic modulus of the probe, it can adapt to friction tests of varying magnitudes, providing accurate test results. 2. The present invention realizes the real-time monitoring of the friction force of macroscopic droplets, providing a new method for studying the transport characteristics of macroscopic droplets on the surfaces of different solid materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0014] Figure 1 It is a structural schematic diagram of the present invention; Figure 2 Schematic diagram of the testing principle of the present invention.

[0015] In the figure, 1-probe, 2-forced sheet, 3-droplet to be tested, 4-plate to be tested, 5-testing platform, 6-laser transmitter, 7-laser receiver. DETAILED DESCRIPTION

[0016] The technical solution of the present invention is further described in detail below with reference to the accompanying drawings: The present invention can be implemented in many different forms and should not be considered to be limited to the embodiments described herein. On the contrary, these embodiments are provided to make this disclosure thorough and complete and will fully convey the scope of the invention to those skilled in the art. In the accompanying drawings, components are enlarged for clarity.

[0017] like Figure 1As shown, the present invention discloses a device for macroscopic droplet friction force testing, which is used to measure the friction force between a droplet to be tested placed on a test plate and the test plate. The droplet to be tested is any one of aqueous droplets, oily droplets, and ionic liquid droplets. The device includes a probe, a force-applying sheet, a laser sensor, and a test platform. The probe is a long thin sheet with a mirror surface on one side and an elastic modulus ranging from 100 to 5000 μN / mm. The probe is vertically arranged with its upper end fixedly connected to the outside world. The force-applying sheet is a rectangular sheet with an elastic modulus greater than 5000 μN / mm. The center of its upper end face is vertically fixed to the lower end of the probe, and the contact angle between the lower end face and the droplet to be tested is less than or equal to 60°, and is used to drag the droplet to be tested to move on the test plate; The test platform is used to carry the test board and the test droplets on the test board, and can drive the test board to move vertically or horizontally; The laser sensor includes a laser transmitter and a laser receiver. The laser transmitter is used to transmit laser light toward the mirror surface of the probe; the laser receiver is used to receive laser light reflected by the mirror surface of the probe and record position information of the reflected laser light.

[0018] The probe has a thickness of 100 μm or less and is preferably made of a polished silicon wafer or a glass capillary coated with gold, silver, or lead. The stiffening sheet is preferably made of any of a quartz glass sheet, a mica sheet, and an alumina sheet. The stiffening sheet is preferably secured to the probe using an epoxy adhesive.

[0019] like Figure 2 As shown, the present invention uses the principle of an optical lever to amplify tiny probe deformations. Laser light is irradiated at a specific angle onto the probe's mirror surface. The reflected laser light is sensed by a laser receiver and its position is recorded. Even small probe deformations can significantly change the position of the reflected laser light.

[0020] The present invention also discloses a method for measuring the device for macroscopic droplet friction testing, comprising the following steps: Step 1) Adjust the position of the laser emitter on the mirror surface of the probe, and use the laser receiver to record the position voltage signal of the reflected laser, which is used as the initial voltage signal; Step 2) Take N samples of known friction force, where N is a preset sample quantity threshold. The sample includes a test droplet and a test plate. For each sample: In step 2.1, place the sample on the test platform and adjust the position of the test droplet through the test platform so that it contacts the lower end surface of the force-adding sheet; In step 2.2, the test platform drives the test plate to move horizontally at a constant speed in a direction perpendicular to the probe mirror, causing the test droplet and the test plate to move relative to each other. At this time, the probe mirror bends, and a laser receiver is used to record the position voltage signal of the reflected laser during movement; Step 2.3) Subtract the initial voltage signal from the position voltage signal of the reflected laser during movement to obtain the displacement voltage signal; Step 3) Fit the friction force and the corresponding displacement voltage signal of N samples to obtain the relationship between the friction force and the displacement voltage signal; Step 4) Place the droplet to be tested and the plate to be tested on the test platform, and adjust the position of the droplet to be tested through the test platform so that it contacts the lower end surface of the force-applying sheet; Step 5) The test platform drives the test board to move horizontally at a constant speed in a direction perpendicular to the probe mirror, so that the test droplet and the test board move relative to each other. At this time, the probe mirror bends, and a laser receiver is used to record the position voltage signal of the reflected laser during the movement; Step 6), subtracting the initial voltage signal from the position voltage signal of the reflected laser when the droplet to be measured and the plate to be measured move, to obtain the displacement voltage signal of the droplet to be measured and the plate to be measured; Step 7) Substitute the displacement voltage signals of the test droplet and the test plate into the relationship between the friction force and the displacement voltage signal to obtain the friction force corresponding to the displacement voltage signals of the test droplet and the test plate, that is, the friction force between the test droplet and the test plate.

[0021] It will be understood by those skilled in the art that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by those skilled in the art in the art to which this invention belongs. It should also be understood that terms such as those defined in common dictionaries should be understood to have meanings consistent with their meanings in the context of the prior art and, unless defined as such, will not be interpreted in an idealized or overly formal sense.

[0022] The specific implementation methods described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific implementation method of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the scope of protection of the present invention.

Claims

1. A device for macroscopic droplet friction testing, for measuring the friction between a droplet placed on a test plate and the test plate, wherein the droplet is any one of aqueous droplets, oily droplets, and ionic liquid droplets, characterized in that: Including probe, afterburner sheet, laser sensor and test platform; The probe is a long thin sheet with a mirror surface on one side and an elastic modulus ranging from 100 to 5000 μN / mm. The probe is vertically arranged with its upper end fixedly connected to the outside world. The force-applying sheet is a rectangular sheet with an elastic modulus greater than 5000 μN / mm. The center of its upper end face is vertically fixed to the lower end of the probe, and the contact angle between the lower end face and the droplet to be tested is less than or equal to 60°, and is used to drag the droplet to be tested to move on the test plate; The test platform is used to carry the test board and the test droplets on the test board, and can drive the test board to move vertically or horizontally; The laser sensor includes a laser transmitter and a laser receiver. The laser transmitter is used to transmit laser light toward the mirror surface of the probe; the laser receiver is used to receive laser light reflected by the mirror surface of the probe and record position information of the reflected laser light.

2. The device for macroscopic droplet friction testing according to claim 1, characterized in that: The thickness of the probe is less than or equal to 100 μm.

3. The device for macroscopic droplet friction testing according to claim 1, characterized in that: The probe is made of a polished silicon wafer or a glass capillary coated with gold / silver / lead.

4. The device for macroscopic droplet friction testing according to claim 1, characterized in that: The reinforcement sheet is made of any one of quartz glass sheet, mica sheet and alumina sheet.

5. The device for macroscopic droplet friction testing according to claim 1, characterized in that: The reinforcement sheet is fixedly connected to the probe by epoxy adhesive.

6. A method for measuring the friction force of a macro droplet according to claim 1, characterized in that: The following steps are involved: Step 1) Adjust the position of the laser emitter on the mirror surface of the probe, and use the laser receiver to record the position voltage signal of the reflected laser, which is used as the initial voltage signal; Step 2) Take N samples of known friction force, where N is a preset sample quantity threshold. The sample includes a test droplet and a test plate. For each sample: In step 2.1, place the sample on the test platform and adjust the position of the test droplet through the test platform so that it contacts the lower end surface of the force-adding sheet; In step 2.2, the test platform drives the test plate to move horizontally at a constant speed in a direction perpendicular to the probe mirror, causing the test droplet and the test plate to move relative to each other. At this time, the probe mirror bends, and a laser receiver is used to record the position voltage signal of the reflected laser during movement; Step 2.3) Subtract the initial voltage signal from the position voltage signal of the reflected laser during movement to obtain the displacement voltage signal; Step 3) Fit the friction force and the corresponding displacement voltage signal of N samples to obtain the relationship between the friction force and the displacement voltage signal; Step 4) Place the droplet to be tested and the plate to be tested on the test platform, and adjust the position of the droplet to be tested through the test platform so that it contacts the lower end surface of the force-applying sheet; Step 5) The test platform drives the test board to move horizontally at a constant speed in a direction perpendicular to the probe mirror, so that the test droplet and the test board move relative to each other. At this time, the probe mirror bends, and a laser receiver is used to record the position voltage signal of the reflected laser during the movement; Step 6), subtracting the initial voltage signal from the position voltage signal of the reflected laser when the droplet to be measured and the plate to be measured move, to obtain the displacement voltage signal of the droplet to be measured and the plate to be measured; Step 7) Substitute the displacement voltage signals of the test droplet and the test plate into the relationship between the friction force and the displacement voltage signal to obtain the friction force corresponding to the displacement voltage signals of the test droplet and the test plate, that is, the friction force between the test droplet and the test plate.

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