A method for preparing a DIC micro area speckle based on butterfly scales

Abstract

A DIC micro area speckle preparation method based on butterfly scales, relates to the field of deformation detection, including the following steps: collecting butterfly wing surface, collecting scales, obtaining scales dispersed on water surface, cleaning the surface of speckle sample with hydrophilic bottom layer and drying, spraying low surface tension liquid to the water surface area where the scales are located, after completion, standing, slowly contacting the hydrophilic bottom layer of the sample with the water surface area where the scales are located, carrying out scale transfer printing, then naturally drying in a non-strong air flow environment, spraying a transparent flexible protective layer on the surface of the transferred scale layer and curing; the method can be applied to flexible matrix and stretchable scene, the flexible protective film has excellent flexibility and cooperative deformation ability, the scales have high contrast and excellent imaging characteristics, the specific scale gray scale contrast is much higher than that of traditional artificial speckle, and stable imaging can be realized under complex illumination, and the method is particularly suitable for DIC measurement of flexible electronic, soft robot, biological soft tissue and other large deformation materials.

Description

Technical Field

[0001] This invention relates to the field of deformation detection technology, specifically to a method for preparing DIC micro-area speckle patterns based on butterfly scales. Background Technology

[0002] Digital image correlation (DIC) methods obtain displacement and strain fields by tracking the grayscale feature changes of speckle images on the sample surface before and after loading. The quality of the speckle pattern directly affects the stability of correlation matching, subpixel positioning accuracy, and reliability of local strain identification. Ideal speckles typically require characteristics such as high contrast, randomness, appropriate size, sufficient grayscale gradient, stable adhesion, and coordinated deformation with the matrix.

[0003] Existing methods for preparing speckle patterns mainly include spraying, powder coating, particle adhesion, etching, photolithography, laser processing, and transfer printing. Spraying is simple, but it is prone to problems such as uncontrollable speckle size, blurred boundaries, agglomeration, and localized reflections on micro-area samples. Etching and laser processing can obtain more regular patterns, but the equipment cost is high, the process time is long, and it may alter the surface condition of the sample. Traditional transfer printing methods have high requirements for the flatness, roughness, and wettability of the receiving surface, making them difficult to adapt to micro-curved surfaces, uneven surfaces, and flexible substrates.

[0004] For small-sized irregular components, thin film materials, elastomers, biological soft tissue substitutes, and microstructured surfaces, speckle layers not only need stable optical recognition capabilities, but also must deform synchronously with the substrate under tension, bending, compression, or cyclic loading without slippage, peeling, cracking, or significant thickening. Therefore, there is an urgent need for a low-cost, low-damage method that can rapidly form high-quality speckles on complex surfaces. Summary of the Invention

[0005] In view of this, the present invention proposes a method for preparing DIC micro-area speckle based on butterfly scales. Using butterfly scales as raw materials, DIC micro-area speckle is prepared on the sample surface based on the Marangoni aggregation effect, which solves the shortcomings of existing methods in terms of micro-area speckle size control, multi-morphological surface adaptation, flexible substrate adhesion and imaging stability under complex lighting conditions.

[0006] To solve at least one of the above-mentioned technical problems, the present invention provides a method for preparing DIC micro-area speckle patterns based on butterfly scales, comprising the following steps: A method for preparing DIC micro-area speckle patterns based on butterfly scales includes the following steps: Step S1: Collect butterfly wing surfaces to collect scales, resulting in scales that are left to stand still and dispersed on the water surface; Step S2: Clean the surface of the speckled sample with a hydrophilic underlayer and dry it; Step S3: Spray a low surface tension liquid onto the water surface area where the scales are located, and let it stand after completion; Step S4: Slowly bring the hydrophilic bottom layer of the sample into contact with the water surface area where the scales are located to perform scale transfer, and then let it dry naturally in an environment without strong airflow. Step S5: Spray a transparent flexible protective layer onto the surface of the transferred flake layer and cure it.

[0007] The technical effects of this invention are: 1. The main raw material in the method of this invention, scales, is readily available and extremely low in cost. Black butterfly wings can be obtained from butterfly farms, defective specimens, or naturally deceased individuals. A single wing can be used for dozens of small-sized samples, and the material cost is negligible.

[0008] 2. The scales have the characteristics of high contrast and excellent imaging. Specific scales, such as black scales, have a natural light absorption rate of ≥80%. Combined with a white matte hydrophilic substrate, the grayscale contrast far exceeds that of traditional artificial speckle (such as spray paint and toner), and can still form stable images under complex lighting conditions.

[0009] 3. The scales have strong adhesion and do not rely on chemical adhesives. They utilize the physical anchoring effect of the micro-tooth structure of the scales themselves, combined with the outer protective film, to achieve firm fixation. Even if the sample undergoes large deformation (>50% strain), the scales will not peel off.

[0010] 4. The method of the present invention is applicable to flexible substrates and stretchable scenarios. The flexible protective film has excellent flexibility and cooperative deformation ability, making the method of the present invention particularly suitable for DIC measurement of large deformation materials such as flexible electronics, soft robots, and biological soft tissues, which is impossible to achieve with traditional hard speckle (such as metal microspheres and etched spots).

[0011] 5. The scales are uniform in size and naturally match the micro-region DIC. The natural size of butterfly scales is 35. ~150 It closely matches the optimization requirements of micro-area DIC for speckle size and can be used directly without sieving.

[0012] 6. The method of the present invention meets the statistical requirements of DIC. The adsorption of scales during the water transfer printing process has natural randomness and no periodic artifacts, which meets the core requirement of DIC for the spatial randomness of speckle patterns.

[0013] 7. The method of the present invention is simple and does not require expensive equipment. The entire preparation process only requires conventional equipment such as soft brushes, spray bottles, water tanks, and ovens. It does not require laser processing, photolithography or plasma treatment, and is suitable for promotion in ordinary laboratories.

[0014] 8. The method of the present invention is environmentally friendly and non-toxic, with good biocompatibility. The materials used are natural flakes, water-based paint, and water-based polyurethane, which do not contain organic solvents or heavy metals. They are friendly to the human body and the environment and have potential biomedical application value.

[0015] 9. The patterning and density of the method of the present invention can be precisely controlled. By controlling the position of the anhydrous ethanol spray and the sample immersion path, the scales can be selectively transferred to the sample surface, avoiding material waste caused by full-area coating.

[0016] 10. The scales used in this invention have a complete structure and good repeatability. Compared with scraping or grinding, the wet brush peeling method can preserve the original micro-nano structure of the scales to the maximum extent, ensuring the consistency of performance between batches and facilitating the establishment of a standardized spot-making process. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the overall process of the present invention; Figure 2 This is a microscopic scanning image of the butterfly scales in this invention; Figure 3 This is a diagram illustrating the light absorption characteristics of butterfly scales in this invention; Figure 4 This is a schematic diagram of the DIC micro-area speckle composite structure in this invention; Figure 5 This is a flowchart illustrating the actual process of using ethanol to induce the aggregation of butterfly scales and the transfer of hydrophilic and hydrophobic interfaces in non-planar tubular samples in Example 2 of the present invention. Figure 6 This is a diagram showing the results of speckle pattern preparation on the curved surface of the pipe sample in Example 2 of the present invention. Detailed Implementation

[0019] The present invention will be further described in detail below with reference to the embodiments and accompanying drawings.

[0020] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention.

[0021] See Figure 1 A method for preparing DIC micro-area speckle patterns based on butterfly scales includes the following steps: Step S1: Collect butterfly wing surfaces to collect scales, resulting in scales that are left to stand still and dispersed on the water surface; like Figure 2 As shown, the base of butterfly scales has a micron-sized tooth-like structure. These micro-tooths are embedded in the base film in the natural wing to achieve a firm connection. After transfer, the micro-tooths can form a mechanical interlock with the hydrophilic primer or the sample surface, significantly enhancing the initial adhesion of the scales and achieving effective fixation without relying on chemical adhesives.

[0022] The scales should originate from black, dark brown, or other low-reflectivity dark-colored butterfly wings. Black scales naturally have a light absorption advantage over light-colored scales, specifically as follows: Figure 3 As shown; preferred materials include naturally shed wing scales, damaged specimens from artificial breeding, or wing materials obtained through compliant channels. Chromaticity coordinates, visible light reflectance, and standard imaging grayscale are used as selection criteria.

[0023] Specifically, the surface chromaticity of the scales meets the following conditions: under a D65 standard light source or an equivalent stable white light source, In chromaticity coordinates, the scale surface Value no greater than 35, preferably 5-30. The value is between -5 and 15. The value is between -10 and 20. The average reflectance of the scales in the visible light range of 400nm to 700nm is no greater than 25%, preferably no greater than 20%; in an 8-bit grayscale image, the average grayscale value of the scales is no greater than 90, the average grayscale value of the white matte underlayer is no less than 180, and the average grayscale difference between the scales and the underlayer is no less than 80.

[0024] The method for collecting scales includes the following steps: Step S11: Select low-reflection dark butterfly wings, place the wing surface on a clean platform, and gently brush along the natural arrangement of the scales with a soft brush moistened with deionized water to peel the scales off the wing membrane surface. During the scale removal process, grinding, strong scraping, and high-shear agitation should be avoided to preserve the micro-tooth, ribs, and windowpane-like micro-nano structures at the scale roots. If necessary, obviously broken, agglomerated, or contaminated scales can be removed using low-magnification microscopy, sieves, or image recognition methods to ensure that the scales entering the surface aggregation step meet the above-mentioned quantitative screening requirements.

[0025] Step S12: Then, use a dropper or spray to rinse the scales into a glass petri dish or water tank containing deionized water. Let the scales disperse by standing in the deionized water container. Due to the natural superhydrophobicity of the scales, they can float on the water surface and form a dispersed state. The initial flake dosage in the deionized water container is per 1.5mg~3.0mg on the water surface, which can be adjusted as needed according to the target speckle coverage.

[0026] Before peeling, the scales need to be sampled and counted using an optical microscope. The length of a single scale is 35 mm. ~150 Between, with a width of 10 ~80 Between, the equivalent circle diameter is 20 ~120 The proportion of scales that are obviously broken, folded, curled, contaminated or clustered should not exceed 20%, preferably not exceed 10%.

[0027] Step S2: Clean the surface of the speckled sample with a hydrophilic underlayer and dry it; Butterfly scales are natural superhydrophobic materials (contact angle >150°). When a hydrophilic sample is immersed in water and comes into contact with hydrophobic scales floating on the water surface, the scales will spontaneously detach from the water surface and adsorb onto the hydrophilic solid surface in order to reduce the interfacial free energy. This process does not require any external adhesives and is purely driven by interfacial energy. The transfer speed is fast, the scale orientation is random, and the distribution is uniform.

[0028] To ensure that the scales can form a speckle pattern, the sample surface should be hydrophilic. Therefore, a hydrophilic underlayer needs to be set on the surface of the speckle sample. This underlayer should have low specular reflection, high brightness, good hydrophilicity, and stable bonding ability with the substrate.

[0029] The underlying layer can be a white matte hydrophilic coating, a water-based primer containing titanium dioxide or silica particles, a hydrophilic modified acrylic coating, or other thin layers that do not affect the mechanical testing of the sample. Preferably, the surface of the speckled sample is coated with 10 layers. ~30 White or light-colored matte hydrophilic base.

[0030] For metals, ceramics, or composite materials, ethanol, acetone, or deionized water can be used for cleaning in sequence. For polymers, rubber, or hydrogels, a cleaning method that does not damage the substrate should be selected. After cleaning, a white or light-colored matte hydrophilic underlayer is formed on the sample surface.

[0031] Step S3: Spray a low surface tension liquid onto the water surface area where the scales are located, and let it stand after completion; Based on the scales obtained in step S1 that are statically dispersed on the water surface, a low surface tension liquid is lightly sprayed onto the target area. The low surface tension liquid is one of anhydrous ethanol, isopropanol aqueous solution, or ethanol aqueous solution. A local surface tension difference is formed on the water surface, causing the floating scales to aggregate under the action of interfacial flow due to the Marangoni effect. When the water layer flows outward due to the Marangoni effect, the superhydrophobic scales are carried along with it, achieving rapid aggregation in seconds. By changing the spray position, spray volume, and spray frequency, the position, area, and density of the scale layer can be adjusted.

[0032] By varying the flake concentration and ethanol spray position within the same water tank, flake aggregation zones of different densities can be obtained. For micro-samples where only speckling is required in the gauge length, the gauge length of the sample can be brought into contact with the high-density area first, and then the clamping end can be positioned to avoid the flake layer, thereby achieving area-selective transfer.

[0033] Alternatively, by using a masking film, a localized hydrophilic substrate, or a partitioned immersion path, the scales can be deposited only in the areas requiring DIC identification. This method reduces material waste and avoids speckle in the clamping area affecting loading and clamping.

[0034] The volume fraction of the solute in the aqueous solution is 50%~80%, preferably 60%~75%, and the spraying method is per 100cm. 2 Spray 0.1mL~0.3mL onto the water surface, and let it stand for at least 5 seconds after spraying.

[0035] Step S4: Slowly bring the hydrophilic bottom layer of the sample into contact with the water surface area where the scales are located to perform scale transfer, and then let it dry naturally in an environment without strong airflow. The specific method of scale transfer is as follows: the hydrophilic bottom layer of the sample is applied with... The contact angle is optimal, and the speed of immersion or removal from the water surface area where the scales are located is 0.5 mm / s to 5 mm / s. This causes the scales to transfer from the water surface to the hydrophilic bottom surface after the sample surface comes into contact with the floating scales.

[0036] For butterfly scales from any source, a feedback process is adopted, including small-scale dispersion, one-time spraying, one-time transfer, image evaluation, and, if necessary, re-enrichment and transfer. The scale coverage of the target area of ​​the sample should be maintained between 35% and 65%. If the coverage after the first transfer is less than 35%, a second or third enrichment and transfer should be performed in the same target area. If the coverage is higher than 65% or the local agglomeration ratio is higher than 10%, the scale dosage, ethanol volume fraction, or standing time should be reduced and the sample should be re-prepared. If the coverage is 35% to 65%, the local agglomeration ratio is not greater than 10%, and the average gray value of the scales is not less than 80 compared with the gray value of the underlying layer, then the speckle pattern is deemed to meet the recommended requirements for DIC micro-area testing.

[0037] If the speckle pattern does not meet the recommended requirements for DIC micro-area testing, for samples requiring low-density speckle, the amount of scale added, the volume fraction of ethanol, or the number of repeated transfers can be reduced; for micro-area testing requiring high-density speckle, multiple local spraying or repeated transfers can be used, but the number of repeated transfers should preferably not exceed 3 times to avoid excessive scale coverage, local aggregation, and loss of grayscale characteristics.

[0038] For planar specimens, a unidirectional oblique entry and uniform speed withdrawal method can be used. For non-planar specimens, rotation, swinging or repeated contact can be performed during immersion or withdrawal to improve the uniformity of coverage on complex surfaces.

[0039] In addition, after the transfer is completed, the sample should be placed in a clean environment to dry naturally or at low temperature. During the drying process, strong airflow should be avoided to prevent scale migration.

[0040] Step S5: Spray a transparent flexible protective layer onto the surface of the transferred flake layer and cure it.

[0041] A thin, transparent, flexible protective layer is sprayed onto the dried flake layer surface. This layer is one of the following: an aqueous aliphatic polyurethane diluent, a transparent acrylic emulsion, or a silicone rubber diluent. The preferred volume ratio of the aqueous polyurethane to deionized water is 1:2-5; the volume ratio of transparent acrylic acid to deionized water in the transparent acrylic emulsion is 1:5-10; and the ratio of aqueous silicone rubber diluent to deionized water in the silicone rubber diluent is 1:2-4. After curing, the protective layer forms a continuous or semi-continuous film, which on the one hand covers and confines the flakes, and on the other hand maintains transparency and flexibility, reducing interference with speckle grayscale contrast and matrix deformation transmission.

[0042] For flexible sample substrates, the protective layer should be applied using a low-concentration, multiple thin sprays and room temperature curing method; for rigid sample substrates such as metals or ceramics, room temperature curing or low-temperature drying can be used, with a curing time preferably between 10 min and 60 min.

[0043] After completing the preparation according to the above steps, the following is obtained: Figure 4The speckle composite structure shown can further acquire initial speckle images and perform quality evaluation and feedback control.

[0044] The evaluation area is preferably the actual calculation area of ​​DIC, and image acquisition should maintain a fixed light source, fixed exposure, fixed object distance, and fixed magnification.

[0045] Evaluation metrics include coverage, average gray level, difference between speckle and underlying average gray level, gray level standard deviation, equivalent speckle diameter, speckle number density per unit area, local agglomeration ratio, local coverage coefficient of variation, correlation matching quality, and DIC zero-strain displacement noise and strain noise.

[0046] Coverage can be calculated as the ratio of the area of ​​dark speckle pixels to the total pixel area of ​​the evaluation region; the equivalent speckle diameter can be calculated based on the area of ​​a single connected region; the local aggregation ratio can be calculated as the ratio of the area of ​​connected regions with an area greater than 3 times the median speckle area or a major axis greater than the recommended upper limit to the total speckle area. If the speckle is too sparse, the amount of speckle added can be increased, the volume fraction of ethanol can be increased, or the number of repeated transfers can be increased; if the speckle is too dense or aggregated, the volume fraction of ethanol can be reduced, the aggregation time can be shortened, or the concentration of speckle on the water surface can be diluted; if the imaging reflection is obvious, the gloss of the underlying layer can be reduced or the illumination angle can be adjusted; if the speckle falls off during loading, the concentration of the protective layer can be increased, the curing time can be increased, or the hydrophilicity of the underlying surface can be improved.

[0047] Example 1: Preparation of DIC speckle pattern in tensile specimens of titanium alloy flat plates: Titanium alloy miniature tensile specimens were selected, cleaned with ethanol and deionized water, and dried at room temperature. A thin layer of white matte hydrophilic primer was sprayed onto the gauge length of the specimens to form a base layer with a thickness of approximately 30 μm. After the base layer cured, the 8-bit average grayscale value was measured to be no less than 180, the water contact angle was no greater than 60°, and there was no obvious specular reflection on the surface.

[0048] Take a dark-colored butterfly wing and gently brush it along the scale arrangement direction with a soft-bristled brush moistened with deionized water to transfer the scales to a petri dish containing deionized water. Before transfer, randomly collect at least 200 microscopic images of the scales and select those with a length of 35 mm. ~150 Width 10 ~80 The scales must have an integrity rate of no less than 80% and an average grayscale of no more than 90 on the 8-bit surface. After the scales float naturally on the water surface, spray the target area on the water surface twice with an ethanol aqueous solution with a volume fraction of 60%, so that the scales gather into a transferable area of ​​about 1cm to 3cm within 10s.

[0049] A titanium alloy sample with a substrate is slowly brought into contact with the scale aggregation area at an angle of approximately 45° and then uniformly lifted out of the water at a speed of approximately 1 mm / s to 3 mm / s. After natural drying, a thin layer of water-based polyurethane diluted at a volume ratio of 1:3 is sprayed onto the surface and cured at room temperature for approximately 20 minutes to obtain high-contrast random speckle patterns. After acquiring the initial speckle image, if the coverage is 35% to 55%, the average grayscale difference between the scales and the substrate is not less than 80, and the local agglomeration ratio is not greater than 10%, it is considered a qualified speckle pattern; if the requirements are not met, feedback adjustment is performed. This sample can be used for uniaxial tensile DIC measurement.

[0050] Example 2: Preparation of speckle patterns on the curved surface of pipe samples: Select small-diameter metal wire, polymer cylinder, or metal tube samples. Fix the sample on a rotatable clamping device, clean the surface, and then spray with a white matte hydrophilic undercoat.

[0051] Using anhydrous ethanol, and following the same conditions and procedures as in Example 1 before transfer, a strip-shaped or ring-shaped scale accumulation area is formed on the water surface. One end of the pipe sample is brought into contact with the water surface at an inclined angle, and slowly rotated during immersion and withdrawal to uniformly transfer the scales along the circumferential direction. The specific operation procedure is as follows: Figure 5 As shown, thus obtaining the following Figure 6 The transfer-printed tubular sample is shown. After transfer, a thin, transparent, flexible protective layer is sprayed on, demonstrating that the method of this embodiment can solve the problems of occlusion, sagging, and localized reflection that easily occur on surfaces with small radii of curvature when preparing speckle patterns using traditional spraying methods.

[0052] Example 3: Partitioned transfer of samples with microgrooves and uneven surfaces: Select samples with microgrooves, pits, protrusions, or rough morphologies. After cleaning the surface, form a hydrophilic underlayer using a thin-spray method. If the sample surface has deep microgrooves, the coverage continuity within the grooves can be improved by using a low-viscosity underlayer material.

[0053] Using the same conditions and operations as in Example 1, the water surface scale layer is controlled into a locally high-density area. During transfer, methods such as repeated immersion in sections, slight oscillation, or contact in different directions are employed to ensure that the scales cover the tank walls, boss sides, and curved transition areas. After transfer, a low-concentration protective layer is applied for encapsulation. This embodiment is suitable for microstructures, 3D printed small components, and mechanical samples with complex surface morphologies.

[0054] Example 4: Preparation of DIC speckle patterns for monitoring the movement trajectories of small living organisms: Small, live organisms were selected as the subjects for motion trajectory monitoring, preferably earthworms, leeches, larvae of soft-bodied insects, or other small, non-invertebrate organisms with a mucus layer, a slightly moist surface, or a soft epidermis. Before monitoring, the organisms were placed in clean, moist petri dishes, moist filter paper, or a moist substrate similar to their living environment for 5-10 minutes to acclimate. The preferred ambient temperature was 15-25°C, and the relative humidity was not less than 60%. In this embodiment, no white matte primer was sprayed on the organism's surface, and no water-based polyurethane, acrylic, silicone rubber, or other surface sealing layers were applied to the outside of the scales, to avoid altering the organism's surface wettability, aeration, mucus secretion, and natural movement behavior.

[0055] Obtain dark butterfly scales using the method in step S1, prioritizing those with a length of 35 mm. ~150μm, width 10 Scales with a diameter of ~80μm, an integrity rate of not less than 80%, and an 8-bit average grayscale of not more than 90 are preferred. For live biomarking, the amount of scales added should be reduced to form a low-density floating layer on the water surface. A 50% (v / v) ethanol aqueous solution can be sprayed onto the water surface area away from the organism to allow the scales to locally aggregate within 10 seconds. After spraying, allow the scales to stand for 60 seconds, or transfer the aggregated floating layer to a clean water surface free of ethanol before marking, in order to reduce the impact of residual ethanol on the activity of the live organism.

[0056] During labeling, the dorsal or lateral side of a small live organism is lightly brought into contact with a low-density layer of floating scales, or a soft-bristled brush, glass needle, or micropipette tip moistened with deionized water is used to gently transfer a small number of scales to the body surface. For earthworms, it is preferable to avoid the head, tail, and areas of significant sensitive contraction, forming discrete scale marks only in the middle of the dorsal side or the area of ​​the body segment to be monitored. The scales adhere to the live organism through capillary adsorption and wet adhesion via water, polysaccharides, and protein components in the organism's surface mucus. Furthermore, the micro-toothed edges, ribs, and lamellar structures of the scales form micro-scale overlaps with the micro-folds of the body surface, thus attaching to the live organism's surface without the use of primer, sealant, or chemical adhesives.

[0057] The recommended coverage rate for scattered scales on the live organism surface is 35%–50%. If the coverage rate is less than 35%, the organism can be gently transferred once more. If the coverage rate is greater than 50% or continuous aggregation occurs, the organism should be gently rinsed with a damp soft brush or deionized water and then re-marked. After marking, let the organism stand for 3–5 minutes and observe whether it maintains normal peristalsis, crawling, or stimulus response. If obvious curling, prolonged stagnation, abnormal secretion, or dehydration occurs, monitoring should be stopped and the scales removed.

[0058] During motion trajectory monitoring, continuous images can be acquired at 10fps~60fps under visible light conditions. The displacement trajectory, segmental contraction and extension, bending waveforms, and instantaneous movement velocity of the living organism are calculated based on the DIC sub-region matching results of scale speckle. A qualified marker should meet the following conditions: after 5 minutes of continuous monitoring, the scale retention rate should be no less than 80%; the noise level of the feature point location during the static control phase should be no greater than 0.2 pixels; and the average change in movement velocity after marking should not exceed 20% compared to the unmarked blank organism. This embodiment utilizes the natural adhesion of the organism's surface and the microstructure of butterfly scales to achieve unencapsulated, low-interference live motion monitoring, suitable for motion trajectory identification, local deformation tracking, and behavioral biomechanical analysis of small, soft organisms.

[0059] Performance Evaluation 1. Evaluation of speckle quality and determination of process window To verify the speckle density control effect of the method of the present invention, the same white matte hydrophilic substrate (with a white matte hydrophilic coating sprayed on), the same transfer sample (10×20×10 mm titanium alloy, with a transfer surface of 10×20 mm), the same amount of scales added (20 mg), and the same water surface area (1000 mm²) were used. 2 Using a 25mL beaker (with a water surface area) and under the same optical microscope imaging conditions, the volume ratio of ethanol to water was varied. The speckle coverage and average 8-bit grayscale value of the transferred samples were statistically analyzed. The specific results are shown in Table 1. Table 1 Results of speckle density regulation As shown in Table 1, when the ethanol volume fraction is too low (below 40%), the scales do not aggregate sufficiently, resulting in low coverage. Conversely, when the ethanol volume fraction is too high (above 80%), excessive scale accumulation can easily occur, leading to excessively high coverage and a significant decrease in the average grayscale value. Considering coverage, grayscale value, and pattern recognizability, an ethanol volume of 50%–70% of the total solution volume represents the optimal process window.

[0060] 2. Quantitative comparison experiment between the method of this invention and existing DIC speckle preparation methods. To quantify the effectiveness of this invention compared to existing technologies, samples of the same material, size, and surface substrate were selected to prepare butterfly scale speckle patterns, black and white spray paint speckle patterns, toner adhesion speckle patterns, and polymer microsphere speckle patterns, respectively. The speckle pattern implementation method of this invention refers to Example 1. Existing DIC speckle methods include spray paint speckle, toner adhesion speckle, and polymer microsphere speckle. The black and white spray paint speckle pattern was achieved using a pneumatic airbrush (nozzle diameter 0.5 mm, air pressure 0.25 MPa), first spraying a matte white primer (approximately 10 mm thick). Dry for 1 hour), then at a distance of 15cm. Angle pulse spraying of matte black paint (1 second per spray, 3 sprays in total, 3 minutes apart) forms a speckled pattern of droplet deposition and drying film.

[0061] Toner adhesion speckle will reduce thickness to 50 Pressure-sensitive double-sided adhesive tape (3M 9448A) was applied to the sample surface, and the sample was evenly sprinkled through a 100-mesh sieve with an average particle size of 10 mm. The laser printer toner is then gently blown with a bulb syringe at 0.05 MPa for 10 seconds to remove loose toner, forming toner adhesion spots.

[0062] Polymer microsphere speckle with a diameter of 15 Transparent polystyrene microspheres were dispersed in a 1:1 volume ratio of ethanol / deionized water to form a 1 wt% suspension. This suspension was then sprayed for 2 seconds using a pneumatic spray gun (0.2 mm nozzle, 0.15 MPa air pressure, 12 cm distance). The microspheres are fixed by hot air drying for 30 seconds.

[0063] All samples were tested under the same microscope, light source, exposure time, DIC software, and sub-region parameters. The DIC sub-region size was 21 pixels with a step size of 3 pixels. The test items included speckle equivalent diameter and its coefficient of variation, boundary gray-scale gradient, coverage, average gray-scale difference, zero-strain displacement noise, zero-strain strain noise, speckle retention rate after tension or bending, and effective matching rate after cyclic loading.

[0064] Spray-painted speckles are formed by atomized droplet deposition and drying to form a film. However, they are prone to blurred boundaries, droplet coalescence, and uneven thickness on micro-area samples. This invention improves the grayscale gradient at the speckle boundary by more than 15%, reduces zero-strain displacement noise by more than 20%, and achieves uniform layer thickness. Carbon powder speckles are formed by particle spreading or adhesive fixation. They are prone to agglomeration, poor adhesion, and uneven coverage on curved surfaces. This invention improves the speckle retention rate by more than 10% after cyclic loading. Polymer microsphere speckles are formed by microsphere spraying or adhesion. Transparent or translucent microspheres have insufficient contrast. This invention improves the uniformity of grayscale distribution by 20% and reduces strain field noise by more than 20%. Photolithography or etching speckles are prepared by regular patterning or surface removal processing. This method has high equipment costs and can change the surface state of the substrate. This invention has a single sample preparation cost of less than 10 yuan and improves the effective matching rate in complex areas by more than 10%, resulting in better DIC micro-area imaging and deformation tracking effects.

[0065] The above description is merely a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the embodiments of the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for preparing DIC micro-area speckle patterns based on butterfly scales, characterized in that, Includes the following steps: Step S1: Collect butterfly wing surfaces to collect scales, resulting in scales that are left to stand still and dispersed on the water surface; Step S2: Clean the surface of the speckled sample with a hydrophilic underlayer and dry it; Step S3: Spray a low surface tension liquid onto the water surface area where the scales are located, and let it stand after completion; Step S4: Slowly bring the hydrophilic bottom layer of the sample into contact with the water surface area where the scales are located to perform scale transfer, and then let it dry naturally in an environment without strong airflow. Step S5: Spray a transparent flexible protective layer onto the surface of the transferred flake layer and cure it.

2. The method for preparing DIC micro-area speckle patterns based on butterfly scales according to claim 1, characterized in that: The chromaticity of the scale surface described in step S1 meets the following conditions: under a D65 standard light source or an equivalent stable white light source, in the CIE L*a*b* chromaticity coordinates, the L* value of the scale surface is not greater than 35, the a* value is between -5 and 15, and the b* value is between -10 and 20.

3. The method for preparing DIC micro-area speckle patterns based on butterfly scales according to claim 2, characterized in that: The scales have an average reflectivity of no more than 25% in the visible light range of 400nm to 700nm; in an 8-bit grayscale image, the average grayscale value of the scales is no more than 90, the average grayscale value of the white matte underlayer is no less than 180, and the average grayscale difference between the scales and the underlayer is no less than 80.

4. The method for preparing DIC micro-area speckle patterns based on butterfly scales according to claim 1, characterized in that: The scales are characterized by a length between 35μm and 150μm, a width between 10μm and 80μm, an equivalent circle diameter between 20μm and 120μm, and the proportion of scales that are obviously broken, folded, curled, contaminated, or agglomerated is no more than 20%.

5. The method for preparing DIC micro-area speckle patterns based on butterfly scales according to claim 1, characterized in that: The method for collecting scales described in step S1 includes the following steps: Step S11: Select low-reflection dark butterfly wings, place the wing surface on a clean platform, and gently brush along the natural arrangement of the scales with a soft brush moistened with deionized water to peel the scales off the wing membrane surface. Step S12: Rinse the scales into a container of deionized water and let them stand to disperse; The initial flake dosage for flushing into the deionized water container is per 100mm 2 1.5mg~3.0mg on water surface.

6. The method for preparing DIC micro-area speckle patterns based on butterfly scales according to claim 1, characterized in that: In step S2, the surface of the speckled sample is coated with a 10μm~30μm white or light-colored matte hydrophilic underlayer.

7. The method for preparing DIC micro-area speckle patterns based on butterfly scales according to claim 1, characterized in that: The low surface tension liquid mentioned in step S3 is one of anhydrous ethanol, isopropanol aqueous solution, and ethanol aqueous solution, wherein the volume fraction of solute in the aqueous solution is 50%~80%; The spraying method is per 100cm 2 Spray 0.1mL~0.3mL onto the water surface, and let it stand for at least 5 seconds after spraying.

8. The method for preparing DIC micro-area speckle patterns based on butterfly scales according to claim 1, characterized in that: The requirements for scale transfer in step S4 are as follows: the scale coverage in the target area of ​​the sample is between 35% and 65%, the local agglomeration ratio of scales is not greater than 10%, and the average gray value of the scales is not less than 80 compared with the gray value of the underlying layer.

9. The method for preparing DIC micro-area speckle patterns based on butterfly scales according to claim 1, characterized in that: The specific method for scale transfer in step S4 is as follows: the hydrophilic bottom layer of the sample is immersed in or removed from the water surface area where the scales are located at a contact angle of 30° to 90° and a speed of 0.5 mm / s to 5 mm / s, and the non-planar sample can be rotated, swung or repeatedly contacted when immersed or removed.

10. The method for preparing DIC micro-area speckle patterns based on butterfly scales according to claim 1, characterized in that: The transparent flexible protective layer mentioned in step S5 is one of the following: aqueous aliphatic polyurethane diluent, transparent acrylic emulsion, and silicone rubber diluent. In the aqueous aliphatic polyurethane diluent, the volume ratio of aqueous polyurethane to deionized water is 1:2~5; in the transparent acrylic emulsion, the volume ratio of transparent acrylic acid to deionized water is 1:5~10; and in the silicone rubber diluent, the ratio of aqueous silicone rubber diluent to deionized water is 1:2~4. The curing method for the transparent flexible protective layer is room temperature curing or low temperature drying, with a curing time of 10 min to 60 min.

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