CN-121994160-A - Method for measuring bending deformation of micron-sized multilayer composite film

CN121994160ACN 121994160 ACN121994160 ACN 121994160ACN-121994160-A

Abstract

The application relates to the technical field of microscopic photometry and discloses a method for measuring bending deformation of a micron-sized multilayer composite film, which is characterized in that a surface layer of an observation section is activated, and nano-sized optical tracer particles are grafted in situ by chemical bonding to construct an anti-slip three-dimensional body speckle field; aiming at the limit of the ultra-shallow depth of field of high-magnification imaging, a laser scanning confocal microscope is utilized to conduct depth direction continuous layer scanning under a micron-level view field to obtain three-dimensional volume data with high signal to noise ratio, and a three-dimensional full-field displacement field is obtained by utilizing a three-dimensional volume feature tracking algorithm to further solve a three-dimensional strain field. The system solves the problems of difficult micro-scale narrow section speckle manufacture, difficult local fold fluctuation observation and difficult calculation caused by plane assumption failure, and realizes the accurate measurement and characterization of the three-dimensional deformation of each single layer and interface of the multi-layer composite film.

Inventors

ZHANG QINGCHUAN
LIU DONGLIANG
Lan Shihai

Assignees

中国科学技术大学

Dates

Publication Date: 20260508
Application Date: 20260330

Claims (7)

1. The method for measuring the bending deformation of the micron-sized multilayer composite film is characterized by comprising the following steps of: Step 100, constructing a chemically bonded nanoscale optical tracer field with depth, and connecting nanoscale optical tracer particles in an observation cross section surface layer of the micron-sized multilayer composite film and a near surface layer range with penetration depth by utilizing a chemical bonding technology, wherein the nanoscale optical tracer particles are connected with a film substrate through covalent bonds to form a tracer region with three-dimensional volume distribution characteristics; Step 200, collecting three-dimensional volume data, namely, aiming at the limitation of ultra-shallow depth of field of high-magnification imaging under a micron-scale observation view field, utilizing the optical slicing function of a laser scanning confocal microscope to sweep a layer in the depth direction of the tracing area so as to clearly distinguish the nanoscale optical tracing particles distributed at different depths under large deformation local fluctuation, and obtaining a volume data sequence containing three-dimensional spatial distribution of the nanoscale optical tracing particles; step S300, based on true strain resolving of digital font correlation (DVC), reconstructing the volume data sequence into a three-dimensional gray scale field, tracking the displacement of the nanoscale optical tracer particles in a three-dimensional space by using a digital font correlation algorithm to obtain a three-dimensional full-field displacement field, and further, based on the three-dimensional full-field displacement field resolving the three-dimensional strain field, finally obtaining the three-dimensional full-field displacement field and the three-dimensional strain field at the observation cross section area and the interlayer interface of the micron multilayer composite film.
2. The method for measuring bending deformation of a micro-scale multilayer composite film according to claim 1, wherein the chemical bonding technique in step S100 comprises activating the observation cross-section surface layer and the near-surface layer range having a penetration depth to generate reactive sites, chemically reacting ligands on the surface of the nano-scale optical tracer particles with the reactive sites, and grafting the nano-scale optical tracer particles on the observation cross-section surface layer.
3. The method for measuring bending deformation of a micro-scale multilayer composite film according to claim 2, wherein the activation treatment specifically comprises breaking, hydrolyzing or oxidizing molecular bonds of the observed cross-section surface layer polymer by Ultraviolet (UV) irradiation, plasma treatment or chemical agent treatment to generate polar functional groups containing carboxyl groups or hydroxyl groups as the reactive sites.
4. The method for measuring bending deformation of a micron-sized multilayer composite film according to claim 1, wherein the particle size of the nanoscale optical tracer particles is less than 1 micron.
5. The method for measuring bending deformation of a micro-scale multilayer composite film according to claim 1, wherein in step S200, the depth-direction layer scanning of the trace area specifically comprises: And carrying out continuous step scanning along the depth direction vertical to the observation section to obtain a plurality of two-dimensional slice images with different depths, and carrying out space stacking reconstruction on the two-dimensional slice images according to depth coordinates to generate the volume data sequence containing the three-dimensional spatial distribution of the nanoscale optical tracer particles.
6. The method for measuring bending deformation of a micron-sized multilayer composite film according to claim 1, wherein the nanoscale optical tracer particles are selected from photoluminescent media, light scattering media, or light absorbing media.
7. The method for measuring bending deformation of a micron-sized multilayer composite film according to claim 1, further comprising quantitatively analyzing mechanical behavior of the micron-sized multilayer composite film: Analyzing the strain distribution characteristics of each monolayer section and interlayer interface of the micron-sized multilayer composite film by utilizing the three-dimensional strain field; And extracting displacement vectors at two sides of an interlayer interface based on the three-dimensional full-field displacement field, and calculating relative displacement of the displacement vectors in the tangential direction of the interface to obtain the interlayer relative shearing slippage of the micron-sized multilayer composite film.

Description

Method for measuring bending deformation of micron-sized multilayer composite film Technical Field The invention relates to the technical field of microscopic photometry, in particular to a method for measuring bending deformation of a micron-sized multilayer composite film. Background With the development of flexible electronic technology, devices such as foldable display screens and flexible sensors are increasingly widely used in the consumer electronics field. Such devices are typically composed of multiple layers of polymeric films (e.g., PET protective films, OCA optically clear adhesive, etc.) stacked together, with individual layers typically having a cross-sectional thickness of only a few microns to tens of microns. In actual service or bending testing, the multilayer composite film is required to withstand repeated bending deformations of large curvature (e.g., bending radii as small as millimeters). The thickness section (including the surface layer of the observation section and the near-surface layer range with penetration depth) and the real displacement and strain distribution of the interlayer interface are accurately measured, and the method has important significance for the reliability evaluation and failure analysis of the device. In addition, under the condition of small bending angle, the prepared speckles can be verified to have good contrast ratio and satellite property by observing the outermost slice of the cross section and calculating by utilizing the two-dimensional DIC, and meanwhile, the confocal microscope can be proved to be capable of effectively observing the microstructure. The existing film deformation measurement technology mainly depends on various non-contact full-field displacement and strain measurement methods (such as digital image correlation or digital font correlation and the like) based on feature tracking. In the aspect of characteristic preparation, the prior art generally adopts physical spraying, water transfer printing or electrostatic adsorption and other modes to attach speckle particles to the surface of an object to be detected. However, the polymer surfaces of PET, OCA, etc. are chemically inert and lack reactive groups, making it difficult to directly form strong interactions with the tracer particles. More importantly, the speckle feature size produced by conventional physical spray coating or water transfer printing processes is typically on the order of tens of micrometers to sub-millimeters, even greater than the monolayer thickness of the multilayer film, which can not only produce severe dimensional mismatch, but also introduce non-negligible constraint interference to the fine cross-section by its own physical thickness. Thus, in a very small micrometer-scale field of view (e.g., only a few hundred micrometers range), feature sizes must be reduced to nanometer-scale in order to meet measurement requirements. When the feature size is reduced to the nanometer level, particles are easy to agglomerate in the physical deposition process, so that the speckle field is not uniformly distributed in space and the contrast is insufficient, and uniform nanometer level features cannot be prepared under the micrometer view field. In addition, under the working condition of large deformation, the image features are extremely easy to fall off or slip due to weak binding force limited by physical attachment, so that measurement distortion is caused. In optical imaging, in order to clearly resolve the above nanoscale features, a high magnification microobjective must be employed, but this necessarily results in conventional microscopy systems being faced with the bottleneck of extremely narrow depth of field (ultra shallow depth of field). Meanwhile, in a large-curvature bending experiment, the observation section is often accompanied by remarkable local out-of-plane displacement and microscopic wrinkles. Because the depth of field of the traditional microscope is extremely shallow, the nano features generating local relief can be instantaneously moved out of the focal plane, so that the conventional two-dimensional microscopic imaging cannot acquire a globally clear feature image (namely, cannot completely shoot the local fold three-dimensional features which are fully distributed on different focal planes), and the feature data is lost. In terms of deformation measurement and data calculation, the section of the film can undergo severe rigid rotation, local off-plane displacement and microscopic wrinkles in the bending and folding process. Traditional two-dimensional surface measurement methods (such as 2D-DIC) are based on plane deformation assumption, and often such local off-plane displacement and microscopic wrinkles are erroneously projected as false elongation or shortening in the plane, so that serious projection distortion phenomenon is generated, thereby introducing significant systematic errors, and being incapable of accurately measuring the real