Scientists are experimenting with flexible phone screens to see how they react to stress

The researchers presented their findings in an article that was recently published in the open-access journal Materials, in which they examined the mechanical characteristics of flexible screens.

During the last few years, organic light-emitting devices (OLEDs) have become increasingly important in a variety of industries. These include smart clothing, flexible displays, and a variety of other applications. Flexibility and optimization of flexible OLED display module screens have emerged as important criteria for addressing concerns about portability and economics that have arisen as OLEDs become more widely used in display goods.

The gadget is subjected to excessive stress during the bending operation when the bend radius is small, resulting in it ripping off and causing irreversible damage to the screen and other components. When determining the mechanism of damage and peeling of the adhesive layer of a flexible OLED display module screen, the finite element method can be used. It can also be used to obtain stress and strain results for the screen.

A novel hole-transport layer for the host material was created by combining a novel technology (the ball milling process) with a green halogen-free solvent to produce a novel hole-transport layer for the host material. As demonstrated in this study, this layer not only improved the photoelectric response of the optical monomer-based thin-film device, but it also exhibited excellent stability under continuous stress. In this configuration, however, there is a significant gap between the stacking structure and the actual flexible screen module.

The geometric structure of the U-shaped bending mode is represented by a model. The left reference point remained fixed, and the bending was accomplished by moving the fixture board from position A to position B within the bending time t seconds, which allowed the bending to be completed in one motion. When the bending radius was R and the bending angle was, the lateral gap was equal to the radius of bending. Image courtesy of L. Niu and colleagues in the journal Materials Science and Engineering.

Concerning the Investigation.
Using finite element analysis, the authors of this study developed a bending model for a flexible screen, which they then demonstrated. An imaging experiment was carried out in order to estimate the growth of Mises stress as the bending radius decreased for common U-shaped bending, as well as the redistribution of the tensile and compression zones. Additionally, a water drop bending mode in the shape of a water droplet was investigated in order to reduce the likelihood of structural collapse.

The team used the finite element software ABAQUS to create a realistic stacking model for the flexible screen module, which was then used to test the model. During the discussion, participants learned about the mechanical behavior of OLED flexible screens, including OCA thickness-shape, the impact of bending radius on mechanical behavior, and bending mode (which included water drop shape and U-shaped bending). In order to confirm the findings of the analysis, an imaging experiment was carried out.

The researchers used the ABAQUS software to create a finite element model of the flexible screen, which they then used to simulate the mechanical behavior of the screen. In this case, both the fixture board and the screen module were cemented together, and movement of the fixture board was used to drive the bending of the screen module. The flexible screen module was made up of a series of multi-layered films with varying mechanical properties that were assembled together. Because of the way OCA bonded the layers of film together and coordinated the deformation of each layer during the folding process, it was essential for maintaining the structural integrity of the flexible screen module during the manufacturing process. To simulate a 180-degree folding simulation, the bending radii were set to 3 mm, 2.5 mm, 2 mm, 1.5 mm, and 1 mm, with an overall bending time of t = 18 s. The simulation was carried out with the following parameters:These were set at three different diameters: three millimeters, three millimeters and a half millimeter, two millimeters, one millimeter and one millimeter, and one millimeter and one millimeter.

Observations are made at this point.
A short bending radius, according to the results of the analysis, would not only be effective, but it would also reduce the likelihood of a structure failing. It was discovered that the discrepancy ratio between experimental and simulated ranges for the same bending radius was less than one percent, indicating that both the finite element model and the experimental data were accurate.

The spherical droplet had a radius of 2.286 mm when the bending radius was R = 2 mm, and the bending radius was R = 2 mm when the bending radius was R = 2 mm. S1/S5 had the highest absolute strain increment ratios, while S2/S5 had the lowest absolute strain increment ratios, with a maximum increase ratio of 13.07% and a maximum increment ratio of 18.56%. S1/S5 had the highest absolute strain increment ratios, while S2/S5 had the lowest absolute strain increment ratios. The absolute strain increment ratios in S1/S5 were the highest, with absolute strain increment ratios of 1.0053% and 1.0042%, respectively, being the highest.

S3, S4, and S5 profiles all produced results that were similar to one another in terms of effects on the small OLED screen light-emitting layer, with the highest difference ratios of 1.27% and 3.61% for S3/S5 and S4/S5 being the most significant, respectively. When comparing the S1 and S2 profiles to S5, the maximum stress on the small small OLED display display layer was increased by 13.53% and 24.04%, respectively, when compared to the S5 profile. Plastic strain began to develop on the inside of the CPI layer in the squeezed area and progressed outward until it reached the outside of the layer when the bending radius was 2.5 mm, as shown in Figure 1. The outside tension area did not experience plastic strain until the bending radius reached 2 millimeters. When the bending radius was 1.5 mm, the plastic strain occurred at the outer tension area of the bending radius, which was the outer tension area of the bending radius.

It was discovered that by using R = 2.5 mm the maximum tensile stress was reduced by 23.99% while the maximum compressive stress was raised by 15.82%, resulting in an overall stress reduction of 23.99 percent. The maximum compressive stress increased by 20.22% when R was increased by 3 mm, while the maximum tensile stress decreased by 27.54% when R was increased by 3 mm.

Lastly, some words of wisdom
In the end, the use of finite element analysis for flexible screens has contributed to the clarification of the bending model for flexible screens, which has been previously discussed. It was discovered that the maximum Mises stress increases rapidly as the bending radius is decreased when the commonly used U-shaped bending was used in the experiment. We optimized the performance of the OLED display module and BP layer stack sequences, the single layer with the highest toxicity, the profiles of the OCA layer, as well as the single layer with the lowest toxicity.

The layer material selection was dictated by the redistribution of the tensile and compression zones within the structure, which was done in accordance with the optimization results. An imaging experiment was carried out to determine the maximum slip distance during bending in order to validate the results of the analysis.