Influence of Defect Number, Distribution Continuity and Orientation on Tensile Strengths of the CNT-Based Networks: A Molecular Dynamics Study

Networks based on carbon nanotube (CNT) have been widely utilized to fabricate flexible electronic devices, but defects inevitably exist in these structures. In this study, we investigate the influence of the CNT-unit defects on the mechanical properties of a honeycomb CNT-based network, super carbon nanotube (SCNT), through molecular dynamics simulations. Results show that tensile strengths of the defective SCNTs are affected by the defect number, distribution continuity and orientation. Single-defect brings 0 ~ 25% reduction of the tensile strength with the dependency on defect position and the reduction is over 50% when the defect number increases to three. The distribution continuity induces up to 20% differences of tensile strengths for SCNTs with the same defect number. A smaller arranging angle of defects to the tensile direction leads to a higher tensile strength. Defective SCNTs possess various modes of stress concentration with different concentration degrees under the combined effect of defect number, arranging direction and continuity, for which the underlying mechanism can be explained by the effective crack length of the fracture mechanics. Fundamentally, the force transmission mode of the SCNT controls the influence of defects and the cases that breaking more force transmission paths cause larger decreases of tensile strengths. Defects are non-negligible factors of the mechanical properties of CNT-based networks and understanding the influence of defects on CNT-based networks is valuable to achieve the proper design of CNT-based electronic devices with better performances. Graphical Abstract

Estimation of the Absolute Defects in the Visual Field using OCT in Glaucoma Patients who Cannot Perform a Reliable Test.

Background: To find a method to predict the visual field (VF) of glaucoma patients who cannot perform a reliable test by using RNFL thickness and VF of other glaucoma patients. Methods: Seventy eight primary open angle and pseudoexfoliation glaucoma follow-up patients were included in the study. Optic disc OCT measurements and VF analysis were obtained in the same day. Garway-Heats maps made, RNFL sectors matched with pattern deviation 24-2 VF sectors and absolute defects were counted. Regression analysis were made. Equations generated between RNFL thickness and absolute defect number. Correlation analysis were performed for the numbers of absolute defects and the findings.Results: The regression analysis was significantly linear for defect number and RNFL thickness in sectors 3, 4, and 6 (t values were 0.047, 0.04, and 0.001, respectively, p < 0.05). The analysis was nonlinear in other sectors (t values were 1.66, 0.37, 0.14, 0.88, and 0.36, respectively, for sectors 1, 2, 5, 7, and 8, p > 0.05). The linear and nonlinear equations were generated for these sectors. The correlation between the number of absolute defects of the patient and the number we found by using our formulas in VF Sectors of 1,3,4 and 8 there was a strong correlation (r=0.68, r=0.57, r=0.82 and r=0.58 respectively). In VF sectors 3,5,6 and 7 there was a weak correlation (r= 0.22, r= 0.47, r=0.32 and r=0.48 respectively).Conclusion: We think the method that we found is practical to predict the VF of a patient who can not perform it.