Aggregate-driven reconfigurations of carbon nanotubes in thin networks under strain: in-situ characterization

Abstract

This work focuses on the in-situ characterization of multi-walled carbon nanotube (CNT) motions in thin random networks under strain. Many fine-grain models have been devised to account for CNT motions in carbon nanotube networks (CNN). However, the validation of these models relies on mesoscopic or macroscopic data with very little experimental validation of the physical mechanisms actually arising at the CNT scale. In the present paper, we use in-situ scanning electron microscopy imaging and high-resolution digital image correlation to uncover prominent mechanisms of CNT motions in CNNs under strain. Results show that thin and sparse CNNs feature stronger strain heterogeneities than thicker and denser ones. It is attributed to the complex motions of individual CNTs connected to aggregates within thin and sparse CNNs. While the aggregates exhibit a collective homogeneous deformation, individual CNTs connecting them are observed to fold, unwind or buckle, seemingly to accommodate the motion of these aggregates. In addition, looser aggregates feature internal reconfigurations via cell closing, similar to foam materials. Overall, this suggests that models describing thin and sparse CNN deformation should integrate multiphase behaviour (with various densities of aggregates in addition to individual CNTs), heterogeneity across surface, as well as imperfect substrate adhesion.

A low-cost tabletop tensile tester with optical extensometer

“…Testing samples under various environmental conditions can be achieved by addition of, e.g., a heat chamber, water bath, or placing the CMTT in a glove box under inert atmosphere. Finally, the scalable design and the algorithms can hopefully assist other researchers in exploring, customizing and developing specialized equipment as found for in-situ SEM 19 and TEM 20 characterization.…”

Development and Application of Resistance Strain Force Sensors

“…The in-situ characterization of multi-walled carbon nanotube under external strain has uncovered the prominent mechanisms of CNTs motions [ 62 ]. Inkjet printing techniques have provided outstanding results for flexible resistance sensors in terms of their resistance reproducibility [ 68 ]. The carbon nanotube networks (CNNs) fabricated by inkjet-printing present potential applications for flexible resistance strain sensors [ 69 ].…”