Effect of carbon nanotube alignment on nanocomposite sensing performance

Abstract

The objective of this study is to derive a numerical model of carbon nanotube (CNT)-based thin films that accurately reflect their electrical and electromechanical performance as observed through experimental tests. Although nanocomposites based on CNTs dispersed in polymer matrices have been studied extensively, their nanocomposite properties vary depending on CNT orientations. This study aimed to explain how differences in nanocomposite behavior could be revealed by numerical models considering different CNT alignment conditions. First, a percolation-based thin film model was generated by randomly dispersing CNT elements in a predefined two-dimensional domain. The degree of CNT alignment in the film was controlled by limiting the CNT elements' maximum angle they make with respect to the film's longitudinal axis. Then, numerical simulations on CNT-based film models were conducted. Second, multi-walled carbon nanotube (MWCNT)-epoxy films were prepared via drop casting. Alternating current was applied to the MWCNT-epoxy mixture before curing to prepare films with different degrees of CNT alignment. The electrical and electromechanical properties of these specimens were characterized, and the results were compared with simulations. Good agreement between experiments and simulations was observed.

Recent Advances of Carbon-Based Flexible Strain Sensors in Physiological Signal Monitoring

“…In comparison with the dry approach, the wet preparation shows a simpler process, lower cost, higher efficiency, and larger capacity, and thus, a more uniformly conductive CNT film could be obtained. Such preparation includes variable methods, such as a vacuum filtration process, 63 spin coating, 22 spray coating, 64 printing, 65 layer-by-layer assembly, 66 and so on. These processing methods have a principle to form homogeneous CNT dispersions, especially requiring a surfactant such as SDS (sodium dodecyl sulfonate) 67 to aid the dispersion evenly in solvents.…”

“…However, it still lacks the computational framework capable of direct design of these nanocomposite films, because most studies focused solely on experiments or numerical simulations. Lee et al 63 established a numerical model validated experimentally for a CNT-based film strain sensor. First, a model of a percolation-based thin film was generated by randomly dispersing CNT elements in a 2D domain, as shown in Figure 2n.…”

“…(o) The strain sensitivities obtained from experimental tests and numerical simulations are compared for films with different MWCNT concentrations/number. Reproduced from ref . Copyright 2020, IOP.…”

Review on Conductive Polymer/CNTs Nanocomposites Based Flexible and Stretchable Strain and Pressure Sensors

“…According to this table, the alignment of CNTs within the polymer matrix leads to better performance in terms of sensitivity and repeatability as well wider strain range. Several other numerical works illustrate that CNTs orientation affect enormously the strain sensor performance [ 80 , 81 ] where high sensitivity can be achieved when CNTs are aligned to the direction of loading.…”

“…In general, the alignment of CNTs can be done through electrospinning method or CVD process or post dispersion process using dielectrophoresis effect [ 81 ] or application of high magnetic field [ 82 , 83 ].…”