Influence of Capillary Effects on Electric Response of Well-Ordered Carbon Nanotube Film

Abstract

The interface structure in nanocomposite materials often directly influences the electric, thermal, and mechanical properties of functional architectures and limits their application in many fields, in addition to the characteristics of their nanobuilding blocks. In this work, we report that the electronic transport characteristic of a well-ordered carbon nanotube film is adjusted by the structural evolution of the junction caused by capillary effects. This mechanism can explain the resistance change and recovery throughout the immersion-evaporation process and even the anomalous transient decrease in the resistance. Meanwhile, we establish a relationship between the resistance change ratio of the film and the interfacial tension between the film and the immersion liquid. The ability to achieve a sensitive and repeatable resistance change in a carbon nanotube film could have important implications in the measurement of liquid properties, liquid sensors, and solution analysis and provide a new avenue for the development of new multifunctional architectures.

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“…Interface resistance, an important factor, influences the volume resistance of CNT-based assemblies. It is dependent on the distance, overlapping area of adjacent CNTs, and filling molecules in the intraspace of the film. , We have confirmed in a previous report that liquid can directly regulate the resistance of the CNT film by infiltrating the intraspace . For the initial compacted CNT film, electrons can easily flow through the interfaces between the CNTs from the low potential side to the high potential side (as shown in Figure c).…”

“…The structural damage of the junctions can directly increase the interface resistance, and further decrease the volume conductivity of the film. The magnitude of the resistance change is related to the wetting property between the liquid and the CNTs. − Surfactants are compounds that lower the surface tension (or interfacial tension) between two liquids or between a liquid and a solid. The surfactant aqueous solution of different concentration will cause the change in the wetting behavior between CNTs and water.…”

“…15,16 We have confirmed in a previous report that liquid can directly regulate the resistance of the CNT film by infiltrating the intraspace. 17 For the initial compacted CNT film, electrons can easily flow through the interfaces between the CNTs from the low potential side to the high potential side (as shown in Figure 1c). When the liquid molecules infiltrate the intraspace of the film, the initial electron transport paths are destroyed, including reduction of the efficient contact (such as A or B to G in Figure 1d), the separation of the CNT junctions (such as D, E, F, I, and J in Figure 1d), and the filling of the liquid molecules in the intraspace.…”

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“…While P v is a determinant of the state of evaporation, the selection of μ, σ, and ρ was done considering the related capillary pressure and the dynamics of the flow through the pores of the CF, respectively, and may also be linked to the Capillary number (Ca) = μv s /σ, which considers the relative effects of laminar flow (say, at a velocity v s ) vs capillary flow. 21 Parameterization of the Evaporation Rate. We parametrize Δm t (P v , μ, σ, ρ) as a function of time at various temperatures, through dimensional analysis, 22 yielding…”

“…The rate of mass loss (=d­[ Δm ]/d t = Δ m t ) is typically a function of several variable properties related to the evaporating liquid mixture, e.g., the equilibrium vapor pressure ( P v ), dynamic viscosity (μ), surface tension (σ), and density (ρ) in concert with the related temperature ( T ). While P v is a determinant of the state of evaporation, the selection of μ, σ, and ρ was done considering the related capillary pressure and the dynamics of the flow through the pores of the CF, respectively, and may also be linked to the Capillary number ( Ca ) = μ v s /σ, which considers the relative effects of laminar flow (say, at a velocity v s ) vs capillary flow …”