Carbon nanotube dielectrophoresis: Theory and applications

Abstract

Carbon nanotubes (CNTs) are one of the most extensively studied nanomaterials in the 21st century. Since their discovery in 1991, many studies have been reported advancing our knowledge in terms of their structure, properties, synthesis, and applications. CNTs exhibit unique electrothermal and conductive properties which, combined with their mechanical strength, have led to tremendous attention of CNTs as a nanoscale material in the past two decades. To introduce the various types of CNTs, we first provide basic information on their structure followed by some intriguing properties and a brief overview of synthesis methods. Although impressive advances have been demonstrated with CNTs, critical applications require purification, positioning, and separation to yield desired properties and functional elements. Here, we review a versatile technique to manipulate CNTs based on their dielectric properties, namely dielectrophoresis (DEP). A detailed discussion on the DEP aspects of CNTs including the theory and various technical microfluidic realizations is provided. Various advancements in DEP‐based manipulations of single‐walled and multiwalled CNTs are also discussed with special emphasis on applications involving separation, purification, sensing, and nanofabrication.

Continuous organelle separation in an insulator‐based dielectrophoretic device

“…DEP has been applied to manipulate different analytes from nanometer to micrometer scale [22,23]. For example, the separation of bacteria [24][25][26], DNA [27][28][29][30], proteins [31][32][33][34], and carbon nanotubes [35][36][37] has been reported in insulator-based dielectrophoresis devices. The manipulation of mitochondria has also been successfully demonstrated in an insulator-based dielectrophoresis microfluidic device in the low-frequency regime [38].…”

Length-Selective Dielectrophoretic Manipulation of Single-Walled Carbon Nanotubes

“…The surface conductance can be used to describe the SWNT conductivity, via σ P = 2λ s a −1 , 87 where a is the radius, and intrinsic conductivity is neglected. [63][64][65]69 A lower zeta potential then leads to lower λ s and consequently lower σ p , since σ p governs the dielectrophoretic response of SWNTs at a given σ m via the Re(CM) = −1 + σ p /σ m .…”

“…Dielectrophoresis (DEP) has in recent years achieved prominence as a powerful tool for nanoparticle separation. − DEP has been used to capture proteins, nucleic acids, as well as other biomolecules, − and also carbon nanotubes as we and others reported previously. ,,,− Dielectrophoresis has also been employed to sort SWNTs according to their dielectric properties . When a cylindrical SWNT is introduced into a nonuniform electric field, it will experience a force due to the induced dipole moment. ,, The DEP force acting on a cylindrically shaped SWNT can be expressed as where r refers to the SWNT radius, l to its length, E to the electric field, and ε m to the permittivity of the suspending medium.…”

Polymethyl(1–Butyric acidyl)silane–Assisted Dispersion and Density Gradient Ultracentrifugation Separation of Single–Walled Carbon Nanotubes

“…Even though some dispersing agents display a selective dispersion for metallic or semiconducting SWNTs to some extent, the achieved dispersions are still mixtures of them with various chiral indices. For effective sorting of individually dispersed SWNTs, researchers turn to gel chromatography [40,41], two-phase aqueous extraction [42,43], dielectrophoresis [44,45], and density gradient ultracentrifugation (DGU) [46,47]. Among these techniques, DGU has the advantages of easy operation, large-scale separation, and universal utility for various SWNTs over the others, making it the most popular technique to separate SWNTs in line with their diameter, electronic type, chirality, or even-handedness.…”