Global Alignment of Solution-Based Single-Wall Carbon Nanotube Films via Machine-Vision Controlled Filtration

Abstract

Over the past decade, substantial progress has been made in the chemical processing (chiral enrichment, length sorting, handedness selectivity, and filling substance) of single-wall carbon nanotubes (SWCNTs). Recently, it was shown that large, horizontally-aligned films can be created out of post-processed SWCNT solutions. Here, we use machine-vision automation and parallelization to simultaneously produce globally-aligned SWCNT films using pressure-driven filtration. Feedback control enables filtration to occur with a constant flow rate that not only improves the nematic ordering of the SWCNT films, but also provides the ability to align a wide range of SWCNT types and on a variety of nanoporous membranes using the same filtration parameters. Using polarized optical spectroscopic techniques, we show that meniscus combing produces a two-dimensional radial SWCNT alignment on one side of the film. After we flatten the meniscus through silanation, spatially-resolved nematicity maps on both sides of the SWCNT film reveal global alignment across the entire structure. From experiments changing ionic strength and membrane tribocharging, we provide evidence that the SWCNT alignment mechanism stems from an interplay of intertube interactions and ordered membrane charging. This work opens up the possibility of creating globally-aligned SWCNT film structures for a new-generation of nanotube electronics and optical control elements. KeywordsNematic ordering, 1D crystals, single-wall carbon nanotubes Significant interest in one-dimensional (1D) nanocrystals (NCs) follows from their highly anisotropic properties of electrical and thermal transport, optical absorption, radiative emis-sion, and conduction. Typically, physical attributes observed in these NCs are significantly enhanced along the extended 1D crystal axis relative to the short axes, the latter often 1 arXiv:1907.09499v1 [cond-mat.mes-hall]

Global Alignment of Carbon Nanotubes via High Precision Microfluidic Dead‐End Filtration

“…concluded that the grooves are not the most important aspect for alignment but rather a directional charging of the surface, which can be further enhanced by tribo‐charging the membrane. [ 46 ] Nevertheless, it is commonly agreed upon that alignment occurs near to, but not directly on the membrane surface. [ 27,39,43,44,46 ]…”

“…[ 46 ] Nevertheless, it is commonly agreed upon that alignment occurs near to, but not directly on the membrane surface. [ 27,39,43,44,46 ]…”

“…[ 27,44 ] In all cases, the SWCNTs were dispersed by negatively charged surfactants such as sodium deoxycholate (DOC) or sodium dodecylbenzenesulfonate (SDBS) and at a concentration (≈ 0.004–0.03 wt %) well below the critical micelle concentration (0.24 wt % for DOC [ 27 ] and 0.13 wt % for SDBS [ 47 ] ) of the surfactant. A total volume of 4–5 mL with a SWCNT concentration of ≈ 8–15 µg mL –1[ 27,46,48 ] was then used in a filtration process that was described by He at al. [ 27 ] as being “well controlled and at a slow speed”.…”

Emergent Properties of Macroscale Assemblies of Carbon Nanotubes

“…[ 18 ] Most recently, Walker et al induced machine vision‐driven feedback and surface treatment of the glassware into the process. [ 19 ]…”

Sieve-Like CNT Film Coupled with TiO2 Nanowire for High-Performance Continuous-Flow Photodegradation of Rhodamine B under Visible Light Irradiation

“…CNT film, a macroscopic assembly of nanoscale individual CNTs, can be fabricated by various approaches, such as floating catalyst chemical vapor deposition (FCCVD) [ 16 , 17 , 18 ], dry spinning [ 19 ], solution-based coating [ 20 ], printing [ 21 ] and vacuum filtration [ 22 ], with different types of architectures, including non-woven cloth, vertical alignment, aligned networks, transparent film, random planar film and compressible foams [ 23 ].…”