High-density monolayer carbon nanotube arrays assembled via synergistic shear flow and dielectrophoresis

Densely packed and well-aligned monolayer arrays of carbon nanotubes (CNTs) represent a critical advancement for building high-performance nanotube-based electronics in next-generation semiconductor technologies. Although dielectrophoresis (DEP) is well known for its precise and site-specific monolayer nanotube assembly under ambient conditions, the achievable array density (≤ 50 tubes·μm⁻¹) is fundamentally constrained by multi-physics coupling and inter-tube interactions inherent to DEP processes. To address this limitation, we report a synergistic shear flow-DEP assembly (SSFDA) strategy that additionally introduces a hydrodynamic shear flow to pre-align CNTs within a confined needle channel before DEP deposition. Such shear flow not only applies sustained rotational torque to align suspended CNTs along the flow direction, but also reduces the DEP voltage requirement so that the pre-oriented nanotubes can be high-density assembled under the reduced polarization-induced inter-tube repulsion. This synergistic process yields well-aligned monolayer CNT arrays with a remarkably high density of ~ 110 tubes·μm⁻¹ and an angular half-width at half maximum orientation spread of only 4.5°. Furthermore, top-gate field-effect transistors fabricated from these CNT arrays with a channel length of 300 nm exhibit on/off current ratios up to 10⁶, on-conductivities of 232.04 μS·µm⁻¹, and subthreshold swings of 133 mV·dec⁻¹. Overall, our results establish SSFDA as an efficient and promising route for high-density monolayer CNT array integration, with potential for future scale-up in nanotube electronics.