Fabrication and electrical integration of robust carbon nanotube micropillars by self-directed elastocapillary densification

TL;DR

This paper introduces a novel self-directed capillary densification technique for fabricating robust, high-density carbon nanotube micropillars with improved mechanical and electrical properties, suitable for microfabricated device integration.

Contribution

The authors develop a controlled condensation method for CNT densification, offering more uniform structures and precise density control compared to traditional immersion techniques.

Findings

CNT micropillars' Young's modulus increased by over three orders of magnitude.

Electrical conductivity of CNT micropillars improved significantly.

The method enables scalable fabrication of mechanically and electrically enhanced CNT structures.

Abstract

Vertically-aligned carbon nanotube (CNT) "forest" microstructures fabricated by chemical vapor deposition (CVD) using patterned catalyst films typically have a low CNT density per unit area. As a result, CNT forests have poor bulk properties and are too fragile for integration with microfabrication processing. We introduce a new self-directed capillary densification method where a liquid is controllably condensed onto and evaporated from CNT forests. Compared to prior approaches, where the substrate with CNTs is immersed in a liquid, our condensation approach gives significantly more uniform structures and enables precise control of the CNT packing density and pillar cross-sectional shape. We present a set of design rules and parametric studies of CNT micropillar densification by this method, and show that self-directed capillary densification enhances the Young's modulus and electrical conductivity of CNT micropillars by more than three orders of magnitude. Owing to the outstanding properties of CNTs, this scalable process will be useful for the integration of CNTs as functional material in microfabricated devices for mechanical, electrical, thermal, and biomedical applications.