Additive Manufacturing of Electrically Conductive Nanocomposites Filled with Carbon Nanotubes

Abstract

Herein, two photopolymers containing multi‐walled carbon nanotubes (MWCNTs) are newly developed to 3D print electrically conductive structures via near‐visible light (405 nm) stereolithography (SL) process. A free‐radical resin and a hybrid cationic/free‐radical photopolymer are used as a matrix and loaded with MWCNTs. A solution mixing method is selected to obtain an optimal MWCNTs dispersion. Rheological and photo‐calorimetric analyses are performed by varying filler concentrations (0.25%, 0.50%, 0.75 wt%) as well as electrical properties of the cured nanocomposites are measured. Rheological characterization indicates the free‐radical resin loaded with the 0.25 wt% of MWCNTs as the most suitable material for the 3D printing of electro‐active systems because it guarantees a rapid and homogenous resin recoating in the vat during the printing of two different layers due to its fluidity. The optimal printing parameters for this photocurable MWCNTs‐loaded resin are found through photosensitivity and photo‐calorimetric analyses. Electrically conductive structures with a conductivity value of 0.0006 S cm−1 are successfully printed, showing the immense potential of these conductive polymeric materials in replacing other standard silicon‐based materials manufactured by conventional 2D lithographic processes for the development of electronic devices and microelectromechanical systems (MEMS).

Advances in Monte Carlo Method for Simulating the Electrical Percolation Behavior of Conductive Polymer Composites with a Carbon-Based Filling

“…With the continued addition of conductive materials, the electron transport channels in the polymer matrix become saturated, and the corresponding resistivity no longer changes significantly [ 45 ]. After the polymer material undergoes percolation ( ), the relationship between its electrical conductivity and the filler’s own conductivity, the percolation threshold, and the volume fraction is usually expressed by the following equations [ 43 , 46 ]: where is the polymer composite’s conductivity, is the conductivity-related constant of the conducting material, is the mass fraction of the conducting material, is the polymer composite percolation threshold, and is the conductive network dimensionality critical factor.…”

“…With the continued addition of conductive materials, the electron transport channels in the polymer matrix become saturated, and the corresponding resistivity no longer changes significantly [45]. After the polymer material undergoes percolation (p > p c ), the relationship between its electrical conductivity and the filler's own conductivity, the percolation threshold, and the volume fraction is usually expressed by the following equations [43,46]:…”

3D-Printed MEMS in Italy

“…Another important work came from Iervolino et al [ 126 ], which developed two photo-curable resins containing MWCNTs toward 3D printing electrically conductive structures using near-visible light (405 nm) stereolithography processes ( Figure 19 ). These two resins belong to two different classes of photopolymers: a free radical system and a hybrid system consisting of a cationic/free radical blend.…”

“…24, no. 12, F. Iervolino, A. Bonessa, G. Foti, M. Levi, and R. Suriano, “Additive Manufacturing of Electrically Conductive Nanocomposites Filled with Carbon Nanotubes,” December 2022, with permission of John Wiley and Sons [ 126 ].…”