Nanoimprinted conducting nanopillar arrays made of MWCNT/polymer nanocomposites: a study by electrochemical impedance spectroscopy

Abstract

Conducting vertical nanopillar arrays can serve as three-dimensional nanostructured electrodes with improved electrical recording and electrochemical sensing performance in bio-electronics applications. However, vertical nanopillar-array electrodes made of inorganic conducting materials by the conventional nanofabrication approach still face challenges in terms of high manufacturing costs, poor scalability, and limited carrier substrates. Here, we report a new type of conducting nanopillar array composed of multi-walled carbon nanotube (MWCNT) doped polymeric nanocomposites, which are manufactured on the wafer-scale on both rigid and flexible substrates by direct nanoimprinting of perfluoropolyether nanowell-array templates into uncured MWCNT/polymer mixtures. By controlling the MWCNT ratios and the annealing temperatures during the fabrication process, MWCNT/polymer nanopillar arrays can be endowed with outstanding electrical properties with high DC conductivity (∼4 S m⁻¹) and low AC electrochemical impedance (∼10⁴ Ω at 1000 Hz). Moreover, by electrochemical impedance spectroscopy (EIS) measurements and equivalent circuit modeling analysis, we can decompose the overall impedance of the MWCNT/polymer nanopillar arrays in the electrolyte into multiple bulk and interfacial circuit components, and can thus illustrate their different dependences on the MWCNT ratios and the annealing temperatures. In particular, we find that an appropriate annealing process can significantly reduce the anomalous ion diffusion impedance and improve the MWCNT/polymer nanopillars' impedance properties in the electrolyte.