Nanotube-Enhanced Aerosol-Jet Printed Electronics for Embedded Sensing of Composite Structural Health
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Nanotube-Enhanced Aerosol-Jet Printed Electronics for Embedded Sensing of Composite Structural Health Da Zhao1, Tao Liu1, Mei Zhang1, Jen-Ming Chen2 and Ben Wang1 1. Department of Industrial and Manufacturing Engineering, Florida A & M University-Florida State University College of Engineering, & High-Performance Materials Institute, Florida State University, Tallahassee, FL 32310, U.S.A. 2. Institute of Industrial Management, National Central University, Jhongli City, Taiwan, 32001
ABSTRACT Innovative printing technology enables fine feature deposition (below 10µm) of electronic materials onto low-temperature, non-planar substrates without masks. This could be a promising technology to meet the requirements of present and future microelectronic systems. Silver nanoparticles (NP) ink is widely used for printed electronics; however, its electrical conductivity is low compared to bulk materials. In order to improve the electrical conductivity of printed tracks for the aerosol printing technique, we developed a novel carbon nanotubes (CNTs)/silver NP ink by mechanical stirring and sonication. The produced sample inks with different concentration of CNTs that were printed with Aerosol Jet® printing system. We found that the CNTs bridged the defects in some printed silver lines, thereby lowering the electrical resistivity by 38%. However, no further improvements were observed with a higher CNT concentration in the silver NP ink samples. We hypothesize that CNT bridges connects the defects thus decreasing the resistivity of printed silver lines when CNT concentration is under the percolation level. However, when it is above a concentration threshold, the resistivity of printed silver lines stops decreasing and even increases because of Schottky barrier effect.
INTRODUCTION Printed electronics by direct writing techniques show promise for use in a wide range of applications, such as thin film transistors, solar cells, RFIDs, antennas, sensors and displays. They are affordable, provide high efficiency, good quality, flexibility and are environmentally friendly compared to conventional photolithographic, electroplating and etching techniques [1]. Ink-jet printing is a widely used direct writing technique; however, the continuous and smooth printed patterns can only be achieved when the line width is set at 100 µm or greater [2], not fine enough for high-precision electronics. The M3D Aerosol Jet® process with featured size as small as 10µm provides a solution to high resolution direct writing, which uses aerodynamic focusing to deposit aerosolized materials onto planar or non-planar substrates. The process is a directwrite printing technology, operates under atmospheric conditions, and eliminates the need for lithographic or vacuum deposition. A variety of metallic NP based colloids are used as ink, such as nanosilver, nanocopper and nanogold, due to their good electrical properties. However, compared with the electrical
resistivity of bulk metal materials, printed NP metal tracks show relatively high electrical resistiv
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