Introduction and Motivation

Carbon nanotubes (CNTs) have outstanding mechanical, themal and electrical properties for sensing application
An inkjet printing approach is being explored potential for patterning nanostructured materials.
Integration of CNTs in fiber reinforced composites has a promising future for structural health monitoring
It is necessary to functionalize CNTs for improved compatibility with the polymer matrix is to oxidize the sheet and add a polyethyleneimine (PEI) dendrimer.

Objectives

Explore the effects on the electrical conductivity of printed CNT networks as influenced by the pattern design, solution concentration and printing times.
Examine the influence of surface functionalization on electrical conductivity and establish the relationship between the conductivity and oxidation of CNT sheet.

Processing Techniques

Consecutive Printing

Inkjet printing is a tool to accurately pattern carbon nanotubes and consecutive printing builds-up the thickness of the carbon nanotube film.
Codes were generated to examine the influence of consecutive printing on the film morphology and electrical properties.
The below coding sample demonstrates the general idea of writing a pattern code with pre-determined positions and dimensions (60 x 5 mm).

Influence of Printing on Electrical Properties

Functionalization Approach

Fill a beaker with 250 ml ultra-pure water and add 0.5 g of PEI
Ultrasonicate the water/PEI solution for 1 hour to ensure a uniform solution
Immerse CNT sheet (4.5 x 4.5 cm) in the water/PEI solution and place the outlet of the tubing connected to the ozone generator in the beaker
Keep the ozone generator running for several hours
The following chemical equation is the principle of this procedure

Functionalization and Electrical Properties

Conclusion

The consecutive inkjet printing is an efficient and industrially scalable method to create conductive CNT pathways.
Ozone generation, oxygen oxidation, and PEI functionalization alter the electrical properties of the CNT sheets.

Acknowedgements

This research was funded by the University of Delaware Research Foundation Research Experience for Undergraduates and the Department of Mechanical Engineering.
Office of Undergraduate Research and Experiential Learning, Summer Scholars.