This Small Business Innovation Research (SBIR) Phase I project aims to develop high-performance conductive inks based on graphene technology for the printed electronics industry. Emerging printed electronics market applications require stringent flexibility and conductivity of conductive inks. Components printed with existing conductive inks are challenged by repeated flexing cycles that can break the conductive paths. In this project, a graphene-based ink will be engineered for the combination of electrical, mechanical, and environmental durability properties specified for the flexible printed electronics markets. The effects of different formulation chemistries will be studied to maximize the mechanical flexibility and creasing performance, without detrimentally affecting the electrical conductivity of graphene-based inks.
The broader/commercial impact of this project will be the potential to provide conductive inks that overcome the performance barriers that currently limit next generation printed electronics applications. The printed electronics market is growing across multiple sectors driven by following applications: radio frequency identification (RFID) tags for tracking inventory, smart packaging for anti-theft and anti-tampering purposes, smart cards and printed displays. The new conductive inks are expected to provide superior mechanical robustness, flexibility and enhanced interfacial adhesion to improve lifetime and performance of printed electronics. Furthermore, this technology will eliminate the sintering step of current conductive inks and allow manufacturers to print on low-cost substrates that could not otherwise survive sintering.
The printed electronics market is growing across multiple sectors driven by a handful of leading applications: RFID tags for tracking inventory, smart packaging, smart cards and printed displays. Conductive inks are a critical component to the overall success of printed electronics applications and the primary initial driving force in selecting inks is the match between the ink electrical performance and the conductivity requirements of the application. Manufacturers typically use either metallic inks (primarily silver-based) or traditional carbon-based inks to achieve electrical conductivity of the printed article. Silver-based inks, in particular, currently dominate the printed electronics conductive ink market due to their exceptional conductivity, but they are expensive. The increasing materials cost associated with use of silver-based inks is driving customers to look for other cost-reducing inks alternatives in order to manufacturer components economically. For applications with electrical requirements that do not require the high conductivity of pure silver inks, but cannot be met by conventional carbon-based inks, users are substituting silver inks with silver-carbon ink blends to reduce cost. However, even in a blended form, the high cost of the silver-ink component makes the systems cost prohibitive for many applications. Furthermore, the batch-to-batch variation of the blended inks precludes their use in performance sensitive applications that demand lot-to-lot quality control. In this SBIR program, Vorbeck Materials Corp. developed high performance conductive inks based on graphene technology to provide a high conductivity, highly flexible ink that also delivers overall process cost savings. The Phase I graphene-based conductive ink formulations targeted applications with electrical requirements between those met by silver-inks and carbon-based inks with improved mechanical performance, a critical design consideration for new flexible printed electronics product opportunities. The new graphene inks developed under the Phase I program have conductivity improvements of 400% over commercial carbon inks. These conductivity improvements have been accompanied by improvements in physical properties such as peel and pull adhesion, crease resistance (20% improvement over commercial carbon inks), rub resistance, and scratch resistance. The Phase I performance of the ink demonstrates the possibility for the printed electronics industry to produce existing printed electronics applications at lower cost and with higher functionality as well as to expand into new application areas. The flexibility and mechanical robustness of the graphene-based ink make it a compelling choice to improve lifetime and performance of printed electronics. Furthermore, the considerable silver-replacement savings of the graphene-based ink and eliminating the sintering step will allow manufacturers to print on low-cost substrates that could not otherwise survive sintering will provide a significant processing cost advantage for printed electronics manufacturers.
