M. Orrill, D. Abele, N. Banek, M. Wagner, S. LeBlanc
The George Washington University,
Keywords: carbon, inkjet, nanoparticles
Summary:Proposed applications of drop-on-demand (DOD) inkjet printing extend beyond printing of text and graphics to include rapid manufacturing of thin electrical devices. The most commonly printed electronic materials are silver nanoparticles due to their potentially high electrical conductivity. However, silver is expensive and nanoparticle films require post-processing to recover high conductance. The post-processing step restricts substrate material selection and throughput. These limitations are shared by other traditional electronic materials such as copper, gold, and aluminum. Oxidation of nanoparticles is another significant problem and can severely reduce or prevent electrical conductance, especially for copper and aluminum, which necessitates specialized processing and handling requirements. A recently developed carbon material can address these challenges. In this work we synthesize an inkjet-printable ink with a novel and environmentally benign carbon material. Hollow carbon nanospheres consisting of concentric graphene spheres are made from charred cellulose, a byproduct of a biofuel production process, so they are extremely inexpensive. Additionally, the production of carbon nanospheres reduces the cost of biofuels and serves as a carbon sink because the nanospheres can be created from fast growing plants such as switchgrass, which requires no tending and thrives on marginal, arid land. To synthesize the ink, hollow carbon nanospheres are treated to maximize colloidal stability and solid particle concentration before being dispersed into ethylene glycol. Relevant ink properties, surface tension, viscosity, and dispersed particle size distribution are characterized to be within printable ranges. Printing parameters are determined, and electrical properties of printed hollow carbon nanospheres are characterized. Results will indicate the feasibility of printing the novel carbon nanospheres for a wide variety of applications, such as flexible electronic devices.