Nathalya Ramirez1, Zach McNulty2, Michael Orrill3, Saniya Leblanc3 Characterization of Carbon Nanospheres from Biochar in Ethylene Glycol and Water for Inkjet Printing Nathalya Ramirez1, Zach McNulty2, Michael Orrill3, Saniya Leblanc3 The George Washington University, Washington, DC 1 Department of Physics 2Department of Computer Engineering 3Department of Mechanical and Aerospace Engineering DISCUSSION INTRODUCTION Known for their stability and abundance, carbon nanospheres can be used to make ink. These are extracted from Biochar by pyrolysis, a biological process in the absence of oxygen. Figure 1. Single Hollow Carbon Nanospheres (Left), Agglomerated Clusters (Right) Ink is a colloidal system, a class of materials in which the kinetic units that are dispersed through the solvent are very much larger than the molecules of the solvents. Other examples of colloidal systems are paint, detergents, and aerosols. Figure 2. Electrical double layer and zeta potential properties Most inks need to be stabilized against agglomeration because of their high surface energies. Concentration, viscosity, zeta potential, are some limitations for an ink to be stable. For a ink to be printable and avoid clogging the nozzles, it needs to have a viscosity of the range 8-30 mPa. The rheometer shows that both samples have viscosities of approximately 8 and 10 mPa meaning they are within the printable range. DLS shows that particle distribution is even. The zeta potential measured across the double layer is of magnitude greater that 40 mV which is favorable. Printing process reveals good droplet formation, however, Image analysis shows that there is some agglomeration (Figure 9 and 10) and not enough carbon nanospheres. Figures 9 and 10 show the series of layers printed on a glass slide (10 to 60 layers). Sample I has a higher concentration of carbon nanospheres. Sample II, on the other hand, shows some ethylene glycol and water building up, and eventually expanding. OBJECTIVE Characterize the physical properties of Carbon nanospheres based dispersions for inkjet printing applications. METHODS Sonication Figure 5. Sonication of sample showing dispersion particles Dynamic Light Scattering Figure 7. DLS of sample showing size distribution and zeta potential measurements Rheology CONCLUSIONS Figure 6. Diagram showing sample under rheometer to measure its viscosity Viscosity of Samples I and II show that they are within the printable range. Zeta potential for Samples I and Ii show that dispersion happens over 40 mV which indicates the ink is stable, however the analysis of images taken of printed samples show that droplet formation is achieved, but dispersion does not reach percolation threshold due to the low concentration of carbon nanospheres in the colloidal system. To increase concentration of carbon nanospheres, we have to find a better ethylene glycol, water ratio, pH can be increased, and temperature can be increased to dry the solvents in between layers. Dot-on-demand inkjet printing NEXT STEPS Figure 8. Fujifilm Dimatix DMP-2138 printer used to print layers of carbon-based ink Determine most stable ethylene glycol and water ratio for concentration. Maximize the amount of carbon nanospheres per sample to achieve a greater dispersion and higher conductivity. Make a concentration of ink that will reach the percolation threshold in one layer. Predict and measure the conductivity of the most stable ink that reached the percolation threshold. RESULTS APPLICATIONS Inkjet printing allows for cheaper and faster prototyping. Inkjet printing is a fast growing technique in the fields of tissue engineering, array fabrication, experimental biology, photonics, and nanotechnology with many useful technological advances such as printing environmentally-friendly solar cells, biosensors, and batteries, among others. Environmentally-friendly ink extracted from Biochar. References Figure 9. Image Analysis of Sample I on Fiji Figure 10. Image Analysis of Sample II on Fiji [1] Derby, Brian. "Inkjet Printing of Functional and Structural Materials: Fluid Property Requirements, Feature Stability, and Resolution." [2] Robert J. Foundations of Colloid Science. 2. ed., 1. publ. ed. Oxford [u.a.]: Oxford Univ. Press, 2001. Print. [3] Singh, Madhusudan, et al. "Inkjet Printing-Process and its Applications." Acknowledgements Funding provided by National Science Foundation. Michael Orrill, PhD student, Mechanical and Aerospace Engineering Leblanc’s Lab, Mechanical and Aerospace Engineering Department Figure 10. Image Analysis of Sample II on Fiji Figure 3. Printing Biosensors (Left), Eco Ink (Middle), Printed circuit (Right).