Material jetting of carbon nano onions for printed electronics

As an additive manufacturing process, material jetting techniques allow to selectively deposit droplets of materials in liquid or powder form through a small-diameter aperture, such as a nozzle of a print head. For the fabrication of printed electronics, a variety of inks and dispersions of functional materials can be deposited by drop-on-demand printing on rigid and flexible substrates. In this work, zero-dimensional multi-layer shell-structured fullerene material, also known as carbon nano-onion (CNO) or onion-like carbon, is printed on polyethylene terephthalate substrates using drop-on-demand inkjet printing. CNOs are produced using a low-cost flame synthesis technique and characterized by electron microscopy, Raman, x-ray photoelectron spectroscopy, and specific surface area and pore size measurements. The produced CNO material has an average diameter of & SIM;33 nm, pore diameter in the range & SIM;2-40 nm and a specific surface area of 160 m(2).g(-1). The CNO dispersions in ethanol have a reduced viscosity (& SIM;1.2 mPa.s) and are compatible with commercial piezoelectric inkjet heads. The jetting parameters are optimized to avoid satellite drops and to obtain a reduced drop volume (52 pL), resulting in optimal resolution (220 & mu;m) and line continuity. A multi-step process is implemented without inter-layer curing and a fine control over the CNO layer thickness is achieved (& SIM;180 nm thick layer after 10 printing passes). The printed CNO structures show an electrical resistivity of & SIM;600 & omega;.m, a high negative temperature coefficient of resistance (-4.35 x 10(-2) & DEG;C-1) and a marked dependency on relative humidity (-1.29 x 10(-2) RH% (-1)). The high sensitivity to temperature and humidity, combined to the large specific area of the CNOs, make this material and the corresponding ink a viable prospect for inkjet-printed technologies, such as environmental and gas sensors.

Automated summary

Material jetting techniques allow selective deposition of droplets of materials in liquid or powder form by drop-on-demand printing. This study printed zero-dimensional multi-layer shell-structured fullerene material on polyethylene terephthalate substrates using drop-on-demand inkjet printing. The printed CNO structures showed high sensitivity to temperature and humidity, making them potential candidates for inkjet-printed technologies such as environmental and gas sensors.