Conductive Green Graphene inks for Printed Electronics

Aqueous graphene inks were obtained by liquid-phase exfoliation of graphite and bonded to biodegradable polymers. Consequently, green and eco-friendly graphene inks are proposed that are free of VOCs and harmful organic compounds. Three graphene inks indicated as GGe, GTr, and GTw were prepared with corresponding optimized biopolymer concentrations of 0.1 mg.mL
⁻¹
of gelatin, 1 mg.mL
⁻¹
triton X-100, and 1.5 mg.mL
⁻¹
tween-20. The flake diameter distribution for the graphene inks ranged from 100 nm to 800 nm as measured by dynamic light scattering (DLS). GTr is made of smaller flake diameters followed by GTw and GGe has the largest flakes. Graphene films were printed using aerosol jet technique with a 500 nm thickness and their sheet resistance (sR) was of
$2.6\ \mathrm{k}\Omega/\square$
for GTr,
$5\ \mathrm{k}\Omega/\square$
for GTw, and
$14\ \mathrm{k}\Omega/\square$
for GGe. The low sheet resistance for GTr was assigned to better ink wettability and adhesion on top PET substrates. These electrical resistances are suitable for the fabrication of green chemiresistive flexible sensors.