Abstract
Emerging technologies such as smart packaging are shifting the requirements on electronic components, notably regarding service life, which counts in days instead of years. As a result, standard materials are often not adapted due to economic, environmental or manufacturing considerations. For instance, the use of metal conductive tracks in disposable electronics is a waste of valuable resources and their accumulation in landfills is an environmental concern. In this work, we report a conductive ink made of carbon particles dispersed in a solution of shellac. This natural and water-insoluble resin works as a binder, favourably replacing petroleum-derived polymers. The carbon particles provide electrical conductivity and act as a rheology modifier, creating a printable shear-thinning gel. The ink’s conductivity and sheet resistance are 1000 S m−1 and 15 Ω sq−1, respectively, and remain stable towards moisture. We show that the ink is compatible with several industry-relevant patterning methods such as screen-printing and robocasting, and demonstrate a minimum feature size of 200 μm. As a proof-of-concept, a resistor and a capacitor are printed and used as deformation and proximity sensors, respectively.
Highlights
Emerging technologies such as smart packaging are shifting the requirements on electronic components, notably regarding service life, which counts in days instead of years
Our composite ink successfully addresses those requirements by combining graphite flakes and carbon black to provide electrical conductivity, and by using shellac as a natural and biodegradable binder
Biodegradation of shellac has to occur in compost soil which prevents redispersion of nanosized carbon particles in air
Summary
Emerging technologies such as smart packaging are shifting the requirements on electronic components, notably regarding service life, which counts in days instead of years. Whereas metals maximize electrical performance, reaching bulk conductivities of around 107 S m−1, it represents a waste of valuable resources as well as an environmental concern if integrated in disposable technologies. Indium tin oxide (ITO) is the most prominent electroceramic It is widely used in devices where optical transparency of the electrodes is required, it shows bulk electronic conductivities of around 106 S m−1 and is moisture stable. ICPs can provide optical transparency at lower cost and without the need for annealing Whereas they can reach bulk conductivities of around 106 S m−1, they are often unstable towards atmospheric moisture. Non-toxic, as well as moisture, pH and temperature stable It can provide high electrical performance, with graphene basal plane exhibiting electrical conductivity of around 1 05 S m−124,25. Binders typically being the dielectric phase of Scientific Reports | (2021) 11:23784
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