https://www.sciencedaily.com/releases/2021/12/211220120708.htm

Unnecessary waste, thinks Gustav Nyström, head of Empa's Cellulose & Wood Materials lab: "There is an urgent need for materials that balance electronic performance, cost and sustainability." To develop an environmentally friendly ink, Nyström's team therefore set ambitious goals: metal-free, non-toxic, biodegradable. And with practical applications in mind: easily formable and stable to moisture and moderate heat.

The researchers chose inexpensive carbon as the conductive material, as they recently reported in the journal Scientific Reports. More precisely: elongated graphite platelets mixed with tiny soot particles that establish electrical contact between these platelets -- all this in a matrix made of a well-known biomaterial: shellac, which is obtained from the excretions of scale insects. In the past, it was used to make records; today it is used, among other things, as a varnish for wooden instruments and fingernails. Its advantages correspond exactly to the researchers' desired profile. And on top of that, it is soluble in alcohol -- an inexpensive solvent that evaporates after the ink is applied so that it dries.