Cu-coated cellulose nanopaper for green and low-cost electronics

In this work we have developed low-cost, renewable and sustainable materials based on cellulose for electronic applications. The UV–Vis spectroscopy, water contact angle and differential scanning calorimetry results reveal a marked effect of absorbed water on the physical properties of cellulose nanopaper. Morphological observations reveal that the TEMPO oxidized cellulose-based foils were successfully covered by a 200-nm-thick copper layer by DC sputtering. The obtained low surface roughness, porosity and hydrophilicity of the nanopaper allow an efficient deposition of Cu on synthesized nanopaper. The thermal stability of cellulose nanopaper is markedly increased from 240 to 324 °C after Cu sputtering, results that are especially interesting for applications in which devices should withstand high temperatures. Dynamic mechanical analysis shows that the Cu-covered nanopaper maintains its mechanical stiffness up to ~180 °C. Finally, dielectric spectroscopy measurements reveal that developed Cu-coated nanopaper could emerge as a suitable bio-based material for radiofrequency applications. In this work we explore sputter coating as an alternative method to reduce the intrinsic hydrophilicity of synthesized nanopaper instead of including a polymer in the nanocellulose or functionalizing its surface chemically. The obtained findings highlight the potential application of transparent and mechanically robust cellulose nanopaper in the field of electronics and communication engineering.