Nanoporous kaolin: Cellulose nanofibril composites for printed electronics

Cellulose nano- and microfibrils (CNF/CMF) grades vary significantly based on the raw materials and process treatments used. In this study four different CNF/CMF grades were combined with kaolin clay pigment particles to form nanoporous composites. The attained composite properties like porosity, surface smoothness, mechanical properties and density properties depended strongly on the raw materials used. In general, higher kaolin content (~80 wt%) led to controllable shrinkage during drying, which resulted in improved dimensional stability of composites, compared to a lower kaolin content (~50 wt%). On the other hand, the use of a plasticizer and a high amount of CNF/CMF was essential to produce adequate elasticity for the composites. The performance of transistors when fabricated on the nanoporous composites was strongly dependent on the raw materials used. The formation of the semiconductor layer was affected by the porosity, roughness, hydrophobicity, polarity and absorption properties of the top-most layer at the composite. The developed natural fiber-based substrates may be applied to novel value-added applications in intelligent products, such as sensors and simple displays.