Paper-based electrowetting devices fabricated with cellulose paper and paraffin wax

Paper-based microfluidic devices based on electrowetting principle, more specifically electrowetting on dielectric (EWOD), have attracted increasing attention due to their powerful liquid handling capability as compared to continuous-flow paper-based analytical devices (μPAD) that use capillary effects to control liquids. Here, we demonstrate fabrication of paper-based EWOD devices using cellulose paper as substrate and paraffin wax as dielectric hydrophobic layer by a simple pressing treatment for the cellulose paper and melting or spray-coating of paraffin wax. We optimized the key fabrication parameters according to the surface morphology and hydrophobicity of the obtained wax film, including the pressing pressure, thermal annealing temperature and amount of paraffin wax. Moreover, the EWOD devices fabricated by the spray-coating method demonstrate larger contact angle changes but with smaller contact angle hysteresis under DC electric field when compared with the devices fabricated by the melting method. Our study opens up potential fabrication of hybrid paper-based microfluidic device combining advantages of continuous-flow and electrowetting using cellulose paper and paraffin wax.