A Highly Flexible Superhydrophobic Microlens Array with Small Contact Angle Hysteresis for Droplet-Based Microfluidics

This paper reports a highly flexible superhydrophobic and superhydrorepellent microlens array substrate with very low flow resistance. Even though the microlens array has no nanostructures, it shows hydrophobic property due solely to its geometrical effect. A contact angle of 165deg and hysteresis of 3deg are achieved on a flexible polydimethylsiloxane (PDMS) microlens array substrate with a Teflon (polytetrafluoroethylene) coating. Moreover, double-layered metals (Cr/Au) are sandwiched between the PDMS and Teflon layers for electrostatic or electrowetting-on-dielectric (EWOD) actuation. Due to its low flow resistance and superhydrophobicity, the array can be used as a microfluidic component that reduces external pressure and power consumption for mobility.