Amorphous fluoropolymers as insulators for reversible low-voltage electrowetting

Amorphous fluoropolymers have been used as a hydrophobic “top coat” of insulating materials for electrowetting, to confer the reversibility required for practical applications. The electrical properties of such fluoropolymers (in particular breakdown voltages of less than 20 V/μm) are often implicated in poor electrowetting performance. However, we have recently found that the intrinsic electrical properties, including the breakdown voltage, of appropriately prepared fluoropolymer coatings are sufficient to allow the amorphous fluoropolymer to function both as the insulator and hydrophobic surface for electrowetting. A typical electrowetting material system is then reduced to the basic material components of electrode, insulator, and conducting liquid. This simplicity facilitates both the fabrication of electrowetting devices, the soluble fluoropolymer insulator being directly wet coated onto the electrode materials, as well as the study of charging mechanisms. Reversible electrowetting on insulators thinner than 1 μm and at less than 50 V is also routinely achievable.