Reversible Switching of Icing Properties on Pyroelectric Polyvenylidene Fluoride Thin Film Coatings

In this work a new approach for ice repellent coatings is presented. It was shown that the coatings cause a decrease or increase in the freezing temperature of water depending on the alignment of an external electric field. For this coating the commonly used pyroelectric polymer polyvenylidene fluoride was deposited as a thin film on glass. The samples were dip-coated and subsequently thermally-treated at 140 degrees C for 1 h. All samples were found to cause a reduction of the icing temperature of water on their surface in comparison to uncoated glass. On several samples an external electric field was applied during this thermal treatment. The field application was found to cause a remarkable reduction of the icing temperature where a maximum lowering of the freezing temperature of 3 K compared to uncoated glass could be achieved. The actual achieved reduction of the icing temperature was observed to depend on the polarity of the field applied during the thermal treatment. Furthermore, a repetition of the thermal treatment under oppositely directed electric fields led to a switchable freezing behavior of water according to the direction of the applied field. With an increasing number of cycles of switching of the icing property a slight training effect towards lower freezing temperatures was observed.