Modification of lubricant infused porous surface for low-voltage reversible electrowetting

Abstract

In this study, we develop an innovative low voltage reversible electrowetting of water droplet based on perfluorinated silane-modified slippery lubricant-infused porous surface (SLIPS) that is impregnated by silicone oil. The electrowetting properties of SLIPS modified with and without 1H,1H,2H,2H-perfluorooctyltrichlorosilane (PFOTS) are investigated initially. After modifying the lubricated PTFE membrane with PFOTS, the driving voltage of electrowetting decreases sharply; the threshold voltage is only 5 V, which exhibits an immediate 15-fold decrease compared to that of the unmodified SLIPS. Subsequently, the electrowetting reversibility based on SLIPS modified with different concentrations of PFOTS solution is studied. Our results show that the initial contact angle increases with an increase in the concentration of PFOTS solution, but the electrowetting reversibility has an obvious depravation. The optimal concentration is about 0.03 wt%, in which the electrowetting hysteresis is less than 5°, and a large modulation can be achieved in the contact angle ranging from 107° to 60° with 60 V driving voltage in ambient air. On the basis of surface topography characterization, this low voltage electrowetting is attributed to the contact interface transformation from liquid–oil interface to the combination of liquid–oil and liquid–PFOTS interface. Therefore, the surfaces maintain low surface energy property of PFOTS and retain SLIPS property. In addition, a marked asymmetric contact angle variation with respect to voltage polarity on SLIPS modified with PFOTS is observed for the first time; the low voltage electrowetting occurs at positive voltage but does not occur at negative voltage. Our study provides a new pathway to achieve low voltage electrowetting without decreasing the thickness of the dielectric layer or increasing the dielectric constant.