The Research Of Polarity-dependent Low Voltage Electrowetting Behavior Based On Slippery Lubricant Infused Porous Surface

Recently,it is the inevitable trend of multifunctional and portable devices and systems because of the rapid development of microfluidic technology,and the precise manipulation of micro-scale fluid is the premise and foundation.The electrowetting based on dielectric layer,as a microfluidic phenomenon,can precisely control droplets deformation and displacement on the effect of voltage,and its attractive prospects applications range from flexible electronic paper,liquid zoom lens,microfluidic analysis,to energy collection.But the traditional solid dielectric layer electrowetting was hampered by certain limitations: bad reversibility,the high driving voltage(about 50-200V),droplets shocks and the problem of dielectric layer breakdown which caused by high voltage,which has become the important limit factors of the portable electrowetting devices and systems.Although some of the researchs has succeed in achieving the low voltage electrowetting in the air environment,but there is still limited by poor reversibility and dielectric layer breakdown.And the method of using AC voltage to reduce electrowetting reversible limits the application range of electrowetting.The study found that three-phase contact line pinning of the interface of droplet and the medium layer is an important factor leading to result in a high driving voltage and bad reversibility,the emergence of liquid medium layer can be expected to reduce basal pinning force.Inspired by this idea,the researchers put forward a new model of electrowetting based on slippery lubricant-infused porous surface,which can effectively improve the reversibility of electrowetting and suppressing droplet oscillation,however,the model is still limited by the problem of high driving voltage.Considering of the high driving voltage of electrowetting based on slippery lubricant-infused porous surface,in order to reduce the driving voltage of electrowetting phenomenon,this paper carried out electrowetting effect research by perfluorinated silane modified porous polytetrafluoroethylene(PTFE)membrane.It found that the silicone lubricated 28 microns thick PTFE porous membrane after the hydrolysis/graft with perfluorinated octyl trichlorosilane shows good hydrophobicity,the film can realize the consecutive reversible modulation of contact angle from 112 ° to 58 ° when voltage increases from 0 to 60 V in the air environment,which greatly reduces the positive driving voltage.At the same time upon adjusting the concentration of perfluorinated silane solution,this low voltage electrowetting can be realized with completely reversibility.Experiment also found that liquid-infused film modified by perfluorinated silane electrowetting modulation is complete different from the traditional dielectric layer electrowetting on positive and negative voltage,the low voltage electrowetting occurs at positive voltage but does not occur at negative voltage.Our study provides a new pathway to realize low voltage reversible electrowetting,which not only has very important scientific significance,but also has great practical application value in design and application of microfluidic devices.