Actuating droplets with electrowetting: Force and dynamics  

作　　者：Robert Hennig Vito Cacucciolo Herbert Shea 

机构地区：[1]Soft Transducers Laboratory(LMTS),Ecole Polytechnique Fédérale de Lausanne(EPFL),Neuchatel,Switzerland [2]Politecnico di Bari,Bari,Italy

出　　处：《Droplet》2024年第2期113-124,共12页液滴（英文）

基　　金：supported by the Swiss National Science Foundation(SNSF)under grant No.200020_184661.

摘　　要：Electrowetting on dielectric(EWOD)allows rapid movement of liquid droplets on a smooth surface,with applications ranging from lab-on-chip devices to micro-actuators.The in-plane force on a droplet is a key indicator of EWOD performance.This force has been extensively modeled but few direct experimental measurements are reported.We study the EWOD force on a droplet using two setups that allow,for the first time,the simultaneous measurement of force and contact angle,while imaging the droplet shape at 6000 frames/s.For several liquids and surfaces,we observe that the force saturates at a voltage of approximately 150 V.Application of voltages of up 2 kV,that is,10 times higher than is typical,does not significantly increase forces beyond the saturation point.However,we observe that the transient dynamics,localized at the front contact line,do not show saturation with voltage.At the higher voltages,the initial front contact line speed continues to increase,the front contact angle temporarily becomes near zero,creating a thin liquid film,and capillary waves form at the liquid–air interface.When the localized EWOD forces at the contact line exceed the capillary forces,projectile droplets form.Increasing surface tension allows for higher droplet forces,which we demonstrate with mercury.

关 键 词：CAPILLARY FORCES DYNAMICS 

分 类 号：O35[理学—流体力学]