Tunable contact angle hysteresis on compliant magnetoactive elastomers

Abstract

It is shown that the advancing (ACA) and receding (RCA) contact angles of water on extremely soft (shear modulus of the order of 10kPa) magnetoactive elastomer (MAE) films significantly depend on the applied magnetic field. The difference between these angles, known as the contact angle hysteresis, is examined. The roles of the filler concentration and material softness are elaborated. The highest change in the contact angle hysteresis (CAH) from 34∘ in the absence of magnetic field to 76∘ in a magnetic field of 0.4T is achieved for the softest sample with the lowest mass fraction of iron particles (70wt%). The dependence of the CAH on magnetization history (“magnetic hysteresis”) is observed. This magnetic hysteresis is clearly pronounced for the ACA and has little effect on the RCA. Magnetic field-induced changes of the surface roughness exhibit qualitatively the same hysteresis behavior with regard to the external magnetic field as the ACA. The results are promising for the development of smart surfaces for applications where the dynamic wetting has to be controlled.