Study On The Wettability Of Solid Surface Under Temperature Field

Surface wettability is a basic characteristic of solid surface.It plays great important roles on the lubrication of material surface,microgravity manufacturing and so on.In addition to the surface parameters such as surface groups,the surface texture etc.,external field like temperature field,electric field will also change the wettability of solid surface.In this paper,a contact angle tester with environment and temperature control is designed and manufactured.Wettability of the hydrophilic and hydrophobic solid surface under temperature field has been studied.Firstly,the paper introduces the basic concept of the surface science,such as surface free energy,surface tension etc.The relationship and applications between Young equation and contact angle have been studied,as well as the contact angle related knowledge.Then the latest research status of the wettability with temperature change is introduced.Secondly,the methods,theories and their development of measuring the contact angle on solid surface are summarized.The direct measurement method,the indirect force method and the shape analysis method have been included,which provide the basic knowledge for the design of the contact angle tester with environment and temperature control.Thirdly,the shape analysis method combining with the optical measurement has been used to design and fabricate the contact angle tester.The image processing module and the image optimization command in Matlab have been included,and the Prewitt edge extraction operator is used to extract the three-phase contact line image profile,and use the fitting formula to measure the contact angle value.Finally,four solid surfaces were selected and fabricated,including the smooth Soda-lime glass,the smooth monocrystalline silicon wafer,the smooth PDMS film and the PDMS film with micro-column array.The static contact angle of the water droplets on the four solid surfaces under the temperature field is measured and compared by analyzing the contact angle results.The results show that the static contact angle of water droplets on the hydrophilic surface of Soda-lime glass decreases with the temperature increasing.In contrast,the static contact angle on the surface of the smooth single crystal silicon wafer,the smooth PDMS film and the PDMS film with micro-column array increases with the temperature.The changing amplitude of the static contact angle of all the surfaces above,is not significant.