Study Of Lateral Friction Between Solid And Liquid Interfaces Based On Microcantilever-like Detection Technique

The directional transport of droplets on the surface of materials is one of the important applications for the special infiltration of material surfaces.Based on the study of the infiltration mechanism of biological surfaces,researchers have realized the application of liquid directional transport in microfluidic,self-cleaning,water mist collection and other aspects.However,due to the uncontrollability of droplets during the transmission process,there are still some problems in studying the dynamic interaction mechanism between solid and liquid interfaces.Based on microcantilever-like sensor technology,this paper designed and built a set of lateral friction detection system between solid and liquid interfaces,verified the effectiveness of the system,and studied the changes of lateral friction caused by the changes of solid interface properties and liquid surface tension respectively.The specific work is as follows:(1)A set of lateral friction detection system between solid and liquid interfaces was designed and built,and its effectiveness was verified.The capillary was used as a probe to detect the real-time changes of the lateral friction force on the solid surface,and the lateral friction force on the PDMS surface was detected.The results show that the change process of the lateral friction between the solid-liquid interface is similar to that between the solid-liquid interface,which can be divided into static and dynamic states.When the driving force of the droplet is less than the maximum static friction force,the droplet remains static,but the static friction force increases with the increase of deformation.When the maximum static friction reaches 25.85 μN,once the driving force of the droplet reaches the maximum static friction,the droplet begins to move.The droplet will transition from static state to stable dynamic equilibrium state,and the droplet deformation will decrease after reaching the maximum,until it reaches stability,at this time,the sliding friction is 17.17 μN.(2)The influence of material surface microstructure on lateral friction was studied.The superhydrophobic surfaces of PDMS with different roughness and adhesion were prepared by the template and spraying methods.The real-time variation of the lateral friction when water droplets slide on the sample surface was detected by the detection system of lateral friction between solid and liquid interfaces.The results show that when the surface roughness of the sample decreases from 4.619 μm to 3.512 μm,the wetting state of the droplet changes from Cassie state to Wenzel state,and the lateral friction between the solid-liquid interface begins to increase,which is influenced by the fixed force generated by the space between the surface microstructure.The increase of the lateral sliding friction force is more severe than the maximum static friction force,which increases from 33.59 μN to 51.52 μN,and the lateral sliding friction force increases from15.87±1.9 μN to 40.91±1.2 μN.When the roughness increases,the maximum static friction decreases from 19.32 μN to 9.23 μN,and the lateral sliding friction decreases from 15.26 ±1.6 μN to 3.47±2.1 μN.(3)The influence of surface tension variation on lateral friction was studied.The MWCNT-OH/ DIW nanofluids with different mass fractions and different surfactant types were prepared using deionized water as the base liquid.The change of transverse friction when the surface tension of the fluid changed was studied by the transverse friction detection system.The lateral friction force was studied by means of the lateral friction detection system.The results show that with the increase of MWCNT mass fraction and the increase of fluid temperature,the surface tension of nanofluids decreases,and the lateral friction on the hydrophobic surface of PDMS increases linearly.When the ionic surfactant is used as a dispersant of MWCNT,the surface tension of nano-fluid decreases significantly.Because the surface tension of nano-fluid decreases considerably,the longitudinal adhesion between nano-fluid and PDMS surface increases significantly.As a result,it is difficult to recover from the influence of surface adhesion when the maximum deformation is reached of fluid movement.The lateral friction force after stable movement has no significant change compared with the maximum static friction force.For example,when the CTAB is used as a dispersant,the maximum lateral static friction force is 132.27 μN,and the lateral sliding friction force after stable movement is 126.86μN.Figure [57] Table [6] Reference [116]...