The Development Of Micro-force Measuring Device Based On Interfacial Tension

With the rapid development of modern society,micro-force has been applied widely used in medicine,manufacturing and processing,micro-electromechanical systems and so on Therefore,the study of the measurement of micro-force has attracted broad interest.With the development of surface chemistry and the improvement of observation method,the self-cleaning effect of lotus leaf has been gradually recognized by researchers,which lays a foundation for the artificial preparation of super-hydrophobic surface and promotes the practical application of super-hydrophobic surface.We find that the water droplets on a polypropylene ball of a millimeter-sized diameter will produce a millisecond level of interfacial tension at room temperature.In this paper,we put forward a new method to measure the interfacial tension within a micro-force scale.The main works are as follows:(1)The interfacial tension and the interaction mechanism between the ball and the droplet are studied.First,the formula of interfacial tension is obtained by derivation of the formula from previous study.Then,we choose an appropriate method for the preparation of super-hydrophobic surfaces.After which,we design a simple mechanical device which is used to conduct the stretching experiment.Finally,we conduct the image processing and analyze the rationality of micro-force measurement device.(2)The corresponding parts are redesigned,processed and assembled according to the working principle and characteristics of the device.We choose the appropriate control and drive units,then check the correction accuracy of the moving unit.We later buy an appropriate industrial camera and optimize the image processing program.(3)A new method of measuring the elastic coefficient of cantilever beam is proposed,then we measure the elastic coefficient of the cantilever beams and select the appropriate cantilever beam to conduct the next experiments.The contact angles between the water and the ball are measured and its rationality is analyzed.The accuracy of the device is verified by the given elastic coefficient of the cantilever beam.We further conduct experiments at different stretching rates,the experimental results show that the elastic coefficient of the cantilever beam can be accurately measured only at the lower drawing rate.Besides,we also carry out the tensile test of filaments.However,the results indicate that the mechanical properties of the filaments can not be measured by the current device.We then further analyze the reason of the failure in measuring the filaments which lies in the friction between the target ball and substrate and propose a solution to this problem by hanging the target ball to eliminate the influence of friction.Finally,theoretical error of the equipment is measured to be 2.37%(no more than 5%),it indicates that this equipment satisfies the requirements of the aforementioned design.