微液滴在PDMS软基体表面的动态摩擦行为研究

通过固液界面摩擦力测试装置研究了微液滴在PDMS软基体表面运动时的动态摩擦学行为，并对微液滴体积、滑动速度及软基体力学性能对固液界面动态摩擦行为的影响进行了分析. 结果表明:微液滴在软基体表面运动时表现出最大静摩擦力和动态摩擦力. 最大静摩擦力与微液滴黏度和速度梯度呈正比，动态摩擦力与微液滴体积、滑动速度和基体力学性能有关. 随着微液滴体积的增加，三相接触线长度增加，动态摩擦力增加；随着相对滑动速度增加，三相接触线长度及接触角滞后增加，动态摩擦力增加；随着软基体弹性模量降低，固液界面黏附力增加，固液界面运动能量耗散增加，动态摩擦力增加. 研究结果可为PDMS软基体表面微液滴的精确驱动和运动参数优化提供理论指导，也可进一步丰富固液界面摩擦理论. 

Dynamic Frictional Behavior of Microdroplets on PDMS Soft Substrate

The dynamic frictional behaviors of microdroplets on PDMS surface were studied by a self-made frictional force testing device. The effect of droplet volume, slip velocity, and mechanical properties of the PDMS substrate on the dynamic frictional behaviors were investigated. Results showed that the solid/liquid interfacial friction force consisted of maximum static friction force and dynamic friction force. The maximum static friction force was proportional to the viscosity and velocity gradient. The dynamic friction force was related to the droplet volume, sliding velocity and mechanical properties of the substrate. The dynamic friction force increased with droplet volume due to the increasing of the length of contact line. Moreover, the dynamic friction force increased with sliding velocity because the length of contact line and contact angle hysteresis increased with sliding velocity. Furthermore, solid/liquid interface adhesion force increased with decreasing of elastic modulus. As a result, the energy dissipation and dynamic friction force increased. The results would be helpful to provide theoretical guidance for the precise driving of microdroplets and optimize the motion parameters of droplet on PDMS surface, and then further to enrich the solid-liquid interface friction theory.