Research On Micromanipulation Methods Based On Hydrophobic Condensation And Vibration Adhesion Control

Product requirements of miniaturization and integration make manipulation object extend from macro to microscale. The significance of micromanipulation becomes more and more obvious an is being widely used in many fields, such as microsystem manufacturing, biological microscope operation, optical alignments. In the face of increasingly miniaturization, refinement and complexity during manipulation process, microparts provide higher standard and challenge to operation tools and methods. Characteristics of light weight and fragile structure of microobject demand a higher level of force control when mechanical gripping was employed. Otherwise, the generated stress concentration deform or even destroy the surface of microobject.Micromanipulation method based on dropet has flexibility and self-calibration function, but real-time droplet acquisition is prerequisite for micromanipulation system automation. Meanwhile, adhesion force caused by scale effect disturbs the process of micromanipulation, especially in the releasing stage, where the microobject is not fall off automatically. To solve these problems, condensation mechanism of droplet formation on hydrophobic surface is investigated in this paper. Microobject transfer method based on hydrophobic condensation and vibration adhesion control is proposed to pick-and-place microobjects. Aspects of droplet condensation model, controllable picking method, release strategy of vibration control and droplet auxiliary, and manipulation experiments are conducted in-depth research.Respects of microscale adhesion and hydrophobic condensation mechanism, adhesion production and calculation methods are analyzed through typical configurations. Droplet acquisition method for capillary micromanipulation based on condensation control is proposed. Comparisons of droplet formation on hydrophilic and hydrophobic surface are performed. Models of droplet growth during water condensation on hydrophobic surface, including direct growth, droplets coalesce and droplet movement, are estabilished to analyze the influence of subcooling and saturation temperature on condensation capacity. Influence of probe curvature, temperature gradients and pining effect on the behavior of droplet movement are invetigated to obtain conditions for single stable droplet. Accordingly, experimental analysis of droplet movement are conducted.In the flexibile method of microobject picking, a controllable capillary microgripping method based on water condensation on hydrophbic surface is proposed, and the feasibility of capillary gripping control is analyzed. Process of picking and design of capillary microgripping tool are established. Liquid bridges are modeled during condensation process to investigate capillary force change due to adhesion hysteresis. Three static liquid bridge models, including plane-sphere, concave-sphere and cone-sphere, are established. Parameters of contact angle, liquid bridge volume, liquid bridge height and probe shape factor make effect on capillary picking ability are analyzed, which can guide picking process. By condensation bridge control, the controllability of microobject picking is verified using experimental analysis.In the aspects of release strategy by vibration control and droplet auxiliary, influence of surface roughness on Van der Waals force are invetigated, an active release strategy based on surface modification and vibration adhesion control is peoposed, and the dynamic model of inertial release is establisehd. Release strategy of droplet auxiliary with self-alignment function is studied, and models of two liquid bridge and self-alignment are established to solve offset problems after release. A auxiliary droplet distribution method based on water condensation on hydrophobic surface is presented, and simulation models of liquid bridge stretching are established during microdroplet dispensing. Influences of the contact angle, drawing velocity and tip curvature radius on the acquisition fraction of auxiliary droplet and rupture distance are ivestigated. Experiments demonstrate that the auxiliary droplet can be obtained by regulation of different parameters.In terms of the micromanipulation experiments based on hydrophobic condensation and vibration adhesion control, the condensation microactuator is developlet, and droplet formation ability influenced by structure parameters are analyzed. Capillary force is measeured using an established setup, and experiments of microobject picking are conducted. Besides, a vacuum microgripping tool with integrated vibration releasing capability is developed, and active release properties of the designed tool are analyzed by experiments. On the basis of auxiliary droplet distribution, the auxiliary release process of droplet is peformed by experiments, and droplet size and contact angle for self-calibration capabilities are investigated. Finally, a vibration module is integrated into the codensation microactuator, and micromanipulation experiments(pick-and-place) are conducted using a customized micromanipulation system to further verify the effectiveness of the proposed method and the desigend microgripping tool.