Research On The Adhesive Contact Of Microparts And Micromanipulation Methods Based On Adhesion Forces

Trends of miniaturization and integration of numerous industry products are continually increased recently. Micromanipulation, as an enabling technology, is being widely used in many fields, such as microelectronic engineering, precision manufacturing, bioengineering. The rapid developments of micro and nanotechnology are making more and more functionized microdevices being uitilized in micromanipulation system, on the other hand, higher demands are proposed to manufacture microsystems with smaller dimensions and more functions.Due to the scale effects, various surface forces begin to dominate in the micro meter scales. Adhesion forces often disturb the process of micromanipulation and affect the reliability and efficiency of it, thus restrict their wide applications. Supported by the National Science Funds for Distinguished Young Scholar and the High Technolgy Research and Development Programme of China, this paper focuses on the adhesive contact model between microparts and the micromanipulations methods based on controlling adhesion forces.Considering a mass of adhesion phenomema in micromanipulation, this paper starts from the scale effects in micrometer scales. By analyzing the forces between atoms and molecules, the mechanism and properties of adhesion forces are identified. Then the effects of adhesion forces on tools design and path planning in micromanipulation are investigated. The configurations of manipulating typical microparts are analysed to discuss the properties of adhesion forces.Adhesion is a result of multiple forces with different characters, so that is necessary to distinguish them. Van der Waals adhesion and capillary adhesion are focused in this paper for considering the actual conditions in micromanipulation. For the usual rough surfaces, the fractal geometry methods are adopted to describe the rough surfaces. The adhesive contact model between them is developed based on the elastic contact model of single asperities. The capillary force model between microparts is also developed based on the circle approximation and the parameters that affect the force are discussed in detail. Due to disvantages of the usual microgripper and vacuum tool, the micromanipulation methods based on adhesion force control are proposed according to the predominance of adhesion forces in micro meter scale. In picking process, strengthening the adhesion is positive, so a method using the viscoelastic tool with fast velocities are proposed. The transferring process will be stable if the adhesion force is larger than the gravity of the microobject. To realize the reliable release, a method of controlling capillary forces is suggested.To verify the developed model and methods, a series of experiments are performed. The adhesion force between PDMS tool and microparts are measured to make sure that it is more dominate than the gravity. The adhesion hysteresis is verified to show that it is suitable to strengthen the adhesion with velocity control. The capillary force between microspheres and flats are also measured to verify the developed model. Finally, the micromanipulation experiments based on adhesion force control are performed and the results show that the feasibility of proposed methods.