Stable Grasp and Accurate Release of Microbeads by a Two-finger Microhand

In microscale, the adhesion force between the object and the end-effector becomes one of the main forces affecting the micromanipulation. During operating the micro objects, adhesion force enables us pick up with only one end-effector, but high success rate and stable grasp cannot be guaranteed. Besides, the adhesion force causes the difficulty of release, and release accuracy of the existing release method is not satisfying. To solve these two key problems in micromanipulation, we proposed an optimized two-finger microhand system to achieve both stable grasp and accurate release. One micropipette mounted on a parallel compliant mechanism can be positioned in a 3D space actuated by three piezo actuators, and another micropipette is fixed. The tips of the two micropipettes are heated to form spheroids at the end, and then grinded to achieve hemispherical end-effectors for high success rate stable grasp. The motorized end-effector is coated with the gel to keep the object always stick on it when open the two finger. Then this end-effector is controlled to vibrate to overcome the adhesion force between the end-effector and the object. Experiments of grasp microbeads have been carried out to demonstrate the stable grasp with hemispherical end-effectors. The microbeads have also been released with different vibrate frequencies and amplitudes to quantify its release accuracy under different conditions. Finally, with the proposed grasp and release methods, we apply microbeads to assemble a line.