focused on manipulating a single object using acoustically oscillating bubbles. manipulated multiple micro-objects using twin bubbles attached to a rod, and Chung et al.
analyzed circulatory stream in two dimensions around an oscillating circular cylinder in one direction. In previous work, to manipulate objects using stream, many methods have been proposed. Our manipulator, actuated by three piezoelectric (PZT) actuators, is a suitable tool for generating swirl flow. Unlike the above-mentioned field forces, rotational stream can be generated by using only high-speed end effector motion. However, non-contact manipulation cannot perform physical operation tasks, and complex systems are required for generating the aforementioned field forces. On the contrary, an optical tweezer can manipulate objects selectively, but cannot manipulate many objects simultaneously. The methods using field forces, including acoustic waves, the dielectrophoretic method, stream by bubble, and lift force, can manipulate multiple objects at the same time, but have difficulty in manipulating objects selectively. applied inertial lift force for sorting particles. generated a stream by oscillating a bubble for 3D manipulation of microobjects.
developed a dielectrophoretic method for trapping particles. manipulated single particles and single cells by applying surface acoustic waves. On the other hand, non-contact manipulation utilizes field forces without contact with the end effector, which makes the influence of adhesion forces negligible. Moreover, it is difficult to deal with fragile objects, and contamination of the end effector is a weakness. presented a vacuum tool and voltage control method for precise releasing. utilized high speed motions of an end effector to release object on the desired position. Thus, to release microobjects at the desired position, special releasing strategies are necessary. However, the main difficulty of contact manipulation is releasing micro-objects adhering to the manipulator because of large adhesion forces. In addition, microassembly can be applied to building three-dimensional (3D) microsystems and devices. proposed a local environmental stimulation system using two pipettes controlled by a microhand. applied an automated micro-robotic system for cell injection. succeeded in enucleation of oocyte by cutting the surface of the oocyte. The main advantage of contact manipulation techniques is that physical approaches such as cutting, injecting, and stimulating can be achieved precisely. presented high-speed autonomous manipulation of microshperes utilizing a two-fingered microhand and a MEMS microgripper, respectively. Ĭontact manipulation is mechanical manipulation by direct contact with target objects. The manipulation techniques can be classified in two ways: contact manipulation and non-contact manipulation. To deal with different types of microobjects including biological cells and microparts, many manipulation methods have been proposed. In recent years, micromanipulation systems have become widely used in various applications such as manipulating biological cells or microorganisms, assisting micro-surgical operations, and assembling micro devices. From the analyzed data, we verified that the rotational flow has potential to manipulate micro-objects precisely in 3D space. We analyzed the velocity toward to the root of the end effector and angular velocity around the end effector by formulating models. By changing the amplitude and frequency of the circular motion, the generated swirl flow is analyzed in 3D space using 9.6-μm microbeads. In this paper, we focus on rotational flow created by two-dimensional circular motion of the end effector mounted on the parallel link. To reach the required end-effector frequency and amplitude, which is necessary for generating the rotational flow that can make rotational movement of microbeads having patterned data, the end effector motion is generated by controlling the three piezoelectric actuators at high speed. A compact parallel link produces precise three-dimensional motions. In order to generate an applicable motion that can precisely control the speed and position of a target object around an end effector, a manipulator actuated by three piezoelectric actuators is proposed. This paper presents a non-contact manipulation method using rotational flow generated by high speed motion of a glass needle.