Non-contact manipulation of spherical micro objects using two facing glass micropipettes

Abstract

Non-contact manipulation of spherical micro objects using two facing glass micropipettes is proposed. One micropipette is on the left side of an object, and the other micropipette is on the right side. Each micropipette emits a jet of water and applies hydraulic pressure to the object. The center position of the object is always detected by microscopic image processing. For rotating the object, the micropipettes are arranged point symmetrically with respect to the center of the object and emit water jets. When the left micropipette is on the upper-left side of the object and the right micropipette is on the lower-right side, the object rotates clockwise. Exchanging the upper and lower positions of the micropipettes enables counterclockwise rotation. As the micropipettes come near the edge of the object, the object rotates faster. The micropipettes automatically keep the position relation of point symmetry even if the object moves during rotation; that allows continuous rotation. For moving the object, one or two micropipettes are used selectively according to the moving direction. When the moving direction is near horizontal, one micropipette is used. If the left micropipette is just besides the object and emits a water jet, the object moves right. As the left micropipette comes lower, the object moves in upper-right direction. When the moving direction is near vertical, the left and right micropipettes are used. If the micropipettes emit water jets at the both lower sides of the object, the object moves upward. In the same way, the object can be moved in all directions. The micropipettes automatically repeat rearrangement and water jet emission so as to compensate the error between the desired and actual moving directions. This feedback control enables the object to reach its goal position. The experimental results show that a glass bead with a diameter of about 120 μm can be rotated and moved to its goal position by the proposed method.