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Ch49-I044963.fm Page 243 Tuesday, August 1, 2006 4:04 PM
Tuesday, August
4:04 PM
Page 243
Ch49-I044963.fm
1, 2006
243
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3. VERSATILE MICRO ROBOT
In microscopic operations, an operator needs to operate a tool intricately. Fig.2 (a) shows motion
patterns required to carry out the precise microscopic operation. Because there is no surplus space in
such a narrow area, such movement was difficult for the previous micro robot [6]. To realize these
motion patterns at the same time, a structure was need that could move in XY directions and in
rotation in 9 independently, namely holonomic behaviour. The structure of the versatile micro robot
which is proposed to satisfy the requirements of microscopic operations [7]. Two u-shaped
electromagnets which are arranged to cross each other are connected by four piezo elements so that the
micro robot can move in any direction like an inchworm. Also we designed the special joint at one of
the 4 legs to ensure all legs smooth simultaneous contact on the surface. This layout of actuators can
allow it to move precisely in a holonomic locomotion manner. As shown in Fig.2 (b), the length of
robot is 35 [mm], width is 35 [mm] and height is 15[mm], Weight is 34[g]. We use the stacked type
PZT elements of 5 [mm] x 5 [mm] x 10 [mm]. Each piezo element is connected to each electromagnet
with a plastic insulator. In experiments, we confirmed that the micro robot can move in XY directions.
In experiments, we confirmed that the micro robot can move in XY directions as well as in rotation
with sub micron positioning performance.
Piezo actuator Electromagnet

Rotational
Diagonal motion
motion
Orthogonal
motion

<View field of
microscope>
(a) (b)
Figure 2: Piezo driven micro robot for microscopic operation
4. PRECISE MICRO ROBOT BIO-CELL MANIPUTAION

To perform bio-cell manipulations, the precise positioning of bio manipulation tool such as holding
pipette is required. Furthermore, in order to perform more precise bio-cell manipulations, operation of
the direction of Z as well as the operation of XY is required. In our approach, precise positioning of
micro pipette is carried out by using microscopic image recognition. In order to construct the 3D
information, it is necessary to observe a bio-cell from any direction by rotating a CCD camera around
a bio-cell, or rotating bio-cell on a center. In the microscopic manipulation under microscope, because
it is difficult to move a camera due to the spatial constraint, the constructing 3D information for
precise micro manipulation is carried out by fixing a camera and rotating an object.
In this paper we proposed and used the non contact rotation positioning of an egg cell by pipette
vibration, which genarates a rotational flow near the pipette. In our system, this rotational flow is
generated by using only the versatile micro robots. First, as shown in Fig. 3 (a), the electromagnet 1 is
always activated and electromagnet 2 is always not activated. And the position Fig. 3 (a)-(2) and (a)-
(3) is repeated by expanding and contracting the piezo-electric element between both electromagnets.
By this motion, the pipette on a micro robot can be vibrated with the amplitude of tens of microns.
This proposed mechanism can be carried out non contact rotation operation, without using some
additional actuators for a micro robot. This is a very important factor, in order to construct a simple
and low cost microscopic operation system. Fig.3 (b) shows the microscopic vibration mechanism for
the basic experiment. This mechanism can be attached on the micro robot easily.