Page 260 - Mechatronics for Safety, Security and Dependability in a New Era

Ch49-I044963.fm Page 244 Tuesday, August 1, 2006 4:04 PM
Ch49-I044963.fm
244
244 Page 244 Tuesday, August 1, 2006 4:04 PM
Holding Pipette Phosphor bronze plate

(3) A pipette is vibrated
(1) One of the pair of (2) Expansion and
an electromagnet leg contraction of a piezo- right and left.
is fixing electric element Piezoelectric element
between two legs.
(a) (b)
Figure 3: Microscopic vibration mechanism
In this experiment, the rotational follow in water of schale was generated using the holding pipette
of the bore 15 [urn] and an outside diameter 100 [|im] at a tip of micro pipette. The pipette tip was
bent to 45 [°], and it placed in parallel to the schale bottom, and observed from the schale bottom. To
tracing partial flows, water mixed with black sumi was used. The flow pattern when vibrating a piezo-
electric element by the sine wave of pitch 200 [Hz] and the seal-of-approval voltage±45 [V] is shown
in Fig. 4 (a).
These experimental results show that pipette vibration can generate constant flows, which shows a
fixed flow pattern near the pipette. When changing the pitch and seal-of-approval voltage of a piezo-
electric element, the flow velocity changed, but this flow pattern was almost fixed. Therefore, the
proposed mechanism may be effective in order to control rotation of a miniature ball such as an egg
cell without any mechanical contact.
2 3
© © ©

Horizontal non contact rotation
1 2 3
of ©
Vibration
Bottom of petri i i ©
Flow pattern [tip] Flow pattern [side]
Vertical non contact rotation
(a) (b)
Figure 4: Actual rotational follows around the vibrating pipette in water

As a basic experiment, the non contact rotational positioning of the minute glass ball placed around
a pipette was carried out using our proposed mechanism. The glass minute ball of a diameter 130 [urn]
(UB-67L Union Co. Ltd) was used for this primary experiment. When vibrating a piezo-electric
element by the sine wave of pitch 200 [Hz] and the seal-of-approval voltage±45 [V], a minute ball
rotates horizontal and vertical in the same position at the pipette tip as shown in Fig.4 (b). This motion
occurs based on the straight micro flow and circle micro flow shown in Fig.4 (a). The direction of
rotation of the minute ball in the experimental result of Fig. 4 (b) is the same as the direction of a flow
observed in Fig.4 (a). Therefore, it is guessed that rotational positioning is caused out by this rotational
flow. From these experimental results, it is shown that the proposed mechanism can be used non-
contact rotation positioning in three dimensions.
When the egg cell of the mouse with a diameter 120 [jim] was used as an object of microscopic
operations, the non contact rotation positioning of the egg cell by pipette vibration of a micro robot
was also available in a similar manner. As show in Fig.5 (a), a general sequence of microscopic
operations (rotation positioning of an egg cell in a pipette tip, movement of a pipette and aspiration
fixation) required for an operation can be carried out by using only this mechanism without some
special additional actuators. The rotational speed of egg cell is 33 [degree/s] and rotational resolution
is about 10 [degree] from the experimental result as show in Fig.5 (b).