Page 505 - Handbook of Biomechatronics

Bioinspired and Biomimetic Micro-Robotics for Therapeutic Applications 499

the micro-swimmer is performing in. Carrying piezoelectric ceramics to
generate power, or generate propulsion for that matter, could be problem-
atic because of the immune response issues of the ceramic materials. The
entire swimmer could be coated bioactive or biodegradable materials to
minimize the risk although it is highly possible that the mechanical proper-
ties of the structure would be altered. It may be possible to use acoustic
waves to visualize the robot and to control its final position; however, sound
waves could present a disadvantage of impedance mismatch due to the com-
posite arrangement of various living tissues.
A similar problem arises with MRI due to the interference of magnetic
fields. Thus, techniques like ultrasound and MRI seem to be more suitable
for visual servoing alone, if not improved with additional application-driven
solutions. It is possible to use an onboard power source, such as nuclear
materials as long as they are not in abundance and are properly sealed, how-
ever, might be the last resort for special cases and if the gait in order to leave
the organism is planned for with absolute certainty. It is quite possible that
two or more of these methods and materials will be used to actuate, visualize,
and control the micro-swimmer while the power demand is simultaneously
addressed. Nevertheless, there is a possibility that the end-effector will sim-
ply get lost in the tissue rendered nonresponsive because of any number of
possible glitches. Thus, the design of the robot should be as optimized as can
be, and one should be able to predict the state of the micro-swimmer as
accurately as possible during an operation not to lose control completely.
It would not be too much of an exaggeration if we say this system should
be treated like a satellite sent into deep space where problems will occur
and intervention is quite tough. This leads us to the last section; modeling
the physics of the micro-swimmer robot for design optimization, gait plan-
ning, and real-time control purposes.

4 MODELING A MICRO-SWIMMER ROBOT AS AN
END-EFFECTOR
4.1 Evolution of Equation of Motion

Assume that a design optimization study will be carried out. So, what if one
wants to calculate the swimming velocity of the micro-swimmers without
resorting to demanding computational models and conducting laborious
physical experiments? In that case, one would require a fast model to obtain
the velocity vector up to a certain error limit. In that effect, RFT is the