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Bioinspired and Biomimetic Micro-Robotics for Therapeutic Applications 479
near-infrared fluorescent dye molecules (NIR-797) then released into “the
intraperitoneal cavity of a 4-week-old BALB/c mouse”; an organism bred in
laboratory conditions and commercially available for research purposes. The
fluorescent signal of the swarm, which has the intensity that can penetrate
the tissue of certain thickness, is collected by a fluorescence imaging system.
Location and velocity of the swarm were calculated by the displacement of
its common center of mass. This particular example is important because the
study combines a swarm of cybernetic micro-swimmers with visual
servoing-based data acquisition in an in vivo demonstration.
Once the robot perceives and knows about its environment, special tasks
could be achieved. A recent example is object manipulation. Zhang et al.
(2009) demonstrated the magnetically actuated rigid helical swimmers, only
around 50 μm in length, with a magnetic patch on one end are suitable to
push polystyrene microspheres with a radius of 6 μm. Authors demonstrated
the approach trajectory and manipulation route to be a controlled with the
help of an open-loop control scheme.
A very recent application example is removing blood clots by abrasive
effect of the rotating helical tail of a magnetic robot (Khalil et al., 2017a),
as illustrated in Fig. 6. Authors developed an in vitro scenario where the
tip of the rigid helical tail will remove material by rubbing on the surface
of an actual blood clot obtained from a patient and placed inside a transparent
channel of cylindrical cross section. They were able to demonstrate that the
material removal process was advantageous to pure chemical lysis and pre-
dictable by means of robotic modeling, although visually not easy to access
for the naked eye which, again, represents the problem of accurate visual
investigation during the process.
Fig. 6 Depiction of an autonomous micro-swimmer with rotating rigid-helical
tail removing a blood clot, from a zoomed-in section of a blood vessel, by machining
the surface (Khalil et al., 2017a). The fretting depends on material properties of the
blood clot and the energy transfer to the abrasive contact by the tip of the rigid heli-
cal tail.