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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.
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