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Fig. 6. The speed of microrobots in different actuation
systems
lower-viscosity fluid, the controller performed better. In com- in the horizontal direction and 3.64 mm/s for five spiral num-
parison to the PID controller, the TDE controller responded
faster and less clatter [77]. Using an infrared light-emitting
diode, a wireless remote controller transmits signals. An op-
tical receiver module positioned on the microrobot’s body
receives the transmission signals [78]. With an optimized
control scheme with optical coherence tomography imaging
feedback, the optimal PID output was designed [79].
For microscale applications, the microrobot’s speed is
essential. For evaluating the performance of the microrobot,
maximum speeds can be examined [80]. In this review, the
microrobots’ maximum speeds were obtained to analyze their
performance. The speed of a microrobot has different values
in each system depending on many factors, such as actuation
method, number of coils, size, and shape of the microrobot,
and application environment, Fig. 6 shows that the shape
of coils has a significant association with the microrobots’
maximum speed at the same number of coils but different in
shape will get the different value of the speed.
IV. DESIGN SCHEMES OF MICROROBOT
The reliable, safe, and accurate application of microrobots
requires control and communication with the operator. More-
over, a microrobot’s design must be compatible with the spe-
cific medical application scenario [81, 82]. Biocompatibility
and biodegradability materials should be addressed in the mi-
crorobot for clinical usage, and its efficacy must be evaluated of microrobots. According to related work, magnetism is a
using an in vivo model [83, 84]. Microrobot modeling and
design depend on the operational conditions and tasks that are
required to be executed [7]. On the other hand, the hexahe-
dral microrobot had a greater surface area and volume than
the cylindrical microrobot. It moves more slowly due to a
greater resistive force [85]. The magnetic flux density and the fected by several factors, including the size of the microrobot
number of spirals in the microrobot affect its movement. Two
Bresam & Al-Mumen
different kinds of magnetic spiral microrobots were examined,
with different numbers of spirals (5 and 10, respectively). The
maximum speed at 15 Hz is 11.8 mm/s for ten spiral numbers
bers in the vertical direction [86]. The results of experiments
indicate that speed rises when magnetic flux density and spi-
ral number increase. In particular, at high rotation speeds,
the performance of the microrobot with ten spiral numbers is
better than the microrobot with five spiral numbers.
As a result, the cylindrical microrobot design is advan-
tageous for reducing the resistance to manipulation. There
are various shapes for the design of the microrobot such as
cylindrical [29], helical [13], and rocket [56]. In general,
Helmholtz coils that are circular or square are employed to
create a uniform magnetic field. Therefore, it is essential
to examine the method the Helmholtz coil’s shape performs.
Designing two different types of Helmholtz coils, square and
circular, both with the same electric current parameters. The
magnetic flux density gradually increases from 0.4 to 1 m [87].
As a result, the circular Helmholtz coil produces a greater
magnetic flux density than the square Helmholtz coil. The
designing and controlling of the microrobot must be taken
into account depending on the task they will be accomplishing
and the type of operating environment. However, the speed of
the microrobot is highly dependent on its shape and size.
V. CONCLUSION
In this paper, we have reviewed summaries on the biomedical
application, the actuation process, design, and motion control
promising method for steering magnetic microparticles from
their application location to cancer because external long-
range magnetic fields could reach cancer everywhere in the
body. On the other hand, recent and previous experimental
results indicated that the performance of microrobots is af-
and its location in the body, as well as the composition and
architecture of the tissue or fluid in which the microrobots
operate. The researchers established that the magnetically
actuated microrobot was able to achieve simple forward and
backward movements. Meanwhile, by adjusting the magnetic
field’s strength and direction. The structure of the coil, the
material properties, and the design parameters of the actual
coils are further optimized will cause the microrobot’s speed
of movement has been modified.
The development of modular tracking and controlling sys-
tems for microrobots in real-time is one of the challenges
that must be overcome. By comparison, the TDE controller
performed better than the PID controller. The TDE controller
responded faster and more accurately. In addition, the micro-
robot, which has a greater surface area and volume, moves