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Fig. 1. Block diagram of microrobot system
minimally intrusive tasks due to their ability to enter remote
and narrow areas, which could move freely through the blood
vessels to their desired location [11, 12]. To be most effec-
tive, drug-loaded microrobots must discharge their load in
a controlled and timely manner [8]. As a consequence, the
limited drug release rate over an extended period prevents
the development of microrobot systems for active medication
delivery and controlled drug release [13].
Microrobots could be able to accurately access difficult-
to-reach or inaccessible parts of the human body [14, 15]. The
small force needed for actuation is one of the major features of
microscale robotics. Moreover, the ability to use non-contact
actuation approaches [16, 17]. These features, represented
in the wireless actuation of the microrobots, can be used in
different biomedical applications such as targeted therapy,
telemetry, hyperthermia, radioactive treatment, scaffolding,
stenting, sensing, and marking [18]. Navigating the entire
body, including minor arteries, is challenging. Thus, wire-
less actuation for guided microrobots is a game-changer in
intravascular therapies [19]. The most fundamental compo-
nent of research on microrobots is their scale properties. The
study of various aspects of microrobots is based on a thor-
ough investigation of the fundamental theory. Researchers
are usually interested in microrobots because of their many
uses and potential for microscale exploration. Recently, the
research on microrobots has advanced significantly. Fig. 1
shows the microrobot system. All of the above-mentioned
features will allow microrobots to make choices in technology
for in-vitro tasks involving single-cell placement, cell sorting, is assisted by an external magnetic field [27]. The majority
cell surgery, and biomedical research.
In this article, we will review the related studies on micro- microrobot [28, 29]. Due to the way magnetism functions,
robots. First, a summary of the applications of the microrobots.
Second, the main actuation methods of microrobots. Then,
control the microrobot’s motion and develop strategies. We
have divided the various driving methods into four categories:
magnetic, optical, acoustic, and hybrid actuation. Finally, the
paper is summarized, and the future microrobot characteristics
and performance requirements are conceived.
II. ACTUATION METHOD OF A MICROROBOT
The actuation of microrobots has paved the way for many dif-
ferent uses in the last decade, including microfluidics, targeted
Bresam & Al-Mumen
Fig. 2. Mechanisms of actuation for microrobots
therapy, drug administration, and microsurgery [20]. Most
microrobots are propelled using external electric, magnetic, or
light fields, making microrobots out of stimuli-responsive ma-
terials that alter their shape in response to changes in environ-
mental conditions [21]. This paper focused on the discussion
of external field actuation. The development of microrobots
capable of effective propulsion has taken a lot of time and ef-
fort. These microrobots may perform self-propelled motions
using a variety of propulsion mechanisms [22]. There are
different kinds of actuation sources, including chemical, light,
acoustic field, and hybrid actuation [23]. The mechanisms of
actuation for microrobots are summarized in Fig. 2.
Usually, the actuation of microrobots requires the con-
version of input energy into mechanical energy. Depending
on the type of actuation, it can be classified as physical or
chemical actuation. In addition, hybrid actuation provides
several actuation options. Hybrid externally applied actuation
and self-propulsion are among the modes available [24].
A. Magnetic Actuation
Magnetism has attracted a lot of attention in recent years
for actuating various types of soft robotics, whether using a
system of moveable permanent magnets or electromagnetic
coils [25]. Microrobots can be driven by magnetic fields
in three different ways: rotating, oscillating, and gradient
fields [26]. In general, a wireless microrobot’s locomotion
of magnetic microrobots are simple equipment that is driven
by external magnetic fields that apply torque and force to the
magnetic objects tend to move toward areas with strong mag-
netic fields by moving through the gradient direction of those
fields [30]. Applying a magnetic torque, as illustrated in (1),
to a magnetized micro/nano object is the fundamental concept
of magnetic actuation. An object that is magnetized in a mag-