Wireless Active Capsule Endoscope: State-of-the-Art and Challenges - Biomechatronics in Medicine and Healthcare - page 191

Because the prospective multiple functions of the capsule endoscope are based
on the controllable motion of the capsule, it is a key point to equip the capsule with
a specific locomotion mechanism, so that the robotic capsule can be guided to any
interesting spots in the GI tract and canmove through unimportant areas in a much
faster pace than the natural peristaltic movement (Meng et al. 2004; Fireman et al.
2004). In addition, such a robotic capsule endoscope can work as a platform for
further operations such as biopsy, drug delivery, and so on.
There are two major possible approaches to the development of a locomotion
system for the capsule endoscope: the external approach and the internal ap-
proach. An internal approach implies integration of the locomotion mechanism
completely onto the capsule. The external approach is generally achieved by
magnetic field manipulation and the control system is worn by the patient or to
be put around him/her. In the following, some typical locomotion mechanisms
proposed for an active capsule endoscope will be introduced.

13.3.1 Electrical stimulation

The first locomotion mechanism for capsule endoscope was proposed by Mosse
et al. (2001). They used an acrylic ovoid-shaped endoscope with two stainless
steel electrodes mounted on the tapered section, which apply electro-stimulation
to the intestinal wall. The stimulation caused circular muscle contraction when the
devices were in contact with the intestinal wall, resulting in forward propulsion of
the device. Fig. 13.5 shows a schematic view of the working principle. The tests in
the small intestine and esophagus of an anaesthetized pig produced encouraging
results: the ovoid advanced up and down in the esophagus at 6 mm / s ;andmoved
in the small intestine at up to 4.5 mm / s with the ability to negotiate tight curves.
PSwain et al. (2002) reportedmore investigations on the device. The ovoid was
equipped with bipolar electrodes at both the rear and the front so that it can exert a
forward or backward force. The tests in pigs showed that controlled bidirectional
movement of the device was feasible in esophagus, small intestine and colon. This

Figure 13.5 Schematic diagram of ovoid-shaped device as it moves through the intestine
via electrical stimulation of the intestinal wall. (Reproduced according to Mosse et al.

(2001).)