Biomedical Engineering Reference
In-Depth Information
mechanical work. Electric motors, largely employed in many areas of technology, are examples
of electromechanical actuators, that is, mechanisms that transduce electrical energy into work.
Muscles, instead, are examples of biological materials acting as natural electrochemomechanical
actuators; following a neural electrical command, they transform body's chemical energy (arising
from ATP) into motion. So, a simple question may arise: Why should actuation properties be useful
for certain biomaterials? This question can have several answers. One of them is directly provided
by the latter example. In order to support or even replace injured muscular tissues, “artifi cial mus-
cles” (also known as “pesudomuscular” actuators) would be necessary. They should ideally consist
of biocompatible materials forming biomimetic actuation systems, which are capable of working
with the typical performing features of natural muscles such as in terms of effi ciency, compliance,
lightweight, size, etc. In addition to prosthetic systems, further examples of medical devices requir-
ing biomaterials with actuation properties could be mentioned as well: for instance, implantable
drug delivery systems, implantable devices for analysis of body fl uids, tools for minimally invasive
surgery (e.g., active steerable catheters), etc.
The development of such different types of systems is not trivial and, in some cases, is very
challenging. As an example, despite a large amount of efforts spent to develop prosthetic robotic
arms driven by electric motors, no real “artifi cial muscles” (from a really biomimetic point of view,
as mentioned above) are currently available. In fact, systems developed so far are at least stiff,
heavy, cumbersome, and characterized by low effi ciency. Figure 16.1 shows an example of pros-
thetic arms.
Similarly, nowadays the design of, for instance, either smart drug delivery systems, miniatur-
ized and conformable to the human body, or steerable catheters endowed with actuation properties,
enabling accurate, smoother, and safer endoscopic explorations, fi nds several challenging issues. In
particular, they arise while attempting to simply adapt to such types of systems, conventional mate-
rials, and technologies of actuation. The inadequacy of this approach puts in evidence a strong need
for new materials showing passive and active properties closer to their respective counterparts in
biological tissues. New research avenues in this direction are currently being open by the so-called
electroactive polymers (EAP), as described in the chapter.
FIGURE 16.1
Examples of prosthetic arms. (Photo courtesy of U.S. Army.)
