Biomedical Engineering Reference
In-Depth Information
Antagonist contractile
ESP muscles
(a)
(b)
FIGURE 9.31
(a) “Myster Bony,” a plastic human skeleton equipped with electrically con-
tractile muscle fabrics, riding an exercycle. (b) Schematic of an astronaut in a pressurized
space suit equipped with joint power augmentation artificial muscles.
As MEMS technology develops, the most obvious problem is how to build small
devices. It is equally important to develop techniques to manipulate and assemble the
MEMS components into systems. Historically, grasping and manipulating objects of
any size has been a challenge. As components become smaller, the problem becomes
even more pronounced. For the most part, there are no suitable actuators for the range
of around 10-100
m. Electroceramic materials (piezoelectric and electrostrictive)
offer effective, compact actuation materials to replace electromagnetic motors. A wide
variety of electroactive ceramic (EAC) materials are incorporated into motors, trans-
lators and manipulators, and devices such as ultrasonic motors and inchworms.
In contrast to electroceramics, IPMNCs are emerging as new actuation materials
with displacement capabilities that cannot be matched by the striction-limited and
rigid ceramics. Table 9.1 shows a comparison between the capability of IPMNC
materials and electroceramics and shape memory alloys (SMAs). As shown in the
table, IPMNC materials are lighter and their potential striction capability can be as
high as two orders of magnitude more than that of EAC materials. Further, their
response time is significantly higher than that of SMAs. The current study is directed
towards taking advantage of these polymers' resilience and the ability to engineer their
properties to meet robotic microarticulation and MEMS requirements. The mass pro-
duceability of polymers and the fact that electroactive polymer materials do not require
poling (in contrast to piezoelectric materials) help to reduce cost. IPMNC materials
can be easily formed in any desired shape and can be used to build MEMS-type
mechanisms (actuators and sensors). They can be designed to emulate the operation
of biological muscles and they have unique characteristics of low density as well as
high toughness, large actuation strain constant, and inherent vibration damping.
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