Biomedical Engineering Reference
In-Depth Information
FIGURE 4.56
Linear pH meter using a graduated cylinder with calibrated PAN fiber bundle.
Another type of pH meter designed was a linear gauge type. This device was
simpler in construction but required a larger container, such as a graduated glass
cylinder that was carefully calibrated with various pH solutions to mark points along
the cylinder indicating a range of pH of 2-12 (see fig. 4.56). For this type, a fiber
bundle of the PAN attached from one end to a weight imposing a constant tension
across the muscle was used. The muscle was suspended in pure water free to expand
from one end and fixed from the top. When low pH (acidic) was applied, the muscle
contracted and pulled the weight upward. A needle at the tip of the weight indicated
the change in pH.
4.4.1
S
KELETAL
M
USCLES
M
ADE
WITH
F
IBROUS
PAN A
RTIFICIAL
M
USCLES
Figures 4.57, 4.58, and 4.59 depict the skeletal muscles of the forearm. Figure 4.58
represents an apparatus designed to test a biceps artificial muscle made from PAN
fibers encapsulated in latex membrane. A multichannel peristaltic pump was used
to direct fluid from each of the acid, base, and deionized water reservoirs into and
out of the muscle assembly. The microcontroller board incorporated a Motorola 6811
series processor to control opening and closing of appropriate solenoid valves allow-
ing pH solutions to flow when a command was executed.
A PC interface was used to trigger the analog signals causing the valve sequence
of closing and opening based on an up or down command requirement of the
forearm. The fibers were accordingly contracted or relaxed to simulate the biological
muscle contraction-relaxation. This system was essentially a closed-loop circula-
tory system with each fluid entering and leaving the muscle fiber separately. The
deionized water was used as a rinse cycle between acid or base wash for contraction
and relaxation, respectively. Platform-type spring loaded actuators were also
designed and built for a series of experiments (fig 4.60) including an electroactive
PAN muscle experiment.
