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Thermo-responsive hydrogel-based circular valve 469

cycles of actuation. The SMAHV required all of the 5 seconds of the actuation phase to
reach the maximum displacement. The SMAHV returned to the initial position during the
3 seconds relaxation phase. The time-resolved displacement of the SMAHV with 150 µm
diameter SMA wire when applied with 2.5 A input current for three cycles is shown in
Fig. 20.9B. It is observed that the SMAHV reached a maximum displacement of 0.8 mm
for all three cycles of actuation. The SMAHV required all of the 5 seconds of the actuation
phase to reach the maximum displacement. The SMAHV returned to the initial position
during the 3 seconds relaxation phase.

20.4 Discussion

From the results obtained, the TRHV increases its lumen area when the temperature is
increased and decreases its lumen area when the temperature is decreased. The expansion
and contraction of the valves are highest in the TRHV fabricated using mold 4 and lowest
in mold 3. This would suggest that amongst the five valve samples, mold 4 would offer the
most considerable sterile solution input control, and mold 4 would offer the lowest sterile
solution input control in terms of range based on percentage of expansion and contraction.
The smallest lumen area was observed in the TRHV fabricated from mold 1, and the largest
lumen area was observed in the TRHV fabricated from mold 5. This suggests that
comparatively, the TRHV fabricated from mold 5 would allow the most sterile solution to
flow through, while the TRHV fabricated from mold 1 would allow the least amount of
sterile solution to flow through in the CBI process. Comparatively, while the TRHV
fabricated from mold 5 does not have the most significant expansion and contraction
percentages, it would allow for the broadest range of sterile solution input due to the

difference in magnitude between its state at 23 C and 40 C being the highest. The response

time for the TRHV was observed to be 100 seconds. In the CBI context, 100 seconds is
an improvement of the current CBI process that has the response time in the order of
minutes to hours depending on the nurse-patient rotation shifts. One TRHV is able to
possess multiple lumen areas by adjusting the temperature, which is highly translatable to
the CBI application under the guidelines (there are three levels of adjustment in relation to
observed gross hematuria levels in the discharge, suggesting the need for a minimum of
three valve lumen areas). The TRHV is not an ideal valve due to the lack of consistency
with temperature variations but compared to the manual roller clamp valves, TRHV is
considered as an improvement. However, it needs to be taken into consideration that
temperatures such as 40 C and 50 C are above the body’s homeostatic temperature. Thus a

cooling system for the sterile solution downstream of the valve may be needed to cool the
sterile solution to the temperature of the body. It must also be taken into consideration that
an external heat source and a cooling source need to be added to the current CBI system to
heat and cool the TRHV to achieve target temperatures.