Biomedical Engineering Reference
In-Depth Information
(a)
(d)
Heaters B
Blood vessel
(b)
(e)
Heaters A
(c)
Strain gauge
FIGURE 9.62
Concept of actuation: (a) setting; (b) hold actuation; (c) pulse monitoring; (d) release actuation; and (e) pull out.
(From Mineta et al.,
Sens. Actuators A Phys.
, 143, 14-19, 2008, with permission from Elsevier.)
tion is shown in Figure 9.63. The arms and a base part are made from a TiNiCu SMA film
which is flash-evaporated on a flat substrate.
Two pairs of microheater circuit pattern of platinum film are formed on the root (heater A)
and the halfway point (heater B) on the outer arm. Platinum strain gauge circuits are also
formed on the cantilever in a same platinum film layer. Minimum line and space width
of the strain gauge were 50 and 50
μ
m, respectively. The outer arm is bent at the root and
the halfway point before setting. A blood vessel can be caught between the outer arm and
inner cantilever, when heater A is turned on so that the outer arm deforms and closes. The
strain gauges on the cantilever transduce the periodical diameter variation of the blood
vessel by arterial pulsation into a voltage waveform. The measured waveform is displayed
on a monitor through an external computer system. After use for pulsation monitoring,
(mm)
3.4
8.7
Outer arm
2.05
Canti-
lever
(Resistance thermometer)
(Bending
point)
(Root)
Reference
resistor
Heater-B
Heater-A
Strain
gauge
Outer
arm
(Blood
vessel)
Flat printed circuit (FPC)
Inner arm (Cantilever)
FIGURE 9.63
Structure of micropulsation sensor. (From Mineta et al.,
Sens. Actuators A Phys.
, 143, 14-19, 2008, with permission
from Elsevier.)
