Biomedical Engineering Reference
In-Depth Information
2 mm
2.12
Thickness=180 micrometers
2.25
(a)
(b)
Figure 4.22
(a) The actual cross section after anisotropic etching, (b) the equivalent rectangular
cross section used in closed form formula and finite element analysis. In both cases the thickness
was 180
μ
m
films associated with the second or third beam was observed. In other words, simulation
results showed no cross talk between sensor units due to mechanical load transferring.
In the next simulation, a soft material was considered on top of the first beam and a
distributed load was applied to the object. The Young's modulus of the target object was
then varied between 10 kPa and 1 MPa. Figure 4.23 shows the modeling geometry and
Table 4.1 summarizes the obtained results.
Table 4.1 shows that the maximum deflection varies from 1 to 20.4 μm for a range of
Young's moduli between 10 kPa and 1 MPa. The maximum
σ
x
and the corresponding
PVDF output are also shown in this table.
The relationship between the Young's modulus of soft objects and the PVDF output is
shown in Figure 4.24.
4.2.3 Sensor Fabrication
In order to fabricate the sensor, several process steps were used. First, the top and bottom
silicon parts had to be micromachined. The PVDF films were cut into the designed
Figure 4.23
The finite element model of the sensor when a soft material is placed on the first
tooth and a uniform compressive load is applied (See Plate 5)
