Biomedical Engineering Reference
In-Depth Information
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Distance along the sensor (mm)
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Distance along the sensor (mm)
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Distance along the sensor (mm)
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Distance along the sensor (mm)
Figure 4.12 (a) Comparison between theoretical and experimental stress distribution for 1 N
applied force, concentrated load applied on Tooth 1. (b) Comparison between theoretical and
experimental stress distribution for 1 N applied force, concentrated load applied on Tooth 2. (c)
Comparison between theoretical and experimental stress distribution for 1 N applied force, con-
centrated load applied on Tooth 3. (d) Comparison between theoretical and experimental stress
distribution for 1 N applied force, concentrated load applied on Tooth 4
Since the silicon structure is glued to a rigid base, it can withstand a very high com-
pressive stress; however, the teeth of the sensor may be damaged due to the application
of shear stress along the sensor while handling tissues. This limitation could be reduced
by proper encapsulation of the sensor, (e.g., providing a thin layer of appropriate tissue-
compatible polymer coating). This approach could also reduce the shear force effect. One
of the major limitations of the reported sensor is the lack of DC response due to the
nature of the PVDF piezoelectric film. This limitation could, however, be overcome by
applying a step input force, and the peak value of the transient signals could be captured
to determine the instantaneous output [15]. In reality, the grasping action of a tissue is
close to either a step or a sinusoidal load (see Chapter 5).
The sensor presented here is fairly simple to fabricate and assemble. Compared to other
reported sensor arrays, this design uses only four channels, thereby reducing cross talk
problems when acquiring and processing tactile information. Due to the use of PVDF
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