## 4 Discussion  
### Advantages  
As discussed earlier, unlike the previously reported designs, this design employs a PVDF-based sensing element, which is not only smaller in size, but the whisker itself acts as the sensor. Hence, this makes it much more practical and ergonomic in use. Since the whisker can vibrate like a real biological whisker, we do not need a mechanism to move the whole unit in which this sensor is mounted, which is a major advantage over some of the previously reported designs [5; 22; 23; 24; 25].  
Figure 10: Box plot of voltage amplitude to the excitation frequency of the fabricated sensor. Minimum standard deviation in terms of voltage amplitude of sensor output is 0.0012 V at 200 Hz. Due to the coin-based stimulator, the sensor does not perform as well at lower frequency.  
Figure 9: Box plot of measured frequency versus excitation frequency of the fabricated sensor. The minimum standard deviation in sensor output, in terms of frequency is 0.649 Hz at 200 Hz.  
Previous studies suggest that as rodents whisk, their whiskers move synchronously across the surfaces [44]. With this particular design, since we have a single stimulation unit, a number of whiskers can be stimulated synchronically from the same vibrator. This overcomes issues of developing sophisticated algorithms to synchronise the response of individual whiskers.  
In rodents, the length of the shafts change symmetrically across different arcs on the rodent snout [45]. Hence, the longer shafts resonate at lower frequencies while smaller shafts resonate at higher frequencies [46]. The advantage of our analytical, transfer function and FEM 3D model is that the length of individual shafts can be determined based on materials available and desired frequency.  
Due to the use of PVDF, the sensor has a high frequency bandwidth--a natural characteristic of PVDF, unlike resistive, capacitive or load cell-based designs [31].  
Normally, PVDF-based sensors suffer from inherent drift in their output [31; 47; 48]. The sinusoidal output of the sensor overcomes this limitation, as we can subtract minimum amplitude peak value from maximum amplitude peak value to remove the drift.  
When a load is applied to the end of a beam, the beam is deflected in a curvature, assuming the beam undergoes small deflections within its linearly elastic region, and has uniform cross-section. The mesh size affects the deflection curvature. A small difference in mathematical and simulation results suggests that the material properties and mesh size in the simulation model affect the frequency response of the beam. The analytical and simulation results can be further fine-tuned by variation of mesh size, material properties, temperature and bonding between cantilever and base.  
Beyond tactile sensing, this work can be useful in a number of other areas. Applications such as determination of adhesion of cantilever beams [49], determination of characteristics of beam-shaped micro-oscillators [50], monitoring of an atomic force microscope cantilever with a compact disk pickup [51], detection of biological particles in real time possess [52], various cantilever transducers for chemical and biological sensors [53], study of flow fields created by a vibrating cantilever plates [54; 55], etc. rely on the study of cantilever shapes. The ability to know resonant and anti-resonant frequencies, as discussed in this paper, might prove useful.