Page 103 - Flexible Robotics in Medicine

88 Chapter 4

4.3.1 Biopsy sample volume

It is important to know the maximum volume of biopsy samples the forceps will be able to
grab. This will affect the operator’s judgment on whether this prototype is suitable for the
job. The biopsy samples were obtained by grabbing marshmallows. The volume of the
biopsy sample was estimated to be that of a cuboid because sphere approximations were
found to be poor estimates. Biopsy sample volume will determine the efficacy of the
prototype, as biopsy sample volumes that are too small will mean that operators would need
to perform the biopsy more than once in order to get sufficient tissue (Fig. 4.8).

4.3.2 Stability measurement

The stability of the prototype was quantified based on how much force the prototype was
able to handle without moving (Fig. 4.9). As such, paperclips were hung onto the distal tip
until the prototype started to bend under the weight of the paperclip.

4.3.3 Bending angle measurement

Bending angles were measured to determine the limits in which the distal tip can bend
(Fig. 4.10). There was a slight discrepancy between the calculated value and the actual
measured value because the calculated value did not consider the presence of cables and the
tension of the inputs provided by the control cables. This procedure quantified the total
bending angle and, to some extent, the accuracy of the prototype. Note that this experiment
dealt with the upscaled version of the prototype. Miniaturized versions are likely to have
significant differences.

4.3.4 Actuation time

The speed of motors was calibrated to give a balance of speed (of actuation) and accuracy.
If the motors move too fast, the operator may not have enough reaction time to control the

Figure 4.8
The measurement of obtained biopsy samples.