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Multi-Layer Deformable Design for Prosthetic Hands

Figure 7. Graphical representation of the index finger tissue deformation under pressure.
on the results, the proposed robotic hand can pick up
a water bottle of 450 g, which is larger than that of the
baseline significantly.
Task D: Fingertip pinch screws. This task uses
three types of screws, that is, M1, M2, and M3 in this
task. We conducted this task to validate the two-finger
caging model of our robotic hand. It is noted that our
hand can pinch three types of screws (one for each type)
simultaneously.
Task E: Press and pick up a M1 screw cap with the
fingertip. The task demonstrates the single finger caging
model of the proposed robotic hand. Only the proposed
robotic hand and the real human hand can complete this
task.
Figure 8 demonstrates several examples of the
proposed robotic hand in grasping special objects.
Besides, we report 3 contact-related metrics in Table 2,
that is, the maximum deformation length, the horizontal
sliding resistance, and the resistance of rotating the
contact tangent plane. From these results, it can conclude
that the proposed robotic hand does obtain the superior
deformability compared with previous methods.
Furthermore, the comparison between ours and ours
without the tissue layer validates that the tissue layer is
the key factor in our performance gains.
3.4. Ablation study on finger design
Last but not least, we proposed to analyze the functionality
of the underactuated system. First, we have compared
five different solutions for joint connection in Table 3. Figure 8. Demonstration of our robotic hand in pinching special
objects. The proposed design can pinch (through side-pinch or
The most significant advantage of using rubber bands fingertip-pinch) various objects stably.
as ligaments is that they provide the restoring force after
flexion (about 3.1 N for a 4 mm rubber band), so that
the proposed actuation system can remove the cables for with different attaching knots and displacements of
completing extension. strings. Therefore, as demonstrated in Figure 9, we
Next, we recorded the trajectories of fingertips implemented five different designs of the system, and
during flexion to investigate whether they can fit the included the design from InMoov hand as the baseline
trajectory of the human finger. Our system can be for comparison. Configurations of these designs are
implemented with different configurations, for example, summarized in Table 4.

18 International Journal of Bioprinting (2022)–Volume 8, Issue 1