# 3D Printed Robotic Hand with Piezoresistive Touch Capability
## 6 Conclusions  
The attribution of somatosensory properties (touch sensation) to an upper arm prosthesis, making both the fabrication of the robotic hand and its instrumentation (mechanical and sensory) as affordable as possible, was successfully achieved. Considering the model of the prosthesis used and the patient-centered methodology, it was possible to achieve the highest quality and functionality of the robotic hand at the lowest possible cost. In addition, by mimicking the design of the human arm, it was possible to provide a system with functionality close to that of the human hand, giving the thumb a greater range of movement. In terms of aesthetics, the prosthetic fingers and palm closely mimicked the surface characteristics of the human hand, with uneven and rounded surfaces. This was made possible by the use of 3D printing, which allowed the customization of each parameter of the manufacturing phase (filling, ironing, layer weight, etc. ), producing a high-quality, low-cost prototype that could be easily instrumented and modified as needed and for which the sensory system could be easily installed and removed. The instrumentation of the mechanical system followed a simplistic approach, using simple off-the-shelf components that could be easily replaced if damaged without significantly increasing the cost. The programming of the overall mechanical system focused on refining the motor control to allow more precise hand movements and, thus, control of the force exerted by the prosthetic hand on the objects with which it interacts. By defining the piezoresistive sensor as the main sensing element, the assembly of the sensing glove and its application to the prosthetic hand were straightforward. As the _Arduino_ has only one ADC converter, the programming followed a select-sensor approach, making it possible to locate and measure the interactions between the sensing glove and the specific object at a given moment or continuously, millisecond by millisecond. As with the mechanical system, in the event of malfunction or damage, any part of the sensing glove can be easily replaced at a low cost to the user. The overall test results provided the expected results and predictions, allowing the design and construction of an advanced and cost-effective prosthetic system capable of detecting touch and measuring force which can be designed and customized for each user without increasing the overall cost and allows easy replacement of any part in the event of damage or excessive use. The promising results of this research make this approach an effective tool for the production of customizable prosthetic systems with the possibility of interaction in both directions: patient-prosthesis and prosthesis-patient. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline
**Sensor** & **Analog Reading** & **Voltage (mv)** & **FSR Resistance (\(\Omega\))** & **Conductance (S)** & **Force (N)** \\ \hline A(1) & 200 & 977 & 41,177 & 24 & 0 \\ A(2) & 787 & 3846 & 3000 & 333 & 4 \\ A(3) & 488 & 2385 & 10,964 & 91 & 1 \\ A(4) & 684 & 3362 & 4872 & 205 & 2 \\ \hline A(5) & 0 & 0 & 0 & 0 & NP\({}^{\,*}\) \\ A(6) & 0 & 0 & 0 & 0 & NP\({}^{\,*}\) \\ A(7) & 3 & 14 & 3,561,428 & 0 & 0 \\ A(8) & 0 & 0 & 0 & NP\({}^{\,*}\) \\ \hline A(9) & 157 & 767 & 55,189 & 18 & 0 \\ A(10) & 0 & 0 & 0 & 0 & NP\({}^{\,*}\) \\ A(11) & 0 & 0 & 0 & 0 & NP\({}^{\,*}\) \\ A(12) & 82 & 400 & 115,000 & 8 & 0 \\ \hline A(13) & 96 & 469 & 96,609 & 10 & 0 \\ A(14) & 0 & 0 & 0 & 0 & NP\({}^{\,*}\) \\ A(15) & 7 & 34 & 1,460,588 & 0 & 0 \\ A(16) & 0 & 0 & 0 & 0 & 0 \\ \hline \hline \end{tabular} \({}^{\star}\)NP—No pressure.  
\end{table} 
Table 6: Results obtained by the measurements taken from the 5 th test. **Author Contributions:** Conceptualization, G.F., J.N.-P. and A.P.S. ; methodology, G.F., J.N.-P. and A.P.S. ; software, G.F.; validation, G.F., J.N.-P. and A.P.S. ; formal analysis, J.N.-P. and A.P.S. ; investigation, G.F.; writing--original draft preparation, G.F. and J.N.-P.; writing--review and editing, J.N.-P. and A.P.S. ; project administration, A.P.S.