## 3 Results and Discussion
### Comparison with Commercial Prostheses and Research Developments  
Table 2 presents a summary of the specifications of the developed Carbon HK VO hook in comparison with the Hosmer 5X hook, which is the most commonly used prosthesis in developing countries, and the Ottobock Michelangelo, as an example of a high-tech myoelectric prosthesis. It can be seen that the carbon fiber used as the main material reduces the weight of the device considerably in comparison to the Ottobock, while the continuous regulation system allows for a higher functionality compared to the Hosmer 5X hook.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Requirement** & **(This Study) Carbon HK VO Hook** & **Hosmer Model 5X Hook** & **Ottobock Michelangelo** \\  & **Hook** & & \\ \hline Mass & 100 g & 213 g [13] & \textgreater{}600 g [9] \\ Degree of freedom & 1 & 1 & 2 \\ Gripping force regulation & Continuous regulation system & Discrete regulation system & Continuous regulation system \\ Activation force & Body-powered & Body-powered & Electric/Myoelectric \\ Main material & Carbon fiber & Stainless steel & NA \\ Robustness (works submerged in water) & Yes & Yes & No \\ Ease of installation & Easy & Easy & Hard \\ Affordability (Commercial price) & \textless{}500 USD & \textless{}500 USD & \textgreater{}50 000 USD \\ \hline \hline \end{tabular}
\end{table}
Table 2: Specifications of the Carbon HK VO Hook compared to current available upper limbs prosthetic.  
Force regulation is of great relevance for a prosthesis, since not all objects must be held with the same force. Similar developments, such as the Hosmer 5X, presents the possibility of adding bands to vary force [14]; however, that results in a complex maneuver and additional efforts when constantly adding bands. In the same regard, the Ottobock Model 10A60 Hook only has two levels of force [14]. Yet, users have a total control of the grip force on developments with VC mechanism, such as \"GRIP 5\"; however, discomfort is frequently reported. Contrarily, the continuous force regulation system presented in this study proposes the use of a simple mechanism with no additional components that could increase the total prosthesis's weight.  
In order to develop a feasible prosthesis for users, its manufacturing process must be considered. In this regard, a lot of research has been focused on 3D-printed prostheses, presenting them as \"affordable alternatives\"; however, the additive manufacturing is hard to scale for a larger production. In addition, most of these prostheses are manufactured by FDM (fused deposition modeling) technology, which generates pieces with porous surfaces. The presence of pores favors the accumulation of dirt, viruses, and bacteria, which is not favorable for a hand prosthesis, since cleanliness is of great importance. In contrast, the Carbon HK VO hook presented in this study allows for a manufacturing process that is easily scalable with hydrophobic and antibacterial properties.  
As in our study, the \"Delft Cylinder Hand\" [23] was also developed considering the design requirements of users, achieving a mass reduction with a simple design manufactured in aluminum. Despite having different terminal devices, both body-powered developments (\"Delft Cylinder Hand\" and \"Carbon HK\") achieved significant improvements concerning comfortability by following different strategies.  
In summary, a lightweight, robust, and functional device at an affordable cost has been developed as an appropriate medical device considering the needs and context of the majority of users.