## 4 Discussion  
The proposed device design is based on a line tendon actuation style. This method of actuation was chosen due to the small size and light weight of the tendon. It is different than linkage-based devices, which, although more precise, occupy more space [39]. Despite the device being designed like a body-powered partial hand prosthetic [40], it also has motorized actuation like an externally powered prosthetic [41]. This makes it a hybrid actuated prosthetic with low complexity of control so as to lead to ease of use and reduce prosthetic abandonment, which are historically interlinked [42]. The design describes a device for patients that (a) still have a functional wrist but (b) do not have remaining fingers [43]. The partial hand prosthetic device proposed design tends to lean towards an anthropomorphic style, but this is limited due to the overall goal of being as functional as possible. In this case, the device cannot be simultaneously anthropomorphic and functional without some compromise from a human-like device, like the one in [44]. Even if robotic arms are more advanced than other types of robotic hands, they benefit from a lot of available space as compared to only hands. Furthermore, in the case of partial hand prosthetics, the actuators have even less space because the proposed device houses the residual limb of the patient in the space where arms house their control systems [45]. The functionality of robotic hands grows with the implementation of thumb abduction/adduction and flexion/extension [46]. That said, the complexity of the device grows with this implementation but will be considered in further development of the proposed device. Some improvements to the device may be carried out considering the innovations achieved in the sports prosthetics field. The energy storage and release mechanisms, which use various types of springs, can enhance performance of prosthetics using multi-material 3D printing [47]. Although this approach is promising, the complexity of the device is increased with the addition of the mechanism. Furthermore, the energy return components send the design towards a more mechanomorphic rather than anthropomorphic design. Further development of manufacturing technology for fabrication of tactile sensors may lead to an advanced skin-like textile fabric enabling detection of pressure and temperature for patients that use a prosthetic device equipped with finger sensors [48] and embedded customized 3D-printed sEMG sensors [49]. Moreover, the evolution of conductive ABS- and PLA-based carbon composite parts with electrical conductivity may also contribute to better performance parts for upper limb prosthetics [50]. Previous research has shown that designing sockets for robotic arms and legs can make the difference between acceptance and rejection of prosthetic devices. Consequently, special attention needs to be paid to this subject. The material properties play a crucial role in the design of sockets. Most problems occur with delamination at the layer level and perspiration due to closed designs. To combat this, a bio-based material can be used in the design of such devices [51]. Some efforts have been made related to extended reality for development of prosthetics design with a pioneering methodology and a gamification layer. Despite the high complexity of the system, outcomes are promising [52]. This work is a preliminary study of the design and prototyping of a novel 3D-printed transitional partial hand prosthetic. A comparison between the proposed prototype and other existing models is presented in Table 8.  
Limitations of this study include the absence of clinical trials with subjects to test the fit and function of the device in a real-world experiment. Furthermore, a kinematic analysis to improve function like in [53] may also improve the overall design. The proposed prototype was designed from start to finish in CAD. The alternative to this might have been using a scanned model of the human hand.