A low cost normally closed compliant hand prosthesis, Design and development of a 3D printed hand prosthesis prototype that is active, compliant and low cost

The aim of this thesis is describing the project prototype for a novel hand prosthesis, created in collaboration with the spanish company Ayúdame3D, that, since 2017, develops and distributes 3D printed prostheses in developing countries. Following the desire of improving the quality of life of their patients the company was looking to add to their catalog active devices, this is where the context of this thesis takes place. The project consists of the design and realization of a 3D printed prosthesis that is suitable for wrist level amputees, but could also work for higher level amputations; the main requirements are: external power source, adaptive grasping capabilities, minimal price and availability of the components all around the world. The implementation of all these features represented a big challenge, but also an important stimulus, as the continuous research for better and simpler solutions kept the project interesting and appealing from its beginning to until the very end. The first part of the thesis will be dedicated to the identification of a complete state of the art for upper limb prostheses; this will comprehend both commercially available devices and publications from researchers and amatorial makers from all around the world. With the experience and inspiration resulting from these researches the practical part of the project began with the modeling of a first prototype of hand in a virtual environment; this device was cable driven and actuated by a single motor. The most interesting part about the project surely is the decoupling mechanism that allows the independent movement of each finger; this element will also be central during the evolution of the project that will get through many versions before reaching its final design. One of the key changes made during the advancement of the activity is the switch to a normally closed configuration: first of its kind, in literature, the hand assumes a closed fist configuration while at rest; this solution allows for simpler and smaller actuation mechanism, that is needed to accomplish all the requirement imposed at the beginning of the project. The whole thought and evolution processes, as well as the techniques and software used will be described in the thesis, which comprehends also of the results of some tests performed on the final prototype. In the end some considerations about the performances of the device as well as its future implication will be presented.