Various upper-limb prostheses have been designed for 3D printing but only a few of them are based on bio-inspired design principles and many anatomical details are not typically incorporated even though 3D printing offers advantages that facilitate the application of such design principles. We therefore aimed to apply a bio-inspired approach to the design and fabrication of articulated fingers for a new type of 3D printed hand prosthesis that is body-powered and complies with basic user requirements. We first studied the biological structure of human fingers and their movement control mechanisms in order to devise the transmission and actuation system. A number of working principles were established and various simplifications were made to fabricate the hand prosthesis using a fused deposition modelling (FDM) 3D printer with dual material extrusion. We then evaluated the mechanical performance of the prosthetic device by measuring its ability to exert pinch forces and the energy dissipated during each operational cycle. We fabricated our prototypes using three polymeric materials including PLA, TPU, and Nylon. The total weight of the prosthesis was 92 g with a total material cost of 12 US dollars. The energy dissipated during each cycle was 0.380 Nm with a pinch force of ≈16 N corresponding to an input force of 100 N. The hand is actuated by a conventional pulling cable used in BP prostheses. It is connected to a shoulder strap at one end and to the coupling of the whiffle tree mechanism at the other end. The whiffle tree mechanism distributes the force to the four tendons, which bend all fingers simultaneously when pulled. The design described in this manuscript demonstrates several bio-inspired design features and is capable of performing different grasping patterns due to the adaptive grasping provided by the articulated fingers. The pinch force obtained is superior to other fully 3D printed body-powered hand prostheses, but still below that of conventional body powered hand prostheses. We present a 3D printed bio-inspired prosthetic hand that is body-powered and includes all of the following characteristics: adaptive grasping, articulated fingers, and minimized post-printing assembly. Additionally, the low cost and low weight make this prosthetic hand a worthy option mainly in locations where state-of-the-art prosthetic workshops are absent.

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The World Health Organization (WHO) estimates that there are ≈40 million amputees in developing countries and that only ≈5% of them have access to prosthetic devices. In low income countries, there are only a few big cities capable of providing reasonable healthcare services and transportation from rural areas is usually complicated, expensive, and may take several days. In most of the cases, there is a general lack of trained personnel and materials making, prosthetic workshops limited, difficult to reach, or even non-existent. 3D printing is a manufacturing method that enables fabrication of structures with unusual geometries without the need for any particular manual skill, elaborate tooling, or labour-intensive procedures. Many 3D printing techniques have become easily accessible and have opened a window for creating low-cost functional parts in a simpler way than conventional procedures. The main purpose of the research described in this thesis is to increase the accessibility of prosthetic hands among people living in low-income settings. To achieve this, the goal of the research is twofold: one, to design a transradial hand prosthesis that can be 3D printed with very few and simple post assembly steps and suffice basic user requirements; and two, to develop a 3D modelling process based on 2D photographs for the design of transradial (below the elbow) sockets that can be 3D printed. This thesis began exploring possibilities of non-assembly fabrication using 3D printing techniques. Chapter 2 contains a literature review describing a number of mechanisms fabricated in a non-assembly manner by 3D printing. Chapter 3 reviews the results of fatigue testing in 3D printed polymers in order to determine the 3D printing material and 3D printing settings that ensure best fatigue performance. Chapter 4 continues with a number of design considerations that were formulated for the fabrication of non-assembly mechanisms with 3D printing. We followed these guidelines to design a functional multi-articulated hand prosthesis that was then manufactured by material extrusion 3D printing. This design procedure concluded in a hand prosthesis concept that reduces manufacturing requirements to a single 3D printer and its building material. Chapter 5 contains a functional evaluation of the 3D printed prosthetic hand including mechanical and user testing. To further explore the capabilities of non-assembly 3D printing, in Chapter 6 we initiated a new design process aimed at producing articulated fingers (two degrees of freedom per finger) under this manufacturing framework. For this process, we adopted a bio-inspired design approach by studying the anatomical structures of the human hand that can be translated into components of prosthetic hands and have the potential of offering improved functionality. This bio-inspired designed prosthetic hand achieved superior pinch force as compared to our previous non-assembly BP prosthetic hand. Chapter 7 describes the method employed to obtain and process the 3D models of a stump. The method is based on photos from a smartphone and a Statistical Shape Model (SSM). The algorithm translates the photos into a 3D digital shape and then introduces the digital outcome into the process of automatic anthropometry. The outcome was later used for determining the parameters of a parametric design of a transradial socket that can be 3D printed and fitted onto the user’s residual limb. The error resulting from the automatic measurement was still too large for an acceptable socket design. The thesis ends in Chapter 8 with a pilot study of our new bio-inspired 3D printed hand design in Colombia. We employed a manual measuring method using visual cues of the stump and a measuring tape to obtain the dimensions required for the design of the socket. Through the manual measuring method and parametric socket and shaft designs, the components of the prosthetic device were produced easily and locally on a material extrusion 3D printer. The field testing in Colombia concluded that our design and manufacturing processes based on 3D printing are fast and easy to implement and opens a gateway for the production of prosthetic devices in developing countries. @en

In developing countries, the access of amputees to prosthetic devices is very limited. In a way to increase accessibility of prosthetic hands, we have recently developed a new approach for the design and 3D printing of non-assembly active hand prostheses using inexpensive 3D printers working on the basis of material extrusion technology. This article describes the design of our novel 3D-printed hand prosthesis and also shows the mechanical and functional evaluation in view of its future use in developing countries. We have fabricated a hand prosthesis using 3D printing technology and a non-assembly design approach that reaches certain level of functionality. The mechanical resistance of critical parts, the mechanical performance, and the functionality of a non-assembly 3D-printed hand prosthesis were assessed. The mechanical configuration used in the hand prosthesis is able to withstand typical actuation forces delivered by prosthetic users. Moreover, the activation forces and the energy required for a closing cycle are considerably lower as compared to other body-powered prostheses. The non-assembly design achieved a comparable level of functionality with respect to other body-powered alternatives. We consider this prosthetic hand a valuable option for people with arm defects in developing countries.@en

As additive manufacturing of polymeric materials is becoming more prevalent throughout industry and research communities, it is important to ensure that 3D printed parts are able to withstand mechanical and environmental stresses that occur when in use, including the sub-critical cyclic loads that could result in fatigue crack propagation and material failure. There has so far been only limited research on the fatigue behavior of 3D printed polymers to determine which printing or material parameters result in the most favorable fatigue behavior. To better understand the effects of the printing technique, printing materials, and printing parameters on the fatigue behavior of 3D printed materials, we present here an overview of the data currently available in the literature including fatigue testing protocols and a quantitative analysis of the available fatigue data per type of the AM technology. The results of our literature review clearly show that, due to the synergism between printing parameters and the properties of the printed material, it is challenging to determine the best combination of variables for fatigue resistance. There is therefore a need for more experimental and computational fatigue studies to understand how the above-mentioned material and printing parameters affect the fatigue behavior.

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Lymphedema is a chronic and progressive condition derived from impaired lymphatic system function. Lymphedema is incurable, progressive, disfiguring, disabling and has adverse psychosocial effects. Upper extremity lymphedema is mainly the consequence of breast cancer surgery. Several methods to diagnose lymphedema exist; however, these diagnoses are performed once the disease is already close to an advanced, irreversible stage. There is a need to monitor patients at risk with an efficient device. To solve this unmet need, we propose a portable home-monitoring device for early diagnosis of lymphedema. This paper explores all the aspects of the development of a new medical device, such as the assessment of the clinical need and the state of the art, the specifications for the solution, the definition of the broad outlines of the development plan and some considerations about the usability, the risk analysis, the market and the competitors.

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Fabrication of complex and multi-articulated mechanisms is often seen as a time consuming and demanding process. The development of functional multi-articulated mechanisms that could be fabricated in a single step without the need for post-manufacturing assembly is therefore very attractive. Additive manufacturing (AM) has been pointed out as a feasible solution due to its numerous advantages and high versatility in comparison to other manufacturing techniques. Nevertheless, AM techniques also present different shortcomings that limit the complexity of the mechanism for single step fabrication. Here, we review the applications of AM techniques in fabrication of non-assembly multi-articulated mechanisms and highlight the involved challenges, thereby providing a perspective regarding the advantages and limitations of current AM techniques for production of complex mechanical devices. The paper starts off with basic joint elements in rigid-body and compliant configurations and proceeds with presenting an overview of multiple arrangements of joints and assemblies with embedded mechanical components. For every case of non-assembly fabrication, the limitations of the applicable AM processes are presented and further discussed. This work concludes with a discussion of the major shortcomings found in current non-assembly mechanisms fabricated by AM and recommending alternative techniques and future developments on AM.

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In developing countries, prosthetic workshops are limited, difficult to reach, or even non-existent. Especially, fabrication of active, multi-articulated, and personalized hand prosthetic devices is often seen as a time-consuming and demanding process. An active prosthetic hand made through the fused deposition modelling technology and fully assembled right after the end of the 3D printing process will increase accessibility of prosthetic devices by reducing or bypassing the current manufacturing and post-processing steps. In this study, an approach for producing active hand prosthesis that could be fabricated fully assembled by fused deposition modelling technology is developed. By presenting a successful case of non-assembly 3D printing, this article defines a list of design considerations that should be followed in order to achieve fully functional non-assembly devices. Ten design considerations for additive manufacturing of non-assembly mechanisms have been proposed and a design case has been successfully addressed resulting in a fully functional prosthetic hand. The hand prosthesis can be 3D printed with an inexpensive fused deposition modelling machine and is capable of performing different types of grasping. The activation force required to start a pinch grasp, the energy required for closing, and the overall mass are significantly lower than body-powered commercial prosthetic hands. The results suggest that this non-assembly design may be a good alternative for amputees in developing countries.

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