Additive manufacturing (AM) opens new possibilities for innovative product designs. However, due to a lack of knowledge and restrained creativity because of design fixations, design engineers do not take advantage of AM's design freedom. Especially multi-material AM provides new opportunities for functional integration that hardly considered in ideation. To overcome barriers in the development of solution ideas and utilizing such new design potentials, new design methods and tools are needed. Therefore, in this contribution, a methodological approach for a function-oriented provision of solution principles specific to material extrusion is presented. A tool is developed to facilitate effective guidance in developing solution ideas and to foster a realistic concretization by providing a combination of opportunistic and restrictive AM knowledge. Besides general levers of AM, process-specific design opportunities support the design engineers in exploiting AM's potentials, especially those who are not familiar with Design for AM. Finally, the applicability of the methodological approach is evaluated in an academic study by means of redesigning a hand prosthesis with a grab function.

Material composition complexity offered by material extrusion additive manufacturing offers new opportunities for function-driven part design. Nevertheless, since influencing factors on the interface strength between different materials are not well understood, this complexity is only used infrequently, in part, in design thereby restraining innovation. This paper proposes a systematical approach for identification and quantification of relevant adhesion phenomena that influence interface strength. For this reason, suited test specimen, which utilize the geometric freedom offered by additive manufacturing, are developed for roll peeling tests and peeling resistance of several combinations of rigid and flexible materials is determined. The results show that material choice especially regarding polarity as well as mechanical interlocking in regards to surface roughness and design features have high influence on the interface strength of multi-material parts manufactured by material extrusion. These results are explained through the relevant adhesion mechanisms that determine the interface strength in additively manufactured parts. Finally, criteria that predominantly affect interface strength are deduced and design recommendations for creating functional parts with ill-fitting material combinations are formulated.

Direct additive manufacturing (AM) of sensors has in recent years become possible, but still remains a largely unexplored area. This work proposes a novel resistive sensor design that utilizes the geometric freedom offered by AM, especially by material extrusion, to enable a customizable and amplified response to force and deformation. This is achieved by using a multi-material design made of an elastomer and an electrically conductive polymer that enables a physical shortening of the conductive path under compressive load through a specific definition of shape. A number of different variants of this novel sensor design are tested, measuring their mechanical and electrical behavior under compression. The results of these tests confirm a strong resistive response to mechanical loading. Furthermore, the results provide insight into the influencing factors of the design, i.e., the gap size between the conductive pathing and the stiffness of the sense element support structure are found to be primary influencing factors governing sensor behavior.

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