Creating new 3D printed objects by recombining models found in hobbyist repositories has been referred to as "re-mixing". In this paper, we explore how to best support users in remixing a specific class of 3D printed objects, namely those that perform mechanical functions. In our survey, we found that makers remix such machines by manually extracting parts from one parent model and combine it with parts from a different parent model. This approach often puts axles made by one maker into bearings made by another maker or combines a gear by one maker with a gear by a different maker. This approach is problem-atic, however, as parts from different makers tend to fit poorly, which results in long series of tweaks and test-prints until all parts finally work together. We address this with our interactive system grafter. Grafter does two things. First, grafter largely automates the process of extracting and recombining mechanical elements from 3D printed machines. Second, it enforces a more efficient approach to reuse: it prevents users from extracting indi-vidual parts, but instead affords extracting groups of me-chanical elements that already work together, such as axles and their bearings or pairs of gears. We call this mecha-nism-based remixing. In a final user study, all models that participants had remixed using grafter could be 3D printed without further tweaking and worked immediately.

We present TrussFab, an integrated end-to-end system that allows users to fabricate large scale structures that are sturdy enough to carry human weight. TrussFab achieves the large scale by complementing 3D print with plastic bottles. It does not use these bottles as "bricks" though, but as beams that form structurally sound node-link structures, also known as trusses, allowing it to handle the forces resulting from scale and load. TrussFab embodies the required engineering knowledge, allowing non-engineers to design such structures and to validate their design using integrated structural analysis. We have used TrussFab to design and fabricate tables and chairs, a 2.5 m long bridge strong enough to carry a human, a functional boat that seats two, and a 5 m diameter dome.

We propose a new way of eyes-free interaction for wearables. It is based on the user's proprioceptive sense, i.e., rather than seeing, hearing, or feeling an outside stimulus, users feel the pose of their own body. We have implemented a wearable device called Pose-IO that offers input and output based on proprioception. Users communicate with Pose-IO through the pose of their wrists. Users enter information by performing an input gesture by flexing their wrist, which the device senses using a 3-axis accelerometer. Users receive output from Pose-IO by find-ing their wrist posed in an output gesture, which Pose-IO actuates using electrical muscle stimulation. This mechanism allows users to interact with Pose-IO without visual or auditory senses, but through the proprioceptive sense alone. We developed three simple applications that demonstrate symmetric proprioceptive interaction, where input and output occur through the same limb, as well as asymmetric interaction, where input and output occur through different limbs. In a first user study, participants using a symmetric proprioceptive interface re-entered poses received from Pose-IO with an average accuracy of 5.8° despite the minimal bandwidth offered by the device. In a second, exploratory study, we investigated participants' emotional response to asymmetric proprioceptive interaction and the concept of the user's body serving as interface. Participants reported to enjoy the experience (4.6 out of 5).