Steel-sense: Integrating machine elements with sensors by additive manufacturing

Many interactive devices use both machine elements and sensors, simultaneously but redundantly enabling and measuring the same physical function. We present Steel-Sense, an approach to joining these two families of elements to create a new type of HCI design primitive. We leverage recent developments in 3D printing to embed sensing in metal structures that are otherwise difficult to equip with sensors, and present four design principles, implementing (1) an electronic switch integrated within a ball bearing; (2) a voltage divider within a gear; (3) a variable capacitor embedded in a hinge; and (4) a pressure sensor within a screw. Each design demonstrates a different sensing principle, and signals its performance through (1) movement; (2) position; (3) angle (4) or stress. We mirror our elements physical performance in a virtual environment, evaluate our designs electronically and structurally, and discuss future work and implications for HCI research.