Figure 1. A Tacttoo rub-on tattoo enables feel-through and high-density tactile output. With less than 35µm in thickness, it closely conforms to fine structures of the skin. Tacttoos can be custom-designed for various body locations and taxel densities, and fabricated using DIY tooling.

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This paper introduces LASEC, the first technique for instant do-it-yourself fabrication of circuits with custom stretchability on a conventional laser cutter and in a single pass. The approach is based on integrated cutting and ablation of a two-layer material using parametric design patterns. These patterns enable the designer to customize the desired stretchability of the circuit, to combine stretchable with nonstretchable areas, or to integrate areas of different stretchability. For adding circuits on such stretchable cut patterns, we contribute routing strategies and a real-time routing algorithm. An interactive design tool assists designers by automatically generating patterns and circuits from a high-level specification of the desired interface. The approach is compatible with off-the-shelf materials and can realize transparent interfaces. Several application examples demonstrate the versatility of the novel technique for applications in wearable computing, interactive textiles, and stretchable input devices. CCS CONCEPTS • Human-centered computing → Interactive systems and tools.

Augmenting everyday objects with interactive input and output surfaces is a long-standing topic in ubiquitous computing and HCI research. Existing approaches, however, fail to leverage the objects' full potential, particularly in highly curved organic geometries and in diverse visuo-haptic surface properties. We contribute ObjectSkin, a fabrication technique for adding conformal interactive surfaces to rigid and flexible everyday objects. It enables multi-touch sensing and display output that seamlessly integrates with highly curved and irregular geometries. The approach is based on a novel water-transfer process for interactive surfaces. It leverages off-the-shelf hobbyist equipment to fabricate thin, conformal, and translucent electronic circuits that preserve the surface characteristics of everyday objects. It offers two methods, for rapid low-fidelity and versatile high-fidelity prototyping, and is applicable to a wide variety of materials. Results from a series of technical experiments provide insights into the supported object geometries, compatible object materials, and robustness. Seven example cases demonstrate how ObjectSkin makes it possible to leverage geometries, surface properties, and unconventional objects for prototyping novel interactions for ubiquitous computing.

edge slider buttons Tactlet library real-time control a b c d Figure 1. Tactlets is a novel approach enabling digital design and rapid printing of custom, high-resolution controls for tactile output with integrated touch sensing on interactive objects. (a) A design tool allows a designer to add Tactlet controls from a library and customize them for 3D object geometries. The designer can then fabricate a functional prototype using conductive inkjet printing (b) or 3D printing (c), and explore the interactive behavior of the Tactlet control. (d) This approach allows for rapid design iterations to prototype tactile input and output on a variety of objects. ABSTRACTRapid prototyping of haptic output on 3D objects promises to enable a more widespread use of the tactile channel for ubiqui tous, tangible, and wearable computing. Existing prototyping approaches, however, have limited tactile output capabilities, require advanced skills for design and fabrication, or are in compatible with curved object geometries. In this paper, we present a novel digital fabrication approach for printing cus tom, high-resolution controls for electro-tactile output with integrated touch sensing on interactive objects. It supports curved geometries of everyday objects. We contribute a de sign tool for modeling, testing, and refining tactile input and output at a high level of abstraction, based on parameterized electro-tactile controls. We further contribute an inventory of 10 parametric Tactlet controls that integrate sensing of user input with real-time electro-tactile feedback. We present two approaches for printing Tactlets on 3D objects, using conduc tive inkjet printing or FDM 3D printing. Empirical results from a psychophysical study and findings from two practi cal application cases confirm the functionality and practical feasibility of the Tactlets approach.•Human-centered computing → Human computer inter action (HCI); Haptic devices; Interactive systems and tools; Interface design prototyping;Digital fabrication has been proposed as a new method for rapid prototyping of interactive devices [10,25,34,32,44]. By printing the custom device, rather than manually assembling it from conventional electronic components, the fabrication process can be considerably simplified and sped up. At the same time, as printable electronics commonly are very thin and deformable, more demanding geometries and advanced I/O capabilities can be realized. Prior work has demonstrated ap proaches based on printed electronics to equip custom-shaped 3D objects with various types of printed sensors for capturing user input [11,34,44,45,54] and printable output compo nents, including light-emitting displays [35,54] and actuators for shape-change [7,57].However, tactile output was so far left unaddressed. Fab ricating custom interactive objects that include computercontrolled tactile output still relies on manually assembling conventional components [15,36]. Moreover, the rather large