This project has made the following main contributions to the field of interactive skin:
1. Computational fabrication of interactive skin
We developed functional designs for sensors and output components that can be embedded in interactive skin devices. These components are ultra-thin (typically between 1 and 50 microns) and elastic, so the device can closely conform to the user’s skin and can be ergonomically worn even on highly curved and stretchable body locations. As skin is inherently multi-modal and our goal is to support rich and expressive interfaces, our results contributed designs for a wide variety of components. These include multi-touch, sliding, bending, squeezing, stretching, and pulling input, as well as physiological sensors for electromyography, heart rate and electro-dermal activity. A highlight result is Tacttoo, the thinnest wearable tactile matrix interface presented in the literature. It allows the user to feel real-world objects through the interface, while these can be augmented with computer-generated tactile output. Our vision is to ultimately print a personalized electronic device similarly to how we today print a document, or even how we apply make-up. To this end, we have developed an award-winning method that allows people to use an ordinary desktop inkjet printer to print functional interactive skin devices within minutes. More recently, we have developed a method for fabricating interactive skin devices by sketching directly on one’s body.
2. Interacting with skin interfaces
Skin is a fundamentally different interaction surface than conventional touchscreens. A central aim of this project was to investigate how we can leverage the unique properties of skin for user interaction. For one, we proposed and investigated the concept of body landmarks: haptic or visual features of the human body, such as knuckles or wrinkles, that can be used to guide interaction on the skin. A set of interaction techniques and functional prototypes demonstrated the power of this principle. Second, we have investigated how the skin on user’s fingers can offer a surface for microgestures performed between fingers. Such gestures offer a rapid, versatile and discreet way of input in mobile contexts. We have conceptually explored the design space of these gestures and demonstrated new gestures for settings when hands are busy holding an object. Moreover, we have conducted in-depth investigations of deformation-based input and output. Their results can lead to new and better ways of interacting on the skin than through conventional touch contact alone.
3. Design tools for personalized interactive skin
Our goal is to offer computational support for a wide audience that helps with designing personalized and customized interactive skin devices. This includes personalization to a specific user’s body proportions, customization to specific application contexts, to specific body locations or desired aesthetic goals. We aimed at establishing the foundations for tools that algorithmically generate functional devices based on a high-level design specification. We have contributed algorithmic principles and foundational design tools for generating custom-shaped multi-touch sensors, electro-physiologial sensor tattoos and tactile output devices. Together, our approaches allow non-experts to readily design and fabricate interactive skin devices with desired properties by deferring the detailed technical realization to a computational tool.
4. Evaluation and synthesis of findings
To systematically investigate the usability of on-body user interfaces and derive implications for future designs, we have conducted extensive empirical studies. Highlight results comprise a systematic investigation of the effect of interactive skin devices on the user’s haptic perception. This knowledge informs the material design of interactive skin devices. Furthermore, we have investigated the use of interactive skin in several real-world application cases, including an award-winning paper on text entry. In the last year of the project, we have synthesized our findings and have identified opportunities and challenges for future work in epidermal computing.
