Researchers from Saarland University and the MIT Media Lab have published a paper detailing a means of creating low-cost "quick-and-dirty" prototypes for on-skin human-computer interaction (HCI) sensors — using specially-treated kinesiology tape.
"Skin is personal and sensitive. As a result, design and placement of on-body physical interfaces need to be well thought out," the researchers write in the paper's abstract. "One way of 'getting the design right' is to quickly sketch a multitude of designs to be modified, adjusted, and elaborated on. To date, on-body rapid prototyping methods do not afford these 'quick-and-dirty' design processes.
"We propose using piezo-resistive kinesiology tape as a low-cost and versatile resource for sketching functional on-skin interfaces. Our method uses pretreated kinesiology tape, which is made piezo-resistive through polymerisation, and serves as touch, pressure, and stretch sensor. We illustrate sketching techniques with both pretreated and untreated tape for iterative design of on-skin interfaces. In addition, we contribute a set of sensor primitives that facilitate various input modalities for creating interactive sketches."
The idea behind the project: Making it easier to "sketch" and test an idea for human-computer interaction without the need for expensive sensors or elongated prototype production. The trick: Polymerizing low-cost kinesiology tape with pyrrole, a process which can be easily carried out in a kitchen using nothing more than pyrrole, water, and iron chloride, plus a 55-minute soak. Once treated, the tape becomes piezo-resistive — meaning by applying crocodile clips and a simple microcontroller, the tape can be used as a bend or pressure sensor.
"Using kinesiology tape instead of commonly used pen-and-paper offers unique benefits for sketching on-body interfaces," the team explains. "The practise of applying patches of kinesiology tape to body parts is well-established in athletic and therapeutic contexts,and allows to appropriate a rich repertoire of attachment methods. Made of skin-compatible materials that readily adhere to skin, kinesiology tape offers a very flexible form factor, which is compatible with various body locations, body movement, and forms of interaction."
The team successfully used the technology to create touch sensors, directional sliders, gesture sensors, stretch sensors, and pressure sensors — though in some cases the high resistance of the tape, in the mega-Ohm range, did throw up a few problems.
"While we envisioned our work to fill in the gap of a 'quick-and-dirty' prototyping method for on-skin interactions, the presented sketching techniques and sensor primitives can also be employed in other areas, where deformable input, touch, pressure, or stretch sensors might be required, the team conclude, "for instance in textile interfaces. Our contribution is an enabling technology, and we hope to see it used in workshops and participatory design sessions in the future."