Feeling Is Believing

Despite the hype and anticipation surrounding virtual reality (VR) and augmented reality (AR), these technologies have in many ways been slow to take off. The technology has been available to the public for several years now, but it has not reached the widespread use that many industry experts predicted. Only 23% of US adults have ever used a VR or AR headset, according to a survey conducted by the Pew Research Center in 2020.

There are many reasons why more people are not using VR and AR applications. One major factor is that the cost of the technology is still prohibitively expensive for many consumers. There is also the fact that the technology is still relatively new, and many people are not yet familiar with its capabilities and how it can be used. But perhaps the most important reason behind the slow adoption of the technology is that it is not quite meeting people’s expectations. The promise of an ultra-realistic, totally immersive, Matrix-style experience is simply not being delivered on.

To provide that type of experience, developers need to look beyond the audio and visual components of the technology and also focus on bringing the other senses into the virtual world. The sense of touch is a crucial part of the human experience, and when it is lacking in virtual applications, the experience will fall flat. Reaching out to touch a virtual object and feeling absolutely nothing quickly shatters the illusion.

A trio of researchers at the Human Computer Interaction Lab of Saarland University have been working to improve the tactile component of virtual experiences. They have developed and recently reported on a wearable skin patch that can simulate the feeling of physically touching any number of real-world objects. But what makes this device really novel is that it is incredibly thin, which means it is a true feel-through interface. That is, a wearer of the device can feel objects in the real world normally, and also have that experience enhanced by virtual objects.

The rub-on wearable called Tactoo is composed of a soft, flexible temporary tattoo substrate, electrode layers, and an adhesive layer for attachment to the skin. A conductive PEDOT:PSS ink is used to create the traces that link the electrodes to an external control unit. The taxels (tactile pixels, aka electrodes) have a very small center-to-center spacing of four millimeters, giving the system high tactile resolution. The entire patch is only 35 micrometers in thickness, which gives the device its feel-through capability, while the taxels provide electro-tactile stimulation to simulate the sense of touch when encountering virtual objects.

In one demonstration of Tactoo, a model of a car was used to simulate the propagation of engine vibrations throughout the entire structure. A fingertip-worn patch allowed the wearer to feel the normal curvatures, ridges, and varied surface geometries of the car, while the taxels simulated the additional feel of engine vibrations on various parts of the model car. This allowed the wearer to experience how the vibrations would influence the feel of the car body or tires, for example.

Using the same device, a tactile paper-based user interface was also demonstrated. This allowed feedback to be provided when the user “clicked” on a button that was printed on the paper, or when they moved their finger along a printed slider knob. One can easily imagine how any number of everyday objects can be augmented to become user interfaces using similar techniques.

A small study consisting of ten participants was conducted to determine how well Tactoo was meeting its goal of providing both virtual and feel-through tactile experiences. The volunteers generally reported that the feel-through sensation was very clear, that the virtual sensations were highly perceivable, and that Tactoo was comfortable to wear.

This novel system opens up new opportunities for tactile AR, and was constructed with hobbyist-level screen printing techniques and commercially available conductive inks. As such Tactoo is highly accessible as presently designed. And that also leaves open the possibility that a future version could be developed, using higher-end methods, that would make the device’s performance even better.