Doctoral dissertation

Antti Sand: Ultrasound brings touch sensations to contactless user interfaces

Antti Sand
M. Sc. Antti Sand explores in his dissertation the adding of haptic feedback to unconventional displays over the air and locally. In the studies, virtual objects presented using VR headsets could be felt as if they were real. Touch sensations provided over the air transform also fogscreens into contactless walk-through touchscreens, enabling, for example, hygienic and safe public user interfaces during pandemics.

VR headsets and screens formed of flowing particles, such as fog, can be used to create user interfaces in mid-air. Hand trackers allow users to explore virtual environments with touch and to interact with virtual objects. Without artificial touch sensations, virtual objects do not feel real, however, as the hand passes straight through them, which lessens the user experience and introduces confusion.

Particle screens can be, for example, enticing walk-through screens for public venues. With hand tracking and artificial touch feedback, they can be used as unbreakable touchscreens that automatically remain clean and hygienic.

Tactile sensations can be added to touching virtual objects with wearable vibrotactile actuators, not unlike those found in many hand-held electronic devices. These are proven and cheap and capable of producing strong feedback strengths. Their downsides, however, are that their feedback is limited to fixed locations on the skin and that they might limit hands-free interaction.

Touch sensations can also be generated in mid-air without wearable devices in various ways. One of the most prominent ways is using acoustic pressure. Short pulses of inaudible ultrasound from a large number of tiny speakers can be timed in such a way that the soundwaves meet at a certain location, a focal point, with sufficient pressure to create a touch sensation. This allows for providing sensations of touch while only touching air.

— As technologies, mid-air displays and mid-air touch sensations allow also new kinds of more comprehensive remote presence, where touch can be a part of remote communication, Antti Sand opens the possibilities of the technology.

For practical distances, soundwaves also travel relatively fast. The location of the focal point can be updated seemingly instantly, even faster than our sense of touch can keep track of. This allows for a single fast-moving focal point to feel like a complex shape all at once. For suitable distances and suitably sensitive parts of the skin, this ultrasonic acoustic pressure can be a great way of making virtual objects feel real.

— The sense of touch is important for human interaction as well as for interacting with technology. World acutely aware of pandemics might appreciate hygienic contactless user interfaces. In my dissertation, I have explored solutions for combining these two, Sand says.

Antti Sand is originally from Tampere and graduated as a Master of Science at the University of Tampere. Currently, he lives in Kangasala and is employed at the Tampere University, Faculty of Information Technology and Communication Sciences, as a researcher and a teacher.

The doctoral dissertation of M.Sc. Antti Sand in the field of interactive technology titled On Adding Haptic Feedback to Interaction with Unconventional Display Devices will be publicly examined at the Faculty of Information Technology and Communication Sciences of Tampere University at 12 o’clock on Friday 26 February 2021. The opponent will be Professor Sriram Subramanian from University College London, UK. The custos will be Dr. Ismo Rakkolainen from the Faculty of Information Technology and Communication Sciences at Tampere University.

The audience can follow the event via a remote connection at Teams.

The dissertation is available online at

Photo: Helena Sand