Public defence, Interactive systems, MA Tim Moesgen

Title of the thesis: Understanding and Designing Thermal Motion Feedback for Immersive Experiences

Thesis defender: Tim Moesgen
Opponent: Prof. Jan van Erp, The Netherlands Organisation for Applied Scientific Research & University of Twente, The Netherlands
Custos: Prof. Yu Xiao, Aalto University School of Electrical Engineering 

Heat is something we usually think of as a fixed sensation, warm or cold, present or absent. But heat can also move across the skin, spreading, drifting, retreating. This dissertation asks how that moving quality of heat can be understood, designed, and used in technology, with a particular focus on virtual reality.

Most existing research on thermal interfaces in human-computer interaction has looked at heat as something static and localized, delivered to one spot on the body at a time. The dynamic, moving character of heat has received far less attention, despite being a central part of how people actually experience warmth in daily life, from the shifting heat of sunlight to the wave of warmth in a sauna.

The research began by listening to people's own accounts of heat. Through interviews, body mapping, and hands-on evaluation exercises, the study explored how people experience full-body heat in a traditional Finnish sauna. This grounded the research in lived experience and identified qualities of heat, such as its movement, texture, and intensity, that could inform the design of thermal technology.

Building on this, the research turned to the body itself, running a controlled experiment on the forearm to test whether a sense of continuous heat movement could be created by activating a series of small heating elements one after another. The results confirmed that people do perceive this as smooth, ongoing motion, even though only fixed points on the skin are ever heated.

These findings were then built into a working prototype: a wearable thermal device integrated into a virtual reality sauna experience. Comparing moving heat with heat delivered simultaneously to several points at once, the study found that moving heat feels gradual and spreading, while heat delivered all at once feels stronger and more immediate. This revealed a trade-off between the sense of motion and the sense of intensity, an important consideration for anyone designing thermal devices with multiple heating elements.

A final study examined how what people see affects what they feel. When visual motion in the virtual environment matched the direction of the heat, people judged the direction of the heat more accurately. When the two conflicted, accuracy dropped. This shows that thermal perception in virtual reality cannot be designed in isolation from the visual experience surrounding it.

Taken together, the findings offer new, tested knowledge about how moving heat is perceived and how it can be built into interactive systems. They also raise a methodological point: standard rating-scale questionnaires are not well suited to capturing dynamic, embodied experiences like moving heat, and the dissertation argues for combining behavioral measurements, qualitative accounts, and self-report tools instead.

More broadly, the dissertation suggests a shift in how designers should think about thermal technology. Rather than trying to design a specific thermal experience for someone, the more productive approach is to design the conditions under which a person's own embodied experience of heat can unfold. This work has relevance for virtual and augmented reality, wearable technology, and any application where a sense of realistic, moving warmth could enhance immersion, communication, or wellbeing.

Key words: Thermal experience, thermal motion illusion, perception, wearable technology, VR, immersion

Thesis available for public display 7 days prior to the defence at Aalto University's public display page.

Contact: 
https://www.linkedin.com/in/tim-moesgen/ 
tim.moesgen@aalto.fi