As automotive interfaces transition from mechanical controls to software-defined, material embedded touch surfaces, fundamental questions arise about how tactile feedback, material behavior, and digital information can be combined into coherent user experiences. This dissertation investigates how haptic fidelity, material mediation, and perceptual appropriateness shape interaction in emerging automotive user interfaces. Across four complementary research strands, the work examines how users interpret haptic signals, how materials can bridge analog and digital modes, how haptics perform under realistic driving conditions, and how designers can judge the experiential coherence of multimodal feedback.

The first part introduces the Haptic Fidelity Framework, a perception-oriented categorization that clarifies how different actuator technologies afford distinct levels of expressivity and perceptual bandwidth. A complementary study on haptic perception shows that users primarily describe tactile sensations through evocative, experiential language rather than technical parameters, underscoring the need to align engineering criteria with experiential qualities.

The second part explores how materials can integrate sensing, lighting, and haptic actuation into hybrid “2.5D” interfaces. Through prototyping and qualitative analysis, this work demonstrates that material properties – such as diffusion, and texture – play an active role in shaping interaction semantics and user interpretation.

The third part evaluates high-fidelity piezo haptics in a driving simulator. Results show that haptic feedback improves perceived usability, clarity, and interaction support across representative use cases, even when objective performance measures show limited differences. Participants assessed piezo feedback as more satisfying, expressive, and appropriate, particularly for continuous and search-based interactions during driving.

The final part introduces the Frame–Focus–Glance pipeline, a perception-first design method for shy-tech interfaces (in which technology remains visually restrained and only comes forward when interaction demands it). Through expert exploration, evaluation under calm, non–time critical viewing conditions, and glance-based assessments under short viewing durations representative of driving conditions, the study examines how material diffusion, pixel density, and interface semantics jointly shape perceptual clarity. The results show that knitted textiles perform consistently well across resolutions, whereas woven textiles exhibit strongly resolution dependent behavior. This makes them informative for interface design decisions, but less predictable in perceptual terms for users when applied as an interface substrate.

Taken together, the dissertation provides conceptual, empirical, and design-oriented contributions for integrating haptics and materials in future automotive HMIs. It demonstrates that tactile experience emerges not from actuation alone but from the interplay between technology, material mediation, perceptual thresholds, and context. The resulting framework and methods offer a foundation for designing multimodal, materially coherent, and perceptually appropriate interfaces that balance digital flexibility with embodied interaction. ... Read more

As touchscreen interfaces replace many physical controls in vehicles, safe and intuitive interaction becomes increasingly important. This study evaluated piezo-actuated haptic feedback versus conventional audio-only feedback across 11 use cases in parking and driving contexts. In a within-subject experiment with 23 participants in a fixed-based driving simulator, haptic feedback was rated as more satisfying, helpful, and supportive, particularly for scrolling or confirming actions while driving, despite showing no significant differences in objective performance measures. Participants described haptics as more engaging, though some noted habituation effects and inconsistencies. Audio-only feedback was seen as more stimulating but less consistently preferred. Findings suggest that contextual haptics improves perceived usability. Additionally, the study highlights the potential of semantic haptics—enabled by piezo technology—to convey meaning through expressive tactile patterns. Future research could explore adaptive multimodal systems and assess long-term effects under real-world conditions. ... Read more

Current transformational developments in automotive user interface (UI) technology are causing a shift in emphasis from safety and efficiency to emotion and flexibility. The many factors to consider in parallel make this a difficult process, in which technological affordances all too easily push the user to the background. To address this issue, this paper introduces an interaction model linking the different tangible control elements, including smartphone functionality, and shows how non-driving-related activities (e.g. climate control, multimedia access) can be represented physically. Next, a working prototype is presented that supports the design and development of novel tactile UIs. By integrating layers of sensors and actuators, a flexible UI is created that pushes technology to the background, giving proper attention to the user again and enabling effective research on how to make the digital world tangible for users. ... Read more