Development of Wearable and Portable Chemosensory Systems: Advances in Olfactory and Gustatory Feedback for Immersive Human-Machine Interaction

Abstract

HMIs have evolved into immersive multimodal systems that primarily rely on visual, auditory, and haptic feedback, enabling applications in VR, AR, and MR environments. However, several critical limitations are still observed in conventional HMIs, including incomplete sensory immersion, bulkiness, high power consumption, wired constraints, and limited portability, which hinder vivid sensation and user-friendliness. Particularly, engagement of primal chemosensory pathways, which are closely linked to emotion, memory, and subconscious perception through the limbic system, has largely been neglected. Among the human sensory modalities, chemosensory perception, including olfaction and gustation, which constitute two of the five innate human senses, remains largely unexploited despite its profound physiological and psychological influence on human behavior.

Through this thesis, a new generation of chemosensory HMIs that achieve immersive, latency-free, and emotionally resonant experiences by progressively integrating olfaction and gustation interfaces has been developed. In addition, the research systematically addresses the identified limitations through miniaturized, wireless, wearable, and programmable platforms, advancing from initial olfactory interfaces to completely merged olfaction and gustation systems with high channel density, rapid response, AI-driven synchronization, and biocompatible designs.

Initially, the foundational soft and wearable olfactory interface employs paraffin-wax-based odor generators in thin and flexible electronics for wireless and programmable scent delivery. By optimizing materials, multilayer stack design, and mechanical and thermal actuation, fast response, low-power consumption, and high mechanical stability can be achieved. Furthermore, with demonstrations in 4D movie immersion, emotion modulation through memory-evoked odors, message delivery for disabled users, medical therapy, and VR/AR experiences, the potential of olfaction interface as a steppingstone for multisensory HMIs is clearly illustrated. Following, a skin-integrated wireless odor message delivery system is introduced, while odor generators are further miniaturized to the size of 11 mm × 10 mm × 2.2 mm with a simplified structure. Moreover, benefiting from the odor generators, rapid response times of 0.6 s for heating and 1.36 s for cooling, high array density (0.72/cm³), and stable operation over 10000 cycles can be established. By linking odors to messages and directly engaging limbic pathways for emotion, recognition, and memory processing, the system improves recognition rates 1.5 times and reduces response times 4 times over touch-based methods, proving its potential as an efficient non-tactile communication alternative with broader medical applications, such as olfactory-based memory enhancement and rehabilitation. Then, to build latency-free MR, an intelligent wearable olfactory interface is developed by adopting airflow/heat odor generators and advanced AI algorithms to achieve millisecond-level response time (0.07 s), milliwatt-scale power consumption, and high array density (0.75 unit/cm²). Consequently, the integration of advanced AI algorithms enables zero-latency synchronization for real-time MR integration and efficient olfactory training for patients with degeneration, demonstrating broad potential in HMIs, medical treatment, remote education, and entertainment.

Finally, miniaturized and portable gustation interfaces are developed in lollipop-shaped form to enhance both user-friendliness and portability. The reporting chemosensory interfaces consist of 2 to 9 iontophoresis-based taste generators using edible-grade and tasteful chemicals embedded in agarose gels. Furthermore, taste intensity (0–2 V safe range) can be manipulated wirelessly without external electrodes or skin contact restrictions while multiple channels are switched independent or parallel operation at the same time. On the other hand, taste mass and concentration are calculated by self-developed data-driven mathematical models based on the monitored current and time. Moreover, compact size and low weights are achieved by optimizing electronics on thin FPCBs and using lightweight 3D-printed Nylon exteriors. Then, miniaturized odor generators are integrated into the system to establish an olfaction/gustation combined interface for leveraging olfactory-taste correlation to enhance immersive experience. As a result, demonstrations in medical gustation assessment, immersive remote shopping, and full multisensory MR prove advances in portability, controllability, and user-friendliness for complete chemosensory augmentation.

Consequently, these sequential advancements firmly establish chemosensory interface integration, encompassing both olfaction and gustation, as a foundational pillar for the next generation of HMIs. In summary, by enabling low-latency, emotionally resonant, biologically congruent, and user-conformable interactions, this work opens transformative pathways toward fully immersive entertainment, targeted healthcare therapies, enhanced education, and profound human augmentation in VR/AR/MR ecosystems.

Date of Award	19 Aug 2026
Original language	English
Awarding Institution	City University of Hong Kong
Supervisor	Xinge YU (Supervisor)