Stereo-Smell via Electrical Trigeminal Stimulation

Document Title

Stereo-Smell via Electrical Trigeminal Stimulation

Document Information

• Subject Area: Human-Computer Interaction, Sensory Substitution Technology, Olfaction and Trigeminal Nerve Stimulation
• Keywords: Trigeminal nerve, electrical stimulation, olfaction, directional smell, sensors, sensory substitution, gas detection, intranasal device, human-computer interaction

Research Background and Problem

• Problem or Challenge:

  • Traditional olfactory interfaces rely on physically delivering odor molecules into the nasal cavity, which often involves bulky equipment unsuitable for everyday scenarios.
  • Digital olfactory simulation technologies, such as direct stimulation of the olfactory bulb via electrical signals, show great potential but raise concerns about safety and difficulty in reliably reproducing odors.
  • Olfactory loss (e.g., due to COVID-19 or other diseases) poses challenges in detecting hazardous gas leaks.

• Research Importance:

  • Taste and smell are crucial for understanding daily experiences, such as enjoying food or identifying dangerous odors (e.g., natural gas leaks).
  • Offering an innovative and minimally invasive method to experience directional olfaction through digital stimulation holds significant technological, medical, and social value.

• Research Motivation and Related Work:

  • Existing studies indicate that the trigeminal nerve plays an important role in olfactory perception (e.g., sensing the refreshing feeling of mint).
  • Most olfactory devices focus on delivering chemical odors, with limited exploration of other neural pathways like the trigeminal nerve.
  • Enhancing the convenience of assistive devices for daily use while reducing training requirements is a key research direction.

Solution

• Core Method:

  • Propose a novel intranasal device that converts external gas sensor detection data into user-perceivable directional trigeminal nerve stimulation via electrical signals.
  • The device measures inhalation signals within the user's nasal cavity and communicates with external gas sensors (via Bluetooth), stimulating the trigeminal nerve to produce perceivable odor intensity and direction.

• Innovative Features:

  • Utilize electrical stimulation of the trigeminal nerve instead of direct stimulation of the olfactory bulb, reducing invasiveness.
  • Provide precise intensity and directional information through modulation of parameters such as charge and waveform.
  • Design the intranasal device to be wireless, self-contained, and easy to wear.

• Implementation Steps and Key Technologies:

  1. Device Design: Two printed circuit boards placed in each nostril, secured by magnets at the nasal septum; sensors monitor inhalation in real-time.
  2. Electrical Stimulation Principle: Use biphasic waveform currents and optimize pulse width and charge polarity to control stimulation intensity and direction.
  3. Integration with External Gas Sensors: Receive gas intensity and directional data from external metal oxide sensors via Bluetooth and convert this information into trigeminal nerve stimulation.

Research Outcomes

• Specific Results:

  • Device Construction: A complete intranasal device prototype, compact in size (10x23mm), weighing only 3.4g, integrating a battery, sensors, wireless module, and electrical stimulator.
  • Optimization of Electrical Stimulation Parameters: The first user study revealed how key electrical parameters (absolute charge and net charge) influence odor intensity and directional perception.
  • Virtual Odor Localization Experiment: The second user study demonstrated that untrained participants could successfully locate odor sources using the device.

• Advantages Compared to Existing Solutions:

  • Non-invasive, safer than methods involving direct stimulation of the olfactory bulb.
  • Easy to wear, small in size, suitable for daily use.
  • Provides precise directional and intensity perception without requiring complex training.

• Experimental or Evaluation Results:

  • Two user studies validated the device's effectiveness:
    • The first study identified how pulse width, polarity, and sequence guide intensity and directional perception.
    • The second study showed that users could immediately operate the device and locate odor sources via trigeminal nerve stimulation.
  • User feedback indicated that the electrical stimulation was significant and clear, with some describing it as a "loud sensation."

• Limitations and Future Directions:

  • Limitations:
    • The device can only simulate trigeminal nerve stimulation, not the full olfactory perception from the olfactory bulb.
    • The current prototype relies on external sensors to detect gas types and concentrations.
  • Future Directions:
    • Further design of trigeminal nerve stimulation patterns and parameters to approach richer olfactory experiences.
    • Explore multimodal combined perception by integrating with the olfactory bulb or other interfaces.
    • Focus on co-designing convenient devices for daily use with users suffering from olfactory disorders (e.g., anosmia).