Scentopia is an innovative olfactory interface elegantly worn around the neck. This device boasts six foundational scents that can be artfully blended to fashion an assortment of distinct digital fragrances. Its personalized Spatial Olfaction with dynamic head tracking gives you an immersive experience for virtual reality (VR) and meditation, with scents that surround you. Using watch-level motors and gear systems, along with gyroscope sensing, the released scent will rotate 360 degrees, creating a subtle and varied olfactory experience. The cap for dimensionalizing the scent can be customized in shape, which enhances its fashionable attributes.

Scentopia stands at the intersection of technological innovation and human sensory experience, addressing a key gap in the virtual reality landscape. In an era where immersive digital experiences are becoming increasingly prevalent, it introduces an entirely new dimension by integrating the sense of smell. This relevance is accentuated by the growing recognition of the powerful role scent plays in evoking emotions, triggering memories, and enhancing overall well-being. It redefines digital experiences through scent, while its appropriateness is grounded in fostering a seamless and emotionally resonant interaction with technology. The neck-worn configuration ensures easy access and comfortable wearability, reducing the weight and discomfort associated with traditional head-mounted devices. The technology behind the device ensures an accurate and controlled release of scents, ensuring that the blended fragrances are dispersed in a balanced and harmonious manner. The ability to blend scents empowers users to personalize their experiences, fostering creativity and self-expression. Moreover, it can bring a sense of comfort and connection, bridging geographical distances through scent-triggered memories.

In recent years, we are entering an era of spatial computing. However, the challenge lies in enhancing human perceptual capabilities in spatial environments to create immersive atmospheres. While many researchers focus on enhancing sensory experiences in areas such as visual (e.g., 3D movies), auditory (e.g., spatial audio), and tactile (e.g., 4D movies), the field of olfaction, as a promising domain, is often underrepresented in the realm of immersive experiences. Sentopia introduces the concept of spatial olfaction computing and presents a wearable device that seamlessly integrates olfactory interfaces into a necklace.

Smell has the power to transport us across time and space. The presence of a scent source and its diffusion can be located in space (i.e., scented air volume) even if out of sight. Moreover, it has been shown that scents can convey meaning and complement visual information processing and decision-making (e.g., enabling cognitive shortcuts). Furthermore, scent delivery has been demonstrated to have a profound impact on cognitive, emotion-related responses to audio-visual stimuli and odors and it has the ability to assist in targeted memory reactivation. Imagine a scenario where you find yourself driving while fatigued, in desperate need of an invigorating scent to enhance alertness. Or during moments of restlessness, when a calming aroma can aid in meditation and restoring tranquility. Perhaps you are longing for someone or reminiscing about a particular experience, and a scent resembling that memory can help evoke recollection. Moreover, consider being fully immersed in a virtual reality (VR) game set in a serene forest, where the scent of the forest further enhances the sense of presence. As we know, the scents of a forest change as we move through it, varying with our proximity to odor sources. So they are complex and intermingled. However, this is where the significance of Scentopia comes into play. The main aim of Scentopia was to fabricate a technology that remains constantly present, subtly, and seamlessly providing convenience in various contexts to enhance the user's experience to a certain extent and bring them closer to achieving immersive experiences.

Scent Release

There are various mechanisms for olfactory release such as the use of a fan, and heat. However, using the ultrasonic humidifier module is the best way in this scenario from the perspective of safety and portability.

The base of Scentopia houses an enclosed piezoelectric transducer responsible for regulating scent dispersion. To induce vibration in the piezoelectric element, a 100KHz frequency and 10VAC (20Vpp) are required. An alternating current (AC) voltage causes the plate to oscillate at this frequency, generating ultrasonic sound waves. These ultrasonic frequencies are imperceptible to the user but possess the capability to atomize the liquid, breaking it into minute droplets resembling vapor. Consequently, the device effectively converts the fragrance or essential oil from the reservoir into a fine mist, swiftly diffusing the scent throughout the necklace's vicinity. The essence reservoir boasts a 5ml capacity, allowing for a continuous operation lasting up to 10 hours, with scent release intervals adjustable from 1 to 60 seconds. A default duty cycle frequency of 1 second of scent release every 60 seconds was selected to ensure ample time between bursts for the aroma to dissipate, thus preventing habituation and desensitization, with exceptions for scenarios involving the blending of different scents to create varied sensory experiences.

Spatial Computing

Scentopia achieves spatial olfaction through two primary mechanisms. Firstly, at the fundamental level, six emitters face different directions. By selecting emitters located in various positions, it can easily achieve the effect of scent entering the user's nasal passages from six distinct directions. The second aspect involves the six caps positioned at the top of Scentopia, which are capable of 360-degree rotation. The bottom of each cap is directly inserted into the center of one of the gears, and their rotation is controlled by miniature stepper motors of watch-grade precision. These motors have dimensions of approximately 8mm in diameter and 12.2mm in height and operate at 2-Phase 3 Wire DC 5V. The gears on the motors have nine teeth with a 0.2 module. To complement this gear, two additional gears, also with a 0.2 module, have 54 teeth and are 3D printed from resin. The gear ratio between the gears on the motors and the 3D-printed gears is 6:1. This means that when the motors complete one full rotation, the 3D-printed gears rotate 60 degrees, resulting in a 60-degree rotation of the caps. Therefore, when using the A4988 stepper motor driver at full micro step resolution, it allows precise control of the caps at six different angles. Furthermore, the rotation of the caps is controlled by a gyroscope (model: MPU 6050). Since Scentopia is worn around the neck and the central part is not parallel to the ground, calibration of the gyroscope is required. It's worth noting that because the rotation of the cap occurs in a 2D plane, only the X and Y values obtained from the gyroscope sensor are needed. When the head tilts forward, the cap rotates away from the person (downward), and when the head tilts to the left, the cap also rotates to the left, and vice versa.

Wireless Communication

To endow the necklace with communication capabilities to be remotely controlled, the microprocessor needs to have wireless communication ability. The microcontroller used in Scentopia is ESP32 S2 Mini, which has the feature of Wi-Fi communication. It is compact and energy-efficient. The entire system requires two 3.7V lithium batteries: one for powering the microcontroller and the other for supplying power to the ultrasonic humidifier module.

The current approach to control scent release is to use Scentopia in access point (AP) mode. Users connect to its generated Wi-Fi network and use a web browser (whether on laptops or phones) to access the control interface to select the desired scent. This user-initiated interaction provides users with greater flexibility. The other method of scent release is passive, where the scent is released based on changes in the video scene. This functionality in the project was achieved through Max/MSP-ESP32 S2 Mini communication. After each video segment is played in Max/MSP, it sends a signal to the ESP32 S2 Mini, thereby controlling the release of scent. Another way is to seek cooperation with VR headset product manufacturers to control the release of scents through VR headsets.