Applying Odor Preconcentrator for Enhancing Human Olfaction: Feasibility Study

Introduction The human sense of smell plays important roles in various scenes in everyday life although we are unconscious of the importance in most cases. For example, olfaction provides an alert that lets us notice dangers or risks such as a fire and rotten food. Savory food smells and comfort flower fragrances make our lives richer. However, it is known that the human olfaction deteriorates with our age [1]. There is no device that can improve the deteriorated olfaction whereas impaired vision can be improved using eyeglasses and a hearing aids can improve our audition. The aim of this research project is to develop an olfactory amplifier for humans [2,3]. In chemical analysis, preconcentrators are frequently used to analyze faint chemical substances [4]. We propose to apply this technique to enhance the sensitivity of human olfaction. In the proposed olfactory amplifier system, airborne odor molecules are collected into adsorbent, as in the preconcentrator. When a sufficient amount of odor molecules are collected, the adsorbent is heated to a high temperature to thermally desorb the collected molecules in a short time. The concentrated odors are thus generated. Here we report our new device made with a monolithic silica adsorbent. Results of odor concentration experiments and a sensory test are presented to show that the device can generate a concentrated smell from a faint smell. Method The schematic diagram of our new device that uses a disc-shaped monolithic silica (MonoTrap DSC18, GL Science) as an adsorbent is shown in Figure 1. The cross section of the device is shown in Figure 2. The diameter and thickness of the monolithic silica disk are 10 mm and 1 mm, respectively. This adsorbent is housed in a flow cell which was made by putting a rubber sheet with a hole in the middle between an acrylic plate and a printed circuit board. A meander heater made on the printed circuit board is used for thermally desorbing the collected odor molecules from the monolithic silica disk. Five stainless tubes are attached to the flow cell. Air is sent into the flow cell through the center tube, and is exhausted from the four outer tubes. In the odor concentration experiment, 1.2 ppm 1-butanol vapor packed in a sampling bag was sent into the flow cell at a flow rate of 0.8 L/min for 10 min. The collected gas was desorbed by heating up the monolithic silica to 200 degrees centigrade. Clean air was sent to the flow cell at a flow rate of 20 mL/min to take the concentr