Visual perception and particle size testing method of electronic cigarette smoke

Visual perception and particle size testing method of electronic cigarette smoke
This article discusses the visual perception and particle size testing methods of electronic cigarette smoke. Visually, the color and clumping of electronic cigarette smoke affect the user's visual experience, and the underlying physical principles are Rayleigh scattering and Mie scattering, respectively. The visual perception of smoke is related to the particle size of aerosols, with smaller particles appearing blue and larger particles appearing white. The main methods for measuring particle size include laser particle size analyzer and scanning electron mobility particle size spectrometer, each with its own advantages and disadvantages. Researchers can choose the appropriate testing method according to their needs. The main problem currently faced by electronic smoke aerosol testing is particle size distortion, which is related to the difficulty in capturing aerosol components and the instability of experimental environmental conditions.
When users use e-cigarettes, they are very concerned about the amount of "smoke", in order to achieve both visual satisfaction and actual smoking satisfaction. So what is the difference between visual and actual "smoke", and what are the corresponding research methods?
When it comes to actual "smoke volume", it is necessary to mention a key indicator - Total Particle Matter (TPM). The general detection method for TPM is the "weight loss method", which tests the quality difference of the equipment before and after suction as the TPM value of the equipment. TPM is influenced by the atomization efficiency of the device, and the specific impact mechanism can be found in Exploring the Working Principle of Vapor type Electronic Cigarettes. At the same time, TPM has a huge impact on the taste during suction. The impact mechanism can be found in the Aerosol section of Exploring the Taste of Electronic Cigarettes (III): Aerosol Movement, Sedimentation Characteristics, and Sensory Experience.
This issue mainly discusses the visual perception and particle size testing methods of electronic cigarette smoke.
Visual experience and particle size testing method of electronic cigarette smoke
(1) Aerosol visual perception
Firstly, we will list two visual representations of electronic cigarette smoke. Firstly, when we blow or gently suck from the bottom of the electronic cigarette, the color of the smoke will be relatively light, even blue, resulting in a poor visual experience, as shown in Figure 1; 2 is the smoke that comes out after we have fully aspirated it, with better clumping and a basic white color, providing a good visual experience, as shown in Figure 2. So what are the reasons why different types of smoke appear blue or white?
The causes of blue smoke
Rayleigh scattering: The scattering intensity is inversely proportional to the fourth power of the wavelength of the light, and the shorter the wavelength, the stronger the scattering. In layman's terms, the diameter of particles is much smaller than the wavelength of the incident wave, with an upper bound of about 1/10 (1-300 nm) of the wavelength. In short waves, blue light has the highest energy, so visually, smoke will appear blue. The smaller the particle size, the more obvious the blue color will be.
2. The causes of white smoke
Mie scattering: Scattering that occurs when the diameter of particles in the atmosphere is equal to the wavelength of radiation, and the scattering intensity is proportional to the square of frequency; When the particle size is greater than the visible light wavelength (0.38~0.78) μ m) When the scattering intensity is independent of wavelength, the smoke visually appears white, and the larger the particle size, the more obvious the white color.
(2) Test method for particle size of electronic smoke aerosol
The two commonly used aerosol measurement methods are collection and analysis, and direct reading sensors. There is no strict difference between the two methods. The former can complete complete complete concentration measurement, qualitative and quantitative measurement of aerosols, but it takes a longer time; The latter can provide near real-time particle size distribution information, but it is more expensive.
Currently, the electronic cigarette industry adopts two particle size testing methods
1. Laser particle size analyzer: uses the principle of light scattering to measure particle size and distribution. The particle size test has a wide range, but due to the mutual influence between particles, the accuracy is slightly poor.
2-scan electron mobility particle size spectrometer: Based on the principle that particles of different sizes have different migration abilities in an electric field, particle size testing is achieved with high measurement accuracy, but only 1 can be tested μ Ultrafine particles below m.
Both measurement methods have their own advantages and disadvantages, and researchers can choose according to their own needs. At present, the main problem with electronic smoke aerosol testing is still particle size distortion. On the one hand, some key components in aerosols are difficult to capture and collect, and on the other hand, the environmental conditions of the experiment cannot guarantee the stability of aerosols, such as cold condensation caused by temperature changes during transportation, collision polymerization between different particles, etc.