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Damage Characterization of Hair Shaft by Intense Pulsed Light (IPL) |
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6/2008-Present |
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DESCRIPTION |
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The use of intense pulsed light (IPL) is well known as an effective method for permanent epilation (hair removal). IPL is a wide spectrum, high intensity flash of light that has little or no harmful side effects. While the mechanism for hair removal is known, the specific characteristics are not. Because lasers have been used for the treatment of dermatologic conditions involving blood vessels, such as port wine stains, it is well known how the blood vessels get damaged, and at what rate; however, there is no verified model available for the damage done to the hair follicle by IPL. It is useful to know about the damage characteristics, and a model for characterizing damage to the hair follicle will help dial the IPL to the correct wavelength spectrum and power so as to damage the stem cells in the hair follicle, but not the surrounding tissue. This project looks at the effect of the IPL pulse on ex vivo pig skin. The IPL is applied to pig skin samples, which are then biopsied, stained, and put on slides to examine the thermal damage. The characteristics of thermal damage to collagen are well known, and this data can be correlated to the damage done to the hair shaft through the use of a computer model. The model we will use was created using a Monte Carlo Model (MCM) code to represent the heat source, which is then implemented onto a finite element (FE) heat diffusion model. The goal is that the current model that predicts blood vessels heating and damage will be verified as a good approximation for IPL epilation, or that a modified model will result from this comparison.
Fig 1 Graph of Temperature along central axis of Hair shaft Figure 1 shows how the increased melanin concentration of the hair causes it to absorb more light and thus have a higher increase in temperature. As melanin concentration gets higher and higher, the temperature difference gets higher and higher as well.
Fig 2 Model of the Hair Shaft, Temperature Profile, and Damage profile, respectively The first of these pictures in Figure 2 is the bitmap image used to generate the map of absorption coefficients in order to generate the heat source code. The heat source code is then plugged into code that implements the Finite Element Method (FEM) in order to generate files with data for temperature and damage. The second image shown here is the temperature profile, and the third is the damage profile, both obtained from the dat Using these techniques, we can parametrically study the effects that the pulsed light has on the skin and the hair, and correctly dial it to the appropriate setting based on a person's skin type and hair color. |
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