274 JOURNAL OF COSMETIC SCIENCE polymers. The equipment used was Digital Instruments model Nanoscope IIIa ©. Figure 1 presents a schematic diagram of the hair surface and how AFM, in its contact mode, was used to evaluate hair characteristics. Mattoso et aL (10) described several advantages of the AFM over common electron microscopy techniques, including: ß Greater resolution, which can achieve the molecular or even atomic scale for some materials. ß Generation of digital images from three-dimensional topographic data, which can be quantitatively analyzed in 3D. ß Quantification of variables such as roughness, surface area, and morphology heights. ß Absence of the need for any conductive coating on the sample to be analyzed, but just a little sample preparation, which allows the discernment of surface features that are undetectable by scanning electron microscopy. ß Depiction of variations of surface properties, which can be directly and statistically studied. This paper presents results of AFM use to investigate the morphology of hair fibers exposed and not exposed to UV radiation as well as measurement of the roughness and thickness of cuticle layers. RESULTS AND DISCUSSION SCANNING ELECTRON MICROSCOPY (SEM) Hair damage is the breakdown or removal of structural components or parts of hair that are more vulnerable to chemical breakdown. The exposure to sunlight over prolonged periods induces changes in hair that can be detected at the morphological level, as shown in Figure 2. It can be observed that the unexposed hair (Figure 2a) has more cuticle layers, that the cuticles have a uniform and regular shape, and that they are oriented longitudinally and Cantilever... •Tip : Hair st•rface Figure 1. Schematic diagram of the hair surface and evaluation by AFM.

EVALUATION OF UV HAIR DAMAGE BY AFM 275 .v. • .. : i • .• •'• •.- • • .,,,,,,, ,, ,•,• Figure 2. SEM micrographs comparing hair fibers after exposure to UV radiation. (a) Control: virgin hair, 0 h (5 KV, 5000x) (b) 160 h of UV exposure (5 KV, 5000x). aligned to the direction of the fiber. When exposed to UV radiation, the cuticle un- dergoes a process of chipping, extraction, and erosion, causing dryness of the hair and greater susceptibility to further damaging action, which may involve large segments or sections of scales being ripped from the hair. These observations are further elucidated in the profile in Figure 3, which shows the breakdown mechanism of the cuticles when exposed to UV radiation. The physical and mechanical damages induced by irradiation from UV light are illustrated in these micrographs, where we can deduce that the energy photons cause bubble formation and breakdown and cracking of the cuticle. These results are in agreement with those of Tare et al. (11), who observed changes in cuticle topography after UV irradiation, including a decrease in scale thickness. In the present study, we have identified one physical breakdown mechanism for the cuticle. The first event is the expansion of the superficial layer and the formation of bubbles, Figure 3. Breakdown and mechanical damage to cuticle irradiated for 160 hours. (a) and (b) 160 h of UV exposure (5 KV, 20000x).