皮膚為哺乳類動物最外層的器官，角質層位於皮膚的最外層，幾乎沒有人有做過關於角質層熱性質的研究，我們使用棕櫚酸、膽固醇，和神經胺酸模仿健康皮膚的角質層比例（重量百分比：棕櫚酸/膽固醇/神經胺酸=1/1/2），經由熔融法來製備油脂混合物，利用低溫熱分析儀來找出最穩定且有重複性的循環，以此循環作為基礎進而以小角度X光繞射儀和粉末Ｘ光繞射儀解析油脂混合物的結構和高溫載台光學顯微鏡來觀察油脂混合物的相變化。在本研究中，使用了異位性皮膚炎的仿生角質層油脂比例（重量百分比：棕櫚酸/膽固醇/神經胺酸=1/1/1.13）與正常皮膚的角質層作為比較，由小角度X光繞射儀發現他們的層狀結構分別為9.3和9.5奈米，而且結構上有些不同，使用粉末X光繞射儀可以分析出仿正常角質層的油脂混合物為六方最密結構，而仿正常角質層的油脂混合物為正交晶系結構，進一步使用參比溫度歷史法來計算出異位性皮膚炎和正常皮膚角質層的熱性質，從熱性質的數據來解讀皮膚在人體表層所扮演的腳色，無論是比熱、熱傳系數，和潛熱的數值都不高，所以角質層在人體表層的功能主要為保護作用（抗紫外線、有毒化學藥品侵害）而非作為恆溫的機制。由於角質層所佔面積很大，而且落毛髮是為了可以接觸去避免危險及從觸覺中學習。角質層熔點高達66攝氏度是防止在高溫地區（例如：非洲氣溫可達50度）熔化。由於固態下比熱的差異性(異位性皮膚炎的比熱大於正常皮膚角質層的比熱)，可以明顯的判讀出異位性皮膚炎對冷天氣時較為敏感且易發病的原因之一。Skin is the outermost and the largest organ of the mammals, and stratum corneum (SC) is the outermost tissue of the skin. There is not much research in the thermal properties of the SC. We use palmitic acid, cholesterol, and ceramide type IV (mass ratio of PA/CHOL/CER4(EOH)=1/1/2) to mimic the healthy SC lipid lamellae. The molten method is used to prepare the lipid mixtures. Use low-temperature differential scanning calorimetry (LTDSC) is used to analyze the equilibrium state of the lipid mixtures. Small angle X-ray scattering (SAXS), powder X-ray diffraction (PXRD) diffraction and hot stage optical microscopy (HSOM) are employed to study the phase transformation and nanostructures of the SC lipid blends.In this study, the morphology and thermal property differences between the lipid mixtures of the healthy SC and atopic dermatitis (AD, mass ratio of PA/CHOL/CER4(EOH)=1/1/1.13) are compared. Not only the lamellar structures are 9.5 nm and 9.3 nm, respectively, but also some structures change are observed in SAXS diffraction patterns. The packing of the healthy SC and AD lipid mixtures are hexagonal and orthorhombic phases, respectively. Thermal properties such as specific heat, conductivity and heat of fusion of the health SC and AD lipid mixtures are determined by temperature-history method. Apparently, the role of SC is not for thermal regulation, because of the relatively values of specific heat (3.23±0.14 kJ kg-1K-1), heat conductivity (0.226±0.087 Wm-1K-1), and latent heat (kJ kg-1). The large area of the SC and hairless skin surface mainly are for the sense of touch. The melting point of 66oC prevents SC of early human from melting in Africa of 50oC.The specific heat of AD lipid mixtures is larger than the healthy SC lipid mixtures, and it is one of the reasons of the sensitivity and exacerbation of the AD patients in cold weather.
