微乳液系統可以利用其PIT (Phase inversion temperature )的性質，形成液滴大小均一且粒徑在100nm 左右的分散相，因此非常適合用於製造奈米膠囊，此方法稱為相轉移溫度法(PIT method, Phase inversion temperature method)，亦可利用相轉移法(PIT)製備奈米乳液(nano-emulsion)系統。本研究中採用數種油相(oil phase) 以及混合界面活性劑(mixed surfactants)，找出適當的相轉移溫度， 由結果中可任意設定PIT 以及微乳液的組成，利用本研究方法找到所需的溫度，製備出結構穩定之奈米膠囊。當固定油相及水相比例時，PIT 會隨著界面活性劑分子碳鏈增加而下降，而隨著聚氧乙烯鏈長增加而上升。油相本質與相轉移溫度有關，油相的極性減少時，使系統的相轉移溫度上升。

The phase inversion temperatures method (PIT method) can be apply for micro-emulsion droplet size with particle size in the range around 100nm. PIT method is very suitable for the preparation of nano-emulsion and nano-capsule. This study has tried several kinds of oil (oil phase) as well as mixed surfactants find an appropriate phase inversion temperature. The result can be applied for PIT setting and micro-emulsion compositions. And using this research method can easily find the necessary phase inversion temperature and preparation a structural stable nano-capsule. When the oil phase and water phase fixed, the PIT will decline as the hydrophobic chain of surfactant molecule increases.And the PIT rises as the polyoxyethylened chain length increases. The nature of oil phase
also relative to the PIT, when the polarity of oil phase decreasing the PIT increasing.