液體在旋轉塗佈過程中，由於離心力之作用，使不穩定手指狀會在連續液膜波前處產生。本研究主要以實驗探討在旋轉塗佈中，外加垂直磁場不穩定手指狀之現象。靜止磁流體受外加垂直磁場影響產生尖端分離之現象，磁場越強磁化效應越大，黏度越大磁化效應越小。針對不同時間點加磁場，包括無磁場、同時加磁場與先加磁場進行比較，無磁場之最大半徑大於同時加磁場與先加磁場。在先加磁場方面，可藉此固定手指狀數目，但手指狀較粗導致最大半徑變小。以控制不穩定手指狀為目的，在同時加磁場與臨界半徑前加磁場方面，經由觀察旋塗不穩定手指狀流場現象，發現磁場對磁流體旋塗手指狀之影響，在高轉速旋轉與強磁場之情況下可達到抑制減少之效果，在低轉速旋轉時，磁場主導手指狀形成且數目增加。由無磁場與外加磁場旋塗手指狀之實驗結果進行比較，可歸納出磁場對磁流體旋塗半徑與手指狀之影響。 In spin coating, the instability fingers would arise at the wave front of continuous liquid film. Study the magnetic fluid in spin coating submitted to a perpendicular magnetic field. It produces the phenomenon breakup in peaks that the static magnetic fluid is influenced by the perpendicular magnetic field, the magnetization will increase as increasing the intensity of magnetic field and decrease as increasing the viscosity. We compare the trend of no magnetic field, start magnetic field at the same time and magnetic field before rotation, the maximum radius of no magnetic field is greater than the others. In starting magnetic field before rotation, can fix regular number of fingers, fingering is thicker to cause maximum radius diminish. In order to control fingering instability by starting the magnetic field at the same time and before critical radius. Both of them show the similar fingering phenomena. Additionally, with high rotational speed and strong magnetic field exerted, the number of fingers will decrease. While rotating in low rotational speed, the number of fingers will increase. Comparing with the result of no magnetic field and the presence of a magnetic field, we can summary the influence that magnetic field make coating radius and fingering change.
