本文以MEMS製程製作雙流體氣助式及內衝式微型霧化器，探討其霧化機制、霧化特性及應用在吸入式給藥之可行性。實驗均在室溫下進行，微噴流之破裂機制是以顯微鏡結合高速攝影之照相技術來觀察檢視。此研究中設計之微霧化器分別是微氣助式AMA霧化器及歧管內衝式MMA霧化器，AMA霧化器構造在混合腔正上方有一液體微流道供應液體，左右各有一氣體流道，此氣助式(AMA)微霧化器之噴口水力直徑為46、78及80µm。而MMA霧化器則含有一液體分配器之霧化器，其液體供應經由分配器之歧管將兩股液體注入兩氣體流道，並由氣體運載入混合腔中衝擊，再經微噴口噴出形成噴霧，其噴口水力直徑為44及75µm。此兩型微霧化器之液體微流道水力直徑為30~50µm出口寬/高比(Aspect Ratio)為9 ~ 23。
為了探討液體性質、液體流率及霧化氣體壓力對微液束霧化之噴霧粒徑的影響。此研究應用水、酒精、生理食鹽水(0.45%)及甘油水溶液等為工作流體，使用之液體流率QL= 0.1~1mL/min，其操作壓力從0至8bar，霧化氣體(壓縮空氣)之流率Qg< 1L/min，其操作壓力在0.1至6bar間。而噴霧粒徑是以光學繞射原理之非侵入式Malvern INSITEC RT-Sizer粒徑分析儀來量測，噴霧整個流場之噴霧平均速度是使用IDT/PIV粒子影像速度儀來量測。噴霧演變過程之流動觀察亦使用IDT的高速攝影機系統來執行。結果顯示，基於霧化氣體壓力、液體噴射壓力及韋伯數之變化，AMA型微霧化器在靠噴口處近場之液體破裂機制及方式可分為層流液束破裂、空氣動力破裂方式及紊流模態之霧化機制。實驗觀察亦發現，控制微霧化器之液氣體積流率比(QL/Qg)，可在腔體內產生流體聚焦機制，並產生單液滴噴流及兩束分岔流之液滴噴流，其中分岔液滴噴流之擴張角度隨QL/Qg 之增大而減小，微液滴粒徑(SMD)及微液噴流之破裂長度均隨QL/Qg 之增大而增加。
在霧化性能方面，出口水力直徑為46µm之AMA微霧化器其噴霧粒徑隨氣液質量比(GLR)增大至2.9時，其平均粒徑由14.1µm降至5.3µm。當水力直徑為78µm，被霧化之流體是水，液流率小於2mL/min時，霧化壓力為3~5bar條件下，其產生之噴霧平均粒徑可達徑5~6µm。結果也顯示出口水力直徑為44µm之內衝式(MMA)微型霧化器在液體流率為0.3〜1.0mL/min及氣液質量比(GLR)為0.13至0.38時，其噴霧平均粒徑可達3µm至6µm。在噴霧之速度特性上，咸以粒子影像速度儀來量測，其噴霧速度流場為噴流結構型態且軸向速度具有相似性，其平均軸向速度在噴口下游Z=20mm處低於10m/s，至下游Z=100mm時由於空氣阻力及慣性力變小，速度降至1m/s。
最後，為了評估將AMA微霧化器應用至吸入式給藥之可行性，此研究將氣助式(AMA)微霧化器與圓球擋體及吹口組成吸入器，稱為AMA氣霧系統，在吹口出口測量水霧之粒徑。結果顯示，在霧化氣體壓力大於2bar，液流率0.8~2mL/min下，此氣霧系統測得之SMD可降至2.3μm，DV50同時降至5µm以下，其適於呼吸治療噴霧粒子(< 5µm)的體積百分比可達到68%，此種氣助式(AMA)微霧化器與圓球擋體及90度彎頭吹口組合之氣霧系統為最佳組合，經比較適於呼吸治療之噴霧粒子的體積百分比時，此AMA氣霧系統均優於市售之氣動式霧化器。研究中亦以美國藥典之喉部模型(USP2000 throat)作體外模擬實驗。結果發現，AMA微霧化器加90度彎頭吹口組合之氣霧系統通過喉部模型至測試區為最佳組合，此種組合之噴霧粒子需經過兩處彎頭，可充分攔截大粒子。當液流率1mL/min、霧化氣壓力2bar及18L/min之吸氣下，測試區之氣霧粒子小於5µm之百分比可達到50%。由此研究可得到一結論，預膜型微霧化器(AMA及MMA)之設計可提昇霧化性能，佐以擋體及吹口，性能可達醫藥用吸入器之需求，此裝置可用於治療氣喘、慢性阻塞性肺病、囊胞性纖維症及呼吸照護等。

This dissertation investigates the atomization mechanisms and performance of twin-fluid micro atomizers. It produces micron-sized droplets sprays for the applications of inhaled drug delivery. The micro-atomizers were fabricated via MEMS bulk machining processes. The breakup mechanisms of the micro jet were examined experimentally using photographic technique. All tests were performed at room temperature and atmospheric pressure. The two types of the twin-fluid micro-atomizers were designed in the research program. One is the air-assist type micro-atomizer (AMA type) with three micro channels for the liquid and gas flows. The other one is the manifold type micro-atomizer (MMA type) with four micro channels. The orifice hydraulic diameters of the micro atomizers are less than 100µm. The aspect ratios of orifice are ranged from 9 to 23 for the AMA and MMA atomizers. This dissertation also describes the effects of liquid properties, liquid flow rate, and atomizing air pressure on drop sizes produced by disintegration of the micro-jet. The liquids employed in this study are water, ethyl alcohol, 0.45%NaCl solution, and a glycerin-water mixture. Liquid injection pressure is from 0 to 8bar and liquid flow rate ranging from 0.1 to 4mL/min is supplied with syringe pump. Atomizing gas pressure is varied from 1 to 6bar with volume flow rate less than 1L/min. A nonintrusive Malvern INSITEC RT-Sizer was used to measure drop size distribution of the spray and IDT/PIV system was used to measure the spray velocity. Flow visualization technique was also performed by the IDT high speed camera system. Observations of the breakup mechanisms in the near-field of the atomizer show that the breakup regimes can be described by the mechanisms involving the laminar jet disintegration, aerodynamic disintegration and turbulent mode based on the atomizing gas pressure, the injection pressure and Weber number. A new phenomenon of flow branching of the liquid jet emanating from the atomizer was also observed. Moreover, the ratio of liquid to gas flow rate determines the spreading angle and droplets size of the two-pronged liquid jets. It is also found that the flow focusing mechanism results in the mono-dispersed droplets stream.
Results also show that for AMA with hydraulic diameter 46µm the mean droplet size reduces from 14.1µm to 5.3µm as gas-to-liquid ratio (GLR) ranging from 1.3 to 2.9 and the mean droplet size (SMD) ranging 5 to 6µm can also be achieved by AMA with hydraulic diameter of 78µm under liquid flow rate less than 2mL/min and gas pressure ranging from 3 bar to 5bar. Moreover, for MMA with hydraulic diameter of 44µm the mean droplet size is further reduced from 3µm to 6µm with lower gas-to-liquid ratio ranging from 0.13 to 0.38 under the same pressure range. The axial velocity profile of the micro spray measured by using PIV instrument is essentially a jet flow structure. The mean axial velocity of spray droplets is below10m/s at Z=20mm downstream from the atomizer and reduced to 1m/s downstream Z=100mm. In order to evaluate the feasibility of drug delivery to lung with AMA, the mouthpiece, ball baffle, and micro-atomizer were connected in series and drop size of water spray was measured near the exit of mouthpiece. Results indicate that the finer micro spray with Sauter mean diameter (SMD) of 2.3µm under the test conditions of the air pressure greater than 2bar and the liquid flow rate ranging from 0.8 to 2mL/min can be achieved as the ball baffle and mouthpiece was installed. Dv50 less than 5µm are also obtained and the respirable percentage (< 5µm) of 68% can be achieved by the AMA nebulizing system with bending mouthpiece and baffle.
For in vitro experiments with the mouthpiece and the USP2000 throat model, the AMA nebulizing system with bending mouthpiece is also the best choice because the spray jet travels two bends to measurement region. The respirable percentage of 50% for aerosol measured in measurement region of USP can be achieved under gas pressure of 2bar, suction air of 18L/min, and QL=1mL/min. It turns out that the design of prefilming type micro atomizers can enhance the atomization performance in this research. As installing baffle and mouthpiece, the droplets size and slow velocity is further suitable for the application of drug inhalation to treat asthma, COPD, CF, and respiratory care.

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