評估生物氣膠活性之噴墨霧化器特性研究

Abstract

環境中的生物氣膠可透過感染方式對人體造成不良影響，懸浮於空氣中的致病微生物主要藉由人類呼吸而進入人體，而此微生物在存活的情況下，才能造成人類感染。由於對人體健康的不良影響，故空氣中微生物濃度與活性表現顯得十分重要，若能模擬出微生物飛行於空氣中的真實狀態，可對其活性的表現做出更進一步的探討。 本研究使用壓電噴墨系統(Piezoelectric inkjet)作為微生物的霧化設備，探討各種影響噴墨參數與產生氣膠微粒的粒徑分布和輸出量，同時建立微生物自然沉降的暴露艙，控制艙中的溫度、溼度和暴露時間，對微生物進行活性分析。本研究使用酵母菌(Saccharomyces cerevisiae)作為主要分析的微生物，以Marple Cascade Impactor 多階衝擊器、gelatin filter 和SKC Biosampler液體衝擊瓶採樣，並以亞甲基藍染色法分析酵母菌的活性。 研究中的壓電噴墨裝置可以順利噴出懸浮溶液，在懸浮溶液濃度等於4.6×106 顆/ml 下，噴出的液滴有74%未包含懸浮固體顆粒，在含有懸浮固體顆粒的26%液滴中，有86%只包含單一顆粒，其餘為包含兩顆以上。 酵母菌暴露在高濕度(RH=86%)和低濕度(RH=20%)的空氣環境下，存活率沒有顯著的差異。隨著沉降時間延長至39 分鐘，存活率也沒有顯著的下降，此結果說明酵母菌微粒飄浮於空氣中時，短時間內幾乎不受空氣中濕度高低影響。酵母菌的存活率在不同採樣方法下呈現很大差異，以濾紙過濾或衝擊方式採樣得到的存活率(15%, 10%)比液體衝擊瓶採樣(65%)低很多，顯示生物氣膠採樣方法對微生物的造成的影響更為劇烈。

he survival characteristics of bioaerosols needed to be considered because they influenced the effectiveness of infection. The survivability of bioaerosols was found to depend on a number of interacting factors, and was not easy to predict. Although there have been many publications on the effect of environmental factors on the survivability of airborne infectious organisms, the results were difficult to compare. Therefore, this work aimed to establish a robust approach to characterizing the survivability of bioaerosols. In the present study, an inkjet system was employed to generate monodisperse aerosols. Potassium sodium tartrate solution and suspensions of polystyrene latex and yeast were used as test agent. An appropriate driving signal, i.e., a square wave with voltage 14 -18 V and pulse width 14 - 20 μs under frequency 3000 Hz, was used to squeeze the suspension out of a 50-μm nozzle. A high resolution camera was used to monitor and assure that the droplets were uniform in size. Dispersion air was required to reduce droplet coagulation, especially under high generation frequency. The droplets were introduced into a 3-m vertical chamber (diameter 20 cm) to investigate the effect of relative humidity and airborne time on yeast survivability. An aerodynamic particle sizer was used to monitor the size distribution and number concentration of aerosol particles coming out the inkjet generator. A Marple cascade impactor, a SKC bio-sampler, and gelatin filters were used to sample the challenging yeast particles. The results showed that using inkjet printing method to generate bioaerosols was feasible. The generated droplets were ideally 50 μm with a GSD of 1.06. The optimal concentration of suspension to form droplets was about 4.6×106 #/ml. The fractions of droplets with particle to total droplets, and droplets with one particle to all droplets with particles were about 0.26 and 0.86, respectively. Viability test results showed no significant difference between low humidity (20%) and high humidity (86%). Airborne time up to 39 min under the dried condition of RH 20% did not affect the yeast viability, showing that yeast is resistant to low humidity environmental. However, the viability data from different sampling methods were significantly different: impactor 10%, gelatin filter 15%, and impinger 65%. Accordingly, the bioaerosol sampling methods were more influential on the viability of microorganisms.