微小游泳粒子在固定表面的聚集現象;Accumulation of microswimmers near a no-slip surface

Please use this identifier to cite or link to this item: http://ir.lib.ncu.edu.tw/handle/987654321/72940

Title:	微小游泳粒子在固定表面的聚集現象;Accumulation of microswimmers near a no-slip surface
Authors:	吳冠廷;Wu, Kuan-Ting
Contributors:	物理學系
Keywords:	細菌;表面;低雷諾數;自我推進粒子;生物薄膜;microswimmer;surface;accumulation;entrapment;low Reynolds number;bio-film
Date:	2017-01-19
Issue Date:	2017-05-05 17:19:12 (UTC+8)
Publisher:	國立中央大學
Abstract:	本研究專注於微小游泳粒子(細菌)在固定表面的聚集現象。浮游微生物在表面群聚並附著會形成生物薄膜，密切的影響著人類。常見於牙齒、杯壁和傷口等表面。且可能進一步在輸水管線內部、船殼表面造成生物淤積。雖然已經有許多清除的方法，現今的科學家投入更多的關注於微小游泳粒子與固定表面之間的交互作用，以預防生物薄膜的形成。過去的研究發現，在低雷諾數的狀況下，會游泳的微小的細胞或細菌，如大腸桿菌、新月柄桿菌和精蟲，在黏著於表面之前都容易在固定表面附近徘徊、聚集。已經有許多的實驗證明其中有一些相同的物理機制能夠影響游泳粒子在表面附近的行為，並使其不易游離表面。其中包含微小游泳粒子與固定表面的遠場流體力學、近場流體力學和碰撞交互作用，以及粒子本身的旋轉布朗運動。希望藉由本次研究進一步了解各種交互作用所扮演的角色，以及其實質貢獻。我們分別運用三種不同游泳模式的單鞭毛溶藻弧菌Vibrio. Alginolyticus，Pusher、Puller和bimodal，觀察細菌在表面的游泳軌跡，以及距離表面20µm以內的細菌分佈。此種細菌的游速可由溶液中的鈉離子濃度調整，利於操控細菌與表面的遠場流體力學交互作用強度。實驗結果顯示細菌在表面游泳時的傾角決定其徘徊於表面機率。而其傾角則取決於近、遠場流體力學交互作用之間的競爭或加成。最後，我們亦能了解野生細菌如何利用游泳模式的轉換在不同的環境下維持其在表面的聚集。 ;Microbial processes including biofilm formation or bio-fouling are ubiquitous and influence human extensively from daily lives to various industrial systems. For decades, researchers studied the processes and strategies of bacteria accumulation on surfaces. Considering the initial stage of biofilm formation, before the cell adhesion, swimming cells were reported swim along the surface for a long time. To describe the phenomenon, models of different perspectives of physics had been established, including far and near field hydrodynamic, steric effects and diffusion. To reach a more complete picture for the cell-surface interaction, we manipulated the swimming characteristic of single polar-flagellated bacteria, Vibrio. Alginolyticus, with mutant strains at different swimming speed. Observing the steady-state bacteria distribution within 20µm from a surface, contributions of each mechanism can be evaluated. Our results show that surface accumulation of microswimmers depends on both swimming speed and swimming characteristic. Accumulation of pusher bacteria is reduced as the speed increases. In contrast, accumulation of puller bacteria increases strongly with the speed. None of a previous model can fully explain our observations. By a closer look, the contribution of each mechanisms are assigned. Finally, we show that a microswimmer in nature can accumulate near a surface by a run and reverse swimming characteristic.
Appears in Collections:	[Graduate Institute of Physics] Electronic Thesis & Dissertation

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