Bacterial biofilms consist of communities of cells encased in self-produced extracellular polymeric substance (EPS) at the interface of different phases. While most of our understanding of biofilms to date has been obtained from submerged biofilms formed at the solid-liquid (S-L) interface, the interface between air and liquid provides a niche for the formation of biofilms with unobstructed access to both liquid and gaseous phases, which is of ecological, clinical and commercial significance. But there is a paucity of information on air-liquid (A-L) interface biofilms. Cultivation and characterization of A-L interface biofilms are still limited to traditional methods created for S-L interface biofilms, mostly based on microtiter plates and tubes. In this thesis, two bioreactors have been designed, fabricated and validated to culture A-L interface and air-liquid-solid (A-L-S) interface biofilms. / The first bioreactor, named hanging drop biofilm reactor (HDBR), has been constructed on an open microfluidic platform to hold hanging droplets culturing biofilms in a suspended fashion. Hanging droplets containing microorganisms were accessed from the topside of the microfluidic platform, whilst measurement and harvesting were performed on the underside. The system was driven by evaporating flows. No additional electronic or mechanical actuation was needed. Biofilms were formed in hanging droplet biofilm reactors with bacterial suspensions. After 24 h of incubation under optimized conditions, biofilm-positive phenotype Bacillus subtilis developed A-L biofilms eliciting distinct developmental stages. Formation and dispersal of A-L interface biofilms were for the first time analytically characterized. Biofilms harvested by dripping droplets showed a spherical cap shape with porous structures. This is the first reported attempt to culture A-L interface biofilms inside a hanging droplet on an open microfluidic platform under evaporation flow. / The second bioreactor, named segmented-flow microfluidic air-liquid-solid interface biofilm reactor (SFMBR), has been implemented to grow A-L-S interface biofilms on chip. A distinct A-L-S interface was made available by introducing a gas phase into successive nutrient flows with a T-junction design, forming a segmented gas-liquid flow. Velocity fields were computed by numerical simulation, involving not only the hydrodynamic fields in the gaseous and aqueous phases, but also of the air-liquidand solid-liquid interfaces. Formation of A-L-S interface biofilms along microfluidic channels was observed and characterized by microscopy techniques non-destructively. The effect of hydrodynamics, interface topology and channel hydrophobicity on A-L-S interface biofilm formation was simulated and tested. Biofilms interacted with the shear forces introduced by the passage of A-L interfaces of an air slug with a shear stress of about 0.66 Pa and relaxed after the A-L interface passed. This device is a low-cost on-chip biofilm reactor to culture A-L-S interface biofilms and to measure in situ biological and mechanical properties of growing biofilm. / We have successfully constructed and validated two novel microfluidic strategies utilizing the interfacial phenomenon at the air-liquid interface and evaporating flow to culture and investigate the complex biology of A-L and A-L-S interfaces biofilms. / 细菌生物膜(生物膜)由生长在固、气、液相的界面上的细菌包裹于由其产生的细胞外间质聚合物内组成。固-液界面生物膜可以利用微流系统低耗材高效培养检测。但没有微流系统可研究生长在气-液界面的生物膜。为了填补这个空白，本论文设计了两种微流生物膜反应器(反应器)培养气-液和气-液-固界面生物膜。 / 一种反应器是培养气-液界面生物膜的基于蒸发产生的微流动和微循环的倒悬液滴反应器。我们创新的利用蒸发产生的微流和微循环增加微流系统中材料混合和供氧。我设计了两种倒悬液滴反应器:倒悬液滴气-液界面反应器微孔板和微流气-液界面反应器在静态和流动培养液条件下培养气-液界面生物膜。我们监控并分析了气-液界面生物膜形成过程。第一次报道了气-液界面生物膜生长阶段的划分。了解反应器的特性，如微流动和反应器形态等对应用反应器有至关重要的作用。我们使用粒子图像测这和数值模拟的方法研究了反应器特性。设计了滴落打印的方法收获并离线测量生物膜。这是第一种可以方便、可重复收获生物膜的方法。我们研究了收获后生物膜的抗药性和微结构，发观倒悬液滴反应器培养的生物膜对干燥和灭菌过程有很高的抗性。我们还首次发现了细菌由纳米管连接的气液界面细菌生物膜。 / 另一种反应器是基于微流分段气-液流的分段流微流反应器。这是首个培养气-液-固界面生物膜的微流反应器。我们创新性的应用了分段气-液流为生物膜滴定供养。我们的微流反应器模拟工业标准方法培养气-液-固界面生物膜的反应器。为了研究生物膜在反应器中的生长和流动对生物膜的影响，我们监测了生物膜的生长，用数值模拟的方法研究了分段流的流动。发现了单层菌落储水的现象。我们还首次报道了微流系统中，用粒子图像測速和数值模拟的方法研究生物膜的弹性松弛过程。 / 这里设计的基于液滴的高通量，高效率，低成本，操作简单的生物膜反应器可以加快生物膜的研究。 / Liu, Songlin. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2015. / Includes bibliographical references (leaves 115-130). / Abstracts also in Chinese. / Title from PDF title page (viewed on 19, September, 2016). / Liu, Songlin. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only. / Detailed summary in vernacular field only.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_1290636 |
| Date | January 2015 |
| Contributors | Liu, Songlin (author.), Yung, Pun To (thesis advisor.), Chinese University of Hong Kong Graduate School. Division of Electronic Engineering. (degree granting institution.) |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, bibliography, text |
| Format | electronic resource], electronic resource, remote, 1 online resource (iii, x, 130 leaves) : illustrations, computer, online resource |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons "Attribution-NonCommercial-NoDerivatives 4.0 International" License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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