Ultra-Liquid-Repellent Surfaces: from wetting to anti-biofouling properties

在过去的二十年里，由于生物医学设备的污染而导致的医院获得性感染的大量发生，这是导致长时间住院和死亡的主要公共卫生威胁，引起了人们的极大关注。例如，留置导尿管是大多数医院获得性尿路感染(UTI)的原因，约占所有医院获得性感染的35%-40%。其次是手术部位感染，占所有医院获得性感染的20%。这些感染的发病机制与设备/仪器表面对细菌黏附和微生物定植的敏感性有关。在这种情况下，细菌通过手术器械和导管等医疗设备侵入人体(例如，沿尿路向膀胱和肾脏迁移)，由于受污染的尿液、血液，甚至水/水分等液体的扩散和粘连，变得非常容易。然而，由于对复杂生理液体在生物医疗设备表面(内外)上的润湿和黏附的关注和了解不足，在预防污垢相关感染方面的进展相当有限。“湿”指的是沉积在表面上的液体如何扩散。润湿现象是由界面张力和表面结构决定的。在非可湿表面上的液滴的情况下，液滴可以形成大致球形，显示出接近180度的接触角。这使得与液体驱避剂表面接触的液滴可以很容易地滑动/滚动，并清除表面污染。相比之下，液滴会自发地扩散到完全可湿润的固体表面，形成一层薄膜。基于润湿的应用领域的最新进展表明，具有极强的液体排斥性的表面具有促进抗生物污损性能的巨大潜力。在这项工作中，将展示具有改进的耐久性和抗生物污损性能的表面的设计和应用，从而可以操纵润湿和附着行为。首先，我们将使用最先进的制造技术来制备各种液体排斥表面。这将使我们能够比较和优化制造的表面图案的液体排斥性，从而防止液体渗透到制造的表面结构中，以避免污染和腐蚀。具体地说，我们将研究复杂液体(包括尿液和血液)的润湿和粘合行为，以促进超液体排斥表面的开发。我们将开发方法来测试表面性质如何受到与各种液体的相互作用的影响。在适当的情况下，我们将评估表面缺陷在与污染液体相互作用之前和之后的影响。这是为了通过减少表面缺陷导致的表面相关生物膜生长来改善固有的防污性能。了解液体排斥性的变化是使研究人员能够设计出坚固的抗生物污垢表面的关键，这些表面可用于具有内表面的医疗设备(如导管和结肠造口袋)和医用级金属，以防止侵蚀性污染和腐蚀。

Significant incidence of hospital-acquired infections due to fouling of biomedical devices, which are major public health threats contributing to prolonged hospital stay and death, has generated much attention over the past two decades. For example, indwelling urinary catheters are responsible for most hospital-acquired urinary tract infections (UTIs), which account for approximately 35-40% of all hospital-acquired infections. This is followed by surgical site infections that account for 20% of all hospital-acquired infections. The pathogenesis of these infections is related to the susceptibility of device/instrument surfaces to bacterial adhesion and microbial colonization. Under these circumstances, invasion of the bacteria to human bodies via medical devices such as surgical instruments and catheters (e.g., migrating along the urinary tract to the bladder and kidneys) is made utterly easy by the spreading and adhesion of liquids such as contaminated urine, blood and even water/moisture. However, due to insufficient attention to and understanding of wetting and adhesion of complex physiological fluids on the surfaces (both external and internal) of biomedical devices, there has been rather limited progress in preventing fouling-associated infections.This proposal aims to gain an in-depth understanding of wetting and adhesion for anti-biofouling surfaces relevant for biomedical devices. 'Wetting' refers to how a liquid deposited on a surface spreads out. The phenomena of wetting are governed by interfacial tension and surface structure. In the case of droplets of liquid on a non-wettable surface, the droplets can form a roughly spherical shape, exhibiting a contact angle approaching 180 degrees. This allows droplets that are in contact with a liquid repellent surface to slide/roll off easily and remove surface contamination. By contrast, droplets will spread spontaneously on fully wettable solid surfaces to form a thin film. Recent advances in wetting-based applications have demonstrated that surfaces with extreme liquid repellence have great potential to facilitate anti-biofouling properties. Design and application of surfaces with improved durability and anti-biofouling properties whereby wetting and adhesion behaviours can be manipulated will be demonstrated in this work. Firstly, we will use state-of-the-art fabrication techniques to prepare various liquid repellent surfaces. This will allow us to compare and optimise the liquid repellence of the fabricated surface patterns, and thereby, prevent the impalement of the liquid into the fabricated surface structure in order to avoid contamination and corrosion. Specifically, we will investigate the wetting and adhesion behaviours of complex liquids, including urine and blood, to facilitate the development of ultra-liquid-repellent surfaces. We will develop methods to test how the surface properties are affected by interactions with various liquids. Where applicable, we will assess the impact of surface defects before and after interactions with the contaminating liquids. This is to improve the inherent antifouling properties by reducing surface-associated biofilm growth resulting from surface defects. Understanding how liquid repellence varies is key to enabling researchers to design robust anti-biofouling surfaces that can be used on medical devices with internal surfaces (such as catheters and colostomy bags) and medical-grade metals against aggressive contamination and corrosion.