Fouling behaviour of zwitterionic DLC surfaces

在本项目中，将对以下两种假设的有效性进行实验研究，并将所得结果纳入一个综合模型：1)改性类金刚石涂层（DLC）的表面表现出非常有利的污垢行为，即，如果在使用条件下，这些表面提供相同且显著密度的带正电荷和带负电荷的表面官能团（所谓的两性离子表面），则从过饱和水溶液中吸附蛋白质和盐的能力尤其低。2)。众所周知，具有这种表面的涂层不仅可以在沉积后通过等离子体改性获得，还可以在沉积过程中加入合适的元素或化合物，如氧和氮或二氧化硫和氮。为了验证这些假设，我们将采用等离子体活化化学气相沉积的方法制备DLC涂层。在使用条件下，即在典型的6 < pH < 8的水溶液中电离的功能表面基团，将通过在低碳氢化合物的薄膜沉积过程中添加合适的气体或蒸气将异原子（O， N， S）掺入生长膜中来制备。这样得到的表面将被物理化学表征；特别是zeta势和表面自由能的LW-AB分量将被研究。涂层成分将通过XPS和一定程度的EPMA进行研究，主要通过FTIR-ATR光谱研究与污染相关的表面官能团。经过适当的调节，表面将分别暴露在典型的清洁和污垢条件下，使用乳清分离蛋白（WPI）和牛奶盐（模拟牛奶超滤液，SMUF）作为污垢系统。在实验中获得的数据和见解将作为根据数学模型进行描述的基础。深入了解表面、污垢沉积和清洁机制之间的相互作用，将有助于提高定制表面设计的机会，以及适应的清洁策略。

In the proposed project the validity of the following two hypotheses about the formation of fouling deposits on coated surfaces for applications in chemical process engineering shall be studied experimentally and the obtained results shall be incorporated in a comprehensive model: 1.) Surfaces of modified diamond-like carbon coatings (DLC) show an exceptionally favourable fouling behaviour, i.e., especially low adsorption of proteins and salts from supersaturated aqueous solutions, if, under conditions of use, these surfaces furnish identical and significant densities of positively and negatively charged surface functional groups (so-called zwitterionic surfaces). 2.) Coatings with such surfaces are not only accessible - as already known - by plasma-based modification after deposition, but also by the incorporation of suitable elements or compounds during deposition, such as oxygen and nitrogen or sulfur dioxide and nitrogen. In order to evaluate these hypotheses DLC coatings will be prepared by plasma-activated chemical vapour deposition. Functional surface groups which are ionized under conditions of use, i.e., in aqueous solutions with typically 6 < pH < 8, will be prepared by incorporation of hetero-atoms (O, N, S) into the growing film by the addition of suitable gases or vapours during film deposition from low hydrocarbons. Thus obtained surfaces will be characterised physico-chemically; particularly zeta potentials und LW-AB components of surface free energies will be studied. Coating compositions will be investigated using XPS and to some extent EPMA, fouling-relevant surface functional groups primarily by FTIR-ATR spectroscopy. After suitable conditioning the surfaces will be exposed to typical cleaning and fouling conditions, respectively, using whey protein isolates (WPI) and milk salts (simulated milk ultra filtrate, SMUF) as fouling systems. The data and insights obtained in the experiments will be used as the basis for a description in terms of a mathematical model. An in-depth understanding of the interactions between surface, fouling deposit, and cleaning mechanisms will enable improved opportunities of tailor-made surface design as well as an adapted cleaning strategy.