The Hydrophobicity/Hydrophilicity in Biomolecules & Biosystems

  • Tzu-Chieh Tang

Student thesis: Master's Thesis


A systematical method is proposed here to measure the hydrophilicity and hydrophobicity of biosystems at different scales spanning from the interaction of biomolecules to the surface of organisms. These properties could be further analyzed and coupled with their functions in natural environment. Biologically inspired engineering has emerged as one of the most important inter-disciplinary field of applied science in the past decade. Using the principles of Nature's design which are utilized by organisms when adapting to the environment, researchers develop bioinspired materials and devices that can provide solutions to challenges in the field of engineering. In both Nature and the artificial world, water molecules participate in numerous critical processes. The interplay between the surface and water not only determines the physical properties of a material, but also plays a pivotal role in the chemical reactions that might take place at the interface. Thanks to the advance in force reconstruction in atomic force microscopy (AFM), the water layer on the surface can be now detected at extremely high resolution. In this study, we firstly tested the ability of AFM force reconstruction in observing the surface's affinity to water molecules using flat inorganic samples like mica and graphite. A firm correlation of change in force profile and relative humidity was proposed. Next, to investigate the interaction between a biomolecule and functionalized surface, we reported the change in apparent height of the DNA molecules under various ion strengths and relative humidity. Based on this preliminary understanding of this technique, we expanded the spectrum of samples to a larger and more complicated scale: the surface of organisms. The hydrophilicity of different scales of a gulf parrotfish was studied. The importance of surface property of a scale might explain the mechanisms of mucus adhesion and anti-biofouling at nanoscale. This brings not only new perspectives on basic biological studies, but also principles that could be applied in the engineering field. Higher efficiency and lower energy cost in engineering could be achieved by learning from Nature.
Date of Award2014
Original languageAmerican English
SupervisorMatteo Chiesa (Supervisor)


  • Hydrophilicity and Hydrophobicity; Atomic Force Microscopy (AFM); DNA; Biosystems.

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