Underwater Atomic Force Microscope: Instrumentation, operation, and measurements

We developed and tested an Underwater Atomic Force Microscope (UAFM) system and conducted in situ measurements in a deep sea environment. The developed UAFM is compact, mobile, and mountable on underwater vehicles or submersible seafloor platforms. It is intended for in situ observation of microorganisms (e.g., bacteria) and microparticles (e.g., mineral components) with a nanometer-scale spatial resolution in various ocean environments and particularly near hydrothermal features in the deep sea. We developed two unique instrumental mechanisms that allow the UAFM system to be remotely operated from a research vessel. The first is a self-sensitive cantilever, obviating the manual alignment of optics that is needed when using an optically based deflection sensor. To allow the self-sensitive cantilever to be used in electrolytic solutions such as deep sea water, the surface of the cantilever was coated with a thin layer of Parylene. The second innovation is that the observation specimens are remotely introduced into the main UAFM unit and fixed on the sample stage using a filter-integrated sample scanner. The UAFM is operated by a control system on a single-board computer, running over a specially written program. This system can be used to collect information on oceanic ecosystems and material circulation patterns by monitoring the spatial distribution of the micrometer-scale particles and analyzing their interactions with other physical and chemical parameters.