DNA is an extremely versatile building material for the development and assembly of functional nanostructures and nanodevices. There are numerous examples of DNA based ¿nanomotors¿ in the literature. This research is directed at developing an array of surface-immobilised proton-fueled DNA nanomachines based on a transition from a four-stranded to a double-stranded DNA structure. This process can be reversibly actuated by solution pH cycling between 5 and 8, producing a conformational change which elongates or shortens the separation distance between ends of the DNA. Neutron reflectivity is ideally suited to non-invasive investigations of the thickness changes and surface coverage of these devices. The structural and kinetic information obtained from this study will inform future device optimisation and our understanding of the operation mechanism of such DNA motor systems.