DNA is a versatile building material for nanotechnology. We have recently studied a surface-tethered single-domain DNA motor by neutron reflection (IR) for the first time. We showed that NR can reliably detect its pH-dependent conformational changes and melting temperature. Building on these results, this project aims to develop a more-powerful multi-domain DNA motor system where each DNA motor contains several i-motif-domains. We will study how intra- and inter- molecular domains affect their thickness and switching kinetics, and its application as a pH-triggered drug delivery carrier. NR is ideally suited for such studies because it is non-invasive, label-free and can detect small thickness and conformational changes of biomolecules on surfaces. The results obtained here will be very useful in guiding the design and optimization of novel DNA motors and functional devices.