Sensitivity of a mechanical device to environmental changes can be enhanced through miniaturization. This has led to some key advances in nanoscience, which include the imaging of surfaces with atomic and molecular resolution, measurement of inertial mass at the atomic scale and monitoring of biological processes in liquid. Controlling the effects of surfaces and fluid dissipation presents significant challenges to achieving the ultimate sensitivity of these devices. Particularly, the fluid-structure interaction of resonating microcantilevers in fluid has been widely studied and is a cornerstone in nanomechanical sensor development. In this talk, I will give an overview of work being undertaken in our group dedicated to exploring the underlying physical processes in these and related systems. This will include exploration of recent developments that focus on cantilever sensors with embedded microfluidic channels, gigahertz nanoparticle resonators in fluid and examination of the effects of surface stress on the resonant properties of cantilever sensors.