The invention is notably directed to a scanning probe sensor for a scanning probe microscope. The scanning probe sensor comprises a probe tip having a ferromagnetic fluid and a magnetic field generator adapted to generate a magnetic field acting on the ferromagnetic fluid. Furthermore, a sensor controller is provided and configured to control one or more parameters of the magnetic field generator, thereby controlling the shape of the fluid. The invention further concerns a related scanning probe sensor, a related method and a related computer program product.