For more than a decade, the workhorse sensors for MRFM have been silicon cantilevers with a resonance frequency of 3-5 kHz. They reach a force sensitivity of a few aN per root Hz when cooled to liquid He temperatures. Recently, several groups started investigating the use of silicon nitride membranes as improved force sensors. These devices are typically in the MHz range and feature quality factors beyond 100 millions, which may allow the detection of forces below 100 zN. In addition, these membranes can be combined with laser cavities to reduce the readout noise down to the Heisenberg limit. Our lab is exploiting the exciting properties of silicon nitride membranes to realize a new generation of extremly sensitive scanning force microscopes, and to establish an alternative platform for nano-​MRI.