Micro-fabricated mechanical sensors for lateral molecular-force microscopy

Atomic force microscopy (AFM) has been very successful in measuring forces perpendicular to the sample plane. Here, we present the advantages of turning the AFM cantilever 90° in order for it to be perpendicular to the sample. This rotation leads naturally to the detection of in-plane forces with some extra advantages with respect to the AFM orientation. In particular, the use of extremely small (1 μm wide) and soft (k≅10–5 N/m) micro-fabricated cantilevers is demonstrated by recording their thermal power spectral density in ambient conditions and in liquid. These measurements lead to the complete characterisation of the sensors in terms of their stiffness and resonant frequency. Future applications, which will benefit from the use of this force microscopy technique, are also described. -- Highlights: ► Micro-fabrication of ultra-soft silicon nitride sensors. ► SEW detection system enables the use of extremely small cantilevers. ► Choice of sensor geometry permits control of thermal excitations and axial rotations. ► LMFM can be used in a force regime not previously associated with AFM.