“Torsional tapping” atomic force microscopy using T-shaped cantilevers

Torsional oscillation of atomic force microscope cantilevers has been shown to offer increased optical lever sensitivity, quality factor, resonant frequency, and stiffness as compared to flexural oscillation. In this letter, T-shaped cantilevers are oscillated torsionally to give a tapping motion at the tip. This gives many of the advantages of small cantilevers, without the requirement for specialized detection optics. In order to demonstrate the capability of this technique, high resolution images of LH2 membrane protein crystal structures are presented. Reduced settle time and tip-sample force under error signal are also demonstrated.