Small cantilevers for force spectroscopy of single molecules

We have used a simple process to fabricate small rectangular cantilevers ou t of silicon nitride. They have lengths of 9-50 mu m, widths of 3-5 mu m, a nd thicknesses of 86 and 102 nm. We have added metallic reflector pads to s ome of the cantilever ends to maximize reflectivity while minimizing sensit ivity to temperature changes. We have characterized small cantilevers throu gh their thermal spectra and show that they can measure smaller forces than larger cantilevers with the same spring constant because they have lower c oefficients of viscous damping. Finally, we show that small cantilevers can be used for experiments requiring large measurement bandwidths, and have u sed them to unfold single titin molecules over an order of magnitude faster than previously reported with conventional cantilevers. (C) 1999 American Institute of Physics. [S0021-8979(99)04916-6].