Force spectroscopy based on temperature controlled atomic force microscope head using piezoresistive cantilevers

We have built a double temperature controlled atomic force microscope (AFM) head, based on the force detection using piezoresistive cantilevers. The temperature of the sample is controlled to better than +/- 2 mK in a temperature interval up to 60 degrees C. The force sensitivity is 300 pN and is limited by the intrinsic low frequency noise of the piezoresistive cantilevers. By using a colloidal probe of the radius of R approximate to 10 mu m, the normalized force sensitivity is F/R approximate to 0.02 mN/m. Although this is comparable to the sensitivity of a surface force apparatus (SFA), the piezoresistive AFM requires only approximate to 1 mu l of a fluid material, that is typically 10.000x less compared to the SFA. The capability of the force spectroscopy using a piezoresistive AFM head is illustrated by measuring the structural forces in the nematic liquid crystal. (C) American Institute of Physics.