A NEW ATOMIC-FORCE MICROSCOPY TECHNIQUE FOR THE MEASUREMENT OF THE ELASTIC PROPERTIES OF BIOLOGICAL-MATERIALS

We developed a new technique to measure elastic properties by using th e atomic force microscope (AFM) tip to press samples into grooves etch ed in a GaAs substrate. We measured the Young's modulus of beta-chitin fibres with cross-sections less than 40 mn X 20 nm to be 1-2 X 10(11) N/m(2). In the isotropic approximation, the Young's modulus of the S- layer sheath of the archaeobacterium Methanospirillum hungatei was 1-3 X 10(10) N/m(2). By testing the sheath to breaking strength we estima ted the bacterium can sustain an internal pressure as high as 100-200 atmospheres (1-2 x 10(7) N/m(2)).