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 the atomic force microscope (AFM) tip to press samples into grooves etched in a GaAs substrate. We measured the Young's modulus of β-chitin fibres with cross-sections less than 40 nm x 20 nm to be 1-2 x 10¹¹ N/m². In the isotropic approximation, the Young's modulus of the S-layer sheath of the archaeobacterium Methanospirillum hungatei was 1-3 x 10¹⁰ N/m². By testing the sheath to breaking strength we estimated the bacterium can sustain an internal pressure as high as 100-200 atmospheres (1-2 x 10⁷ N/m²).