THE ROLE OF ATOMIC FORCE MICROSCOPY IN ADVANCING DIATOM RESEARCH INTO THE NANOTECHNOLOGY ERA - Life at the Nanoscale: Atomic Force Microscopy of Live Cells - page 407

and triradiate forms (100 KPa). The girdle region of both fusiform and ovoid
forms was ive times softer than the valve, suggesting that this region is poor
in silica and enriched in organic material ( Fig. 19.4b,c ) . In addition to being
a low modulus, viscoelastic polymer, the EPS coating has been shown to be
non-adhesive. Force measurements on P. viridis showed no adhesion. 13 For C.

australis , an adhesion force of 13 nN recorded on the EPS valve coating was

ive times less than that over the position of the raphe. 14 Even though the

(b)

(a)

(c)

Figure 19.4 . (a) Top graph shows an AFM force measurement on the EPS coating of
living Pinnulari viridis cells. Bottom graph shows a force measurement on the silica
cell wall after removal of the EPS. The slope of the cantilever delection signal (force)
is steeper, indicating a stiffer material. 13 (b - c) Mechanical properties of the fusiform
girdle and valve interface. 22 (b) Force measurements indicate a stiffer material for the
valve compared with the girdle. (c) Histogram of the Young's modulus values, valve
(black gaussian it), girdle (red gaussian it).