3D nanotomography of wood fibres

Typically imaging of wood cells by 3D nanotomography is performed with the help of TEM or cryo TEM. To get a proper transmission signal, samples should be cut down to 100 nm thickness or even less. In this project we want to avoid extreme sectioning of wood pieces where observation area includes only a part of the wood cell wall, but rather visualize fully two wood cell walls in conjunction. 3D nanotomographer at P05 beamline of DESY can provide us with field of view down to 30 um, resulting in resolution up to 20 nm.

The challenge comes to cutting a sample, which would include 2 wood cell walls in conjunction, avoiding deformation of their structure by cutting protocol or composition by addition of stabilizing fillers. The sample should be in diameter within FOV of beam at P05 (30 – 50 um) and long enough to not get a signal from the sample holder (300 – 500 um). FIB SEM cannot help us with resolving such challenges as we want to avoid deposition of any heavy material on a surface of our sample, such as Ga. Such dense material would absorb a lot of energy from beam and result in sample heating and degradation as well as loss of resolution. Therefore, cryo trimming with cryo ultramicrotome seems to be the only technique which could satisfy mentioned demands for sample preparation.