Ultra afm

A series of ethanol/deionized water concentration (50%, 75%, 90% and 100%) were used to dehydrate samples. After this step, to maintain the fibre and the cell-wall structure during surface preparation, samples were embedded in a mixture containing increasing proportions of LR (London Resin) White acrylic resin/ethanol (25%, 50%, 75% and 100%). Then, the polymerization of the resin was finalised in an oven at 60 °C for one night. The aramid fibres were introduced into an epoxy resin (Struers Epofix) for 24 h and polymerization took place at room temperature. To obtain reliable measurements with the atomic force microscope, we must minimize their roughness at the nanometer scale. Consequently, the samples were prepared using an ultramicrotome (Leica Ultracut R) with two consecutive diamond knives (Diatome Histo and Ultra AFM), to cut very thin sections (about 50 nm) at low cutting speed (≈1 mm/s) and thus reduce sample deformations.

Green stems and mature flax fibres samples were dehydrated with a concentration series of ethanol/deionised water (50%, 75%, 90% and 100%) and then embedded in a mixture containing increasing ratios of LR White acrylic resin/ethanol (25%, 50%, 75% and 100%), waiting for few hours at each embedding step, in order to maintain the fibre and the cell-wall structure during surface preparation. Final resin polymerization took place in an oven (60 • C, overnight). Aramid fibres were placed directly in an epoxy resin (Struers Epofix) that polymerizes at ambient temperature for 24 h. One stem sample and one sample containing several tens of mature flax fibres and another one containing several tens of aramid fibres were prepared. They were then machined, to reduce their crosssection, and an ultramicrotome (Leica Ultracut R) is then used with diamond knives (Diatome Histo and Ultra AFM) to cut a series of very thin sections (about 50 nm thick in the last steps) at low cutting speed (≈1 mm/s).