Observations of Wood Cell Walls with a Scanning Probe Microscope

Abstract

Scanning Probe Microscopes (SPMs) observe specimen surfaces with probes by detecting the physical amount of a material between the cantilever and the surface. SPMs have a high resolution and can measure mechanical characteristics such as stiffness, adsorptive properties, and viscoelasticity. These features make it easy to identify the surface structure of complex materials; therefore, the use of SPMs has increased in recent years. Wood cell walls are primarily composed of cellulose, hemicellulose, and lignin. It is believed that hemicellulose and lignin surround the cellulose framework; however, their detailed formation remains unknown. Therefore, we observed wood cell walls via scanning probe microscopy to try to reveal the formation of the cellulose framework. We determined that the size of the cellulose microfibril bundle and hemicellulose lignin module composite was 18.48 nm based on topography and that the size of the cellulose microfibril bundle was 15.33 nm based on phase images. In the viscoelasticity image, we found that the viscoelasticities of each cell wall of the same cell were not the same. This is because the cellulose microfibrils in each cell wall lean in different directions. The angle between the leaning of the cellulose microfibril and the cantilever affects the viscoelasticity measurement.

Nano-indentation reveals a potential role for gradients of cell wall stiffness in directional movement of the resurrection plant Selaginella lepidophylla

“…The large standard errors of the experimental data, in particular at high frequencies, can be attributed to tissue heterogeneity, which varies with position in all regions within the stem. Our results are consistent with the viscoelastic behaviour observed with nano-indentation, including AFM, of dried secondary cell walls in flax fibres and wood [51][52][53] .…”

Nanocellulose-Based Thermoplastic Polyurethane Biocomposites with Shape Memory Effect

“…Cellulose MicroFibrils (CMFs) (e.g., MicroFibrillated Cellulose or MFC) which are a type of cellulose nanofiber containing multiple elementary fibrils with both crystalline and amorphous regions and have a high aspect ratio with a width of 10-100 nm and length of 0.5-10 µm long [55,56]. the standard terms and their definition for cellulosic nanomaterials.…”

“…• Cellulose MicroCrystals (CMCs) (e.g., MicroCrystalline Cellulose or MCC) which are a type of cellulose nanostructured material and are approximately 10-15 µm in diameter, contain mostly crystalline regions, and are composed of aggregated bundles of cellulose chains; • Cellulose MicroFibrils (CMFs) (e.g., MicroFibrillated Cellulose or MFC) which are a type of cellulose nanofiber containing multiple elementary fibrils with both crystalline and amorphous regions and have a high aspect ratio with a width of 10-100 nm and length of 0.5-10 µm long [55,56]. Cellulose nano-objects include nanocellulose which, depending on the morphology, particle size, and method of isolation, is divided into three types [29,39,58]:…”