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<p>Atomic Force Microscopy in PeakForce Quantitative NanoMechanics mode (AFM PeakForce QNM) under controlled relative humidity (RH) was applied to continuously monitor the indentation modulus (IM) of Norway spruce (<i>Picea abies</i>) earlywood (EW) and latewood (LW) tracheid cell walls over three absorption/desorption (S/D) cycles. The IM of the different cell wall layers were close between early- and latewoods indicating small differences between their chemical compositions. AFM nanoInfraRed measurements (AFM NanoIR) indicate variations in lignin and cellulose with an increase of lignin and a decrease of cellulose from the S2 to the S1 and finally to the CC (cell corner). Earlywood and latewood cell walls display the same hygronanomechanical behavior during S/D cycle, i.e., the IM values decrease during absorption up to 85% and re–increase during desorption. Gaussian fits of the IM distribution were narrower for late wood than early wood and vary with the type of layer and with the relative humidity. The responses of the indentation moduli to RH of the cell wall layers in early- and latewood were fitted according to a three-parameter logistic function. Significant differences are observed for the S2 in both EW and LW indicating a higher slope in the response of indentation moduli to RH between 15 and 50% RH in desorption as compared to absorption. For both desorption and absorption, the comparison between EW vs. LW reveals differences in CC and S1, with a higher slope in moduli response to RH in LW between 15 and 50% RH and the opposite between 50 and 85% RH.</p>

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Online monitoring of the hygromechanical properties of spruce tracheid cell walls at the nanoscale

  • 期刊论文

  • 发表日期：

    2026年6月1日

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  • Raphaël Coste,
  • Véronique Aguié–Béghin,
  • Hugues Clivot,
  • Dominique Derome,
  • Michaël Molinari,
  • Brigitte Chabbert

摘要

Atomic Force Microscopy in PeakForce Quantitative NanoMechanics mode (AFM PeakForce QNM) under controlled relative humidity (RH) was applied to continuously monitor the indentation modulus (IM) of Norway spruce (Picea abies) earlywood (EW) and latewood (LW) tracheid cell walls over three absorption/desorption (S/D) cycles. The IM of the different cell wall layers were close between early- and latewoods indicating small differences between their chemical compositions. AFM nanoInfraRed measurements (AFM NanoIR) indicate variations in lignin and cellulose with an increase of lignin and a decrease of cellulose from the S2 to the S1 and finally to the CC (cell corner). Earlywood and latewood cell walls display the same hygronanomechanical behavior during S/D cycle, i.e., the IM values decrease during absorption up to 85% and re–increase during desorption. Gaussian fits of the IM distribution were narrower for late wood than early wood and vary with the type of layer and with the relative humidity. The responses of the indentation moduli to RH of the cell wall layers in early- and latewood were fitted according to a three-parameter logistic function. Significant differences are observed for the S2 in both EW and LW indicating a higher slope in the response of indentation moduli to RH between 15 and 50% RH in desorption as compared to absorption. For both desorption and absorption, the comparison between EW vs. LW reveals differences in CC and S1, with a higher slope in moduli response to RH in LW between 15 and 50% RH and the opposite between 50 and 85% RH.