Abstract

Drying-induced collapse in soft plant tissues results from complex interactions between liquid and vapor transport through cellular microstructures. This study investigates collapse mechanisms in microscopic parenchyma cells interconnected by nanoscale pit channels of oil palm wood. By varying drying relative humidity (h) from 0.1 to 0.7 at 70 °C, we observe a non-monotonic collapse strain rate, with a minimum at h = 0.4, contrasting the monotonic decrease in moisture removal rate. Two distinct collapse regimes are identified: a zero-collapse regime linked to free liquid removal from large pores, and a linear-collapse regime associated with intracellular liquid extraction through nanoscale channels. Linear constants derived are used to quantify the maximum drying strain of the parenchyma cell matrix (Formula presented.) representing collapse efficiency as a function of h. A physical model is successfully developed to describe (Formula presented.) by coupling the Knudsen-diffusion vapor flux through nanoscale pit where the meniscus resides with capillary-driven liquid flux in the flow zone. When the maximum available liquid flux becomes insufficient to sustain the vapor flux, the meniscus retreats into the large cell cavity, resulting in the termination of cell collapse at (Formula presented.) The nonlinear dependence of collapse strain on h arises from competing effects of a logarithmically decreasing vapor driving force and linearly increasing vapor mobility, modulated by nanoscale confinement. These results offer mechanistic insights into drying-induced collapse in soft, liquid-filled tissues and advance understanding of fluid–structure interactions in porous soft materials.