FEM Modeling of the Microneedle Insertion Into a Cellular Structure for Microsampling of Plant Fluids

Microneedle‐based access to plant phloem enables sustainable energy harvesting and in situ biochemical sensing, but its performance is limited by defense responses such as callose deposition triggered by mechanical overstimulation of cell walls. This study presents a combined numerical–experimental framework for investigation how microneedle penetration dynamics influence transient stress fields within plant cellular tissue. A 3D finite element model of tomato stem tissue was reconstructed from SEM data, incorporating elastic–plastic cell walls, compressible intracellular fluid, and an augmented‐Lagrangian contact to simulate cell‐wall rupture and middle‐lamella delamination. Simulations reveal that lower insertion velocities significantly reduce stress transients and localize stress propagation, favoring single‐cell failure over multicell delamination. This effect results from a reduced rate of energy transfer into the tissue during insertion, limiting elastic energy accumulation and mechanical loading of mechanosensory pathways associated with callose secretion. Microneedle prototypes were fabricated and tested on tomato stems. Despite the quasistatic experimental velocities, displacement‐based comparison showed good agreement with numerical predictions. Both approaches confirmed that slower penetration shifts energy partitioning toward elastic storage and rheological dissipation. Overall, the developed mesoscale FEM framework reliably captures microneedle–tissue interactions and provides a transferable tool for optimizing minimally disruptive microneedle insertion strategies.