Microfluidic Plant-on-a-Chip Platforms for High-Resolution Real-Time Imaging of Root–Pathogen Dynamics

Abstract

The rhizosphere constitutes one of the most complex and biologically dense microenvironments, where plant roots continuously interact with diverse soil biota ranging from beneficial rhizobacteria to destructive phytopathogens. Deciphering the spatiotemporal mechanisms governing root–pathogen dynamics is essential for developing targeted crop protection strategies. Traditional methods such as agar plates and hydroponic systems fail to recreate the physical geometry, chemical gradients, and fluidic dynamics of natural soils while imposing severe optical limitations that prevent high-resolution imaging. Plant-on-a-Chip (PoC) and Root-on-a-Chip (RoC) platforms, adapted from mammalian organ-on-chip engineering, have emerged as transformative tools that overcome these methodological bottlenecks. Fabricated primarily via soft lithography using optically transparent polydimethylsiloxane (PDMS), these microfluidic devices manipulate picoliter fluid volumes within sub-millimeter channels to mimic soil-like microenvironments. When integrated with advanced live-cell microscopy including confocal, differential interference contrast, and atomic force microscopy these platforms enable non-destructive, real-time visualization of root–pathogen interactions at single-cell resolution. This review systematically examines microfluidic design paradigms, fabrication methodologies, and imaging techniques while presenting mechanistic insights into oomycete chemotaxis and infection kinetics, bacterial wilt pathogenesis, nematode feeding site induction, and competitive exclusion by beneficial rhizobacteria. Key pathosystem dynamics revealed include Phytophthora zoospore klinokinesis within 300 μm of host roots, Ralstonia biofilm-driven xylem hydraulic failure, and Bacillus subtilis protective barrier formation. Despite current technical challenges including PDMS hydrophobicity, root growth constraints, and device delamination emerging innovations in thermoplastic materials, 3D soil-mimetic architectures, multi-species synthetic communities, and standardized EcoFAB protocols promise to advance plant microfluidics toward high-throughput screening of agricultural chemicals and pathogen-resistant cultivars.