In-Field Detection of Plant Pathogens Using Three-Dimensional-Printed Microneedles and a Portable Platform.

Plant diseases threaten global food security, necessitating efficient, field-deployable diagnostics. Traditional approaches, including morphological assessments and conventional sampling methods such as swabs or multistep DNA extraction, are often unreliable in the early stages of infection when visible symptoms are absent and subsurface pathogens remain inaccessible, underscoring the need for molecular tools. Here, we present a microneedle (MN)-based diagnostic platform integrated with loop-mediated isothermal amplification (LAMP) and lateral flow assay (LFA), supported by a custom-built portable heater (LAMPbox). The MNs enable the direct extraction of plant fluids and associated pathogens, offering a rapid, simple, and efficient sampling approach. In this study, two MN types were evaluated: poly(vinyl alcohol) (PVA) and stereolithography-printed MNs fabricated from a plant-derived resin. The 3D-printed MNs exhibited superior mechanical robustness, with a displacement ratio of only 3.3% compared to 24.5% for PVA MNs, and provided an ∼12% higher DNA yield than conventional swab-based methods. Integrated with the LAMPbox, this platform enabled reliable detection of Puccinia triticina with clear differentiation between healthy and infected leaves. This work establishes 3D-printed MNs as mechanically robust and effective tools for pathogen sampling while demonstrating the feasibility of a low-cost, portable, and sustainable system for early plant disease diagnosis.