Spatial and temporal detection of root exudates with a paper-based microfluidic device

Root exudates control critical processes in the rhizosphere, retaining water, selecting for beneficial microorganisms or solubilising nutrients prior to uptake by the plant. Analysing root exudation patterns however is challenging because existing methods are often destructive and unable to resolve spatial and temporal variations in the production of root exudates. Here, we present a paper-based microfluidic device with integrated colorimetric sensors for the continuous extraction of root exudates along plant roots. The microfluidic device used standard filter paper wax printer to create channels for water to carry the exudates towards the sensors. TiO2 nanotubes/alginate hydrogel-based sensors were used to analyse the glucose content of the root exudates of living plants. The study shows that the paper microfluidic substrate successfully extracts the released glucose from the root, and transfers it to the hydrogel-based sensor to be calorimetrically detected from independent sections of the root at different times, up to 7 days. The method was tested on two different wheat varieties Triticum aestivum (rgt Tocayo and Filon varieties), where significant differences in exudation patterns were recorded. The researchdemonstrates the feasibility of low cost technological solution for high precision screening and diagnostic of the biochemical composition of root exudates. ### Competing Interest Statement A patent claim has been submitted to protect the intellectual property of the developed chip. Daniel Patko, Lionel Dupuy, Lourdes Basabe Desmonts, and Fernando Benito Lopez. MICROFLUIDIC DEVICE, Submission number: 300496138, Application number: EP23382947.2, File No. to be used for priority declarations: EP23382947. (2023) Under evaluation.