Capillary microsampling enables on-site collection and storage of plant sap

Plant sap analysis typically relies on destructive sampling and immediate freezing, limiting field deployment and longitudinal studies. We introduce a minimally invasive microfluidic device that extracts sap from the stem of Solanum lycopersicum and dries it in situ, enabling storage analogous to dried blood spots in humans. Using both artificial phytohormone mixtures and tomato sap, we assessed the stability of dried samples stored at room temperature for up to seven days and observed no substantial degradation of key phytohormones. Device performance was further validated in a paired sampling experiment, showing strong agreement with a conventional stem severing method for tZR and ABA quantification. These findings demonstrate that dried sap sampling via a microfluidic device provides a practical, field ready alternative to destructive methods, supporting repeated sampling from the same plant and enabling longitudinal metabolic monitoring.