Precision Vascular Delivery of Agrochemicals with Micromilled Microneedles (μMMNs)

We demonstrate use of makerspace techniques involving subtractive microtechnologies to fabricate micromilled microneedles (mu MMNs) of stainless steel (SS) for precise delivery of agrochemicals into vascular bundles of plant tissue. Precision delivery is of immense importance for systemic pathogen control in specific areas of plant tissue. Optimization of the micromilling allows for selective removal of SS at the microscale and the microfabrication of a 5 x 5 array of mu MMNs having both base width and height of 500 mu m to enable precise puncture into the stem of citrus saplings. Atomic Absorption Spectroscopy reveals up to 7.5 x increase in the uptake of a therapeutic cargo while Scanning Electron Microscopy reveals that specific sites of the vascular bundle; either xylem or the phloem can be uniquely targeted with customized mu MMNs. Such rapid and cost-effective customization with intricate designs along with scalability is enabled by makerspace microfabrication. Additionally, a 19 x 20 array of micromilled mesoneedles has been fabricated and affixed to a paint roller as an applicator system for real-world field testing outside the laboratory. Initial results indicate reliable behavior of the applicator system and the technique can be applied to the systemic delivery of agrochemicals while conserving the loss of the agrochemical with increased application efficiency.