Managing the escalating number of formidable tree ailments and pests has landscape professionals juggling their tool chest to find the most effective and profitable treatments. A common treatment method is macro-injection, in which liquids are drilled into the trunks of trees. However, this invasive process can damage the trees and attract disease, so many landscapers are opting to add micro injection services as well. Adding injection services requires a lot of planning. That includes finding a distributor, charting how to increase profits from the new service and ensuring that they’re offering their customers the best method for their region’s conditions.
The key to the success of micro injection is the passive multiphase flow system within which it’s performed. The system’s fluid phases interact and produce the desired double emulsion via harmonized pulsating flows.
The pulsating flow patterns are carefully designed so that the alternating flows steer the Droplet phase into the injection station (Fig. S1a). This interaction creates two intense vortices inside the Droplet phase and enables the injection to be made through the microneedle while keeping Injected confined in Droplet. Once the injection is complete, the net flow pattern reverses and the laminar flow field remains dominant downstream of the injection station. The inertial force of the pulsating flow also drives the double emulsion toward the downstream termination (Fig. S1b).
Using the same open source, free software, the multiphase dynamics of this passive microinjection system is simulated by integrating a finite volume method with direct numerical simulation (DNS) and a second-order accurate scheme. The governing equations for the multiphase systems are solved using the Gerris library, which supports a hybrid method for discretization and time integration. The dynamic viscosity of the fluids, Current, Droplet and Injected are set to 2 x 10-3 Pa.s, 1.1 x 103 kg m-3 and 2.6 x 10-2 N m-1, respectively.
The pulsating flows are generated by the inlet flows at the main channel, T-junction, microneedle and top part of the cross-junction. The amplitude of the flows at each inlet is precisely controlled to achieve the desired pulsating flow patterns and durations for each microinjection cycle. The geometry of the T-junction and corresponding injection flow rate ratio is also meticulously modified to manage the formation of the Droplet phase. In addition, the wetting properties of the fluids are set to ensure that the Microchannel is completely wetted by the Current phase and the injection station is only partially wetted by the Droplet phase. The pulsating flow pattern and the wetting properties of the Droplet and microneedle are adjusted to achieve a precise double emulsion. The resulting system is robust and easy to operate. The synchronized flow pattern ensures the precise injection of the microneedle into the Double Emulsion and the downstream termination. This passive, automated and high-precision microinjection system can be applied to a variety of biotechnology applications, including cell biology and gene therapy. The system can be further adapted to inject DNA, RNA, proteins, metabolites and other small molecules into cells.