Figure 2.

Mechanical testing of the microneedle patch and active fluid transport (localized streaming) based on Mg particles embedded in dissolvable microneedles. a) Schematic illustration of the mechanical setup used. b) Mechanical analysis of a single microneedle tip under different loads and SEM images of microneedle tips before and after application of each load. Scale bars, 200 μm. c) Schematic of the fluid transport of active Mg particles in the presence of tracer particles. d) Mean square displacement of tracer particles using Brownian motion as control or in the presence of the active Mg particles at pH 6.0. Scale bar, 100 μm. e) Flow trace images of the trajectory (over 1s) of 0.9 μm polystyrene tracer particles at pH 6.0 without the presence of active particles (Brownian motion) (i), and with active particles (ii) at pH 6.0. Scale bars, 100 μm. f) Time-lapse images of two microneedle tips without active particles, showing the dissolution in PBS pH 6.0 of the transient polymer by diffusion (i) and with the Mg particles accelerating the dissolution of the transient polymer due to their fast activation (ii). Scale bars, 400 μm. g) COMSOL Multiphysics simulation of the flow generated by the absence (i) and presence (ii) of Mg particles within the MN structure.