To begin, prepare the exosome loaded microneedle patch and paste its backing onto a 45-degree inclined surface. Position the patch under a stereo microscope. Turn on the illuminator and capture the morphology of the patch using a four times objective lens.
For mechanical testing, cut out a three-by-three array from the patch and place it with the tips facing upwards on the rigid platform of a tensile meter. Adjust the height of the probe to bring it close to the needle tips without touching them. Set the parameters to stop automatically when the pressure reaches 20 Newton.
Compress the needle tips vertically at a 0.5 millimeter per minute speed before recording the load versus displacement profile. The tips in the exosome loaded microneedle patch exhibited a conical shape arranged in a 10-by-10 array with sharp and intact needle tips. The tip of the microneedle can withstand the force of two Newtons, allowing it to penetrate through the skin barrier.
