(Fig 1b) Optimization of microneedle length in device prototype development: the effect of microneedle length on blood flow rate and pain sensation.

To determine the optimal microneedle array dimensions for
use in our device, we began by evaluating the effect of microneedle length on
blood flow rate and perceived pain over a range of 750 to 1250 µm. This was
investigated by inserting microneedle arrays into the skin using a snap dome
mechanism and then applying vacuum to the puncture sites to encourage blood
flow. Pain sensation scores were obtained from each participant
immediately after each microneedle array actuation, using the Wong-Baker FACES
pain scale, with '0' corresponding to "no hurt" and '10'
corresponding to "hurts worse."