(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."