Designing a Placebo Microneedle Stamp: Modeling and Validation in a Clinical Control Trial

Recently, several clinical studies have been conducted using microneedles (MNs), and various devices have been developed. This study aimed to propose and confirm the feasibility of a placebo control for activating MN clinical research. A 0.5 mm MN stamp with 42 needles was used as a treatment intervention, and a placebo stamp with four acupressure-type needles that did not penetrate was proposed and designed as a control for comparison. First, to check whether the placebo stamp did not invade the skin and to set an appropriate level of pressure to be provided during skin stimulation, two participants were stimulated with five different forces on the forearm, and then the skin was dyed. Secondly, to evaluate the validity of the placebo control group, a blinded study between the MN and placebo stamps was performed on 15 participants. We confirmed that the placebo stamp did not penetrate the skin at any intensity or location. Both types of stamps reported relatively low pain levels, but the MN stamp induced higher pain compared to the placebo stamp. Based on the speculation regarding the type of intervention received, the MN stamp was successfully blinded (random guess), whereas the placebo stamp was unblinded. However, according to a subgroup analysis, it was confirmed that the group with low skin sensitivity was completely blind. Blinding the placebo MN stamp had limited success in participants with low skin sensitivity. Future research on suitable placebo controls, considering the variations in MN stamp length and needle count, is warranted.