# Novel stereo DIC characterisation of microneedle and hypodermic needle insertion

## TL;DR

This study compares the strain on skin from microneedles and hypodermic needles, finding microneedles cause significantly less strain.

## Contribution

A novel digital image correlation setup was used to quantify strain differences during insertion of microneedles and hypodermic needles.

## Key findings

- Hollow silicon microneedle arrays exert 75% less maximum normal strain than 25-gauge hypodermic needles.
- Strain quantification was discretized per individual needle, aiding future device design.
- Microneedles are shown to be a gentler alternative for transdermal applications.

## Abstract

Microneedles are minimally invasive devices, designed for pain-free drug delivery. Until now, the degree of strain exerted on the skin during microneedle insertion, in comparison to gold standard hypodermic needles, has not been quantified.

This paper presents experimental results from a novel digital image correlation setup to quantify maximum normal strain exerted on a skin-mimicking membrane by hollow silicon microneedles and 25-gauge stainless steel hypodermic needles through contact, deformation, rupture, and device insertion.

Findings here have shown 1 × 5 hollow silicon microneedle arrays exert significantly lower maximum normal strain compared to 25-gauge hypodermic needles. There is an average of 75% decrease in the maximum normal strain experienced by the membrane when using microneedle devices in comparison to that of the 25-gauge hypodermic needles. This quantification of strain has been discretised to each individual needle in the microneedle device, allowing for informed design choices for future device iterations.

These findings suggest the hollow microneedle devices to be a gentler alternative for transdermal applications, potentially improving patient comfort and reducing tissue trauma when compared to the gold standard, traditional 25-gauge hypodermic needle.