Dermal ISF Collection Using a Si Microneedle Array

Microfabricated needle arrays for minimally invasive bioassay and drug delivery have been the subject of a great deal of excitement and research for nearly two decades. In particular, the application of microneedles to accessing and analyzing dermal interstitial fluid, in lieu of venous blood, could greatly facilitate point-of-care diagnosis and health monitoring in austere environments. However, there have been only a few successful demonstrations of in vivo collection of ISF from human skin using a microfabricated needle array. In this paper we present an empirically determined requisite feature of microfabricated hollow silicon needles that enable collection of ISF from human skin during in vivo testing. Success was only achieved by microneedles with this specific geometric feature, or shape. To inform microneedle design and fabrication, a silicon etch simulation program was developed to predict 3D shape evolution. The microfabrication process, a simulation example and in vivo test results are presented.