An autonomous microneedle-based bio-analysis system

The objective of this paper is to present a novel integrated microneedle system with optical sensing capabilities. A simple, cost-effective mechanism, which precludes the requirement of an external characterizing device, has been proposed. Microneedles were fabricated and characterized for their mechanical and fluid flow properties before the optical sensing capability was integrated. The characterization will include the effects of design variations on the buckling and penetration force of these microneedles, and on the fluid flow characteristics. The lengths of the needle shaft tested were 500 μm, 1000 μm and 1500 μm respectively. A simple horizontal loading set up consisting of a load cell and a micromanipulator was designed. A rigid orthogonal surface was used in order to study the buckling force, while a mechanically "skin-like" material was used to determine the penetration force. The buckling force was found to vary between 54 gF and 100 gF for needles with shaft lengths of 1500 and 500 μm, respectively. The penetration force was found to be independent of shaft length and was approximately 8 gF. The flow rate of the microneedles was characterized over a range of 0 - 100 psi using distilled water and air as the fluid media. Some of the preliminary characterization of these microneedles using a CCD is also presented.