Microfabricated microneedles for minimally invasive drug delivery, sampling and analysis

Utilizing current Micro Electro Mechanical Systems (MEMS) technologies, different microneedle designs have been fabricated and integrated with various microfabricated microfluidic devices. Microneedle technology promises to revolutionize health care by allowing the precise injection of therapeutic agents to prescribed locations below the skin. In addition, microneedles can be used for sample collection for biological analysis, delivery of cell or cellular extract based vaccines, and sample handling providing interconnection between the microscopic and macroscopic world. Microneedles are desired because the small size and extremely sharp submicron tip radii reduce both insertion pain and tissue damage in the patient. Microneedles may be used for low flow rate continuous drug delivery such as the continuous delivery of insulin to a diabetic patient. Microneedles may be a variety of sizes and shapes since the needles are defined lithographically as opposed to being machined as a single part.; Three different aspects of the microneedle field are examined. The first expands upon prior work on micromolded polysilicon microneedles with improved microneedle fabrication. Fluid flow in microneedles is studied, analyzed, and compared from experimental, theoretical, and computational viewpoints.; The second area is the development of a microdialysis needle capable of separating small organic molecules from complex biological solutions. The microdialysis needles were designed and fabricated together with analytical modeling to describe diffusion across semi-permeable membranes. Experiments verify the permeability of the diffusion membranes.; Finally, an integrated planar microfluidic system capable of sampling and analyzing biological solutions with feedback controlled drug delivery in response to metabolite levels is examined. The integrated microfluidic system includes the assembly of microneedles with on-chip flow channels and electronics together with previously designed positive displacement micropumps, microvalves and a planar electrochemical sensor for biological detection. Multichannel fluidic control for biological sampling, sensor cleansing and recalibration is demonstrated with integrated sensor operation. Microneedles are integrated for both biological sampling through the microdialysis needle as well as continuous and controllable drug delivery profiles. The microneedles were integrated into a short-term drug delivery device capable of delivering therapeutics intradermally.