Fabrication of Nano-Injection Needles for Neural Pathway Study in Mice

The potential of micro-needles to provide an interconnection between the microscopic and the macroscopic worlds makes it one of the most revolutionary fields in health care, allowing for precise transdermal drug delivery of highly targeted small doses of the active compound. Current micro electro mechanical systems (MEMS) technologies, originally designed for the micro-electronics industry, have been utilized in the fabrication of different micro-needle designs and their integration with various micro-fabricated micro-fluidics devices. The target of this thesis is to achieve a micro-needle injection system to deliver several strains of pico-liter volumes of a fluid combination of transgenic virus and luminescent compound, to be injected into the visual cortex of mice in order to study the structure and function of the neural networks of the brain. Micro-needles having a body dimension of 10 mm x 10 mm and a shaft 1 mm wide and 3 mm long have been constructed from silicon wafers, using technologies originally developed for integrated circuit (IC) fabrication. Silicon wafers have also been used in the fabrication of the needle channels having a width of 4 μm and a total depth of 60 μm with a 20 μm deep channel at the base of the 40 μm trench. Both wet and dry bulk micromachining techniques have been used to create the needle bodies and channels. The optimum fabrication method has been found to be the deep reactive ion etching (DRIE) and SiO2 deposition using the plasma enhanced chemical vapor deposition (PECVD) has been used to seal the channels.