| Determining the electrical response of a neural network to acoustical, electrical, or other types of stimulation is a topic of great interest. The use of drugs to alter the chemical environment of neurons is vital for further insight into the workings of the nervous system. Implied in this function is the use of chemical delivery systems to control fluid in terms of quantity and time. Many of the necessary components for pico-liter level chemical delivery are described in this thesis.; The focus of this research includes process improvements to the existing chemical delivery probes as well as the development of process-compatible shutters for limiting unwanted chemical delivery, flowmeters for confirmation and quantification of the flow, pumps and valves for the control of fluid movement, and integrated flexible interconnects to connect the probe to a reservoir. These process improvements include altering the trench shape from chevrons to slashes, increasing the spacing between trenches, use of a new contact process.; A shutter has been developed which requires no additional masking or processing steps and only drops 8% (44Torr) of the injection pressure. This shutter reduces unintended delivery of fluid by approximately 25 times.; An integrated flowmeter has been developed which requires only two extra masking steps. This hot-wire anemometer rests on a dielectric window and is capped with an air chamber. The flow resolution is better than 50pL/sec and can be improved to about 9pL/sec with on-chip circuitry.; The final step in controlling drug delivery is the incorporation of pumps and valves. A 70μm-radius thermopneumatic device actuated using the phase-change of a low-boiling-point liquid (cyclopentane) requires only 7mW to close the valve in 100μsec. A pumping cycle implemented using a three-valve peristaltic pump can deliver 3pL of fluid while raising the surrounding temperature by less than 0.5°C.; The addition of integrated fluidic cables can provide flexible multi-channel tubing. These fluidic cables can be realized with no additional masking steps. This fluidic interconnect is almost twice as flexible as polyimide tubing. Together, all these components provide a foundation for realizing minimally-invasive, chronically-implantable chemical delivery systems needed for research at the cellular level. |
