A shuttered probe with in-line flowmeters for chronic in-vivo drug delivery

This paper describes a micromachined microprobe for in-vivo drug delivery at the cellular level. The probe was developed to support research in neuropharmacology as well as for eventual use in neural prostheses. Extending a standard process for the realization of electrical recording and stimulating probes, the drug delivery probe adds microchannels, fluidic cables, dielectric shutters over the injecting orifices, and in-line flowmeters to verify the intended dose. These fluidic components require three masks in addition to the normal probe process. The fluidic cables are 1.5X more flexible than the polyimide tubing formerly used and can be integrated with the probes, while the shutters reduce the unintended delivery of drugs into tissue by a factor of 25 compared with an open orifice. The flowmeter operates in pulsed mode as a hot wire anemometer, with a power dissipation of 1.5 mW and a flow resolution of about 150 pL/sec. The temperature rise in tissue near the flowmeter is less than 1/spl deg/C. Process compatibility with on-chip microvalve and micropump structures has also been explored.