A Drug-Delivery Probe with an In-Line Flowmeter Based on Trench Refill and Chemical Mechanical Polishing Techniques

A thermal microflowmeter has been integrated into a bulk micromachined recording probe to monitor drug delivery in the central nervous system at the cellular level Based on trench refill and chemical mechanical polishing (CMP) processes, the drug delivery probe achieves a 50 mum² cross-sectional area and partial or all dielectric channel sidewalls. The flowmeter uses an arsenic-doped polysilicon heater/sensor supported on a dielectric membrane over the flow channel. Efficiencies of 27.2degC/mW are achieved. At input powers of 0.1 mW and 0.2 mW, the flowmeter can detect volumetric flows of 280 pL/sec and 160 pL/sec for a channel cross-section of 50 mum², corresponding to flow velocities of 5.6 mm/sec and 3.2 mm/sec, respectively.