An implantable time of flight flow sensor

A micro time of flight (TOF) electrochemical impedance (EI) flow sensor μEIFS suitable for implantation and integration with a catheter was developed. The transducer utilizes two pairs of electrodes to monitor using EI measurement the passage of a gas bubble generated upstream. High precision measurement of bubble TOF (SD <; 6% of mean) was achieved over the velocity range 0.83-83 μm/s. The volumetric flow rate was inversely proportional (linearized, r² = 0.99) to time of flight. Biocompatible construction (only Parylene C and platinum), low power consumption, and low profile thin film format make the μEIFS ideally suited for chronic in vivo monitoring with immediate application in tracking flow within hydrocephalus shunts.