title: An Universal packaging technique for low-drift implantable pressure sensors.
abstract: Monitoring bodily pressures provide valuable diagnostic and prognostic information. In particular, long-term measurement through implantable sensors is highly desirable in situations where percutaneous access can be complicated or dangerous (e.g., intracranial pressure in hydrocephalic patients). In spite of decades of progress in the fabrication of miniature solid-state pressure sensors, sensor drift has so far severely limited their application in implantable systems. In this paper, we report on a universal packaging technique for reducing the sensor drift. The described method isolates the pressure sensor from a major source of drift, i.e., contact with the aqueous surrounding environment, by encasing the sensor in a silicone-filled medical-grade polyurethane balloon. In-vitro soak tests for 100 days using commercial micromachined piezoresistive pressure sensors demonstrate a stable operation with the output remaining within 1.8 cmH2O (1.3 mmHg) of a reference pressure transducer. Under similar test conditions, a non-isolated sensor fluctuates between 10 and 20 cmH2O (7.4-14.7 mmHg) of the reference, without ever settling to a stable operation regime. Implantation in Ossabow pigs demonstrate the robustness of the package and its in-vivo efficacy in reducing the baseline drift.
authors.affiliation: School of Electrical and Computer Engineering, Purdue University, 1205 W. State St, West Lafayette, IN, 47907, USA. Albert.Kim.1@Purdue.Edu.|Birck Nanotechnology Center, Purdue University, 1205 W. State St, West Lafayette, IN, 47907, USA. Albert.Kim.1@Purdue.Edu.
authors.forename: Albert
authors.initials: A
authors.lastname: Kim
authors.affiliation: Department of Urology, Indiana University School of Medicine, 535 Barnhill Dr. Suite 420, Indianapolis, IN, 46202, USA. crpowell@iupui.edu.
authors.forename: Charles R
authors.initials: CR
authors.lastname: Powell
authors.affiliation: School of Electrical and Computer Engineering, Purdue University, 1205 W. State St, West Lafayette, IN, 47907, USA. bziaie@purdue.edu.|Birck Nanotechnology Center, Purdue University, 1205 W. State St, West Lafayette, IN, 47907, USA. bziaie@purdue.edu.
authors.forename: Babak
authors.initials: B
authors.lastname: Ziaie
mesh_terms: D000818:Animals; D009038:Motion; D019064:Product Packaging / Q000379:methods*; D019736:Prostheses and Implants; D013552:Swine; D014160:Transducers, Pressure; D001743:Urinary Bladder; D014867:Water
chemical_list: D014867:Water
keywords: Baseline drift; Implantable sensors; Pressure sensor; Sensor packaging