Development of an SU-8 Fabry-Perot blood pressure sensor

This paper presents the fabrication method and testing of an interferometric pressure sensor designed for intravascular blood pressure measurements. A cap containing a pressure-sensing diaphragm was mounted onto the end of a fiber optic cable. The Fabry-Perot interferometer, formed between the reflective diaphragm and the fiber´s end, measured the diaphragm deflection. Microfabricated from the biocompatible polymer, SU-8, the device is fast, simple, and inexpensive to manufacture. Its small dimensions (<300μm outer diameter) reduce the risk of infection and thrombosis and allow for its insertion into small vessels. The sensor showed a linear response to pressure from 0 to 125 mmHg with approximately 1-2 mmHg resolution. The use of an optical displacement transducer allowed a series of careful measurements of drift and hysteresis of SU-8 materials in different environments. This data may be valuable to other researchers working with SU-8.