A MICROMACHINED PRESSURE-TIME RECORDER FOR MEDICAL APPLICATIONS

We present a simple micromachined device to determine the pressure-tim e product for medical and surgical applications. The device operation is based on the flow of a viscous fluid through a micromachined channe l under applied pneumatic pressure. A fluid-dynamical model for flow o f a viscous fluid through a microchannel, various channel geometries, the device fabrication and its operation under constant applied pneuma tic pressure are presented. The length of an advancing fluid column in the microchannel is proportional to the magnitude of the pressure-tim e product. Castor oil is employed as the working fluid. Devices capabl e of measuring the pressure-time product from 75 to 3000 psi min have been fabricated and tested. The simple design configuration, operation without an external electrical power supply and direct measurement wi thout any additional circuitry are some of the attractive features of such as pressure-time recorder. Other possible applications of such a device are also described briefly.