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Micromachined intraluminal devices for active and passive electromagnetic measurements of flow

Publication Type:

Conference Paper

Source:

18th IEEE International Conference on Micro Electro Mechanical Systems (IEEE Cat. No.05CH37610), IEEE, Miami Beach, FL, USA, p.863-6 (2005)

Keywords:

blood flow measurement; micromachining; micromechanical devices

Abstract:

This paper outlines architectures for implantable (active and passive) sub-systems intended for monitoring of intraluminal blood flow by electromagnetic transduction, and presents the fabrication and test results of select components within these sub-systems. Central to both schemes is a ring-shaped intraluminal stainless steel cuff with two electrodes. In the presence of a magnetic field, it produces a voltage proportional to the flow velocity. It is fabricated by micro-electro-discharge machining and deployed by an angioplasty balloon. Cuffs deployed within 3-mm i.d. silicone tubes demonstrate linear and symmetric responses of 3.1-4.3 ?V per cm/sec over 180 cm/sec with magnetic fields of about 0.25 T. In the passive monitoring scheme, voltage from the cuff modulates a varactor that is also connected to an antenna stent (stentenna). This approach is explored using a hybrid diode for the varactor and a stentenna deployed within a mock artery. Preliminary tests in saline indicate that an external transmitting coil will experience shifts in phase spectrum of 2.0-3.3 KHz/mV of output from the cuff