Stentenna: a micromachined antenna stent for wireless monitoring of implantable microsensors

This paper reports on a micromachined stent that has been developed to serve as an antenna for wireless monitoring of implantable microsensors. A 4 mm long, 3.5 mm diameter design is fabricated from 50 μm thick stainless steel foil using a batch-compatible micro electro-discharge machining process. As it is expanded during deployment, the stent transforms from a mesh that fits snugly around the angioplasty balloon into an inductive coil. This is accomplished by strategically located breakable links which change its electrical characteristics during the plastic deformation into its final shape. This 20 nH coil is coupled to a capacitive pressure microsensor that is approximately 1.2×4×0.5 mm³ in dimensions. Wireless monitoring is demonstrated by showing that the resonant electrical loading provided by this LC tank to a separate transmitting coil shifts by 400 KHz over a pressure change of 800 Torr. The tests are performed in a liquid environment.