A wireless microsensor for monitoring flow and pressure in a blood vessel utilizing a dual-inductor antenna stent and two pressure sensors

Abstract

This paper reports a micromachined antenna stent (stentenna) that is integrated with implantable microsensors for wireless sensing of blood flow and pressure with no battery. A device that has 20-mm length and 3.5-mm diameter (after expansion) is fabricated from 50 pm thick stainless steel foil by using batch-compatible micro-electro-discharge machining. This is coupled to two micromachined capacitive pressure sensors of approximately 1.4x1.8x0.5 mm' dimensions. A 0.5-pm thick parylene layer provides electrical insulation. The integrated device is deployed inside a silicone mock artery with a standard angioplasty balloon. The planar structure is plastically deformed to a tubular shape, resulting in dual helical coils with 50-60 nH each. These L-C tanks are used to wirelessly probe pressures at two points along a channel for flow-rate detection.Fluidic experiments that emulate a blockage in the mock artery demonstrate that the resonant impedance and phase provided by the LC-tanks to a separate transmitting coil shift by 5-40 MHz over flow-rate change of 150-300 mL/min. Pressure sensitivity is 273 ppm/Torr, which is >lOOx higher than past results.

Long term, implantable blood pressure monitoring systems

“…The hermetic enclosure protects the sensitive portion of the system from the body and the biocompatible coating is used to improve the interface of the implant with body. In previous work, the hermetic housing has been formed from a silicon-glass anodic bond (Najafi and Ludomirsky 2004;Park et al 1998;Takahata et al 2004;DeHennis and Wise 2006;Ziaie and Najafi 2001), a glass-glass fusion bond (Allen 2005), chemical vapor deposited oxide (Eggers et al 2000), and ceramic (Fonseca et al 2006).…”

“…In 2004, Takahata, et al, at the University of Michigan presented a combination of an arterial stent and a passive telemetry (no battery) blood flow and pressure sensor (Takahata et al 2004(Takahata et al , 2003. The stainless steel stent was fabricated using micro-electro-discharge machining and the pressure sensors were formed using bulk and surface micromachining and anodic bonding.…”

Development of implantable catheter flow sensor into inside of bronchi for laboratory animal

“…Two miniaturized pressure senors developed by MEMS were integrated into a stent structure for monitoring pressure change after the stent implant (Takahata et al 2004). A strain gauge was embedded into a contact lens for intraocular pressure monitoring (Leonardi et al 2003).…”

Integration of temperature detection onto catheter flow sensor for bronchoscope

“…These micro-needles have been used as trans-dermal drug delivery systems [8][9][10][11][12][13] since the late 1990s. Their use was also expanded to develop a miniaturized soft transplantation tool [14], a stent structure with the function of detecting pressure in blood vessels [15], a contact lens that monitored eye pressure [16], and a healthcare chip for home medical diagnosis [17].…”