Study of the Effect of Distance and Misalignment between Magnetically Coupled Coils for Wireless Power Transfer in Intraocular Pressure Measurement

Abstract

An analysis of the effect of distance and alignment between two magnetically coupled coils for wireless power transfer in intraocular pressure measurement is presented. For measurement purposes, a system was fabricated consisting of an external device, which is a Maxwell-Wien bridge circuit variation, in charge of transferring energy to a biomedical implant and reading data from it. The biomedical implant is an RLC tank circuit, encapsulated by a polyimide coating. Power transfer was done by magnetic induction coupling method, by placing one of the inductors of the Maxwell-Wien bridge circuit and the inductor of the implant in close proximity. The Maxwell-Wien bridge circuit was biased with a 10 MHz sinusoidal signal. The analysis presented in this paper proves that wireless transmission of power for intraocular pressure measurement is feasible with the measurement system proposed. In order to have a proper inductive coupling link, special care must be taken when placing the two coils in proximity to avoid misalignment between them.

Design and Simulation of an Integrated Wireless Capacitive Sensors Array for Measuring Ventricular Pressure

“…( b ) Flexible LC prototype implanted in a rabbit’s eye [45,46,47,48]. Reprinted from Microelectronic Engineering, Vol.159, Félix Gil Carrasco, Daniela Díaz Alonso, Luis Niño-de-Rivera, Biocompatibility and implant of a less invasive intraocular pressure sensor, Pages No.…”

“…The conception of the implantable capacitive array and the inductive coupling link are designed for accomplish practical, accurate, and real-time wireless pressure sensing. This novel design is supported by our previous work: (a) A magnetically coupled planar coils for wireless power transfer in intraocular pressure measurements [45]; (b) An aluminum based thin film technique for the fabrication of capacitive sensors [46,47], and (c) The implantation of an experimental LC prototype beneath the conjunctiva of a rabbit’s eye using a very simple surgery. The sensors array has the capability to adjust between the conjunctiva and the cornea without an aggressive invasive procedure; the LC array did not suffer rejection; tissue irritation disappears after three weeks; the prototype showed good stability, and the rabbit tolerated this implant during six months before its sacrifice [48].…”

Design and evaluation of a wireless CMOS energy harvester for biomedical sensor networks

“…This means that for a required VOUT and given distance between the reader and transponder, P TX stemming from the current i TX driving the primary power amplifier must be considerably increased as VOUT is ideally a monotonic function of i TX [2]. The relationship between the device geometry ratios, specified system requirements for the current dissipated at the primary side i 1 , output voltage of the rectifier VOUT , and other parameters can be expressed as [6] where L 1 , L 2 , R 1 , C 1 , and R L are the primary inductance, secondary inductance, secondary parasitic resistance, secondary resonant capacitance, and secondary load, respectively. A rectifier implemented in modern CMOS process can be expected to have considerably reduced substrate leakage current compared with its counterpart implemented in bipolar junction transistors (BJTs) [1, 2].…”

An Integrated Wireless, Full-Range, Capacitive Sensor System Designed for Measuring Ventricular Pressure

“…The conception of the implantable capacitive array and the inductive coupling link are designed for accomplish practical, accurate, and real-time wireless pressure sensing. This novel design is supported by our previous work: a) A magnetically coupled planar coils for wireless power transfer in intraocular pressure measurements [45]; b) An aluminum based thin film technique for the fabrication of capacitive sensors [46][47], and c) The implantation of an experimental LC prototype beneath the conjunctiva of a rabbit´s eye using a very simple surgery.…”

“…a) Aluminum based capacitive pressure sensor fabricated over a thick polyimide substrate and capped with a thin polyimide film. b) Flexible LC prototype implanted in the rabbit´s eye[45,[47][48].…”