A 4.7 T/11.1 T NMR Compliant 50 nW Wirelessly Programmable Implant for Bioartificial Pancreas In Vivo Monitoring

This paper presents a 50 nW wirelessly powered implant for the noninvasive monitoring of a bioartificial pancreas postimplantation in nuclear magnetic resonance (NMR) animal studies. The proposed implant increases NMR signal sensitivity across a 190–470 MHz frequency range in both 4.7 and 11.1 T magnetic fields through the use of a wirelessly programmable resonator. An integrated split capacitive array provides 51.8 pF tuning range and 52 fF resolution while maintaining resonant Q and reducing parasitic contributions. The implant supports forward data telemetry at 5–250 kbit/s using an envelope detector front-end and a 2.4 MHz oversampling clock/data recovery (CDR) receiver. An integrated logic-controlled RF-DC converter and strongly coupled resonant wireless link provide sustained reliable energy transfer during NMR acquisition. NMR signal isolation from the wireless power transmissions is achieved through frequency allocation and orthogonally embedded coil design that provides increased mechanical strength for incorporating device components. Experimental results in tissue-equivalent gel phantoms and small animal studies show an increase in acquired signal-to-noise ratio (SNR) by 141% (7.7 dB) and 83% (5.3 dB) within 4.7 and 11.1 T magnetic field strengths, respectively, with an approximate 100% (6 dB) increase in SNR within the region of interest (ROI) at higher image resolutions.