Mutual inductance of air-cored coils: Effect on design of radio-frequency coupled implants

Flack, F. C.; James, E. D.; Schlapp, D. M.

doi:10.1007/bf02474736

Cited by 79 publications

(28 citation statements)

References 3 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…The obtained phase-dip-distance product analogous to gain-bandwidth product was higher for larger reader coils. Both the near-field and far-field coil coupling situations were well described by (15) and were in good agreements with theoretical expectations [14], [31], [34]- [36]. With these findings, the ultimate reader coil can be properly designed and realized as part of the glasses-type reader shown in Fig.…”

Section: A On-bench Characterizationsupporting

confidence: 82%

Wireless Intraocular Pressure Sensing Using Microfabricated Minimally Invasive Flexible-Coiled LC Sensor Implant

Chen

Saati

Varma

et al. 2010

J. Microelectromech. Syst.

242

130

View full text Add to dashboard Cite

Abstract-This paper presents an implant-based wireless pressure sensing paradigm for long-range continuous intraocular pressure (IOP) monitoring of glaucoma patients. An implantable parylene-based pressure sensor has been developed, featuring an electrical LC-tank resonant circuit for passive wireless sensing without power consumption on the implanted site. The sensor is microfabricated with the use of parylene C (poly-chlorop-xylylene) to create a flexible coil substrate that can be folded for smaller physical form factor so as to achieve minimally invasive implantation, while stretched back without damage for enhanced inductive sensor-reader coil coupling so as to achieve strong sensing signal. A data-processed external readout method has also been developed to support pressure measurements. By incorporating the LC sensor and the readout method, wireless pressure sensing with 1-mmHg resolution in longer than 2-cm distance is successfully demonstrated. Other than extensive on-bench characterization, device testing through six-month chronic in vivo and acute ex vivo animal studies has verified the feasibility and efficacy of the sensor implant in the surgical aspect, including robust fixation and long-term biocompatibility in the intraocular environment. With meeting specifications of practical wireless pressure sensing and further reader development, this sensing methodology is promising for continuous, convenient, direct, and faithful IOP monitoring.[ 2009-0111]Index Terms-Implantable microdevice, intraocular pressure (IOP), LC pressure sensor, parylene, wireless sensing.

show abstract

Section: A On-bench Characterizationsupporting

confidence: 82%

Wireless Intraocular Pressure Sensing Using Microfabricated Minimally Invasive Flexible-Coiled LC Sensor Implant

Chen

Saati

Varma

et al. 2010

J. Microelectromech. Syst.

242

130

View full text Add to dashboard Cite

show abstract

“…Assuming all sources and fields have a time dependence , the electromagnetic fields due to the transmit magnetic current density and the induced receive current density satisfy (2a) (2b) Substituting them into the Poynting theorem yields (3) Rearranging terms, the transmitted power density is related to the received power density and losses by (4) The term on the left is the complex transmitted power density. On the right, is the radiation loss; the imaginary part of is the sum of dielectric loss and induced-current loss; and is the complex received power density.…”

Section: Model and Problem Formulationmentioning

confidence: 99%

Optimal Frequency for Wireless Power Transmission Into Dispersive Tissue

Poon

O’Driscoll

Meng

2010

IEEE Trans. Antennas Propagat.

406

245

View full text Add to dashboard Cite

Abstract-RF wireless interface enables remotely-powered implantable devices. Current studies in wireless power transmission into biological tissue tend to operate below 10 MHz due to tissue absorption loss, which results in large receive antennas. This paper examines the range of frequencies that will optimize the tradeoff between received power and tissue absorption. It first models biological tissue as a dispersive dielectric in a homogeneous medium and performs full-wave analysis to show that the optimal frequency is above 1 GHz for small receive coil and typical transmit-receive separations. Then, it includes the air-tissue interface and models human body as a planarly layered medium. The optimal frequency is shown to remain in the GHz-range. Finally, electromagnetic simulations are performed to include the effect of load impedance and look at the matched power gain. The optimal frequency is in the GHz-range for mm-sized transmit antenna and shifts to the sub-GHz range for cm-sized transmit antenna. The multiple orders of magnitude increase in the operating frequency enables dramatic miniaturization of implantable devices.Index Terms-Implantable medical devices, wireless power transfer.

show abstract

“…The first systems designed to meet this challenge appeared in the early 1970s (38,39). They used two modified versions of classical IPT systems without the feedback loop.…”

Section: Quasi-conventional Techniquesmentioning

confidence: 99%

Prosthetic Power Supplies

Trigui

Mehri

Ammari

et al. 2015

Wiley Encyclopedia of Electrical and Electronics Engineering

View full text Add to dashboard Cite

During the last few decades, implantable medical devices (IMDs) changed the landscape of modern medicine. Combining many technologies and employing smart medical devices within the human body, they allowed a continuous and automatic management of numerous health issues, such as pacemakers and implantable cardiac defibrillators, cochlear implants, bladder controllers, endoscopic capsules, nerve stimulators, lab‐on‐a‐chip, and artificial retinal prosthesis. Due to their continuously increasing potential, IMDs are getting more complex, thus requiring more energy to operate. Most of these advanced implantable devices are extracorporeally powered or battery charged through wireless power transfer (WPT) mechanisms. Following the basic principle of IMD power supplies, we introduce various power transfer techniques, and then focus on the inductive links and various methods to maximize the energy transferred to implantable devices and the calibration methods of these WPT techniques.

show abstract

Mutual inductance of air-cored coils: Effect on design of radio-frequency coupled implants

Cited by 79 publications

References 3 publications

Wireless Intraocular Pressure Sensing Using Microfabricated Minimally Invasive Flexible-Coiled LC Sensor Implant

Wireless Intraocular Pressure Sensing Using Microfabricated Minimally Invasive Flexible-Coiled LC Sensor Implant

Optimal Frequency for Wireless Power Transmission Into Dispersive Tissue

Prosthetic Power Supplies

Contact Info

Product

Resources

About