Magnetoelectric-based Wireless Power and Data Transmission to Small Biomedical Implants
Open Access
- Author:
- Hosur, Sujay Sheshagiri
- Graduate Program:
- Electrical Engineering
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- December 10, 2024
- Committee Members:
- Madhavan Swaminathan, Program Head/Chair
Abhronil Sengupta, Major Field Member
Mehdi Kiani, Chair & Dissertation Advisor
Weihua Guan, Major Field Member
Xiaogang Hu, Outside Unit & Field Member - Keywords:
- Magnetoelectric transducers
Wireless power transfer
Magnetic field
Efficiency
Wireless interrogation
Low-frequency operation
Biomedical implants
Inductive coils
Ultrasound
Magnetic-ultrasound (MagSonic)
Miniaturization
Wireless energy
Implantable medical devices
Polydimethylsiloxane (PDMS) coating
Integrated circuit
Neural Stimulation
Neural Recording - Abstract:
- This dissertation focuses on the study and analysis of millimeter (mm) scale magnetoelectric (ME) transducers used as wireless power receivers and/or data transceivers in small implantable biomedical devices (IMDs) using low-frequency magnetic fields. ME transducers, comprising layered magnetostrictive and piezoelectric materials, are more efficient than inductive coils in converting low-frequency magnetic fields into electric fields, particularly in applications that require miniaturized devices such as biomedical implants. Therefore, ME transducers are an attractive candidate for wireless power transfer (WPT) using low-frequency magnetic fields, which are less harmful to the human body and can penetrate easily through different lossy media. In the first part of this dissertation, a comprehensive study on the ME transducer used as a power receiver in a WPT link is presented. The impact of different ME design parameters on the WPT link performance is studied. Several ME transducers with different sizes (ME volume: 5-150 mm3) are studied. The second part of this dissertation compares the ME WPT with state-of-the-art modalities, particularly for biomedical implant applications operating under safety limits. Here, the power receiving capability of ME, US, and inductive coil receivers with similar volumes is compared through measurements. In the third part of this dissertation, methods for biocompatible coating and packaging of ME transducers within a small IMD are investigated to achieve optimal ME response. Here, the effects of biocompatible coating and packaging using Polydimethylsiloxane (PDMS) on ME response are described. The results are presented through measurements. Several bio-implant applications require data communication between the implant and the external unit to provide acknowledgment, send vital information, or any such. Hence, in the fourth part of this dissertation, a technique called monotonic energy transmission (MET), for short-range wireless data transfer from small implantable devices with mm scale dimensions to an external unit using the ME effect is introduced. This technique is combined with pulse position modulation (PPM) to further increase the data rate. The fifth part of this dissertation presents a hybrid magnetic-ultrasonic interrogation approach (called MagSonic) realized through a single ME transducer at the implant site which can generate and receive both magnetic field and ultrasound. Significantly higher received power (up to 4 times more) and data rate > 100 kbps are demonstrated for the first time with a single ME transducer. MagSonic interrogation method’s high robustness towards misalignments is also demonstrated. For the final part of this dissertation, a fully wireless ASIC, operating with the hybrid MagSonic modality using a 5.1×2.3×1.7 mm3 ME transducer, is presented for neural stimulation and recording applications.