Wireless Power Transfer and Data Communication for Implantable Autonomous Monitoring and Detection of Epilepsy In Vivo

The impact of technological advancement became significant and still has an essential role to play in the diagnosis and treatment of diseases. Nowadays, personalized medicine and therapy are on the rise as a consequence of the developed and cheaper medical technologies which enables the monitoring and evaluation of many parameters of patients. One of the areas where the technological developments in biomedical applications can be used most effectively is the neurological monitoring systems. The brain-machine interface (BMI) allows controlling external software or hardware by transmitting neural information. Besides, BMI can be used for recovering lost functions such as walking. In addition, as brain signals can be analyzed in a more efficient way, advanced monitoring can be used to understand the cause and to treat neurological disorders such as Epilepsy or Parkinson's diseases. The development of closed-loop systems is still going on to detect the abnormalities in neural signals and prevent them by applying short electrical pulses.

Epilepsy is a chronic discomfort that affects many people throughout the world. The major form of treatment is long-term drug therapy, and surgery is an alternative for patients who do not respond to drug treatment when a seizure is limited to one area. Continuous monitoring of neural activity is commonly used for the diagnosis of epileptic zones. Thanks to the advances in electronics, sensor systems, and fabrication methodologies, this thesis proposes a completely implantable wireless neural monitoring system which eliminates the wires and possible complications due to them.

The power requirement of the active components in the implanted system is supplied by a hybrid solution composed of wireless power transmission and a rechargeable battery. A 4-coil inductive link is used for remote powering. A stable and ripple free supply voltage for the implanted system is generated by the use of active half-wave rectifier and low drop-out regulator blocks. Additionally, the automatic resonance tuning mechanism is developed to maximize the power transfer efficiency. Furthermore, the power feedback generation structure is designed to make sure that the delivered power is reached.

Wireless data communication solutions between the external unit and the implanted system are presented. Configuration parameters of the implanted system are transferred by modulating the powering signal source and changes in the powering signal is decoded by the embedded electronics. Two alternative methods, namely narrowband and ultra-wideband transmitters, are designed to transmit the amplified, quantized and analyzed neural activities. The transmitters can be used interchangeably to provide longer transmission distance or higher data rate.

The designed electronic circuits are fabricated and packaged with biocompatible materials for in vivo characterization. The operation of remote powering and wireless data transmission units are validated in a rat.