Etude et validation experimentale de l'evolution du contact electrode-tissus nerveux.

摘要

The work presented in this master thesis is dedicated to characterise the evolution of the contact between nerve tissues and a stimulation electrode, during several months of implantation. Target applications are autonomous neurostimulators as urinary implants which are dedicated to rehabilitate bladder function in paraplegic patients. Results of this study will lead to adjust stimulation parameters depending on evolving contact characteristics, thus providing safe and efficient stimulations to the patient.; As a first part, we studied the various electrochemical mechanisms occurring on electrode-electrolyte contact. It allowed us to build an electrical model based on passive components representing the interface. In order to quantify this model, we considered three electrochemical analysis methods: complex impedance spectroscopy, galvanostatic double pulse method and cyclic voltammetry.; The second part deals with building an implantable monitoring system. It allowed us to follow chronic evolution of the electrical model. It consists of a miniature implant equipped with a bidirectional wireless communication link. It is based on a 2 mm2 full custom integrated circuit designed and fabricated in CMOS 0.18 mum technology, enabling the use of selected analysis methods.; Results of our project show the functionality and versatility of the monitoring tool through several in vitro experimentations. They demonstrate the ability to extract with accuracy the electrical model parameters using each integrated analysis method.; The main contribution of this work is the definition of a complete and functional system dedicated to study the electrode tissues contact, which includes the selection of the measurement methods as well as the electronic and microelectronic conception of the system. Concerning the blocks constituting the dedicated integrated circuit, the current source and the analogue to digital converter were custom made for the project. Finally, the topology of the instrumentation amplifier, in spite of being based on previous work of the Polytsim laboratory, was fully reviewed to fit with our application.