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Title: A programmable stimulator for functional electrical stimulation
Keywords: FES, stimulation, stimulator, charge balance, tissue damage, programmable
Issue Date: 18-Aug-2010
Citation: TAN YI JUN JASON (2010-08-18). A programmable stimulator for functional electrical stimulation. ScholarBank@NUS Repository.
Abstract: Functional Electrical Stimulation or FES has been used widely for many applications, aiming to restore lost body functions due to nerve damage or injury. One of the applications of FES is to restore hand functions for patients suffering nerve damage along the arm such that neural signals from the brain cannot reach the hand muscles due to nerve denervation caused by the injury. Research work has been ongoing for such FES systems and current stimulator systems involve an implanted stimulator with wire leads to electrodes controlled wirelessly by an external unit. Implanting wire leads complicates the surgical process and external control unit is cumbersome for users and provides limited hand functions and programmability. Therefore, in recent years, numerous researches are done on neural recording, either from the brain cortex or from peripheral nerves such that these neural signals can act as triggers for stimulation, thereby eliminating the need for an external control unit. Hence, modern day FES systems usually consist of a front-end neural recording circuitry and a back-end stimulation circuit. The idea is to detect a neural signal, decodes it and sent information wirelessly to the stimulator circuit for adequate stimulation. This thesis presents a programmable single-channel stimulator for such application. The overall system is implemented in two architectures and both architectures are incorporated into a single chip. Stimulation parameters like stimulus amplitude, pulsewidth and frequency are programmable. In recent years, concerns of tissue damage due to stimulation are becoming the main focus of designing stimulator circuits and experiments show that rectangular balanced biphasic stimulus can reduce such tissue damage. Therefore, charge balance accuracy becomes one of the concerns in the design of the stimulator. The proposed stimulator in this thesis has been implemented using AMS 2P4M 0.35um CMOS technology. It is also fabricated and verified with silicon results. Measurement results show that both stimulator versions are able to output a rectangular biphasic stimulus with programmable stimulation parameters. Achieved charge balance, for both stimulator versions, is also below the stated safety tolerance level of 0.4uC. A comparison study is also done to analyze the performance of each stimulator version. Lastly, some suggestions for improvements and future work are proposed to improve the overall stimulator circuit.
Appears in Collections:Master's Theses (Open)

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