Online Charge Balancing With Active Impedance Monitoring in Programmable Stimulator to Extend Electrode Lifetime.

Area of Science:

• Biomedical Engineering
• Neuroscience
• Medical Devices

Background:

• Neurostimulation offers an alternative to pharmaceutical pain management.
• Invasive electrodes are used for targeted nerve stimulation.
• Electrode longevity is a critical challenge in neurostimulation therapies.

Purpose of the Study:

• To develop a programmable neurostimulator for analgesic nerve stimulation.
• To implement active impedance monitoring for real-time feedback.
• To enhance electrode lifespan through charge-balanced stimulation.

Main Methods:

• A programmable stimulator on a Printed Circuit Board (PCB) with constant-current and capacitor-coupled biphasic modes.
• Custom STM32 microcontroller library for adjustable pulse duration (1 µs to 10 s) and frequency (0.1 Hz to 100 kHz).
• Active Impedance Monitoring (AIM) unit for frequency response analysis (1 Hz to 10 kHz) and a novel charge-balancing algorithm.

Main Results:

• The stimulator generates up to ±1.6 mA current pulses with high precision.
• AIM unit accurately calculates electrode/tissue resistance and RC time constants (>90% precision).
• Charge-balancing algorithm achieved <5% error, extending electrode lifetime >288 million pulses in vitro.

Conclusions:

• The developed programmable neurostimulator effectively delivers analgesic nerve stimulation.
• Active impedance monitoring and charge balancing significantly improve electrode durability.
• This system offers a promising solution for long-term, reliable neurostimulation therapies.