Thermal safety considerations for implantable micro-coil design.

Area of Science:

• Biomedical Engineering
• Neuroscience
• Materials Science

Background:

• Implantable micro-coils offer promising neuromodulation via magnetic brain stimulation.
• Understanding the thermodynamic profile of these devices is critical for safe and effective design.

Purpose of the Study:

• To quantify the thermal profile of bent wire micro-coils.
• To mitigate thermal impacts associated with micro-coil stimulation.

Main Methods:

• Utilized fine wire thermocouples and COMSOL finite element modeling.
• Examined thermal gradients near micro-coils under various stimulation parameters (voltage, frequency, repetition rate).
• Tested different coil wire materials, including platinum/iridium and gold.

Main Results:

• Observed temperature increases from <1 °C to 8.4 °C, dependent on stimulation parameters and materials.
• Identified micro-coil hot spots contributing to thermal gradients.
• Demonstrated mitigation of thermal gradients through material selection and geometric design.

Conclusions:

• Gold wire micro-coils showed a 5-6 fold decrease in thermal impact compared to platinum/iridium.
• Thermal gradients from gold coils remained below the ISO 14708-1 safety limit of 2 °C for all tested parameters.
• Material choice is key to managing thermal safety in active implantable medical devices.