IMEC has developed a two-channel wireless EEG (electroencephalography, or monitoring of brain waves) system powered by a thermoelectric generator. It derives power from body heat dissipated naturally from the forehead. The wearable EEG system operates completely autonomous and maintenance-free with no need to change or recharge the batteries. This is a major advantage for body-worn sensors, a key theme in the Human++ program within the Holst Center.

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The entire system is wearable and integrated into a headband. The small
size, power consumption of 0.8 mW and autonomous operation increase the patient's autonomy and quality of life. Potential applications are detection of imbalance between the two halves of the brain, detection of certain kinds of brain trauma and monitoring of brain activity.

The EEG system uses IMEC's proprietary ultra-low power biopotential readout ASIC to extract high-quality EEG signals with extremely low power consumption. A low-power digital signal-processing block encodes the extracted EEG data, which is sent to a PC via a 2.4 GHz wireless radio.

The thermoelectric generator is composed of 10 thermoelectric units interconnected in a flexible way. At room temperature, the generated power is about 2.0 mW to 2.5 mW, or 0.03 mW/cm². This is the theoretical limit of power generation on human skin. Higher power generation would cause an uncomfortable sense of cold in the patient. The EEG system is operational in less than one minute after switching on the device.

Future research targets further reduction of the power consumption of the different system components, including the radio and processor. Also, a semiconductor process for manufacturing thermopiles is under development. This will allow a significant reduction of the production cost.

For more information on thermoelectric wireless medical sensors, click here.