Technology Description

The inventors have designed, implemented, and demonstrated an integrated circuit architecture for robust and automated detection of heartbeats from a two-electrode ECG signal. This uses sufficiently low power (~20μW) that it can be powered entirely by human body heat from a cm-scale TEG module at ~20mV, including wireless transmission of data. The architecture specifically addresses the challenge of motion artifacts, where moving cables and electrodes create changes in the measured bioelectrical signal that can lead to errors in heart beat detection. This is a common challenge for most wearable sensor devices and most bioelectrical measurements (ECG, EEC, EMG, etc.). This approach performs motion-resilient heart beat detection directly in the circuit hardware using very low average power, which enables battery-less operation using energy harvesting (as described separately in OSU-19-19). The approach could also be used to improve accuracy and extend battery life of battery-powered bioelectrical signal monitors.

Features & Benefits

• Battery-less
• Resilient to motion artifacts
• Very low power

Applications

• Heart beat biosensor
• Wearable electronics
• Health monitoring

Background of Invention

Wearable devices are expanding beyond consumer and entertainment applications, including continuous monitoring of vital signs for medical diagnostics, due to extended ambulatory measurement capabilities compared to fixed clinical environments. Continuous long-term use is difficult for battery-powered devices in a wearable form-factor, whereas ambient energy harvesting promises power autonomy to enable indefinite lifetime for true battery-less devices. However, accurate measurement of vitals under real-world motion conditions is energy intensive, making it difficult to provide reliable and medically relevant data using typical micro-watt power levels available from energy harvesting. This circuit can start up and operate at very low voltage while effectively filtering noise that results from motion of the wearer.

Status

Patent pending, seeking development partners   

The graph shows the accuracy of the present circuit (red) compared to actual heart rate (grey) and heart rate without mitigating motion artifacts (blue). This architecture remains very accurate with motion.