An ultraflexible organic differential amplifier for recording electrocardiograms

Differential amplifiers based on organic thin-film transistors (OTFTs) are attractive for monitoring human vital signs because of their signal amplification and noise elimination capabilities. However, substantial variations in OTFTs lead to the degradation of signal processing performance in circuits and restrict the development of organic differential amplifiers capable of recording weak physiological potentials. Here, we report a 2-μm-thick ultraflexible organic differential amplifier capable of processing physiological signals with high signal integrity and sensitivity. Our approach uses a circuit design and compensation technique that suppress the mismatch among OTFTs to less than a few percent. This leads to a common-mode noise attenuation factor below −12 dB, even during bending to ~50 μm. Using our flexible amplifier, we monitor electrocardiogram signals, where the power of 60 Hz electrical harmonic noise was reduced ~60 times during amplification, yielding electrocardiogram signals with a signal-to-noise ratio of 34 dB.