This paper presents an electroencephalogram (EEG) acquisition and biomarker-extraction system based on flexible, thin-film electronics. There exist commercial, single-use, flexible, pre-gelled electrode arrays; however, these are fully passive, requiring cabling to transfer sensitive, low-amplitude signals to external electronics for readout and processing. This work presents an active EEG acquisition system on flex, based on amorphous silicon (a-Si) thin-film transistors (TFTs). The system incorporates embedded chopper-stabilized a-Si TFT low-noise amplifiers, to enhance signal integrity, and a-Si TFT compressive-sensing scanning circuits, to enable reduction of EEG data from many channels onto a single interface, for subsequent processing by a CMOS IC. Further, the system uses an algorithm, by which spectral-energy features, a key EEG biomarker, are extracted directly from the compressed signals. We demonstrate a prototype, performing EEG acquisition from a human subject, and compressed EEG data. The TFT amplifier achieves a noise PSD of 230 nV/√Hz. reconstruction and seizure detection via analog replay of patient Seizure detection, at up to 64× compression, achieves error rates <;8%. Reconstruction is demonstrated at up to 8× compression.