Continues Synthesis of Free-Standing SWNT Films for Bioelectrode Applications

Thin single-wall carbon nanotube (SWNT) films have garnered significant attention due to their high optical transmittance, electrical conductivity, and mechanical flexibility. High-volume applications in energy devices and electronics have been demonstrated using carbon nanotube films as platform materials. In this work, we developed an advanced floating catalyst chemical vapor deposition (FCCVD) method for the direct production of freestanding SWNT aerosols and roll-to-roll collection. This FCCVD method can produce over 10 m2/h of continuous freestanding SWNT films, which is two orders of magnitude higher than other FCCVD methods, paving the way for a broad range of applications. The typical film thickness is less than 10 nm, and a sheet resistance of about 65 ohms/sq @ 90% optical transmittance has been achieved. This makes the films suitable for direct use as transparent electrodes in energy devices and flexible electronics.<br/>Specifically, the ultra-thin conformal SWNT films have been applied as dry bioelectrodes for surface electrophysiology monitoring. We demonstrate electrocardiogram (ECG), electromyography (EMG), and forehead electroencephalogram (EEG) monitoring on the skin in a tattoo-like form, as well as multifocal electroretinography (ERG) recording on the eyes via a smart contact lens. The CNT electrode design achieves low contact impedance and a high signal-to-noise ratio (SNR), comparable to commercial Ag/AgCl wet electrodes. The ultra-thin form factor and skin attachment reduce susceptibility to motion noise, a common drawback of dry electrodes. Additionally, the dry CNT electrodes offer advantages in terms of cost, flexibility, stability, and biocompatibility.