High Performance Flexible Organic Electrochemical Transistors for Monitoring Cardiac Action Potential.

Flexible and transparent electronic devices possess crucial advantages over conventional silicon based systems for bioelectronic applications since they are able to adapt to nonplanar surfaces, cause less chronic immunoreactivity, and facilitate easy optical inspection. Here, organic electrochemical transistors (OECTs) are embedded in a flexible matrix of polyimide to record cardiac action potentials. The wafer-scale fabricated devices exhibit transconductances (12 mS V-1 ) and drain-source on-to-off current ratios (≈105 ) comparable to state of the art nonflexible and superior to other reported flexible OECTs. The transfer characteristics of the devices are preserved even after experiencing extremely high bending strain and harsh crumpling. A sub-micrometer poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate) layer results in a fast transport of ions between the electrolyte and the polymer channel characterized by a cut-off frequency of 1200 Hz. Excellent device performance is proved by mapping the propagation of cardiac action potentials with high signal-to-noise ratio. These results demonstrate that the electrical performance of flexible OECTs can compete with hard-material-based OECTs and thus potentially be used for in vivo applications.

Versatile Flexible Graphene Multielectrode Arrays.

Graphene is a promising material possessing features relevant to bioelectronics applications. Graphene microelectrodes (GMEAs), which are fabricated in a dense array on a flexible polyimide substrate, were investigated in this work for their performance via electrical impedance spectroscopy. Biocompatibility and suitability of the GMEAs for extracellular recordings were tested by measuring electrical activities from acute heart tissue and cardiac muscle cells. The recordings show encouraging signal-to-noise ratios of 65 ± 15 for heart tissue recordings and 20 ± 10 for HL-1 cells. Considering the low noise and excellent robustness of the devices, the sensor arrays are suitable for diverse and biologically relevant applications.