Graphene Field-Effect Transistors for In Vitro and Ex Vivo Recordings

Recording extracellular potentials from electrogenic cells (especially neurons) is the hallmark destination of modern bioelectronics. While fabrication of flexible and biocompatible in vivo devices via silicon technology is complicated and time-consuming, graphene field-effect transistors (GFETs), instead, can easily be fabricated on flexible and biocompatible substrates. In this work, we compare GFETs fabricated on rigid (SiO₂/Si and sapphire) and flexible (polyimide) substrates. The GFETs, fabricated on the polyimide, exhibit extremely large transconductance values, up to 11 mS·V^-1, and mobility over 1750 cm²·V^-1·s^-1. In vitro recordings from cardiomyocyte-like cell culture are performed by GFETs on a rigid transparent substrate (sapphire). Via multichannel measurement, we are able to record and analyze both: difference in action potentials as well as their spatial propagation over the chip. Furthermore, the controllably flexible polyimide-on-steel (PIonS) substrates are able to ex vivo record electrical signals from primary embryonic rat heart tissue. Considering the flexibility of PIonS chips, together with the excellent sensitivity, we open up a new road into graphene-based in vivo biosensing.