Cu-modified electrolyte-gated transistors based on reduced graphene oxide

Electrolyte-gated transistors (EGTs) have attracted extensive attention due to their versatility and excellent performance in different fields of electronics. Here, we report on coplanar EGTs based on reduced graphene oxide (rGO), whose gates (flexible Au micro-electrodes) were modified by electrodeposition of either compact or porous Cu coatings (Cu-modified EGTs). The Cu coatings yielded a dramatic change in the minimum gate voltage spanning from -50 mV to -300 mV, which allowed extremely versatile tuning of the device signal. Furthermore, steady measurements led us to carry out prolonged measurements (>2 hours) under a constant bias in NaCl 0.1 M solution which was driven onto the EGTs by using homemade paper fluidics. Transient characterization studies pointed out a potentiometric sensitivity of around 1-3 mV with a signal-to-noise ratio (SNR) close to 5-10 for both electron and hole transport regimes. Since the response time of our Cu-modified EGTs was as low as 80 ms, we succeeded in monitoring emulated action potential (eAP) featuring a characteristic frequency equal to 0.1 Hz.