Once our indigo thin film samples started to seem promising and readily producible it was time to put more thought into the electronic measurement setup. Just a simple circuit was required to test for memristor behavior; here’s a snapshot of the first diagram I sketched on our lab whiteboard…

Since we want to test for changes in the resistance of the carbon-indigo-aluminum layer structure, sensing the drop across the structure positioned as the lower “rung” of a voltage divider seemed to make the most sense in order to avoid shorting the voltage source or running too large a current through the layers. Of course, this requires having a rough idea of what the high conductance-state resistance of the memristor junction should be; I assumed the 10k value from Nascimento et al. [IEEE Electron Device Letters 42, 1468 (2021)].