The chip was then treated with Cr etchant for approximately 30 seconds to remove the 7 nm Cr layer, followed by immediate rinsing with water and drying with nitrogen gas, thereby exposing the bottom Au electrode. Finally, the liftoff of the photoresist revealed the bottom micropore electrode, where a 20 µm 2 window exposed the underlying Au electrode, while the rest of the chip remained insulated by the alumina layer.