Fig. 5: Block, timing diagrams, and implementation of a proposed electrochemical biosensor system.
a A block diagram of the system, consisting of the proposed memristor-based transducer for practical implementation, a signal processing (SP) block, such as an ADC, an MCU, and a display. b A timing diagram of the biosensor, comprising initialization (init.), sensing (sens.), and reading (read.) stages. In the initialization stage, the switches of S/W1, S/W2, and S/W3 are connected in positions 1, 1, and 1, respectively. 1 V was applied to VR for 40 ms, initializing the memristors to a high resistance state (HRS). During the sensing stage, S/W1, S/W2, and S/W3 were connected in positions 2, 2, and 2, respectively. More precisely, S/W1 was switched to position 2 only during ten consecutive pulses with a unit pulse time (TPULSE) of 20 μs to minimize voltage stress on the memristors. 1.2 V was applied to VD, along with the necessary voltages to VREF and VGS. If the voltage (VOUT) across the memristors exceeded the threshold level of about 0.7 V (VSET), the memristor shifts to a low resistance state (LRS); otherwise, it remained in HRS. In the reading stage, S/W1, S/W2, and S/W3 were connected in positions 1, 2, and 1, respectively. 0.3 V was applied to VR for 80 μs. A voltage drop occurred across the memristors, and the potential at VOUT was sensed through the ADC and processed via the MCU to determine the memristor resistance of RM. c Images of an implemented prototype of the biosensor system, comprising a sensor electrode, an IC-board, a mem.-board, and an organic light-emitting diode (OLED) display.
