Fig. 4

2D CA model of the SWNT/POM network. a CA model on a 2D grid consisting of POM cells (blue spheres) connected with black SWNT wires and the source (S, right) and drain (D, left) electrodes. The network is on 20×14 intersection points on a 2D regular grid, and 45% of which are randomly chosen as ‘detects’ (D_f = 45%), while the rest are the POM cells. b Notation of cell interaction for the state transition. The transition direction at time t is selected to yield the largest gradient for state \(\Delta a_{i,j}^k\) among all k neighbours. c State transition probability showing \({\boldsymbol{P}}_c^B\). d, e Schematics for two types of state transition rules applicable (d) when a_i,j < a_TH and (e) for discharging when a_i,j >a_TH. f Calculated impulse generation results for 3000 cycles in a 30×30 array with \({\boldsymbol{P}}_c^A\), V_B = 6, a_TH = 5 and D_f = 45%. Hereafter, AN30 denotes the results for a 30×30 array with \({\boldsymbol{P}}_c^A\) and DF45 denotes D_f = 45%. The inserted images are snapshots of the numbers of states in each cell at a given time. g, h Calculated I–V characteristics for AN30DF20 and BN30DF45, respectively, with a_H = 5. g The inset shows \({\boldsymbol{P}}_c^A\). The definition of current is the number of charges transferred to the drain electrode N_c averaged over 5000 cycles. h The inset shows I–V for a single cell with \({\boldsymbol{P}}_c^B\), directly connected with the electrodes. i Noise generation in the base current, plotted over 5000 cycles with stepwise increment of V_B for AN50 with a_TH = 40