Fig. 4. IC transmission depth scales with TX array geometry and operating voltage to enable low-voltage, long-range, and geometrically scalable communication in physiological environments.

(A) Effect of electrode geometry (W, D, and L) on IC response above f_IC frequencies. Larger and warmer colored symbols correspond to larger responses. Each datapoint is determined by extracting the average response of 256 cycles per frequency. (B) IC response is linearly positively correlated with the product of W and L, and linearly negatively correlated with D. Inset: Cross-sectional schematic illustrating geometrical parameters of IC device. The blue medium between TX and RX arrays represents the biological tissue; D is the depth of TX inside tissue, W is the interelectrode distance of TX or RX pairs, and L is the length of square electrodes. (C) Estimated communication depth of IC based on electrode geometry and operating voltage (1, 5, 10, 50, 100, and 500 mV; darker shades denote higher voltages). The dashed lines denote the approximate distances between the surface and implants in various human tissues.