Fig. 2: Designs for improved lifetime for stable operation.

a Top-view schematic illustration of the device. Schematic illustrations of key engineering features, including (i) an interlocking folded via structure for joining the R_x coils, (ii) a diode transferred onto a PA substrate, (iii) a pocket for diode insertion, (iv) a diode connection pad with a hole and sawtooth structure and (v) an enlarged view of the connection with W/wax paste, (vi) a connected coil and extension electrode structure fabricated from a single sheet of Mo by a laser-cutting process. Scale bar, 1 mm. b Measured RF behavior (S11) and resonance frequency as a function of time of immersion in 1 × PBS (pH 7.4) at 37 °C. c I-V characteristics before connection (black) and after connection (red) of the bioresorbable PIN diode. d Changes in resistance of serpentine traces for the optimized joined design during cyclic loading (40% compression, 5 mm/s velocity, 70,000 cycles). e Comparison of the degradation period (y-axis), operating lifetime (x-axis), and the change in device stability (color change by stability index) over time for the bioresorbable devices reported here and those in previous reports. The stability index on the right displays the rate of change for each of the following parameters: (i) Maximum EMG amplitude induced by the bioresorbable stimulator over 7 days⁶, (ii) changes in intracranial pressure (ICP)³⁵, (iii) resistance changes in the electrode¹⁰, and (iv) minimum operating voltage required to induce muscle contractions⁸. The yellow solid line indicates the case where the degradation period and operational lifetime are equal.