Wireless Passive Stimulation of Engineered Cardiac Tissues

We present a battery-free radio frequency (RF) microwave activated wireless stimulator, 25 × 42 × 1.6 mm³ on a flexible substrate, featuring high current delivery, up to 60 mA, to stimulate engineered cardiac tissues. An external antenna shines 2.4 GHz microwave, which is modulated by an inverted pulse to directly control the stimulating waveform, to the wireless passive stimulator. The stimulator is equipped with an on-board antenna, multistage diode multipliers, and a control transistor. Rat cardiomyocytes, seeded on electrically conductive gelatin-based hydrogels, demonstrate synchronous contractions and Ca²⁺ transients immediately upon stimulation. Notably, the stimulator output voltage and current profiles match the tissue contraction frequency within 0.5–2 Hz. Overall, our results indicate the promising potential of the proposed wireless passive stimulator for cardiac stimulation and therapy by induction of precisely controlled and synchronous contractions.