Fig. 4: In vivo wireless networking and closed-loop control of implantable devices in a pig.

a Three-dimensional computed tomography reconstruction of implants wireless networking in a pig model showing two devices (loop recorder and VNS node) implanted at the thorax and neck, respectively. Scale bar, 5 cm. b Computed tomography cross-section image showing the metamaterial textile, loop recorder, and VNS node. The distance between two implants and depths of implantation from the metamaterial textile are labeled. Scale bar, 5 cm. c Block diagram of the wireless closed-loop sensing (loop recorder) and stimulation (VNS node) system. When the detected heart rate (HR) increases above the threshold hr_t, VNS node will turn on the stimulation until the heart rate recovers. d Recorded ECG waveforms of the loop recorder with R-peak (RR) intervals labeled (left) and output stimulation signals of the VNS node (right). e RSSI received during Bluetooth interconnection of the two implanted nodes. f Comparison of ∣S₂₁∣ (left) and RSSI (right) with and without the metamaterial textile. Error bars show mean ± s.d. of the transmission spectra within 2.4–2.5 GHz (left) and RSSI values in e (right). g Calculated heart rate during two dose injection cycles. Dashed black lines show the heart rate threshold hr_t. h 5-min change in heart rate after it plateaued during two trials as a function of time (error bars indicate mean ± s.d. of the previous 1-min heart rate). i Comparison of ECG signal segments 5 min after the heart rate plateaued. Fewer peaks detected in 5 s indicate lower heart rate. Peaks are marked with squares. Source data are provided as a Source Data file.