A sound way to deliver power: Implanted medical devices, such as pacemakers and neurological stimulators, require a source of power, usually in the form of a battery. If a battery is implanted with the device, replacing it would require additional surgery. On the other hand, external power packs are prone to lead to infections where their wires enter the body. Hinchet et al. describe a triboelectric generator that can convert externally applied ultrasound into an internal electricity source capable of delivering sufficient energy to recharge a battery on a daily basis. Science , this issue p. 491

Self-powered implantable devices have the potential to extend device operation time inside the body and reduce the necessity for high-risk repeated surgery. Without the technological innovation of in vivo energy harvesters driven by biomechanical energy, energy harvesters are insufficient and inconvenient to power titanium-packaged implantable medical devices. Here, we report on a commercial coin battery-sized high-performance inertia-driven triboelectric nanogenerator (I-TENG) based on body motion and gravity. We demonstrate that the enclosed five-stacked I-TENG converts mechanical energy into electricity at 4.9 μW/cm³ (root-mean-square output). In a preclinical test, we show that the device successfully harvests energy using real-time output voltage data monitored via Bluetooth and demonstrate the ability to charge a lithium-ion battery. Furthermore, we successfully integrate a cardiac pacemaker with the I-TENG, and confirm the ventricle pacing and sensing operation mode of the self-rechargeable cardiac pacemaker system. This proof-of-concept device may lead to the development of new self-rechargeable implantable medical devices.

Korean Circulation Journal 대한심장학회지 순환기 Choi EK. Korean Circ J. 2020 Sep;50(9):754-772. https://doi.org/10.4070/kcj.2020.0171

Background—: We hypothesize that left-sided low-level vagus nerve stimulation (LL-VNS) can suppress sympathetic outflow and reduce atrial tachyarrhythmias in ambulatory dogs. Methods and Results—: We implanted a neurostimulator in 12 dogs to stimulate the left cervical vagus nerve and a radiotransmitter for continuous recording of left stellate ganglion nerve activity, vagal nerve activities, and ECGs. Group 1 dogs (N=6) underwent 1 week of continuous LL-VNS. Group 2 dogs (N=6) underwent intermittent rapid atrial pacing followed by active or sham LL-VNS on alternate weeks. Integrated stellate ganglion nerve activity was significantly reduced during LL-VNS (7.8 mV/s; 95% confidence interval [CI] 6.94 to 8.66 versus 9.4 mV/s [95% CI, 8.5 to 10.3] at baseline; P =0.033) in group 1. The reduction was most apparent at 8 am , along with a significantly reduced heart rate ( P =0.008). Left-sided low-level vagus nerve stimulation did not change vagal nerve activity. The density of tyrosine hydroxylase–positive nerves in the left stellate ganglion 1 week after cessation of LL-VNS were 99 684 μm ² /mm ² (95% CI, 28 850 to 170 517) in LL-VNS dogs and 186 561 μm ² /mm ² (95% CI, 154 956 to 218 166; P =0.008) in normal dogs. In group 2, the frequencies of paroxysmal atrial fibrillation and tachycardia during active LL-VNS were 1.4/d (95% CI, 0.5 to 5.1) and 8.0/d (95% CI, 5.3 to 12.0), respectively, significantly lower than during sham stimulation (9.2/d [95% CI, 5.3 to 13.1]; P =0.001 and 22.0/d [95% CI, 19.1 to 25.5], P <0.001, respectively). Conclusions—: Left-sided low-level vagus nerve stimulation suppresses stellate ganglion nerve activities and reduces the incidences of paroxysmal atrial tachyarrhythmias in ambulatory dogs. Significant neural remodeling of the left stellate ganglion is evident 1 week after cessation of continuous LL-VNS.