Contemporary pacemakers (PMs) are powered by primary batteries with a limited energy-storing capacity. PM replacements because of battery depletion are common and unpleasant and bear the risk of complications. Batteryless PMs that harvest energy inside the body may overcome these limitations. The goal of this study was to develop a batteryless PM powered by a solar module that converts transcutaneous light into electrical energy. Ex vivo measurements were performed with solar modules placed under pig skin flaps exposed to different irradiation scenarios (direct sunlight, shade outdoors, and indoors). Subsequently, 2 sunlight-powered PMs featuring a 4.6-cm(2) solar module were implanted in vivo in a pig. One prototype, equipped with an energy buffer, was run in darkness for several weeks to simulate a worst-case scenario. Ex vivo, median output power of the solar module was 1963 μW/cm(2) (interquartile range [IQR] 1940-2107 μW/cm(2)) under direct sunlight exposure outdoors, 206 μW/cm(2) (IQR 194-233 μW/cm(2)) in shade outdoors, and 4 μW/cm(2) (IQR 3.6-4.3 μW/cm(2)) indoors (current PMs use approximately 10-20 μW). Median skin flap thickness was 4.8 mm. In vivo, prolonged SOO pacing was performed even with short irradiation periods. Our PM was able to pace continuously at a rate of 125 bpm (3.7 V at 0.6 ms) for 1½ months in darkness. Tomorrow's PMs might be batteryless and powered by sunlight. Because of the good skin penetrance of infrared light, a significant amount of energy can be harvested by a subcutaneous solar module even indoors. The use of an energy buffer allows periods of darkness to be overcome.

Today's cardiac pacemakers are powered by batteries with limited energy capacity. As the battery's lifetime ends, the pacemaker needs to be replaced. This surgical re-intervention is costly and bears the risk of complications. Thus, a pacemaker without primary batteries is desirable. The goal of this study was to test whether transcutaneous solar light could power a pacemaker. We used a three-step approach to investigate the feasibility of sunlight-powered cardiac pacing. First, the harvestable power was estimated. Theoretically, a subcutaneously implanted 1 cm² solar module may harvest ∼2500 µW from sunlight (3 mm implantation depth). Secondly, ex vivo measurements were performed with solar cells placed under pig skin flaps exposed to a solar simulator and real sunlight. Ex vivo measurements under real sunlight resulted in a median output power of 4941 µW/cm² [interquartile range (IQR) 3767–5598 µW/cm², median skin flap thickness 3.0 mm (IQR 2.7–3.3 mm)]. The output power strongly depended on implantation depth (ρ_Spearman = −0.86, P < 0.001). Finally, a batteryless single-chamber pacemaker powered by a 3.24 cm² solar module was implanted in vivo in a pig to measure output power and to pace. In vivo measurements showed a median output power of >3500 µW/cm² (skin flap thickness 2.8–3.84 mm). Successful batteryless VVI pacing using a subcutaneously implanted solar module was performed. Based on our results, we estimate that a few minutes of direct sunlight (irradiating an implanted solar module) allow powering a pacemaker for 24 h using a suitable energy storage. Thus, powering a pacemaker by sunlight is feasible and may be an alternative energy supply for tomorrow's pacemakers.

Objective: Cardiac pacemakers require regular medical follow-ups to ensure proper functioning. However, device replacements due to battery depletion are common and account for ~25% of all implantation procedures. Furthermore, conventional pacemakers require pacemaker leads which are prone to fractures, dislocations or isolation defects. The ensuing surgical -interventions increase risks for the patients and costs that need to be avoided. Methods: In this study, we present a method to harvest energy from endocardial heart motions. We developed a novel generator, which converts the heart's mechanical into electrical energy by electromagnetic induction. A mathematical model has been introduced to identify design parameters strongly related to the energy conversion efficiency of heart motions and fit the geometrical constraints for a miniaturized transcatheter deployable device. The implemented final design was tested on the bench and in-vivo. Results: The mathematical model proved an accurate method to estimate the harvested energy. For three previously recorded heart motions, the model predicted a mean output power of 14.5, 41.9 and 16.9 μW. During an animal experiment, the implanted device harvested a mean output power of 0.78 μW and 1.7 μW at a heart rate of 84 and 160 bpm, respectively. Conclusion: Harvesting kinetic energy from endocardial motions seems feasible. Implanted at an energetically favorable location, such systems might become a welcome alternative to extend the lifetime of cardiac implantable electronic device. Significance: The presented endocardial energy harvesting concept has the potential to turn pacemakers into battery- and leadless systems and thereby eliminate two major drawbacks of contemporary systems.