Synchronous Generations of Electrical and Cellular Energies without Battery, Wiring even Generators: Inevitable Electrical Stimulation via Body-Mediated Energy Transfer

Wearable technologies have become increasingly prevalent in various fields, ranging from smart devices and IoT to health monitoring and bioelectronics. However, finding a sustainable power source remains a challenge. Despite advancements in battery energy density, the need for frequent charging, heavy weight, and inconvenience continue to hinder the adoption of wearable technologies. Recent proposals for energy generation methods aim to harvest energy from the human body, but they often face limitations, such as being restricted to specific body parts or requiring large area devices like light exposure or physical motion. To address these constraints and eliminate the need for additional devices, researchers have explored utilizing the human body itself as a medium for transmitting energy and signals (nanogenerator-based ultrasound receivers, human body communication). However, the effectiveness of these methods is affected by the location of the energy source on the body, and the energy magnitude diminishes significantly with distance. On the other hand, low-frequency electric fields generated by electronic devices or physical activities can be converted into usable energy through the human body. Given the body's high relative permittivity at low frequencies, the transfer of low-frequency electric fields can be highly efficient regardless of the transmission distance. Nevertheless, existing body-mediated energy harvesting methods often neglect the physiological effects on biological tissue, such as cellular vitalization or necrosis. Although these electromagnetic waves inevitably affect biological tissues, conventional body-mediated technologies have not considered such physiological effects at all. In the end, ignorance of the correlation between physiological effects and body-mediated energy transfer undermines the latent ripple effect of this technology.<br/>In this study, we aim to validate through various pre-clinical and clinical trials that body-mediated energy harvesting leads to local electric field concentration in the body, resulting in positive physiological effects. By focusing on the design factors and employing a trade-off approach between usability and energy strength, we propose a method for designing electrode grounds that can be implemented in practical applications. The waveform (AC and DC) and intensity (10 - 3000 mV/mm) of these electric fields can be adjusted by controlling several variables (grounding method, external resistance, charging capacitor) depending on the purpose (usefulness, energy strength) without using any additional battery or wiring. Practical body-mediated wearable devices were implemented using conductive threads and fabrics, and body-mediated bioelectronics for zero-powered ion release and electrical stimulation was also implemented through stimuli-responsive ion-diffusive hydrogel. Complex mechanisms for the body-mediated energy transfer and electric field concentration have been demonstrated in various environments through in human body, ex-vivo setup and simulations. In in-vivo setup we confirmed the positive effects of 1) wound healing and 2) hair regeneration of mice. Eventually, through clinical protocols, we have observed a 3) reduction in muscle fatigue of up to 6.4% using such electrical stimulation designs. Particularly outstanding is that when cellular energy is generated by electrical stimulation under the skin, electrical energy is generated outside the skin, allowing 4) small electronics (1.5 mW) to be operated synchronously. These findings underscore the potential of the human body to harvest low-frequency electrical energy from physical activities or electronic devices while offering positive physiological effects. Overall, this research will contribute to the advancement of wearable technologies by providing insights into the relationship between body-mediated energy generation and physiological effects, paving the way for comfortable and sustainable power sources.