In a remarkable stride toward revolutionizing implantable medical technology, a research team led by Professor Jinho Chang from the Department of Electrical Engineering and Computer Science at DGIST (Daegu Gyeongbuk Institute of Science and Technology) has unveiled a groundbreaking ultrasound-based wireless charging system. This innovative technology promises to transform how batteries within implantable medical devices are powered, enabling rapid and efficient charging deep inside the human body. Most notably, the team has achieved world-class energy efficiencies that allow a commercial battery to be fully charged in just under two hours using ultrasonic energy transmission, a feat previously deemed highly challenging due to biological constraints.
The rise in global aging populations combined with an increase in chronic diseases and accidents has soared the demand for implantable medical devices such as pacemakers and neural stimulators. However, the longevity of these devices is critically limited by their batteries, which currently require periodic surgical replacement. These repeated surgeries not only impose significant physical and emotional stress on patients but also carry inherent medical risks including infection and complications related to anesthesia. This pressing issue underscores the imperative need for technologies capable of wirelessly transmitting energy through tissue to recharge implantable batteries, preventing invasive procedures and enhancing patients’ quality of life.
Wireless power transfer systems utilizing ultrasound have been explored before, harnessing the mechanical vibrations of acoustic waves to generate electricity. However, their practical implementation in human implants has been thwarted by the strict limitations in ultrasound intensity permissible inside biological tissues for safety reasons. Moreover, the design of existing piezoelectric harvesters — devices that convert mechanical energy into electrical energy — has struggled with constraints in size and efficiency, as compactness is vital for implant integration and functionality. Consequently, the power output from such devices has traditionally fallen short of reliably sustaining or rapidly recharging implantable batteries.
Professor Chang’s team has tackled these challenges head-on by engineering a novel sandwich-structured piezoelectric energy harvester, aptly named SW-PUSH. This design strategically stacks two piezoelectric layers in a laminated configuration to maximize ultrasonic energy harvesting. The front layer absorbs the initial ultrasonic waves, converting them into electrical energy, while the rear layer recaptures residual ultrasound that passes through the first layer, thus extracting additional power that would otherwise be lost. This dual-layer approach cumulatively boosts energy conversion efficiency by over 20% compared to traditional single-layer harvesters, marking a significant improvement in power output density within the spatial constraints of implantable devices.
Experimental validations of the SW-PUSH harvester illustrate its outstanding capabilities in real-world scenarios. In controlled underwater setups, mimicking the acoustic properties similar to human tissue, the device fully charged a commercial 140mAh battery in merely 100 minutes at a distance of 30 millimeters from the ultrasonic source. Parallel trials involving swine tissue approximately 30 millimeters thick demonstrated that a smaller 60mAh battery could be completely charged within 80 minutes, firmly establishing the harvester’s efficacy in living tissue analog environments. These performance metrics not only eclipse those of preceding technologies but do so by a factor of two or more, setting a new benchmark for ultrasonic wireless charging.
Central to this advance is the precise optimization of piezoelectric materials and the engineering of the laminated structure to mitigate acoustic impedance mismatch, a common source of energy loss in ultrasonic transmission. By fine-tuning the thickness and mechanical properties of each piezoelectric layer, Professor Chang’s team has maximized the conversion of ultrasonic pressure waves into usable electrical current. The integration of this sandwiched configuration also ensures mechanical robustness and biocompatibility, essential parameters for any implantable device intended for long-term operation within the dynamic and delicate human body.
Another notable aspect of the SW-PUSH system is its potential for rapid commercialization, as articulated by Professor Chang. By integrating this ultrasonic charging technology with cutting-edge semiconductor components specifically designed for high-efficiency energy management, they envision a holistic wireless charging solution that can fully power implantable devices in under an hour. Such a system could dramatically reduce patient hospital visits, minimize surgical interventions, and pave the way for smaller, more reliable implants that are continuously charged throughout their operational lifetime.
From a safety perspective, the use of ultrasound for wireless power transfer presents distinct advantages over other modalities such as electromagnetic induction or radiofrequency waves. Ultrasound waves possess superior tissue penetration characteristics and lower absorption rates in human tissue, enabling efficient energy delivery with minimal thermal effects. Moreover, adhering to established safety guidelines for ultrasound intensity ensures that this technology operates well within safe exposure limits, offering a patient-friendly solution that mitigates risks associated with electromagnetic interference or tissue heating.
This pioneering research was generously supported by South Korea’s Ministry of Science and ICT under the Future Pioneering Convergence Science and Technology Development Project, formerly recognized as the STEAM Research Program. Its findings have been peer-reviewed and published in Biosensors and Bioelectronics, an authoritative journal well-regarded for its emphasis on advancements in biosensor technologies and bioelectronics engineering. The publication solidifies the significance and scientific rigor of the SW-PUSH harvester, highlighting it as a seminal contribution to biomedical device engineering.
As implantable medical technology continues to evolve towards greater autonomy and miniaturization, the ability to efficiently and wirelessly recharge internal batteries emerges as a cornerstone challenge. The advancements made by Professor Chang and his team not only address this challenge but also open avenues for further explorations in ultrasonic energy harvesting, potentially benefiting a broad spectrum of biomedical devices beyond cardiac and neural applications, including drug delivery systems and implantable sensors.
Looking ahead, the interdisciplinary collaboration among electrical engineers, material scientists, and medical professionals will be crucial to transition this pioneering technology from experimental models into clinical realities. Integrating SW-PUSH into commercially viable medical implants will necessitate extensive biocompatibility testing, long-term durability assessments, and regulatory approvals, but the promising results to date suggest a near future where implantable devices can be charged wirelessly, safely, and efficiently without invasive procedures.
In summary, the sandwich-structured piezoelectric ultrasound harvester represents a monumental leap in the pursuit of seamless wireless power transfer for implantable biomedical electronics. The combination of innovative material design, enhanced conversion efficiency, and patient safety concerns heralds a new chapter in medical device technology, one where the burdens of battery replacement surgeries may become a relic of the past. With further development and commercialization, this ultrasonic harvester holds the potential to dramatically improve patient care and implant performance worldwide.
Subject of Research: Wireless power transfer, piezoelectric energy harvesting, implantable medical devices, ultrasonic wireless charging
Article Title: Sandwich-structured piezoelectric ultrasound harvester for wireless power charging of implantable biomedical electronics
News Publication Date: 16-Jul-2025
Web References: DOI: 10.1016/j.bios.2025.117789
Image Credits: Manufactured laminated piezoelectric element-based ultrasonic harvester (SW-PUSH)
Keywords
Piezoelectricity, Wireless power transfer, Ultrasound energy harvesting, Implantable medical devices, Biomedical electronics, Energy conversion efficiency
