Body-Powered Implants Could End Battery Replacements in Medical Devices

The global implantable medical device market reached $26.4 billion in 2023 and is projected to grow at 8.2% CAGR to $46.5 billion by 2030, while the wearables sector hit $115 billion and is expected to exceed $265 billion by 2030. Despite this explosive growth, conventional battery technology remains a critical bottleneck — batteries in pacemakers, deep brain stimulators, and cochlear implants require periodic surgical replacement, imposing risks, costs, and reliability concerns. This review systematically evaluates five alternative energy harvesting strategies capable of powering devices from the body's own energy reservoirs.

Electromagnetic wireless power transfer (WPT) encompasses inductive coupling, far-field RF, magnetically coupled resonant (MCR), and mid-field approaches. A notable example is a smart contact lens hybrid system combining WPT with a zinc–air biobattery, generating over 1.5 V DC at 13.56 MHz to operate LEDs. A mid-field WPT system with a compact 9×13 mm² implantable antenna demonstrated over 5.6 mW of delivered power at 1 W transmitter output through simulated pork muscle tissue. MCR-WPT with closed-loop control further stabilized voltage despite coil displacement, advancing practical wearable integration.

Ultrasound wireless power transfer (US-WPT) offers a distinct advantage: ultrasonic waves penetrate electrically conductive biological tissue without the electromagnetic interference that limits RF approaches. The review details piezoelectric receiver designs — including PVDF and PZT-based transducers — that convert ultrasonic mechanical energy into electricity. US-WPT is considered especially promising for deeply implanted devices such as cochlear implants, though challenges remain around tissue heating, beam alignment, and efficiency over longer distances.

Spontaneous organ activity harvesting — capturing energy from heartbeats and tissue motion — uses piezoelectric, triboelectric, and electromagnetic induction mechanisms. Researchers have demonstrated piezoelectric harvesters integrated into pacemaker leads that extract energy directly from cardiac mechanical motion, with permanent magnet stacks achieving flux densities of 1.43 T. Thermoelectric generators (TEGs), exploiting the Seebeck effect across body-environment thermal gradients using bismuth telluride (Bi₂Te₃) and silicon germanium (SiGe) materials, offer continuous passive power for wearables such as fitness trackers, though conversion efficiency remains constrained by the small temperature differentials available (~2–5°C across skin).

Glucose-based biofuel cells represent perhaps the most elegant solution: enzymatic oxidation of endogenous glucose in blood or interstitial fluid generates electrical current continuously, with particular appeal for diabetic monitoring devices. The review also covers triboelectric nanogenerators (TENGs) for harvesting kinetic energy from voluntary movement. Critically, the authors argue that no single modality will suffice — hybrid systems integrating multiple harvesting mechanisms, adaptive AI-driven power management algorithms, and smart biocompatible materials are the most viable path to clinical translation. They identify the biocompatibility-power density paradox and dynamic coupling efficiency in physiological environments as the field's two most pressing unsolved challenges.