Author – Eugene Kraemer
“The day will soon come when I will show the world that the transmission of power without the aid of any wires is possible.” – Nikola Tesla, 1885
Tesla’s vision is closer to reality than ever, particularly in the field of implantable medical devices. Transcutaneous Energy Transfer (TET) enables wireless power delivery across intact skin using magnetic coupling, eliminating the need for through-skin (percutaneous) cables. The underlying principles of inductive wireless power transfer are already used in implants such as cochlear implants, retinal prostheses and some neurostimulators, primarily for low-power operation or recharging. But its greatest promise may lie in powering life-sustaining cardiac devices such as ventricular assist devices (VADs) and total artificial hearts (TAHs).
For patients dependent on mechanical circulatory support, TET represents a fundamental shift in system architecture. By removing the need for using infection-prone percutaneous drivelines, fully implanted systems reduce one of the most persistent causes of morbidity. Beyond clinical risk reduction, the impact on daily life is significant. Patients gain greater freedom of movement, simplified hygiene, and fewer constraints on routine activities, contributing to improved safety, independence, and quality of life.
Recent reviews and conferences identify TET as one of the most active research areas in next-generation cardiac support systems. The core principles are well understood, and functional systems have been demonstrated in both laboratory and clinical settings. The challenge is shifting from demonstrating feasibility to ensuring long-term safety, efficiency and reliability suitable for routine clinical use.
The Current Landscape of TET Technology
The concept of wireless power transfer in implants is not new. Many commercially available hearing implants and neurostimulators already use inductive links for power delivery. Extending these principles to cardiac devices, however, brings tougher engineering and biological constraints. The power levels are higher, the thermal margins are tighter and the alignment tolerance is far less forgiving
Most TET systems developed today use an external transmitter coil, often worn as a belt or patch, that magnetically couples with an implanted receiver coil. The implanted side then rectifies and regulates the energy to charge an internal battery, allowing short periods of untethered operation. The historic AbioCor TAH pioneered this hybrid configuration with both internal and external coils and an implantable battery buffer.
Recent advances have focused on Resonant High-Q Magnetic Coupling, which tunes the transmitter and receiver coils to the same frequency. This allows more efficient energy exchange, better tolerance to coil separation and reduced alignment sensitivity compared with basic inductive links. Researchers are also exploring metamaterials and optimised coil geometries to increase power transfer efficiency and reduce energy absorption in tissue.
Core TET Challenges
Despite clear progress, there remain fundamental engineering and regulatory challenges that must be solved before TET can become standard in implantable life-support systems.
Thermal safety remains one of the biggest design constraints. Transferring several to tens of watts of power through skin and subcutaneous tissue generates heat through both resistive and dielectric losses. If not properly controlled, this can cause tissue damage. Newer TET systems rely on active thermal monitoring, intermittent energy transfer and careful system-level design to keep temperatures within safe limits.
Maintaining alignment between the external and internal coils is another major challenge. Patients move, breathe and change posture, which alters the coupling efficiency. Resonant systems improve alignment tolerance but are also more sensitive to detuning caused by tissue loading, temperature drift, presence of metallic objects nearby and more. Unchecked, this can lead to localised heating. The latest research explores adaptive coil geometries and programmable pulsatile transfer protocols to stabilise coupling and minimise thermal load.
Implantable power systems must operate reliably for years within a biological environment. This requires hermetic packaging, corrosion-resistant materials and robust electronics that withstand mechanical and thermal stress. Titanium housings, ceramic feedthroughs and biocompatible coatings are standard, but the integration of high-power electronics in confined spaces adds new challenges. The long-term safety and performance of implantable lithium-ion batteries also remain critical factors.
Developing TET for life-supporting implants involves one of the most stringent regulatory pathways in medical technology. Wireless power systems must comply with limits for electromagnetic exposure, electromagnetic compatibility (EMC) and device-specific safety standards. Comprehensive in-vitro, in-vivo and clinical testing are required before approval. Modern expectations also include detailed management of battery safety, software lifecycle and cybersecurity – areas that now play an important role in system acceptance.
Emerging Innovations and Trends
Innovation in TET is accelerating across materials, architectures and control systems.
New multi-coil transmitter arrays are being developed to improve coupling efficiency and reduce power losses due to misalignment. Those adaptive array systems capable of flux steering can dynamically adjust the magnetic field to maintain coupling as patients move.
Control system innovation is another key trend. Closed-loop thermal management, perfusion-based cooling designs and intermittent energy transfer are helping maintain safe temperature profiles while maximising the power delivery. Some groups are also investigating early-stage hybrid approaches that combine magnetic TET with ultrasonic or magnetoelectric micro-harvesting, offering new flexibility for powering smaller or distributed implant systems.
Recent work across the cardiac device industry, along with growing research activity in the field, shows how these innovations are moving closer to a clinically deployable solution.
Looking ahead
The trajectory of transcutaneous energy transfer suggests that progress will be driven less by isolated advances and more by how well individual elements are integrated into a coherent system. As power levels increase and use cases move toward long-term, life-supporting applications, interactions between energy transfer, thermal behaviour, control strategies and packaging become increasingly difficult to separate.
Many of the remaining challenges are already visible in practical use. Patient movement, anatomical variation, and long-term tissue response all influence coupling efficiency and thermal margins in ways that are difficult to capture through static optimisation alone. Addressing these effects requires systems that can monitor their operating conditions and adjust behaviour over time, rather than relying on fixed assumptions about alignment or load.
There is also a growing recognition that thermal performance cannot be treated as a secondary outcome of efficiency improvements. Heat generation and dissipation are distributed across the entire system, from power electronics and enclosures through to surrounding tissue, and must be managed accordingly. Similar considerations apply to alignment, where control and feedback play an increasing role alongside mechanical design.
Taken together, these trends point toward TET systems that are more adaptive, more integrated, and more closely coupled to their operating environment. Whether transcutaneous energy transfer becomes a routine feature of future cardiac support systems will depend on how effectively these system-level challenges are addressed in real clinical conditions.
