Neurotech Firms Pursue Advances in Wireless Energy Transfer

by Jeremy Koff, senior consulting editor

November 2025 issue

For more than half a century, active implantable medical devices have been constrained by the need to move energy into the body safely and efficiently. Whether used to power a device directly or recharge a deeply implanted battery, energy transfer physics have limited implant placement, longevity, size, and patient convenience. While electronics, sensing, materials, and algorithms have advanced rapidly, energy transfer from outside the body to within remains one of the defining limitations of implant design.

Today, these constraints are being challenged on several fronts, signaling one of the most significant architectural shifts since the earliest commercial implants. Advances in externalized power delivery, reductions in implant energy requirements, and more efficient deeptissue recharging are converging toward devices that run longer, charge faster, and can be placed deeper in the body where therapy is needed.

At the center of this transition are a number of companies integrating novel technologies into active implants to overcome the thermal, depth, and alignment limitations that have long defined inductive power systems. Among the companies are Resonant Link Medical, Neuspera, Presidio Medical, and Nalu Medical.

Regulatory Considerations in Wireless Energy Transfer

Regulatory standards impose strict thermal safety limits on medical electrical devices—including wireless and implantable systems—to prevent patient burns or tissue damage. IEC 606011 specifies maximum allowable temperatures for external surfaces that contact patients or operators, imposing limits based on materials and contact duration. In 2024, the FDA released a draft guidance document providing recommendations for testing medical devices that produce tissue temperature changes—whether heating or cooling—as an intended or unintended consequence of device operation. Together, these frameworks form the regulatory basis for assessing thermal safety in wireless power transfer and rechargeable implant systems, requiring manufacturers to demonstrate that heat generation during charging, powering, or highdutycycle operation remains within clinically acceptable limits and does not exceed thresholds used in regulatory body (e.g. FDA) evaluations.

A Brief History Built on the Limits of Inductive Physics

The challenge of delivering energy into the body dates back to the earliest implants. Externally powered systems followed two paths: RFpowered systems that required an external unit worn continuously, and rechargeable systems that used an external device only during charging.

Powering and recharging rely on the same inductive-coupling physics—an alternating current in a transmitter coil generating a magnetic field that induces current in a receiver coil—yet they differ in how energy delivery affects the surrounding tissue. Continuous powering creates a sustained thermal load because energy must be delivered without interruption, while recharging is intermittent and can be optimized into short, high-efficiency sessions that generate less cumulative heating.

Early RFpowered implants emerged around 1960. In 1960, Schuder and colleagues demonstrated highefficiency inductive coupling to power an experimental artificial heart, establishing foundational methods for later implants. When spinal cord stimulation was first demonstrated in 1967, early systems used an implanted epidural lead connected to a subcutaneous RF coil that coupled to an external transmitter containing both the power source and waveform generator. When activated, the external unit delivered an RF carrier signal that the implanted coil rectified to deliver tonic dorsalcolumn stimulation.

As implantable batteries improved, rechargeable systems became more practical. The late neurotech entrepreneur Alfred Mann helped to advance three industries over five decades: the first commercial rechargeable pacemaker (Pacesetter Systems, 1973); one of the earliest rechargeable SCS systems (Advanced Bionics, early 2000s); and the first rechargeable sacral neuromodulation system (Axonics, 2019).

Although each advance expanded clinical possibilities, both RFpowered and rechargeable systems face the same technical challenge: balancing system efficiency with strict limits on heat deposition in tissue, constraints that worsen with implant depth.

Rechargeable systems also required patients to hold an external charger firmly against the skin—often for long periods and with limited posture freedom. As implants migrated deeper into pelvic and thoracic areas—and as emerging devices demanded more power—the limitations of conventional inductive coils became increasingly restrictive.

Recently, several companies have begun addressing these challenges by enabling deeper, more efficient inductive coupling and reducing thermal losses.

Modern Approaches to the Energy Challenge

Innovators have attacked the energytransfer problem from three angles: increasing transfer efficiency, lowering the energy implants require, and redesigning the architecture of internal and external components.

Neuspera Medical re-imagined energy entry into the body by moving beyond traditional nearfield inductive coupling. Their mid-field electromagnetic powering supports a very small implant whose therapy is powered in real time by a wearable external transmitter, eliminating the need for a large implanted battery. Early clinical work in sacral neuromodulation validated the feasibility of deep powering without an implantable battery.

Presidio Medical approached the problem by reducing energy demand itself. Their ultra-low-frequency stimulation approach is designed to deliver similar or better analgesia with substantially lower energy requirements than conventional SCS, enabling smaller batteries and less frequent recharging.

Nalu Medical created a microIPG architecture with minimal onboard energy requirements, shifting most of the energy burden to an external wearable. Their miniaturized system demonstrated that fullfeatured neuromodulation can be supported with a far smaller implanted unit.

These innovations—batteryless powering, ultralowpower therapy, and ultraminiaturized IPGs—address different aspects of the energy problem. But none fully solved one of the most persistent challenges: safely and rapidly recharging a battery deep within the body. This is where Resonant Link Medical enters.

Resonant Link Medical: Rethinking The Inductive Coil

Resonant Link Medical focuses on reinventing coil architecture rather than incrementally improving conventional wound coils. Their multilayer resonant structures use stacked foil conductors separated by engineered dielectrics, embedding capacitance directly into the geometry.

By shaping current distribution across layers, the design mitigates AC and proximity losses that limit traditional highfrequency inductive systems. This allows the use of frequencies that would otherwise exceed thermal limits, enabling deeper power transfer—up to 5–6 cm (and in some cases even greater)—shorter charge cycles, and better alignment tolerance. Fabricated using PCBlike processes, the coils support predictable, scalable manufacturing.

This architecture directly addresses the dominant failure modes in existing wirelesspower systems and resolves a design barrier that has limited nextgeneration implants for years.

As Features Capital co-founder Jeff Chu stated, “Resonant Link Medical’s breakthrough wireless power technology enables interventions that were previously impossible and accelerates product development.”

A Future Where Implants Can Go Anywhere

The combined advances from Neuspera, Presidio, Nalu, and Resonant Link indicate a shift toward an era where energy transfer no longer dictates implant design. Batteryless powering, ultralowpower therapy, and deep, efficient recharging open the possibility of smaller, longerlasting devices that integrate more seamlessly with patient lifestyles.

For the first time, the industry is approaching an era where energy transfer becomes an enabling capability—rather than a limiting factor—and where implants can be placed anywhere in the body, expanding therapeutic possibilities across a wide range of chronic conditions.