Materials
triboelectric materials are the primary candidates, each offering a different route to converting motion into electrical output.
Piezoelectric materials generate charge under mechanical deformation, making them well suited to dynamic environments such as cardiac motion or respiration. Triboelectric systems, by contrast, rely on contact electrification and electrostatic induction, often using polymer-based structures that are easier to fabricate and integrate into flexible devices. Recent research highlights both the opportunity and the limitations of these approaches. A 2024 review in Sensors identifies piezoelectric and triboelectric nanogenerators as leading platforms for wearable and implantable self-powered systems, noting their compatibility with flexible substrates and low-power electronics. At the same time, it emphasises that output levels remain modest and highly dependent on environmental conditions, particularly in physiological settings where motion is irregular and low frequency. This distinction is shaping how developers think about energy harvesting in practice. Fully self- powered devices remain a long-term goal, but near- term applications are more likely to rely on hybrid architectures. In these systems, functional materials contribute to energy generation while conventional power sources provide baseline reliability. For wearable devices, this model is already proving viable. Motion-driven energy harvesting can support intermittent sensing, reduce battery drain and enable event-triggered operation. In implantables, the challenge is greater, but the potential reward is correspondingly higher.
From concept to cardiac applications Implantable devices represent the most compelling test case for self-powered materials. Here, even incremental improvements in power management can translate into significant clinical benefits, particularly by reducing the need for replacement procedures. Progress in this area has been steady, if incremental. Early demonstrations showed that piezoelectric materials could harvest biomechanical energy from organs such as the heart and lungs. It has been demonstrated that conformal piezoelectric devices are capable of generating electrical output from organ motion in large-animal models, establishing the feasibility of organ-mounted energy harvesters. More recent work has moved closer to system-level applications. A 2021 study in Nature Communications reported a self-rechargeable cardiac pacemaker system with triboelectric nanogenerator, capable of converting body motion into stored electrical energy. Similarly, a 2024 study extended this concept further, demonstrating a battery-free intracardiac pacemaker in a swine model based on triboelectrification and electrostatic induction.
These developments illustrate both the progress and the remaining challenges. While energy harvesting can
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now be integrated into implantable architectures, achieving consistent, long-term performance in vivo remains difficult.
A 2025 study published in Smart Materials and Structures provides useful insight into where those challenges lie. The work describes a piezoelectric energy harvester designed for leadless pacemakers, tested over more than 35 million simulated cardiac cycles and under in vivo conditions. The piezoelectric ceramic itself remained structurally stable, but degradation of the silver electrode led to an 18.1% reduction in peak voltage output. The implication is clear. In many cases, the limiting factor is not the active material, but the interfaces, coatings and packaging that surround it. For medtech developers, this shifts the focus from material performance alone to the broader system in which that material operates.
Stretchability, softness and sensing fidelity
If energy harvesting is one half of the story, mechanical compliance is the other. The ability of a device to conform to tissue without degrading performance is increasingly recognised as a critical factor in long-term sensing. Elastomeric thin films and bio-integrated polymers are central to this shift. These materials enable devices that stretch, bend and compress without losing electrical functionality, allowing sensors to maintain intimate contact with dynamic biological surfaces.
This is particularly important for applications such as continuous physiological monitoring, where signal quality depends on stable coupling between device and tissue. Even small mismatches in mechanical properties can introduce noise, drift or artefacts over time. Advances in this area are moving rapidly. A 2023 study in Nature Communications demonstrated stretchable electronic systems with moduli approaching that of biological tissue through the use of soft interlayer designs. These systems showed reduced foreign-body response and improved long-term integration in vivo, highlighting the importance of mechanical matching in bioelectronic interfaces. For body-worn devices, the benefits are immediate. Flexible patches and electronic skins can track motion, pressure and physiological signals with higher fidelity, even under continuous deformation. For implantables, the impact is longer term, potentially enabling devices that remain functional for years rather than months.
High-k ceramics and composite architectures
While much attention is focused on soft materials, high-permittivity (high-k) ceramics continue to play a critical role in next-generation devices. Materials such as barium titanate offer high dielectric constants, enabling increased capacitance and improved sensitivity in compact form factors. In flexible systems, these
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