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3D-Printed PEDOT:PSS Aerogels for Wearable Thermoelectric Devices – A Breakthrough in Stretchable Materials by KU Leuven

September 24, 2025 Services 149

The related research has been published in the peer-reviewed journal Advanced Science.

A research team led by Professor Francisco Molina-Lopez at KU Leuven has, for the first time, demonstrated a method for the omnidirectional 3D printing of PEDOT:PSS aerogels. This technique enables the direct fabrication of both stretchable interconnects and high-aspect-ratio thermoelectric (TE) pillars. This breakthrough paves the way for novel designs of flexible power sources and sensor devices in cutting-edge fields such as wearable electronics and soft robotics.

This new method combines direct ink writing (DIW) with in-situ freeze-drying technology, enabling for the first time the direct printing of free-form porous PEDOT:PSS aerogel structures on silicon substrates and elastomer surfaces. By adjusting the process route, the team successfully prepared aerogels that combine ultra-low thermal conductivity (0.065 W·m⁻¹·K⁻¹) with stretchable conductivity. This method overcomes the long-standing challenge of integrating fragile aerogels with stretchable substrates, thereby realizing 3D thermoelectric structures that were previously unattainable.

Overview of materials, processing, and integration for 3D stretchable electronics

3D Printed Aerogels for Energy and Sensing

The researchers prepared two types of PEDOT:PSS inks. One involved mixing lithium salt and GOPS additives to enhance stretchability and conductivity. The second method relied on filtration and solvent exchange to remove excess PSS, thereby reducing thermal conductivity and improving thermoelectric efficiency.

This dual-route strategy allows the aerogels to be tailored for specific applications: the additive-based formulation is best suited for stretchable interconnects, while the filtered variant provides a higher figure of merit for TE devices.

Material morphology characterization of aerogels made from selected compositions

Demonstration devices included arched interconnect structures with a failure strain of up to 15%, maintaining stable resistance over 200 strain cycles. Vertical TE pillars generated 26 nW·cm⁻² of radiant energy under skin-like conditions (ΔT ≈ 15 °C), outperforming dense PEDOT:PSS pillars under contact resistance-limited conditions.

Stretchable interconnect structure based on a planar arched aerogel structure (3D printed on an elastomer substrate)

DIW Combined with In-Situ Freeze-Drying

Traditional PEDOT:PSS films often shrink or delaminate when processed on elastomers. By directly printing the ink onto silicone and performing in-situ freeze-drying, researchers at KU Leuven obtained aerogels with high shape fidelity, strong adhesion, and 3D geometries such as arches and pillars.

Spectroscopic analysis revealed that the salt additives shortened the π-π stacking distance, improving electrical conductivity, while filtration promoted the formation of ordered lamellae, thereby enhancing thermoelectric performance. Together, these methods form a versatile material library for tailoring electromechanical and energy harvesting functions.

Thermoelectric performance of 3D printed pillars

Implications for the Industry

Although inorganic thermoelectric materials like bismuth telluride dominate, their brittleness and high cost limit their application in flexible wearable systems. Conversely, conductive polymers like PEDOT:PSS face challenges due to the insufficient power output of thin-film devices. To address this, researchers at KU Leuven utilized emerging technologies such as machine learning for ink optimization and lattice structure customization. By combining omnidirectional direct writing with freeze-drying technology, they produced mechanically robust, porous PEDOT:PSS aerogels. This material can be directly integrated with elastomers, enabling the printing of stretchable interconnects and efficient thermoelectric pillars, significantly expanding the design space for wearable power sources, skin electronics, and soft robotics.