A team from KU Leuven,a leading Belgian research university, has demonstrated the first omnidirectional 3D printing of PEDOT:PSS aerogels, enabling stretchable interconnects and high-aspect-ratio thermoelectric (TE) pillars. The research, led by Francisco Molina-Lopez, was published in Advanced Science.
The new method integrates direct ink writing (DIW) with in-place freeze-drying to produce free-form, porous PEDOT:PSS structures directly on silicone substrates. By tuning processing routes, the researchers achieved aerogels that combine ultralow thermal conductivity (0.065 W·m⁻¹·K⁻¹) with stretchable, conductive performance, paving the way for practical use in wearable electronics and soft robotics. This approach overcomes longstanding challenges in integrating fragile aerogels with stretchable substrates, enabling previously unattainable 3D thermoelectric architectures.
3D printed aerogels for energy and sensing
The team prepared two classes of PEDOT:PSS pastes. One combined lithium salts and GOPS additives to enhance stretchability and conductivity. A second route relied on filtration and solvent exchange to remove excess PSS, lowering thermal conductivity and enhancing thermoelectric efficiency.
This dual-route strategy enabled aerogels to be tailored for specific applications: additive-based formulations were best suited for stretchable interconnects, while filtered variants delivered higher figures of merit for TE devices.
Demonstrator devices included arched interconnects with failure strains up to 15% and stable resistance over 200 strain cycles. Vertical TE pillars generated 26 nW·cm⁻² under skin-like conditions (ΔT ≈ 15 °C), outperforming dense PEDOT:PSS pillars under contact-resistance-limited operation.
Omnidirectional DIW with freeze-drying
Conventional PEDOT:PSS films often shrink or delaminate when processed on elastomers. By printing pastes directly on silicone and applying freeze-drying in situ, KU Leuven’s researchers achieved aerogels with high shape fidelity, integrated adhesion, and 3D geometries such as arches and pillars.
Spectroscopic analysis showed that salt additives shortened π–π stacking distances, improving conductivity, while filtration promoted ordered lamellae associated with improved thermoelectric behavior. Together, these routes provide a versatile materials library for tailoring electromechanical and energy-harvesting functions.
Organic thermoelectrics in additive manufacturing
While inorganic thermoelectrics such as bismuth telluride remain dominant, their brittleness and high cost limit applications in soft and wearable systems. Conducting polymers like PEDOT:PSS are lightweight, printable, and biocompatible, but thin-film devices have struggled to deliver sufficient power.
By combining omnidirectional DIW with freeze-drying, KU Leuven’s approach produces mechanically robust, porous PEDOT:PSS aerogels that integrate directly with elastomers. The ability to print both stretchable interconnects and efficient TE pillars expands the design space for wearable power sources, skin electronics, and soft robotics.
Expanding the design space for 3D printed thermoelectrics
A wave of recent research is exploring how additive manufacturing can reshape thermoelectric device design. Earlier this year, researchers demonstrated how machine learning–optimized inks can be used to 3D print high-performance thermoelectrics, underscoring the role of data-driven material design in boosting energy conversion. Other groups have reviewed the potential of lattice structures to enhance efficiency by tailoring heat and charge transport through architected geometries. Meanwhile, advances in screen-printed thermoelectric devices have shown scalable pathways to flexible, low-cost energy harvesters. The KU Leuven study builds on these efforts by introducing omnidirectional DIW of PEDOT:PSS aerogels, offering both stretchability and ultralow thermal conductivity in 3D organic thermoelectrics.
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Featured image shows overview of the materials, processing, and integration for 3D stretchable electronics. Image via Advanced Science.
