Direct Ink Writing of PEDOT:PSS Aerogels for Thermoelectric Applications in Soft Electronics

Soft electronics, characterized by their mechanical softness and stretchability, mimic the form factor of biological systems, offering significant potential for applications in soft robotics, wearable electronics, biomedical devices, and tissue engineering.<br/>Powering wearable electronics remains a significant challenge that could be addressed by thermoelectric (TE) materials, which can generate electrical power from temperature gradients between the body temperature and the environment. Organic thermoelectric (OTE) materials, especially conducting polymers like PEDOT:PSS, are abundant, sustainable, and inherently soft, making them ideal for wearable applications. PEDOT:PSS aerogels, due to their highly porous structure, offer ultra-low thermal conductivity that enhances the temperature gradient across the material, improving the efficiency of TE power generation. Moreover, the lightweight of aerogels reduces the overall device mass, making them ideal for portable and wearable applications. By requiring ≈90% less material compared to dense structures, aerogels offer a cost-effective and sustainable solution for TEs.<br/>Traditional fabrication techniques of planar OTE fall short for the production of emerging soft electronics that extend beyond flat surfaces . Direct Ink Writing (DIW) emerges as a key method for additive manufacturing of complex, three-dimensional structures essential for soft electronics. Developing OTE inks suitable for DIW without compromising their mechanical and thermoelectric performance remains challenging.<br/>To address this, we developed a PEDOT:PSS paste with suitable rheology for DIW. To ensure material shape retention, the printed parts were lyophilized, resulting in a flexible and conducting aerogel with high TE performance. The paste formulation allows to balance electrical conductivity and mechanical stretchability of the 3D printed OTE aerogels. Our DIW process enabled the fabrication of complex, three-dimensional structures that are mechanically robust, maintain their shape, and can be integrated on stretchable substrates.