Microsphere-Templated Conductive Syntactic Foams for Recyclable and Additively Manufactured Soft Electronics

Soft, conductive materials that simultaneously offer mechanical compliance, electrical conductivity, recyclability, and scalable manufacturing remain difficult to achieve. Here, we introduce recyclable, 3D-printable PEDOT:PSS syntactic foams based on polymer microspheres coated in situ, enabling precise control over porosity, mechanical properties, and electrical conductivity. Microsphere-templated conductive shells provide a unique materials architecture that unites porosity control, tailorable flexibility, electrical functionality, recyclability, and additive manufacturability, which are capabilities that are challenging to achieve in conventional conductive foams. The resulting foams exhibit low elastic moduli comparable to soft biological tissues, stable electrical conductivity over a wide void-fraction range, and excellent compatibility with fused filament fabrication. Importantly, the foams can be thermally reshaped, and the conductive microsphere component can be recovered from the matrix by selective dissolution, while preserving structural integrity and electrical performance. To demonstrate functional relevance, the conductive foams are integrated into soft wearable electrodes, enabling reliable acquisition of electrocardiogram (ECG), electromyogram (EMG), and in-ear electroencephalogram (EEG) signals, including clear alpha-band modulation. Overall, this work establishes conductive syntactic foams as a recyclable and manufacturable materials platform for soft and wearable electronic systems.