A stretchable RF filter based on screen-printed Ag–Cu conductive films for deformable electronics

Abstract The advancement of soft robotics, wearable electronics, and deformable wireless systems necessitates radio-frequency (RF) filters that maintain stable performance under mechanical deformation. Although various stretchable conductive materials and filter designs have been explored, existing solutions often suffer from complex fabrication, high cost, significant RF loss, or limited evaluation under diverse deformation modes. To address these challenges, this work presents a low-cost, scalable stretchable combline bandpass filter operating at approximately 2.4 GHz, fabricated by screen-printing a stretchable silver-copper (Ag–Cu) conductive paste on a flexible polydimethylsiloxane (PDMS) substrate. The thermal behavior, sintering-induced microstructural evolution, and electrical properties of the printed films are systematically investigated, enabling optimization of the sintering process and filter geometry. Experimental results demonstrate that the filter retains a clear passband with insertion loss of 5–6 dB under planar, bending, uniaxial stretching (up to 15% strain), and biaxial balloon-inflation deformations, exhibiting only minor variations in impedance matching. This work highlights the feasibility of using screen-printed Ag–Cu films to achieve mechanically robust and electromagnetically stable RF filters, offering a cost-effective and manufacturable solution for next-generation deformable wireless systems.