Manufacturing techniques and characterization of 2.45 GHz silicone-based microwave antennas

Flexible antennas are gaining increasing interest, particularly when deployed to supply energy to sensors in wearable contexts. The utilization of polymer-based substrates, such as PDMS, has opened the door to innovative solutions, striking a promising balance between performance and ease of customization. To facilitate this, fabrication techniques that integrate inkjet printing with the casting of PDMS have offered a more agile approach to the realizing of such devices. This study introduces the design process of a rectenna system operating at 2.45 GHz, specifically tailored for wearable wireless power transfer (WPT) applications. A two-component PDMS compound, SILPURAN 6000/05 A/B, has been used to fabricate a flexible substrate. The geometry of this substrate can be easily customized, allowing for specific thickness adjustments to optimize rectenna performance. Simultaneously, inkjet printing has been employed to achieve high-precision metallization at a relatively low cost and short fabrication time. An experimental campaign was conducted, enabling the electromagnetic characterization of the polymer. Subsequently, the linear and nonlinear subnetworks of the rectenna system were optimized through EM/nonlinear co-simulation. This optimization led to a remarkable 45% RF-to-dc conversion efficiency for a received power of 0 dBm. The prototype of the radiating element has been successfully realized and experimentally validated, showing promising performance. These advancements position the system as an attractive solution for flexible and wearable Radio Frequency applications.