Flexible Antenna Design for Wearable and RF Energy Harvesting in the Mid-Band Wireless Spectrum

The integration of polydimethylsiloxane (PDMS) into flexible RF electronics and antenna systems is advancing wearable communication technologies toward a new era. This study introduces a flexible miniaturized microstrip antenna designed for wearable devices and radio-frequency (RF) energy harvesting applications. The proposed design integrates dual parasitic elements into a planar PDMS-based patch structure, while employing Nickel–Copper (Ni–Cu) ripstop fabric as the conductor within a hybrid polymer-textile framework. The geometry enhances bandwidth and stabilizes radiation patterns without enlarging the foot-print, while the chosen materials impart flexibility, biocompatibility, and textile durability. The antenna is fully grounded with a net geometry of 20  20  2 mm3. The design is optimized in Computer Simulation Technology (CST) Microwave Studio (MWS) simulator and its performance is analyzed under the free space and on-body conditions, with the accomplishment of bending and Specific absorption rate (SAR) analyses. It operates over 5.8 GHz-6.88 GHz covering mid-band frequency spectrum which includes 5.8 GHz ISM band, 6 GHz band (WiFi 6E/7) and 5G Sub-6 GHz band, ensuring it suitable for a wide spectrum of modern wire-less communication. The antenna attains a free space return loss of − 35.269 dB and an impedance band-width of 1.08 GHz, ensuring compatibility with diverse RF energy sources. It efficiently captures RF energy with a gain of 2.473 dB at 6.06 GHz and a directivity of 6.874 dBi, while converting RF energy into electrical energy with a maximum efficiency of − 4.403 dB (38 %). An experimental prototype of the proposed antenna is fabricated, and the measured result of return loss in free space is in good agreement with the simulated one. The findings of this study contribute to the advancement of energy-autonomous wearable devices and offer valuable insights for future developments in wearable energy harvesting systems within the mid-band wireless spectrum.