The rapid advancement of 5th Generation (5G) technology has driven the demand for high performance millimetre-wave (mmWave) antennas with enhanced efficiency and scalability. However, designing microstrip patch antennas (MPAs) at mmWave frequencies presents challenges in optimizing gain, bandwidth, and Voltage Standing Wave Ratio (VSWR) while maintaining cost-effectiveness and fabrication feasibility. This study proposes a novel MPA design incorporating an ET-shaped slot and three parasitic rectangular patches to achieve a balance between gain, bandwidth, and VSWR. The Micro-Electro-Mechanical Systems (MEMS)-based design explores tantalum and copper as alternative patch materials for 28 GHz radio frequency (RF) energy harvesting in 5G mmWave systems. CST simulations are conducted to evaluate key performance metrics, including VSWR, gain, and reflection coefficient, S_11 across material thicknesses of 35 µm, 1 µm, and 700 nm. Among the tested configurations, the 1 µm thick tantalum patch demonstrates the best performance, achieving an S_11 of -21.474 dB, a VSWR of 1.18, and a gain of 6.14 dB at 28 GHz. These findings highlight tantalum’s potential as a scalable, high-performance material for MEMS-based 5G mmWave antenna applications.