Mettu Goutham Reddy

Conventional fabrication approaches for reconfigurable microfluidic systems have several inherent limitations. Polydimethylsiloxane (PDMS)-based channel fabrication suffers from low mechanical strength and poor scalability. Achieving fully monolithic structures with PDMS is also challenging. Additionally, computer numerical control (CNC)-based fabrication increases production costs, prolongs processing times, and limits design flexibility. To address these challenges, this work presents a reconfigurable polarization converter based on additive manufacturing, in which the microfluidic channels are directly integrated into the substrate. This integration enables a fully monolithic structure and eliminates the need for multilayer assembly or external microfluidic modules. The resulting metasurface enables polarization reconfiguration through controlled actuation of liquid metal within the channels. The fabricated prototype was experimentally verified, and the measured results show good agreement with simulations. Integrating microfluidic technology with additive manufacturing offers a scalable, low-profile solution for multifunctional and reconfigurable electromagnetic system components.

This paper presents the first additively manufactured, single-layer, polarization-insensitive, fluidically switchable band stop frequency selective surface (FSS) for electromagnetic (EM) shielding applications. The unit cell features a meandered square-loop metallic pattern with a fluidic cavity embedded within the substrate via fused deposition modeling. Frequency tuning is realized by controlling the fluidic state of the cavity through an automated pump system. In the absence of water, the structure resonates at 3.5 GHz; introducing distilled water into the cavity lowers the resonance to 2.6 GHz, achieving a 29.5% tuning range. The proposed FSS provides a minimum shielding effectiveness of 30 dB for both cases. An equivalent circuit model is developed to interpret the tuning mechanism, and both simulation and experimental results confirm the effectiveness of the design. The proposed FSS maintains stable performance up to 60 ^∘ under both TE and TM polarizations. With its simple, low-profile, single-layered design, this FSS offers strong potential for EM shielding and interference mitigation applications.

A multifunctional reflective type frequency selective surface (FSS) is proposed for both linear to linear polarization (LP to LP) and linear to circular polarization (LP to CP) conversion. The unit cell features a circular loop modified with two symmetric arc shaped slots rotated at 45°, and a single metallic arc segment placed opposite the slots, creating structural asymmetry that facilitates polarization transformation under normal incidence. To ensure reflective operation, the FSS is fabricated on a 1.6 mm thick FR4 substrate with a metallic backing. The simulation results are further validated through experimental measurements of the fabricated prototype. The proposed FSS achieves LP to LP conversion over the 13.54–14.12 GHz range and dual band LP to CP conversion across 12.90–13.27 GHz, 14.81–27.40 GHz. The proposed design have small footprints of 0.27 λ 0 × 0.27 λ ₀ , λ ₀ being the lowest operating wavelength and demonstrate angularly stable characteristics up to 30 ^∘ incidence. With its simple structure and multifunctional performance, the design offers a compact and effective solution for advanced radar, wireless communication, and polarization sensitive sensing systems applications.

This paper presents a novel triple-band frequency selective surface (FSS) designed as a bandstop filter operating at 3.24, 6.08, and 10.88 GHz, corresponding to the S, C, and X bands, respectively. The design is notable for its polarization insensitivity, exhibiting a consistent frequency response for both TE and TM modes. A key feature of the proposed design is its stability at oblique incidence angles up to 45° for both polarizations. The proposed model is validated using an equivalent circuit model. A detailed examination of the electric field and surface current distribution is conducted to explain the resonance behavior. The fabricated triple bandstop FSS prototype shows good agreement between simulation results and experimental measurements. The structure is highly compact, with each unit cell area of 0.25λg×0.25λg, where λg represents the guided wavelength.

This work demonstrates the development of an additive manufacturing-based transition from a microstrip to an empty substrate integrated waveguide (ESIW). An expanded ESIW section with a sharp dielectric taper allows for wideband impedance matching. The proposed transition is validated by simple, inexpensive and reduced complexity using additive manufacturing (AM) technique. The top and bottom of ESIW are covered with copper-coated polylactic acid (PLA) substrate of 0.5 mm thickness. The via holes in the ESIW are replaced by spraying copper on the internal walls. The proposed model’s veracity was further established by evaluating it against a subtractive manufacturing (SM) prototype. The measured results obtained using AM (SM) have an insertion loss of less than 2.24 dB (0.92 dB), a return loss better than 17.7 dB (18.08 dB), and 73.4 (60.8) % fractional bandwidth (FBW) over 10-21.6 (10-18.75) GHz.

This paper presents a novel frequency-reconfigurable self-diplexing antenna (SDA) utilizing a hybrid substrate-integrated waveguide (SIW). The antenna comprises a radiating slot, a feeding network, and a hybrid SIW cavity featuring half-mode circular and half-mode rectangular SIW structures. The unique feature of this antenna lies in its fine-tuning capability of each resonant frequency by inserting or injecting solid and liquid dielectrics into designated etched pockets. Experimental results demonstrate that the proposed structure can be effectively tuned within the frequency range of 2.7 to 3.47 GHz for the lower band and 4.05 to 4.96 GHz for the upper band. The mutual coupling between the ports is better than 20.4 dB, and the antenna maintains consistent radiation patterns across the entire operating range. The proposed tunable antenna, featuring precise frequency tuning capability, compact size, and stable radiation patterns, is well suited for various applications, including wireless communication systems, biomedical telemetry, microwave imaging, WiMAX, and Wi-Fi.

This work introduces a novel frequency tunable self-diplexing antenna (SDA) design based on substrate integrated waveguide (SIW) technology. A modified A-shaped slot is employed on the cavity’s top plane, which is excited by two independent 50 Ω microstrip feed lines to operate at each resonant frequency. The frequency flexibility of the proposed antenna allows for fine-tuning at each resonance frequency. The frequency flexibility has been achieved by employing the substrate’s air-and liquid-filled pockets. The proposed antenna can be configured to operate in the 3.5-3.8 GHz and 5.53-6.2 GHz bands, as demonstrated by the simulation results. With distilled water-filled pockets, the proposed antenna offers peak gains of 5.04 dBi and 5.26 dBi. The proposed SDA exhibits competitive features such as a highly compact size of 0.22λg and high isolation (>27dB), which makes it suitable for handheld communication devices. The simulated and measured circuit responses are in good agreement.

This work describes a frequency switchable SIW based self-diplexing antenna (SDA) whose both bands can be controlled independently. Two orthogonal microstrip feed lines are employed to simulate the SIW resonator at two separate frequencies in the full-wave EM simulator (HFSS). Air-filled pockets are incorporated into the substrate to tune the antenna resonance frequency. The resonant frequencies can be independently tuned by changing the volume of the liquid-filled in each pocket. Simulated results show that the proposed antenna can be tuned from 3.56 to 4 and 4.4 to 5.05 GHz in the lower and higher frequency bands, respectively. The proposed antenna has peak gains of 5.04 dBi and 5.65 dBi with distilled water filled pockets. This antenna model has a simple design, good isolation, and reconfigurability compared to previous designs, which meets the growing need for RF device simplification and integration in WLAN, INSAT, and cable-free FOR3 applications.