Multilayer Substrate Research Articles

Broadband Differential-Line-to-Waveguide Transition in Multi-Layer Dielectric Substrates With an X-Shaped Patch Element in 280 GHz Band

A broadband differential-line-to-waveguide transition covering the 260–300 GHz band was developed in this study. This transition consists of a differential line inserted from the narrow wall of the waveguide that excites an X-shaped patch located at the waveguide center. As the two corners of the patch are excited electromagnetically via differential signal lines in the opposite phase, orthogonal current components that radiate the TE <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{10}$</tex-math> </inline-formula> mode into the waveguide are generated. Broadband operation is achieved via the double resonance of the X-shaped patch and a cavity formed by the via-hole arrangement with apertures patterned in a multi-layer substrate. The transition geometries are optimized via electromagnetic simulation using a finite element method. Transition performance is evaluated through measurements and simulations.

Multimodal Wrinkle Micro‐Nanoarchitectonics by Patterned Surface Material Properties for Transformative Structural Coloration

AbstractWhen an external stimulus is used to generate nanoscale wrinkles on the ductile top surface of a multilayered substrate, the geometrical and optical features are known to be controlled by the material and structural properties of the laminated film. Herein, a thin tri‐layer film is fabricated that can generate various wrinkles on transparent and flexible films in the presence of external mechanical bending. In particular, the wavelength of the wrinkles is shown to be controllable on the tens of nanometers scale by modulating the material properties of each layer. This active modulation plays a critical role in determining the resulting structural color spectra. In other words, the wrinkles function as a diffraction grating so that the film displays bright structural colors under bending conditions. After the bending stress is released, the wrinkles disappear, and the film returns to its transparent state. Finally, the remarkable potential of the material and structural patterning technique is demonstrated for structural coloration applications such as multimodal displays and novel barcode‐based anti‐counterfeiting.

Interface feature via key factor on adhesion of CrN multilayer and alloy substrate

CrN multilayer coatings were deposited on 316L stainless steel, which has a high modulus, and TC4 titanium alloy, which exhibits the opposite properties, to reveal adhesion mechanisms and deformation behavior of the coating/substrate systems. Because of the different microstructures, the coatings’ morphologies varied from single polygon on the 316L to polygon and rectangle-mixed shapes on the TC4. On 316L, the cracks initiated from the Cr/CrN interfaces and propagated into the CrN layer, which stopped within it. On TC4, the cracks propagated through the CrN layer. The coherent nanocrystal interfaces in CrN/Cr/316L exhibited orderly bending, revealing the presence of strong interfacial bonds. The undeformed interfaces in CrN/Cr/TC4 indicated incompatible deformation and weak bonds. This was consistent with the fact that on TC4, the Cr/CrN interface tensile stress was high, at 123.1 GPa, while it was lower on 316L, at 99.3 GPa. The Wp/We ratio of CrN/TC4, namely 1.94, was lower than that of CrN/316L, namely 2.61. This indicated that CrN/316L had a high energy-absorption ability because of compatible plastic deformation. The failure mechanism observed between the coating/TC4 was attributed to the differences in their moduli, which led to incompatible deformation, high interfacial tensile stress, and low absorption capability for external work.

Variable Dielectric and Thermomechanical Properties of Oxide Ceramic/1,2‐PB/SBS/EPDM Composite Film Materials with Multilayer Structure

AbstractThe variable dielectric properties of multilayer structural ceramic/polyolefin composite film substrate materials with silicon dioxide (SiO2) and titanium dioxide (TiO2) powders as fillers and 1,2‐polybutadiene/styrene‐butadiene‐styrene triblock copolymer/ethylene‐propylene‐diene terpolymer/(1,2‐PB/SBS/EPDM) as polymer matrix were systematically investigated. Single‐layer SiO2, TiO2 and SiO2/TiO2/polyolefin‐based composite films denoted as A, B and H, respectively, were prepared by the flow casting method, and then multilayer structural composite substrates with different stacking methods were prepared by the hot pressing method. Four different layering modes were used: ABAB, AABB, ABBA, and BAAB. It was found that the dielectric constants of all four modes were within the scientific range. Compared to the other four types of laminated substrates, however, the fifth composite substrate with four identical film laminations made from a blend of two fillers (HHHH) exhibited better thermal stability and had a lower dielectric loss (0.00206) at 10 GHz compared to the other four types of laminated substrates. On the other hand, the other four types of laminated substrates have better mechanical properties compared to the hybrid substrates. This work provides a new idea for the preparation of oxide ceramic/polyolefin‐based dielectric composites that meet the requirements of different dielectric and thermomechanical properties.

A Review on Integrated ZnO-Based SERS Biosensors and Their Potential in Detecting Biomarkers of Neurodegenerative Diseases.

Surface-enhanced Raman spectroscopy (SERS) applications in clinical diagnosis and spectral pathology are increasing due to the potential of the technique to bio-barcode incipient and differential diseases via real-time monitoring of biomarkers in fluids and in real-time via biomolecular fingerprinting. Additionally, the rapid advancements in micro/nanotechnology have a visible influence in all aspects of science and life. The miniaturization and enhanced properties of materials at the micro/nanoscale transcended the confines of the laboratory and are revolutionizing domains such as electronics, optics, medicine, and environmental science. The societal and technological impact of SERS biosensing by using semiconductor-based nanostructured smart substrates will be huge once minor technical pitfalls are solved. Herein, challenges in clinical routine testing are addressed in order to understand the context of how SERS can perform in real, in vivo sampling and bioassays for early neurodegenerative disease (ND) diagnosis. The main interest in translating SERS into clinical practice is reinforced by the practical advantages: portability of the designed setups, versatility in using nanomaterials of various matter and costs, readiness, and reliability. As we will present in this review, in the frame of technology readiness levels (TRL), the current maturity reached by semiconductor-based SERS biosensors, in particular that of zinc oxide (ZnO)-based hybrid SERS substrates, is situated at the development level TRL 6 (out of 9 levels). Three-dimensional, multilayered SERS substrates that provide additional plasmonic hot spots in the z-axis are of key importance in designing highly performant SERS biosensors for the detection of ND biomarkers.

Exploring the Piezoelectric Properties of Bismuth Ferrite Thin Films Using Piezoelectric Force Microscopy: A Case Study.

Over recent decades, the scientific community has managed to make great progress in the theoretical investigation and practical characterization of bismuth ferrite thin films. However, there is still much work to be completed in the field of magnetic property analysis. Under a normal operational temperature, the ferroelectric properties of bismuth ferrite could overcome the magnetic properties due to the robustness of ferroelectric alignment. Therefore, investigation of the ferroelectric domain structure is crucial for functionality of any potential devices. This paper reports deposition and analyzation of bismuth ferrite thin films by Piezoresponse Force Microscopy (PFM) and XPS methods, aiming to provide a characterization of deposited thin films. In this paper, thin films of 100 nm thick bismuth ferrite material were prepared by pulsed laser deposition on multilayer substrates Pt/Ti(TiO2)/Si. Our main purpose for the PFM investigation in this paper is to determine which magnetic pattern will be observed on Pt/Ti/Si and Pt/TiO2/Si multilayer substrates under certain deposition parameters by utilizing the PLD method and using samples of a deposited thickness of 100 nm. It was also important to determine how strong the measured piezoelectric response will be, considering parameters mentioned previously. By establishing a clear understanding of how prepared thin films react on various biases, we have provided a foundation for future research involving the formation of piezoelectric grains, thickness-dependent domain wall formations, and the effect of the substrate topology on the magnetic properties of bismuth ferrite films.

Surface acoustic wave resonators on thin film piezoelectric substrates in the quantum regime

Lithium niobate (LNO) is a well established material for surface acoustic wave (SAW) devices including resonators, delay lines and filters. Recently, multi-layer substrates based on LNO thin films have become commercially available. Here, we present a systematic low-temperature study of the performance of SAW devices fabricated on LNO-on-insulator and LNO-on-Silicon substrates and compare them to bulk LNO devices. Our study aims at assessing the performance of these substrates for quantum acoustics, i.e. the integration with superconducting circuits operating in the quantum regime. To this end, we design SAW resonators with a target frequency of and perform experiments at millikelvin temperatures and microwave power levels corresponding to single photons or phonons. The devices are investigated regarding their internal quality factors as a function of the excitation power and temperature, which allows us to characterize and quantify losses and identify the dominating loss mechanism. For the measured devices, fitting the experimental data shows that the quality factors are limited by the coupling of the resonator to a bath of two-level-systems. Our results suggest that SAW devices on thin film LNO on silicon have comparable performance to devices on bulk LNO and are viable for use in SAW-based quantum acoustic devices.

Modeling of Practical Substrate Thickness in Multilayer Printed Circuit Board for Millimeter-Wave Packaging

This paper proposes a modeling of the practical substrate thickness so that it is possible to accurately design by predicting the dielectric thickness that varies for each circuit of a multi-layer printed circuit board (PCB) in the manufacturing process. The amount of dielectric to be filled into the empty space of the pre-stacked metal layer varies depending on the ratio of pre-stacked metal to the entire area during the high-temperature and high-pressure process, so the dielectric thickness between the inner layer and the outer layer metal varies. When the patterns are complex and non-uniform in design, the difference in the ratio of the pre-stacked metal occurs between the entire area and the partial area of the strip. For this reason, the dielectric thicknesses are manufactured differently for each circuit. Therefore, this paper proposes a practical dielectric thickness equation and a reference area to calculate the copper foil residual ratio. To find the optimal reference area for calculating the copper foil residual ratio, microstrip lines with the same width and length but different ratios of the surrounding pre-stacked metal were analyzed. Finally, a dielectric thickness prediction equation is proposed, and verified not only on a multilayer substrate with a thickness of 40 μm but also with 20 μm to show that it is a highly reliable radio frequency (RF) modeling solution.

Spectroelectrochemical behavior of parallel arrays of single vertically oriented Pseudomonas aeruginosa cells

Pseudomonas aeruginosa is a Gram-negative opportunistic human pathogen responsible for a number of healthcare-associated infection. It is currently difficult to assess single cell behaviors of P. aeruginosa that might contribute to acquisition of antibiotic resistance, intercellular communication, biofilm development, or virulence, because mechanistic behavior is inferred from ensemble collections of cells, thus averaging effects over a population. Here, we develop and characterize a device that can capture and trap arrays of single P. aeruginosa cells in individual micropores in order to study their behaviors using spectroelectrochemistry. Focused ion beam milling is used to fabricate an array of micropores in a Au/dielectric/Au/SiO2-containing multilayer substrate, in which individual micropores are formed with dimensions that facilitate the capture of single P. aeruginosa cells in a predominantly vertical orientation. The bottom Au ring is then used as a working electrode to explore the spectroelectrochemical behavior of parallel arrays of individual P. aeruginosa cells. Application of step-potential or swept-potential waveforms produces changes in the fluorescence emission that can be imaged and correlated with applied potential. Arrays of P. aeruginosa cells typically exhibit three characteristic fluorescence behaviors that are sensitive to nutritional stress and applied potential. The device developed here enables the study of parallel collections of single bacterial cells with well-defined orientational order and should facilitate efforts to elucidate methods of bacterial communication and multidrug resistance at the single cell level.

Measuring complex refractive index through deep-learning-enabled optical reflectometry

Optical spectroscopy is indispensable for research and development in nanoscience and nanotechnology, microelectronics, energy, and advanced manufacturing. Advanced optical spectroscopy tools often require both specifically designed high-end instrumentation and intricate data analysis techniques. Beyond the common analytical tools, deep learning methods are well suited for interpreting high-dimensional and complicated spectroscopy data. They offer great opportunities to extract subtle and deep information about optical properties of materials with simpler optical setups, which would otherwise require sophisticated instrumentation. In this work, we propose a computational approach based on a conventional tabletop optical microscope and a deep learning model called ReflectoNet. Without any prior knowledge about the multilayer substrates, ReflectoNet can predict the complex refractive indices of thin films and 2D materials on top of these nontrivial substrates from experimentally measured optical reflectance spectra with high accuracies. This task was not feasible previously with traditional reflectometry or ellipsometry methods. Fundamental physical principles, such as the Kramers–Kronig relations, are spontaneously learned by the model without any further training. This approach enables in-operando optical characterization of functional materials and 2D materials within complex photonic structures or optoelectronic devices.

Synthesis of ZnO Nanoflower Arrays on Patterned Cavity Substrate and Their Application in Methylene Blue Degradation

A novel method was proposed to fabricate a ZnO seed layer with a protrusion and matrix structure, and then ZnO nanorods could be synthesized on it using the hydrothermal method to form ZnO nanoflower arrays (NFAs) easily. A patterned sapphire with a matrix cavity was used as the template, ZnO gel was deposited on the multilayer substrates using spinning coating, and the prepared seed layer with a protrusion and an array-patterned structure was moved to a Si substrate using the lift-off method. Because the ZnO seed layer exhibited a matrix and protrusion structure, ZnO nanorods were grown vertically downwards and formed ZnO NFAs. The XRD patterns resulting from analyses showed that the diffraction peaks of the five growth directions of ZnO NFAs increased as growth time increased. Furthermore, SEM and FIB analyses indicated that the length, width, aspect ratio, and total surface area of ZnO NFAs grown on the transferred seed layer increased as the synthesis time increased. Different ZnO NFAs synthesized for varying synthesis times were used to investigate methylene blue degradation, with the effect of ZnO NFAs on methylene blue degradation determined using the Beer-Lambert law. Our results demonstrate that the effect of ZnO NFAs on methylene blue degradation was enhanced with increasing synthesis time.

Experimental investigation of damages in the bimorph piezoelectric energy harvester with multilayer composite substrate

Composite materials, regarding their lightweight, can be considered a suitable option for the next generation of piezoelectric energy harvesters, which are used for supporting low-power applications. Also, due to the broader selection range and different stacking sequences, one of the advantages of these materials is that they can provide better stiffness adjustment of the structure to achieve the desired frequency of energy harvesting from the ambient vibration. Despite all these advantages, one of the challenges in the widespread use of this type of material is the complex damage behavior and less information about their damage behavior compared to other traditional materials. The bimorph piezoelectric energy harvester studied in this work has a three-layer woven substrate in the form of [0/90]; its behavior and performance in the presence of some well-known damage mechanisms in the composite structures, such as the mid-layer transverse cracks are investigated. A crack density-based stress transfer method, from a micromechanical point of view, is employed to calculate stiffness reduction due to damages in the bimorph. The effect of the damping coefficient on analytical modeling is considered, and the parameter of the damping ratio is given by the experimental test. Effects of damages on the mechanical parameters like resonance frequency, as well as the electrical parameters like output voltage, are investigated. It is observed that the presence of fabricated transverse cracks in the mid-layer of the bimorph piezoelectric energy harvester increases the value of the damping ratio and also decreases its stiffness. Finally, the output voltage is investigated, which reduces by the mid-layer transverse cracks.

Efficient carbon removal and excellent anti-clogging performance have been achieved in multilayer quartz sand horizontal subsurface flow constructed wetland for domestic sewage treatment

The present study aimed to investigate the application of a multilayer quartz sand substrate horizontal subsurface flow constructed wetland (HSFCW) for campus sewage treatment. It aimed to assess the pollutant removal efficiency and anti-clogging performance under the suggested maximum organic loading rate (250 g/m2/d). The results of the multilayer HSFCW (CW6) were compared to the mololayer HSFCW (CW1) for the removal of the chemical oxygen demand (COD), solid accumulation, and microbial communities. During operation, the combination conditions of high hydraulic loading rate (HLR) with low COD concentration were better for COD removal under a high organic loading rate (OLR) of 200–300 g/m2/d. The maximum removal rate reached 80.4% in CW6 under high HLR, which was 13.8% higher than that in CW1, showing better adsorption and biodegradation ability of organic matter. Impressive clogging resistance capacity was found in CW6 due to the lower contents of the insoluble organic matter (IOM) that are prone to clogging, indicating full degradation of organic matters, particularly IOM, in CW6 under high HLR. Less abundance of unclassified Chitinophagaceae (under low HLR), Pedobacter and Saccharibacteria_genera_incertae_sedis (under high HLR) in CW6, which contributed to aerobic membrane fouling, helped to prevent clogging. Moreover, Brevundimonas, Cloacibacterium, Citrobacter, Luteimonas contributed to IOM degradation, thus further enhancing the anti-clogging performance. In view of the better clogging resistance performance, the application of CW6 operated under high HLR and low COD concentrations was recommended to achieve economical, efficient, and steady COD removal for domestic sewage treatment in long-term operation.

NOISE THEORITICAL INVESTIGATIONS FOR TRI-DIMMENSIONAL NMR CIRCUIT: TOWARDS THE NANOSCALE

In recent years, NMR/MRI portable devices have drawn attention of numerous researcher teams. They are used for variety of applications, from medical diagnosis to archaeological analysis, nondestructive material testing evaluation of water presence in building materials and food emulsions. Different magnets designs have been proposed by many groups of research. They can be divided into two groups: the magnets ex-situ and the magnets in situ .The first group has the simple configuration with the sensitive volume near their surface and the samples under test are located outside the magnets. Thus, they can be used for the experimental investigation of objects with any dimension. Although the ex-situ magnets have simple shape and light weight, they are difficult to achieve in terms of homogeneity of the magnetic field in the sensitive volume. &#x0D; In comparison, the in-situ magnets have their static field reinforced inside their bore center and canceled outside of the structure. Thus, their magnetic field is roughly homogeneous inside the structure. &#x0D; But drawbacks still exist and can be amplified, especially the in depth problem of Signal/Noise. Calculations, in a microscopic point of view, are develop, first applied to resistances and inductances imbedded in this circuit. &#x0D; Before, from any point source, we calculate the impedance spreading out. For this, our approach is using Transmission Line Model, over or into a multi-layered substrate; it can be also derived by solving Poisson's equation analytically to obtain the associated Green’s kernel. We implement our algorithms in MATLAB. Thus, it permits to extract impedances between any two embedded contacts, real or virtual, of any shape or thickness.

Poly (l-lactic acid)-based modified nanofibrous membrane with dual drug release capability for GBR application

Electrospun multilayer nanofibers guided bone regeneration (GBR) with a new design were developed in this study. The synthesized multilayer GBR was composed of two distinct layers. Poly l-lactic acid (PLA) incorporated with simvastatin (SIM) was designed as PLA/SIM layer to contact with a bone defect. In addition, the hydrophilic gelatin (GT) containing thymol (THY) was fabricated as GT/THY layer to contact connective tissue, potentially for bacterial gathering. Due to the different chemical nature and weak cohesion of the hydrophilic and hydrophobic layers, hybrid fibers made of PLA/SIM and GT/THY were electrospun as cohesion promoters between these layers. The microstructure and characteristics of the synthesized multilayer substrate, named GT/PLA, were evaluated, and different fibrous monolayers were fabricated to determine the optimal concentrations of drugs.Scanning electron microscopy (SEM) images showed continuous, smooth, randomly aligned, and bead-free fibers. In addition, there were no drug particles on the fiber surfaces which displayed the good placement of those inside the fibers. The mats exhibited satisfactory tensile strength (4.60 ± 0.14 MPa) and favorable physicochemical properties, including proper porosity percentage (<50 %) and appropriate pore size. Suitable swelling behavior (293 ± 0.05 %) and adequate degradation rates were also approved by characterizing swelling and degradability in vitro. The GT/PLA membrane exhibited a prolonged and sustained SIM release and controlled THY release with high antibacterial efficiency. Cell viability, cell attachment assay, and nuclear staining using 4′,6-diamidino-2-phenylindole (DAPI) showed that the designed GT/PLA substrate had good biocompatibility and cell attachment. Cell infiltration testing also showed that the cells were finely prevented by the outer layer (GT/THY). Overall, the obtained results in this study indicated the great potential of the prepared GT/PLA for use as a GBR which can develop osteogenic and antibacterial biomimetic periosteum optimizing the clinical application of GBR strategies.

Dynamics of diverse polarization singularities in momentum space with far-field interference

Polarization singularities in momentum space, including bound states in the continuum (BICs) and circularly polarized states (CPSs), render great potential in singular and chiral optics. As far-field topological signatures of Bloch modes in photonic crystal slab, the dynamic evolution of the polarization singularities is observed by tuning the geometric parameters of the slab itself. Here, we combine the photonic crystal slab with a reflected multilayer substrate in which interference between the reflected optical field and the upward radiation of the Bloch mode brings us an extra degree of freedom to manipulate the polarization singularities without breaking the structural symmetry. As the polarization singularities evolve with the spacing between the photonic crystal slab and the substrate, the CPSs and extrinsic BICs are both generated from charge reversal of the at-\ensuremath{\Gamma} intrinsic BIC and then collide with the off-\ensuremath{\Gamma} intrinsic BICs. Importantly, all BICs are topologically protected from splitting throughout the whole dynamic process owing to the preservation of structural symmetry. Our findings suggest an alternative route to pursue ultrahigh-$Q$ CPS resonances and merge diverse BICs, which is potentially applicable in chiral optics, topological photonics, and beam modulation.

USE OF MULTILAYER DIELECTRIC FOR SLOT PHASED ARRAY ANTENNAS

It is of interest to study slot spiral radiators as part of a phased array with structural elements in the form of multi-layer dielectrics that make up a multilayer substrate and a spiral cover, which, by changing the parameters of a multilayer dielectric, can significantly change the frequency properties of the radiator and its overall dimensions. The purpose of the work is to develop a mathematical model for a phased array in the form of a periodic structure with slotted spiral radiators using multilayer dielectrics in the design, and its numerical analysis with the study of its frequency properties when choosing the topology of the spiral, the parameters of the dielectric layered medium, followed by determining the design dimensions of the spiral as an element of the phased antenna arrays. A mathematical model of a phased array is presented in the form of a periodic structure with slotted radiators using multi-layer dielectrics in the design. The method is based on the conversion of the electrodynamic problem of excitation to an integral equation with its subsequent transformation to a one-dimensional Fredholm integral equation of the first kind. The directional and polarization characteristics of the phased antenna arrays element are determined, and a numerical analysis of its frequency properties is carried out.

A magnetically controlled microfluidic device for concentration dependent in vitro testing of anticancer drug.

Compartmentalizing magnetically controlled drug molecules is critical in several bioanalytical trials and tests, such as drug screening, digital PCR, magnetic hyperthermia, and controlled magnetic drug targeting (MDT). However, several studies have focused on diluting the nonmagnetic drug using various passive devices based on traditional microfabrication and 3D printing techniques, leading to the requirement of sterilized cleanroom facilities and expensive equipment, respectively. This work develops a strategically designed and straightforward lithography-free process to fabricate a magnetic microfluidic device using a multilayered PMMA substrate for concentration-dependent compartmentalization of a magnetically controlled anticancer drug. The device contains an array of outlet chamber wells connected to five primary separation microfluidic channels for collecting different drug concentrations. The microfluidic design geometry, magnet configuration, and fluid flow rate are optimized using FEM (Finite Element Method) simulations to attain a systematic concentration gradient region within the microfluidic channel. A stair-step-like patterned magnet creates an attenuating magnetic force between 0.01-0.24 pN on magnetic nanoparticles, capable of generating the concentration gradient for the clinically acceptable flow range of Q = 0.6-1.1 μL min-1. The chamber well of the device is designed to adapt different cell cultures and simultaneously expose five different concentrations by introducing a predefined concentration from the inlet. As a result, this innovative design provides a predictable concentration control in each well through a single injection port to minimize drug loading errors. The concentration gradient generation of the drug and exposure to cell culture chambers are controlled using the magnetic and drag forces capable of running a time-varying dose screening experiment. The concentration range of the compartmentalized drug sample in the device is determined as 10-480 μg mL-1 using inductively coupled plasma mass spectrometry (ICPMS) measurement and fluorescence intensity. The cytotoxicity test of MCF7 and NIH3T3 cells using the device was consistent with the results obtained with the manual dilution method, resulting in the reusability of the device.

Моделирование распыления многослойных подложек фокусированным ионным пучком

The level set method was generalized for simulating the evolution of the surface of multilayer substrates under focused ion beam irradiation. For a correct description of such process the calculations took into account the sputtering yield angular dependences, the densities of the irradiated materials and it was considered that sputtered atoms can escape from different layers of the substrate. Comparison of the calculation results with experimental data for test structures formed in a two-layer silicon dioxide–crystalline silicon substrate showed that the developed simulation method makes it possible to predict the shape of structures fabricated by a focused ion beam with good accuracy.

High-Gain Circularly Polarized Antenna Array for Full Incident Angle Coverage in RF Energy Harvesting

In this paper, a high-gain circularly polarized (CP) hexagonal antenna array is proposed for RF energy-harvesting applications. The hexagonal antenna array is intended to operate at the frequency of 5.8 GHz. It is composed of 6 multilayer substrate CP antennas excited by an X-shaped aperture-coupling feed structure. A frequency selective surface (FSS) was added to further improve the gain, resulting in a maximum gain of 12.7 dBi per element. The main advantage of the proposed hexagonal antenna array is the ability to cover 360 degrees in the azimuth plane with a high gain in all directions without the use of any additional circuitry, allowing the effective absorption of ambient RF energy. A prototype was fabricated and measured, and a good agreement with the simulation results is achieved. In addition, a rectifier is used to convert RF energy absorbed by the antenna into DC energy at the frequency of 5.8 GHz. The measured RF-to-DC conversion efficiency of 44.5% and a DC output voltage of 423 mV at -10 dBm are observed. The performance of the rectenna array with one and six rectifiers has been demonstrated. With the use of a DC combiner, the total RF to DC efficiency of the array is 67.75%, with a DC output voltage of 1.115 V from -10 dBm has been recorded. Due to the immunity to misalignment of the CP antenna, the proposed rectenna array is very suitable for wireless power transfer (WPT).