Patch Layer Research Articles

Design and verification of a dual‐band wearable antenna based on characteristic mode theory

AbstractIn this article, a novel design method is proposed based on characteristic mode theory (CMT). Based on the proposed method, a linearly polarised dual‐band wearable antenna with double‐layered substrates sandwiched by three layers of copper circle patches is designed and optimised step by step. The structure and excitation position of the antenna are obtained by progressively tailoring a classical circle patch antenna. Firstly, the characteristic mode analysis is performed on the middle‐layer planar circle patch to find the modes that can be excited in the designed frequency band. Secondly, the configuration of the middle layer is adjusted step by step based on the modal current distributions to realise the mode shift. Then, the top circle patch is changed to a metasurface to increase the number of modes and expand the mode bandwidth. Finally, the location of the excitation port is selected based on the modal electric fields to successfully obtain the desired performance of the antenna. The prototype of the proposed antenna with a radius of 2.6 cm fed by a single probe is fabricated and experimentally verified. The antenna operates in the 2.45 and 5 GHz bands, and the measured 10 dB impedance bandwidths on the two bands are 1.2% and 39.7%, respectively, which agrees well with the expectation predicted by the CMT. It should be noted that the desired antenna performance is achieved by step‐by‐step derivation using the CMT, rather than applying the theory to illustrate the working principle of antennas. The proposed design method can be broadly employed to various antenna designs.

A two-stage federated optimization algorithm for privacy computing in Internet of Things

With the advent of the Internet of things (IoT) era, federated learning plays an important role in breaking through traditional data barriers and effectively realizing data privacy and security in the process of sharing. However, the demand of the practical problems makes the algorithm still have great challenges in effectively balancing various factors, such as privacy security, accuracy, computing efficiency and so on. To challenge this problem, a two-stage federated optimization algorithm based on robust and multitasking learning is designed. In optimization client local model stage, an adaptive weight assignment mechanism is adopted to guide robust learning based on multiple untrusted sources data, which aims to ensure the credibility and robustness of the client model and obtain a reliable client model. To address the information leakage problem during the server–client global model optimization stage, a privacy patch layer is added to the client local model in multitask learning and maintain its privacy parameters stored on the client model during the global model parameter aggregation process, which aims to meet the personalized requirements and performance requirements of protecting the model privacy. To effectively measure the performance of our algorithm, two extensive experiments are carried out to verify the robustness and accuracy of model under different datasets, respectively. In addition, simulation results show that our algorithm successfully suppresses the impact of corrupted or irrelevant sources on performance, and its performance is better than the other two robust distributed learning baseline methods in the client local model optimization stage. At the same time, our algorithm achieves better accuracy performance than other advanced personalized optimization algorithms in the server–client global model optimization stage. Finally, it achieves a good balance between robustness, computational efficiency and model privacy protection.

Coaxial laser cladding of cobalt-base alloy StelliteTM6 on gray cast iron/investigations on friction, wear versus commercial brake pad, and corrosion characteristics

Environmental legislation and the electrification of vehicles place increased requirements on brake disks in terms of wear and corrosion resistance. Departing from a preliminary study, the present investigation examined the friction and wear behavior as well as the corrosion properties of Stellite™ 6 coatings on gray cast iron, which were deposited by laser cladding. The friction and wear experiments were conducted on a pin-on-disk tribometer at contact pressures of 1.0 and 2.0 MPa as well as rotation speeds of 0.2, 0.4, 0.6, 0.8, and 2.0 m/s. The pins are manufactured from an automotive semi-metallic brake pad. The friction behavior of gray cast iron and Stellite™ 6 coatings is similar under changing test conditions. The tribological behavior is strongly influenced by the microstructural and mechanical properties of the coatings and the brake pad material. A third body layer of contact patches is formed on Stellite™ 6, which mainly consists of brake pad components. The transformation of the Co-matrix (fcc → hcp), subsurface fatigue, and tribo-oxidation are the main wear mechanism for Stellite™ 6. The electrochemical characteristics were analyzed by potentiodynamic polarization, and the corrosion rate was determined with Tafel plots in 3.5% NaCl solution, respectively. Compared to gray cast iron, Stellite™ 6 coatings have a pronounced corrosion resistance due to the formation of a protective passive layer of Co and Cr oxides. This corrosion resistance is mainly influenced by the microstructure. The corrosion rate of the coatings increases in parallel with the Fe dilution.

Dual-mode orbital angular momentum generated based on dual-polarization coding metasurface

In this paper, a dual-polarization 4-bit coding metasurface is proposed to achieve the flexible manipulation of different polarization electromagnetic wave reflection angles and the generation of dual-mode vortex beams by independent manipulation of orthogonal linearly polarized waves. The proposed metasurface is composed of an H-type metal patch, dielectric substrate, and metal grounding layer from top to bottom. To prove the proposed concept, we design and fabricate four coding metasurfaces based on the superposition theorem and holographic theory. One of the coding metasurfaces is designed to verify the ability to manipulate the beam angle, and each of the other three coding metasurfaces is designed to carry a vortex beam with different topological charges under orthogonal linearly polarized waves with a central frequency of 24 GHz. The experimental results show that the theoretical design is highly consistent with the simulation results. Therefore, it is verified that our proposed 4-bit dual-polarization coding metasurface has a strong and flexible ability to manipulate the beam reflection angle and generate a high-performance dual-mode vortex beam antenna. Because of the wide application prospect of vortex beams in the communication field, we have reason to believe that the proposed ultra-thin dual-mode vortex generator will have potential applications in wireless communication systems in the fields of images and microwaves.

167: AN ADOLESCENT MALE WITH CONGESTIVE HEART FAILURE FROM A RARE CAUSE

Introduction: A sinus of Valsalva aneurysm is an abnormal dilatation of the aortic root located between the aortic valve annulus and the sinotubular junction. It can either be congenital or acquired. The right coronary sinus is most commonly involved, followed by the noncoronary sinus. Rupture of the sinus of Valsalva aneurysm is extremely rare in children. Description: A 16-year-old previously healthy male was admitted with 1 month of worsening fatigue, bilateral leg swelling and orthopnea. He was hypertensive and tachycardic with a grade 3 holosystolic murmur over the precordium. The rest of his physical examination was normal. A chest x-ray showed cardiomegaly and an EKG showed ventricular bigeminy and inverted T waves. His pro-BNP was elevated to 1880 pg/mL but troponin and inflammatory markers were normal. A transthoracic echocardiogram (TTE) showed a ruptured aortic noncoronary sinus of Valsalva aneurysm into the right atrium with left to right shunting, aortic root dilatation and aortic valve regurgitation. A cardiac CT confirmed the TTE findings. He underwent surgical repair. Intraoperatively, a large fenestrated aneurysmal tissue was noted and was excised, with the defect repaired using two layers of autologous pericardial patches. A transesophageal echocardiogram (TEE) showed no residual defect and no aortic insufficiency. He was extubated the next day, but postoperative course was complicated by an accelerated junctional rhythm with ventricular bigeminy that was successfully treated with an esmolol infusion and later transitioned to atenolol. Discussion: Sinus of Valsalva aneurysm is present only in 0.09% of the general population. The mean age of diagnosis is between 30-45 years, and it is usually asymptomatic unless it ruptures. The right ventricle followed by the right atrium are the most common locations of the rupture. Cardiac catheterization and angiography is the gold standard for diagnosis but a TTE is the first line. Cardiac CT and MRI are supplemental tests. Ruptured aneurysms or unruptured symptomatic aneurysms indicate surgical repair. With the onset of heart failure symptoms, arrhythmias and aortic insufficiency diagnosed on a TTE, a surgical repair with patch closure was opted for our patient with a good postoperative outcome.

Frequency multiplexed metasurface for polarization conversion in full-space

In order to solve the problem of a single function in passive metasurface, a frequency multiplexed metasurface using full-space to realize different polarization conversion modes is proposed. On the basis of the fundamental theory of metasurface polarization transformation, a spliced coupling of multilayer structures was utilized. A compact architecture of five metallic layers and four dielectric layers was fabricated, and the principle analysis of polarization transformation was also performed. In the metallic part, two layers of oblique arrows and one layer of oblique rectangular patches constitute a low-frequency transmission structure, one layer of cross-shaped patches are constituted a high-frequency reflection structure, and one layer of rectangular patches constitutes an intermediate filter structure. Thus, it achieves a variable frequency polarization multiplexing function for transmission on one side and reflection on the opposite one. When the x- and y-polarized waves in the 6.3 GHz–8 GHz band are incident on the low-frequency unit side, they are converted into left- and right-hand circularly polarized transmitted waves, respectively. The axial ratio is less than 3 dB, and the transmission amplitude is up to 0.84 and 0.8. When 45° linearly polarization incident waves in 16.4 GHz–16.8 GHz and 16.9 GHz–18 GHz bands impinge on the high-frequency unit side, the cross-polarized wave reflection is realized. The measured and simulated results are in good agreement. The metasurface proposed in this paper has potential applications in communication frequency multiplexing and multifunctional integration.

Multifunctional Silk Fibroin Methacryloyl Microneedle for Diabetic Wound Healing.

Diabetic wound is one of the common complications in diabetic patients, which exhibits chronic, hard-to-heal characteristics. The healing process of wounds is impaired by several factors, including excessive oxidative stress, blocked angiogenesis, and bacterial infection. The therapeutic effects of traditional microneedle patches remain not satisfactory, due to their difficulty simultaneously targeting multiple targets to treat diabetic wounds. As such, there is an urgent need to develop a multifunctional microneedle (MN) patch for promoting the healing of diabetic wounds. A multifunctional MN patch with antioxidant, proangiogenesis, and antibacterial capacitieswasfabricated to target the pathogenesis of diabetic wounds. Silk fibroin methacryloyl, which has excellent biocompatibility, stable mechanical properties, and well processability, and is selected as the base material for multifunctional MN patches. Prussian blue nanozymes (PBNs) and vascular endothelial growth factor (VEGF) are encapsulated in tips of MN patches, Polymyxin is encapsulated in base layers of MN patches. Based on synergic properties of these components, multifunctional MN patches exhibit excellent biocompatibility, drug-sustained release, proangiogenesis, antioxidant, and antibacterial properties. The developed multifunctional MN patches accelerate diabetic wound healing, providing a potential therapeutic approach.

Wearable Fabric μ Brain Enabling On-Garment Edge-Based Sensor Data Processing

Advances in artificial intelligence (AI) is an enabler for innovative wearable on-garment edge-driven AI. Such AI technologies are leveraging bioinspired methods to develop spiking neural networks (SNNs) that mimic the workings of the human brain to produce higher performance edge-based processing capabilities. Such advancements are driving the development and emergence of neuromorphic computing with SNN architectural designs. Taking inspiration from these, this article proposes and demonstrates a wearable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Brain multilayer SNN smart garment, with an event-driven artificial SNN embedded into the garments fabric. The fabric-based multilayer SNN is interchangeable and scalable through its fabric hidden layer (FHL) and fabric patch design and can be interconnected with textile-based analog monitoring sensors. The prototype was tested to check the functionality of the individual and collective nodes of the SNN as well as evaluating the wearable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Brain for fault tolerance scenarios (ripping and fraying) proving the prototype remained intact following the disconnection of fabric node Patches 5 and 8. Two application demonstrators were identified and tested. The first application focused on the detection of touch sensation on a forearm using the wearable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Brain; here, real-world use cases were checked against the expected output. Fluctuations were encountered when voltage output readings were above and below the set threshold level of 2.3 V. The second application interfaced the wearable <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu $ </tex-math></inline-formula> Brain to live neurons to demonstrate how textile pressure sensors on the surface can lead to stimulation of neurons, when validated we observed an 11-s timeframe where the brain slice was stimulated.

Dual-Square-Split-Ring-Enclosed Microstrip-Based Sensor for Noninvasive Label-Free Detection.

In this article, we present the use of a metamaterial-incorporated microwave-based sensor with a single port network for material characterization. The proposed sensor consists of a microstrip patch layer enclosed with a dual-square-shaped metamaterial split-ring. This structure has the dimensions of 20 × 20 × 1.524 mm3 and a copper metallic layer is placed on a Rogers RT 6002 with a partial back layer as a ground. Two resonant frequencies are exhibited for applied electromagnetic interaction using a transmission line. The dual split rings increase the compactness and accumulation of the electromagnetic field on the surface of the conducting layer to improve the sensitivity of the sensor. The numerical studies are carried out using a CST high-frequency microwave simulator. The validation of the proposed sensor is performed with an equivalent circuit model in ADS and numerical high-frequency simulator HFSS. The material under test placed on the proposed sensor shows good agreement with the frequency deviation for different permittivity variations. Different substrates are analyzed as a host medium of the sensor for parametric analysis.

Mode Purity Improvement of High‐Order Vortex Waves

Vortex electromagnetic waves can carry orbital angular momentum (OAM) modes of different order number, which are mutually orthogonal. Communication technologies multiplexing different OAM topological charges have attracted extensive attention in improving spectrum utilization. In this regard, the efficient generation of OAM modes becomes a key issue. However, it is difficult to generate high-order OAM modes by using a microstrip antenna with a simple structure, and the mode purity is usually not high. Methodologically, the OAM wave of a microstrip antenna is mostly achieved by synthesizing degenerate eigenmodes. In this paper, combined with eigenmode analysis, the construction of high-order and high-purity OAM mode microstrip antennas is carried out from the perspectives of radiating element, ground plane, and structural symmetry. For a regular hexagonal patch antenna of the 4th-order OAM mode, the mode purity is improved from about 40% to over 80% by removing the inner conductor of the patch layer, using a circular ground plane, and adding lug patches on the outside. This method of improving mode purity through the analysis of mode significance and characteristic current distribution also has guiding significance for the design of other high-order OAM mode patch antennas.

Decellularized fish swim bladder patch loaded with mesenchymal stem cells inhibits neointimal hyperplasia.

We previously showed decellularized fish swim bladder can be used as vascular patch and tube graft in rats, mesenchymal stem cells (MSCs) have showed the capability to inhibit neointimal hyperplasia in different animal models. We hypothesized that decellularized fish swim bladder patch loaded with MSCs (bioinspired patch) can inhibit neointimal hyperplasia in a rat aortic patch angioplasty model. Rat MSCs were grown in vitro and flow cytometry was used to confirm their quality. 3.6 × 105 MSCs were mixed into 100 μl of sodium alginate (SA)/hyaluronic acid (HA) hydrogel, two layers of fish swim bladders (5 mm × 5 mm) were sutured together, bioinspired patch was created by injection of hydrogel with MSCs into the space between two layers of fish swim bladder patches. Decellularized rat thoracic aorta patch was used as control. Patches were harvested at days 1 and 14 after implantation. Samples were examined by histology, immunohistochemistry, and immunofluorescence. The decellularized rat thoracic aorta patch and the fish swim bladder patch had a similar healing process after implantation. The bioinspired patch had a similar structure like native aorta. Bioinspired patch showed a decreased neointimal thickness (p=.0053), fewer macrophages infiltration (p=.0090), and lower proliferation rate (p=.0291) compared to the double layers fish swim bladder patch group. Decellularized fish swim bladder patch loaded with MSCs can inhibit neointimal hyperplasia effectively. Although this is a preliminary animal study, it may have a potential application in large animals or clinical research.

X-Band Nearfield Shielding Metasurface With Adjustable Reflection/Transmission Zeroes

We introduce, for the first time, a new class of flexible bandstop frequency selective surface that provides very stable nearfield (NF) characteristics in the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -band, unlike the traditional FSSs. The structure's building block uses two layers of patches to reach the NF stability through their interaction. Periodic convoluted square loops on one side of a flexible substrate and periodic square loops on the other side are used. The created multipole resonator operates by changing the local coupling effect between the cells on the sides. It enables a localization of capacitive and inductive characteristics, which provides spatial filtering for both near- and farfield. An accurate equivalent circuit model is developed to validate the coupling effect. It is shown that four operating modes could be defined for the structure, each of which provides specific behavior. A realization for each operational mode is also provided. An <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">X</i> -band NF shielding of at least 30 dB at the center frequency and maximum 10-dB fractional bandwidth of 32% are obtained. The superiority of the NF shielding performance is shown through comparisons among conventional shields. Finally, the measurement results justify the reliable NF shielding performance.

Investigations on Complementary Split Ring Resonator (CSRR) array integrated printed conformal band pass filters for modern wireless communication applications

This paper presents the performance analysis of two different conformal band pass filters (BPFs) loaded with an array of circular complementary split ring resonators (CSRRs). Type-1 bandpass filter has been designed by integrating a 9 × 9 array of circular complementary split ring resonator on the bottom layer of the filter. Similarly, Type-2 bandpass filter has been constructed by loading an array of 5 × 5 split ring resonator on the patch layer of the filter. A comparative study between Type-1 and Type-2 bandpass filters are also evaluated that shows dual pass bands for Type-1 filter and triple pass bands for the Type-2 bandpass filter. Furthermore, the conformality of both bandpass filters are judged through bending deformation analysis with various bending positions at 15°, 30°, 45°, 60° and 90°. During the bending performance analysis, the suggested BPFs retains the dual and triple pass band characteristics without any major deviations in its characteristic's parameters. Various performance parameters like return loss, insertion loss, group delay, bandwidth, and quality factor are measured. Detailed analysis of E and H field distributions and surface current distributions are also presented. The Type-2 bandpass filter shows better performance in terms of filter properties compared to Type-1 band pass filter. Hence, the prototype of Type-2 filter with an area of 30 × 30 mm2 is fabricated and measured. The validated results are agreed with the simulated results which confirms the applicability of the proposed filter for several modern wireless communication applications such as Wi-Max and personal communication systems (PCS) applications.

A Low Profile Circularly Polarized Beam Scanning Patch Array Fed by Parallel Plate Waveguide

A low-cost, low-profile circularly polarized beam scanning patch array is presented. The patch array is fed by the coupling slots of parallel plate waveguide (PPW), which is excited by a substrate integrated waveguide-based plane wave line source generator. By suggesting a new impedance match method, the coupling slots and truncated patch array are combined for circularly polarized radiation. The beam scanning capability is achieved by the variable inclination method. In the PPW guiding wave layer, a circular plate is cut and separated from the main body of the PPW to make it rotatable around its axis. By rotating the assembly of the circular plate and the above patch layer, the phase difference between the adjacent radiation elements could be controlled. Thus, the circularly polarized beam scanning is realized. A Ku-band prototype array is fabricated and measured to verify the design. The measured peak gain is 19.6 dBi and the scanning range is ±40°, in which range the gain variation is below 2.7 dB and the axial ratio is less than 2.8 dB.

A wide axial-ratio beamwidth circularly-polarized oval patch antenna with sunlight-shaped slots for gnss and wimax applications

This paper proposes a quadruple band stacked oval patch antenna with sunlight-shaped slots supporting L1/L2/L5 GNSS bands and the 2.3 Ghz WiMAX band. The antenna produces right-hand circular polarization waves with wide axial-ratio beamwidth of 223/216^{circ } and 231/203^{circ } at two orthogonal cutplanes at L5 and L2 GNSS bands, respectively. Firstly, the resonant modes TM_{110} and TM_{210} are excited inside a single layer oval patch antenna, where resonance frequencies are calculated using Mathieu functions. Meanwhile, it is shown that another version of the mode TM_{110} with similar distribution but orthogonal direction is excitable inside the same oval patch. Then, a second stacked oval patch layer is added, which splits the resonance frequency of each of the modes TM_{110} and TM_{210} into two different values. Depending on the probe feed position and the separation between the two layers, the phase shifts between modes versions in the upper and the lower layers change. Thus, by fine-tuning the probe feed position and the separation between layers, spatially-orthogonal with quadrature-phase-shift versions of the mode TM_{110} are obtained, producing a circularly polarized waves at L2 and L5 bands. Furthermore, sunlight shaped slots are etched into the upper and lower layer patches to fine tune the phase shifts between different modes versions, which enhances the overall axial-ratio beamwidth. Despite the simplicity of the overall structure and the feeding mechanism utilized in the proposed design, wide axial-ratio beamwidths are obtained, as compared to previous works. The proposed antenna shows low reflection coefficient values at 1.14–1.29 GHz (L2/L5), 1.45–1.6 GHz (L1), and 2.26–2.4 GHz (WiMAX). The antenna gains are 5.9, 5.6, 6, and 6.5 dBi/dBic at L5, L2, L1, and WiMAX bands, respectively. The half-power beamwidths are 99/96^{circ }, 102/96^{circ }, 112/85^{circ }, and 65/48^{circ } at two orthogonal cutplanes at L5, L2, L1, and WiMAX bands, respectively.

Direct Numerical Inversion Methods for the Design of Surface Wave-Based Metasurface Antennas: Fundamentals, Realizations, and Perspectives

A recent synthesis paradigm for tailoring the far-field radiation of leaky wave (LW) radiating metasurface (MTS) antennas is reviewed and experimentally validated. The considered antennas are realized with electrically small patches printed on a planar grounded dielectric slab. The patch layer is modeled as an impedance sheet whose spatial variation is initially designed to provide the desired LW effect from a prespecified surface wave (SW) excitation.

Magnetic properties in soft (CoFeB)/hard (Co) bilayers deposited under different Ar gas pressure

We have studied the effect of deposition pressure on the magnetization reversal, domains, anisotropy and Gilbert damping constant in the ferromagnetic (CoFeB and Co) single and bilayer samples. Hysteresis measured by magneto-optic Kerr microscopy for the single layer films prepared at higher deposition pressure indicate no change of loop shape i.e. isotropic behaviour. An enhancement of anisotropy has been observed in the bilayer samples than the single layer samples prepared at a particular deposition condition. However, increasing the deposition pressure to 50 sccm for the bilayer samples, anisotropy gets reduced. For single layer Co film deposited at 10 sccm exhibits branch and patch like domains for different angle between the easy axis and the external magnetic field. However, the Co film deposited at 50 sccm exhibits ripple like domains. In the case of single layer CoFeB, branch and patch like domains are observed deposited at 10 sccm. Patch like domains are found for the CoFeB films deposited at 50 sccm. Pinned labyrinth and ripple kind of magnetic domains along with the big branch domains are found in the bilayer samples. The pinned domains may be due to the interfacial exchange coupling. Similar values of damping constants have been observed for different thin films prepared at different deposition pressure.

X/Ku dual‐band single‐layer reflectarray antenna

AbstractIn this article, a single‐layer dual‐band reflectarray (RA) antenna is proposed. The RA antenna operates at two separated frequency bands with separate feeds. A low‐profile dual‐band unit cell I is designed with a 2 mm thickness without an air layer, which comprises only one dielectric substrate and two layers of metal patches. To achieve 360° phase shift ranges at two bands, unit cell II is presented based on the phase delay line theory. On the basis of proposed unit cells, a single‐layer circular RA (D = 150 mm) is designed, fabricated, and measured. The measured results show a measured peak gain of 20.7 dBi at 10.5 GHz and a 1 dB bandwidth of 17% (9.8–11.5 GHz). Besides, a measured peak gain of 23.6 dBi can be achieved at 15 GHz, and the 1 dB bandwidth is 13.3% (13.8–15.8 GHz) at Ku band.

Dual-polarized elliptic-H slot-coupled patch antenna for 5G applications

A dual-polarized, slot-coupled dielectric patch antenna design is presented in sub-6 GHz for 5G base stations. Proposed antenna is implemented using two dielectric patch layers (main patch and parasitic patch) above a feeding line layer. Excitation is realized by crossed elliptic-H slots in order to create orthogonal ± 45$^{\circ}$ polarizations. Through the use of patches at proper heights together with elliptic-H slots, significant improvement in impedance bandwidth, matching level, isolation and front-to-back ratio is acquired. Prototype antenna has an impedance bandwidth of 18.5\% (3.23--3.85 GHz) for $ S_{11} $, $ S_{22} $ $

A new nanoparticle heterostructure strategy with highly tunable morphology via sequential infiltration synthesis

In this study, sequential infiltration synthesis (SIS) is demonstrated as a novel method for preparation of NP heterostructures with fine morphology tunability via a model system of SiO2–ZnO NP heterostructures. This approach is highly differentiated from conventional atomic layer deposition performed on NPs in that precursors are infiltrated into a polymer matrix, serving as a unique pathway for precursor diffusion, allowing all-around decoration of the NP surface. This approach also offers additional degrees of freedom for controlling the morphology of NP surface decoration with key engineering parameters: (1) terminal functional groups of NPs and (2) functional groups of a polymer matrix. Rational choices for both parameters with the desired reactivity to SIS precursors guide preferred entrapment or chemisorption sites for the precursors, directing the final morphologies of NP surface-decorating materials from patch layers to discrete atomic clusters. With rapid expansion of the library of materials that SIS can grow, this method opens a new venue for versatile and scalable fabrication of NP heterostructures.