High-performance Filters Research Articles

Optimization of plasmonic nanofluid filters for spectral splitting photovoltaic/thermal systems

There remains a scarcity of studies on the utilization and optimization of core–shell plasmonic nanofluid filter although it shows potential in solar energy exploitation. To fill this research gap, this paper introduces an optimization methodology founded on merit function (MF) to optimize the Au@SiO2-based nanofluid filters for enhancing the photovoltaic/photothermal (PV/T) system performance. Initially, the MF model of the nanofluid filtered-PV/T system was constructed based on a reliable optical model and validated by referenced experimental results. Using these models, the effect of nanofluid parameters on the system performance and the mechanism of optimization procedure were investigated. Results indicated that modifying SiO2 shell thickness is a cost-effective means of tailoring the transmittance of the nanofluids compared to adjusting the Au core diameter. The optimization mechanism can be summarized as enhancing electrical efficiency or improving thermal efficiency to offset electricity losses. Furthermore, the MF of the Au@SiO2/EG nanofluid increased from 1.3737 to 1.3844 with optical thickness decreasing from 44 mm to 40 mm by mixing with Ag@SiO2 nanoparticles, indicating the cost-effectivity of blended nanofluid. The MF of the optimized blended nanofluids are 0.007–0.084 higher than those of the referenced nanofluids. This work offers a feasible pathway toward achieving high-performance nanofluid optical filters.

Modification Strategy for High-Performance Coalescing Filters with a Patterned Surface and Its Application to Cartridges

Modification Strategy for High-Performance Coalescing Filters with a Patterned Surface and Its Application to Cartridges

Correction: Wood-based cellulose nanofiber membrane: a novel approach to high-performance air filters

Correction: Wood-based cellulose nanofiber membrane: a novel approach to high-performance air filters

Energy-efficient architecture for high-performance FIR adaptive filter using hybridizing CSDTCSE-CRABRA based distributed arithmetic design: Noise removal application in IoT-based WSN

An energy-efficient architecture of high-performance FIR adaptive filter design using approximate distributed arithmetic (DA), which is integrated with canonic signed digit-based triangular common sub expression elimination (CSDTCSE) and carry-resist adder based Booth recorder adder (CRABRA) is proposed for noise removal in sensor nodes. Distributed arithmetic is coupled with two signed 32-bit, 16-bit radix-8 Booth algorithms and approximate computation under 2-bit adder to design FIR adaptive filter for decreasing partial products (PP) together with accumulation circuits. The truncation of LSB in the PP is presented to approximate the PP to reduce memory complexity and hardware overhead. An approximation recoding adder decreases the energy usage, area, and critical path. Approximate Wallace trees are applied to the PP accumulation to lessen the latency. The canonic signed digit-based triangular common sub-expressions elimination framework is proposed, which significantly reduces a count of logic operators and logic depth in implementing the FIR filter. The proposed algorithm is activated in Verilog coding and synthesized using Xilinx 14.5 ISE simulation software. The proposed design successfully reduces delay, area, and power by maintaining better accuracy with performance.

A technique for the passband and stopband control of wideband band-pass substrate integrated waveguide (SIW) filters designed with elliptic stepped impedances

In this paper, a design technique based on a stepped impedance synthesis is proposed for the first time for the passband and stopband control of band-pass filters in substrate integrated waveguide (SIW) technology. The structure of the band-pass filters is implemented by means of elliptic patterns etched on the top side of the SIW, which work as impedance inverters. The design method consists of previously mapping the height of the elliptic patterns and the phase shift (cut-off angle) of the SIW lines, connected to the input and output ports of the ellipses, as a function of the passband and stopband characteristics of various stepped impedance SIW filters, to then select the design parameters of the band-pass SIW filter that achieve the desired frequency response. This new approach is applied to the design of two fourth-order Chebyshev stepped impedance band-pass SIW filters with different passband and stopband characteristics. One of the band-pass SIW filters is characterized by a fractional bandwidth FBW1 = 14.5% and a spurious-free range SFR1 = 2.8 GHz, while the other filter has a FBW2 = 22.3% and a SFR2 = 1.55 GHz. Both band-pass filters were designed with a SIW TE10 mode cut-off frequency and a higher passband cut-off frequency fixed at fcTE10 = 2.85 GHz and fc,H = 3.9 GHz, respectively. Electromagnetic (EM) simulations showed that the lower passband cut-off frequency fc,L can vary with respect to fc(TE10) by 13.6% and that the first spurious frequency can appear higher than fc,H by 69.3%. The measurement results agreed well with the EM simulations, thus confirming that this method can be useful to design high-performance wideband Chebyshev stepped impedance band-pass SIW filters with a high degree of control on the passband and stopband characteristics.

High-performance plasmonic mid-infrared bandpass filters by inverse design.

Plasmonic spectral filters composed of periodic nanostructured metal films offer novel opportunities for the development of multispectral imaging technologies in the mid-infrared region. However, traditional plasmonic filters, which typically feature simplistic structures such as nanoholes or nanorings, are constrained by a narrow bandpass and significant crosstalk, leading to limited practical performance. Filters designed using inverse techniques allow a substantial degree of freedom in creating intricate structures that align with desired spectral characteristics, including a quasi-square spectral profile, high transmission, wide full width at half maximum, and reduced crosstalk. In this study, we have utilized an inverse design algorithm to engineer high-performance bandpass filters for the mid-infrared range, achieving an average transmittance exceeding 80% within the bandpass window and below 10% in the stop band, which is comparable to that of commercial multilayer Bragg filters. Nanofabrication processes were employed to transfer the designed pattern into the gold film on ZnS substrate that is transparent in the mid-infrared range. The resulting filters exhibit spectral performance analogous to that of the inversely designed models, making them suitable for direct integration with mid-infrared photodetector arrays in multispectral imaging systems.

Wood-based cellulose nanofiber membrane: a novel approach to high-performance air filters

Wood-based cellulose nanofiber membrane: a novel approach to high-performance air filters

Gelatin-reinforced cellulose nanofiber composite cryogels for effective separation of small particulate matter in air

Herein, novel composite aerosol filters solely comprising renewable materials were designed using gelatin as a reinforcement agent and aqueous tert-butyl alcohol (TBA) as a dispersing medium for the cellulose nanofiber skeleton. The prepared composite cryogels exhibited distinct spider-web-like crosslinked structures and nanoporous architectures with porosity exceeding 98.8 % and density of less than 0.018 g/cm3. These composite filters exhibited high filtration efficiency and a robust and flexible mechanical structure due to gelatin reinforcement; furthermore, their quality factor exceeded the target threshold of 0.01 Pa−1 for 300 nm particle size. The filtration performance and mechanical properties of the composite filters could be tailored by adjusting the cellulose nanofiber (CNF), gelatin, and TBA contents, enabling the preparation of cryogels with a firm and strong structure. This study introduces ultraporous solids based on nanocellulose (NC) cryogels, which are promising, novel, and green materials for the production of advanced high-performance filter media for aerosol separation. Furthermore, the aforementioned approach is promising for the preparation of mechanically robust nanoporous biomaterials suitable for diverse applications such as heat and thermal insulation.

Anchoring CoTiO3/TiO2 heterostructure on fiber network actuates flow-through Fenton-like oxidation: Electronic modulation and rapid pollutants degradation

Versatile catalytic oxidation filtration system, especially under low operating pressure conditions, is a frontier technology for organic wastewater purification. Herein, CoTiO3/TiO2 heterostructure was anchored on fiber network (CTO/TOF) to actuate flow-through peroxymonosulfate (PMS) based oxidation toward organics removal. The well-developed built-in electric field in CoTiO3/TiO2 heterostructure induced local charge redistribution, and promoted the targeted adsorption and activation of PMS, thereby facilitating the activation process. Meanwhile, the 3D network of CTO/TOF fully exposes active sites, providing an ideal platform for mass transfer and surface reactions. Above 91% for nimesulide degradation was maintained after 24 h of catalytic permeation under high permeate flux (300.7 L/m2·h), corresponding to ultrafast retention time (4.9 s). Practical application experiments demonstrated that CTO/TOF+PMS system had strong anti-interference capability under diverse conditions. Synergy of radical-nonradical mixed pathways for pollutant removal was verified by electron paramagnetic resonance spectra, quenching tests, and electrochemical measurements. The degradation intermediates and possible degradation pathways of nimesulide were also proposed. The toxicity assessments confirmed decreased toxicity of degradation products. This study is dedicated to designing high-performance filters and broadening Fenton-like oxidation in environmental remediation.

Polyvinylidene fluoride/graphene oxide/polyimide composite high-efficiency PM2.5 filtration nanofiber membranes.

Particulate air pollution is a global environmental problem, with PM2.5 being the primary pollutant. One of the most effective ways to remove particles from the air is through filtration. Therefore, high-performance air filters are urgently needed to combat the harm caused by PM2.5. This study uses an electrospinning technique to prepare high-efficiency polyvinylidene fluoride/graphene oxide/polyimide nanofiber membranes. These composite nanofiber membranes demonstrate high filtration efficiency (99.6%), low pressure drop (123 Pa), remarkable thermal stability (450 °C), and excellent mechanical strength (7 MPa). Considering the advantages, these highly efficient nanofiber membranes can find advanced applications in industrial and civil infrastructures.

High-performance molecular spin filters based on a square-planar four-coordinate Fe complex and covalent pyrazine anchoring groups

We propose a promising method to generate highly spin-polarized currents by connecting a magnetic molecule to carbon electrodes with appropriate anchors, whose HOMOs and LUMOs have distinct features of spatial distribution for the two spin types.

Air-Permeable Building Envelopes for Building Ventilation and Heat Recovery: Research Progress and Future Perspectives

Air-permeable building envelopes (APBEs) utilize the infiltrated or exfiltrated airflow within porous materials to directly change their temperature distribution to reduce heat loss/gain. APBEs effectively integrate building ventilation and heat recovery to achieve excellent thermal insulation while improving indoor air quality. This paper presents a comprehensive review of the fundamentals and classifications, historical evolution over time, opportunities and benefits, and future views on APBEs. It can be treated as a responsive building envelope that enables building envelopes to dynamically change the U-values by varying the infiltrated or exfiltrated airflow rate within a porous material. Previous studies have indicated that the U-value of 0.1 W/(m2·K) can be realized by employing APBEs. Moreover, some research demonstrates that APBEs could act as high-performance air filters that reduce over 90% of particulate matter within fresh, ventilated air. Some factors, such as airflow rate, thickness, and thermal conductivity of porous materials, have a significant influence on the effectiveness of APBEs. For practical applications, integrating the APBE with passive building ventilation can help reduce the initial cost and facilitate decarbonization in buildings. Moreover, advanced control strategies could collaboratively optimize the operation of ABPEs and build energy systems to maximize their energy-saving potential.

A new design of a digital filter for an efficient field programmable gate array using quantum dot technology

Digital filtering algorithms are most frequently used to implement generic-based Field-programmable gate arrays (FPGAs) chips, which are used for higher sampling rates. In the filtering structure, delay and occupied areas play a vital role. Since the existing structures suffered from shortcomings such as high delay and high occupied area, implementing a high-performance digital filter circuit with high speed and low occupied area based on unique technology can significantly improve the performance of whole FPGA structures. One of the best technologies to implement this vital structure to solve these shortcomings is quantum-dot cellular automata (QCA) technology. This paper presents several new efficient full adders for digital filter applications based on quantum technology, including a multiplier, AND gate, and accumulator. The QCADesigner 2.0.3 tool is used to create and validate the suggested designs. According to the results, all designed circuits have simple structures with few quantum cells, low area, and low latency.

Inverse-designed metasurfaces for highly saturated transmissive colors

Advances in augmented reality and virtual reality platforms have sparked interest in high-performance metasurface color filters with elevated resolution, saturation, and durability. However, the predominant use of either dielectrics or metals prevents the realization of efficient “transmissive” color filters for displays. Here, we propose a novel, to our knowledge, approach combining dielectric and metallic components, optimizing complex structures using inverse design with height restrictions on the layers of red, green, and blue. The optimized structure achieved full coverage of the sRGB color space and surpassed 70% efficiency. Experimental validation demonstrated the potential of the inverse design for enhancing the performance of complex structures.

Upscaling of Electrospinning Technology and the Application of Functionalized PVDF-HFP@TiO2 Electrospun Nanofibers for the Rapid Photocatalytic Deactivation of Bacteria on Advanced Face Masks.

In recent years, Electrospinning (ES) has been revealed to be a straightforward and innovative approach to manufacture functionalized nanofiber-based membranes with high filtering performance against fine Particulate Matter (PM) and proper bioactive properties. These qualities are useful for tackling current issues from bacterial contamination on Personal Protective Equipment (PPE) surfaces to the reusability of both disposable single-use face masks and respirator filters. Despite the fact that the conventional ES process can be upscaled to promote a high-rate nanofiber production, the number of research works on the design of hybrid materials embedded in electrospun membranes for face mask application is still low and has mainly been carried out at the laboratory scale. In this work, a multi-needle ES was employed in a continuous processing for the manufacturing of both pristine Poly (Vinylidene Fluoride-co-Hexafluoropropylene) (PVDF-HFP) nanofibers and functionalized membrane ones embedded with TiO2 Nanoparticles (NPs) (PVDF-HFP@TiO2). The nanofibers were collected on Polyethylene Terephthalate (PET) nonwoven spunbond fabric and characterized by using Scanning Electron Microscopy and Energy Dispersive X-ray (SEM-EDX), Raman spectroscopy, and Atomic Force Microscopy (AFM) analysis. The photocatalytic study performed on the electrospun membranes proved that the PVDF-HFP@TiO2 nanofibers provide a significant antibacterial activity for both Staphylococcus aureus (~94%) and Pseudomonas aeruginosa (~85%), after only 5 min of exposure to a UV-A light source. In addition, the PVDF-HFP@TiO2 nanofibers exhibit high filtration efficiency against submicron particles (~99%) and a low pressure drop (~3 mbar), in accordance with the standard required for Filtering Face Piece masks (FFPs). Therefore, these results aim to provide a real perspective on producing electrospun polymer-based nanotextiles with self-sterilizing properties for the implementation of advanced face masks on a large scale.

Fabrication of a superhydrophobic-superoleophilic particle material for oil-water separation and oil extraction

Oil-water separation has become a serious issue due to the increasing oily wastewater discharged in the environment and oil spills from time to time. Superhydrophobic and superoleophilic materials are a promising approach in oil-water separation. However, the preparation procedures for these materials are often complex and expensive, and their stability is not robust enough. In this study, superhydrophobic and superoleophilic particles are successfully prepared via a facile and green mixing method. Fluorocarbon resin, CaCO3 and SiO2 are coated on fly-ash cenospheres to form a stable superhydrophobic-superoleophilic surface, which exhibits a water and oil contact angle of 153.3° and 0°, respectively. To our knowledge, we’re unaware of any previous study reporting a superhydrophobic-superoleophilic material prepared in such a convenient way. The as-prepared superhydrophobic material can serve as high-performance filters for separating various oil-water mixtures, with a separation efficiency up to 99.2%. And it can be applied in water-in-oil emulsion separation. Meanwhile, the as-prepared particles are able to extract oils from oil-water mixtures and the oil-extraction capacity is up to 0.56 g/g. Furthermore, the obtained material has a robust stability against various hash conditions and a good recyclability. The simply-prepared superhydrophobic cenospheres are expected to be a promising candidate for application in diverse oil-water separation situations.

Antifouling treatment enables membranes to deal with oil and grease

PPG Industries Inc, which supplies paints, coatings and speciality materials, has developed and introduced a high-performance ultrafiltration (UF) membrane and filter elements that help to improve the reuse of industrial process water.

Self-configuring programmable silicon photonic filter for integrated microwave photonic processors

Reconfigurable photonic filters show great promise as a potential solution to meet the evolving needs of future microwave communication systems. By integrating high-performance filters into programmable microwave photonic processors, they can provide significant benefits for signal processing applications. The development of an algorithm that can automatically characterize and reconfigure the filter using a single optical input and output port is essential for this purpose. This paper presents an optimization technique for a fully tunable ring-assisted Mach–Zehnder interferometer filter. The proposed filter design eliminates the need for monitoring components and employs a novel algorithm that operates independently in each ring by switching between the two arms of the filter. In addition, the filter can be configured to implement different filter architectures, allowing for flexible filtering requirements. Measurements were performed using the device as an interleaver, implementing different types of infinite impulse response filters in the optical and radio frequency domains. Side-coupled integrated spaced sequence of resonator filters were also implemented by reconfiguring the same device. These results demonstrate the exceptional reconfigurability of the filter design proposed herein in terms of bandwidth and central frequency.

Sustainable approach to oil recovery from oil spills through superhydrophobic jute fabric

Ecosystems suffer from increased oil exploitation and frequent oil spills, which calls for effective, environment-friendly, and economically viable solutions. To address this, abandoned gunny sacks as the concerned jute fabric were superhydrophobically (water contact angle ∼159°) modified, incorporating titanium dioxide (TiO2) nanoparticles and hexadecyltrimethoxysilane (HDTMS), rendering a facile drop casting procedure. The modified superhydrophobic-superoleophilic jute fabric has been identified as a high-performance filter with superior reusability that can separate oil-water mixtures in challenging environmental conditions (including potent acidic, alkaline, highly saline, aqueous, frigid, and blistering water environments) while maintaining high separation efficiency. In continuation, static conditions indulging a batch and continuous oil separation performance and dynamic conditions stimulating turbulence in the oil-water mixture were proficiently carried out, mimicking real-world circumstances. As a result, the modified jute fabric has the advantages of high separation efficiency, stable recyclable properties, and outstanding durability, highlighting its enormous potential for use in practical applications.

Dual UWB bandpass filter with highly band-to-band rejection using stepped impedance stub-loaded resonators for WBAN health-care applications

Abstract With the rapid development of communication technology, the researches of multi-band filtering circuits have become more and more important. Multimode resonator (MMR) is one of the vital methods to provide multi-resonant modes within a single design. In this paper, a dual-band ultra-wideband bandpass filter (UWB-BPF) using stepped impedance stub-loaded resonators (SI-SLR) is presented. The main advantage of using SI-SLR is to have better performance with multimode behavior and more parameters to control resonant modes. SI-SLR combines the advantages of SIR and SLR structures, which gives a compact, high-performance multiband filter. The proposed filter design has compact size, sharp and flat response with low insertion loss (IL), low return loss (RL), and high band-to-band rejection. The filter is designed for UWB communication in wireless body area networks and fabricated on Arlon substrate with relative permittivity ${\varepsilon_{\textrm{r}}} = 3.25$ , thickness $0.8\;{\textrm{mm}}$ . The resulted dual-bands are centered at $4{\textrm{ GHz}}$ and $8.3{\textrm{ GHz}}$ with fractional bandwidths $37{\textrm{% }}$ and $48{\textrm{%}}$ . The simulation was carried out using CST Microwave Studio. The filter provides good passband performances, with IL 0.49 dB and 0.31 dB at the center frequency of lower and higher bands, respectively. The band-to-band 40 dB rejection is realized by adding circular spiral at the input/output of the filter.