Low-cost Fabrication Research Articles

N self-doping hierarchical porous biochar from Chinese medicine residues for efficient removal of malachite green: Critical contribution of N doping to π-π electron donor-donor interactions

N self-doping hierarchical porous biochars are prepared from three kinds of Chinese medicine residues (Lophatherum Gracile (LG), Licorice Radix (LR) and Radix Isatidis (RI)) using KHCO3 as a foaming agent. Among them, LGC shows the best adsorption performance with a maximum adsorption capacity of 3791.5 mg g−1 at 298 K for malachite green (MG). Significant differences of the biochar adsorption behavior are found and the main reason are attributed to differences in sp2 conjugated carbon (ID/IG = 1.46–1.50) and heteroatomic nitrogen (pyridinic-N, pyrrolic-N and graphitic-N) doping. The quasi-secondary kinetic and Langmuir isothermal models are more suitable for describing the adsorption process of biochar towards MG. Further characterization and density functional theory (DFT) calculations showed that the good adsorption of MG by biochar increased with increasing specific surface area (SSA) and pyrrolic-N content. Pore filling effect and π-π electron donor-acceptor (EDA) interactions have been demonstrated to be the predominant driving force of adsorption. Among them, pyridinic-N and graphitic-N further enhance the adsorption performance through the π-π stacking and π-π EDA interactions between MG and biochar, respectively. Pyrrolic-N and other surface functional groups (-COOH, -OH) promote the hydrogen bonding effect. In addition, the good recycling efficiency (close to 70 % after four cycles), excellent multifunctionality and low fabrication cost (13.01 US$ kg−1) of the LGC reveal the potential for practical applications. In addition, all biochar has a wide range of pH suitability (pH = 2.0–10.0). This study provides new ideas for the rapid removal of MG using biochar. In addition, the effects of N self-doping and microscopic N species on the adsorption of biochar provide theoretical guidance for enhancing the adsorption of other macromolecular dyes.

Comparative study of laser-induced graphene fabricated in atmospheric and interface-confined environments

Laser-induced graphene (LIG) has found widespread applications in various carbon-based electronics, such as sensors, optoelectronics, and energy storage devices, due to its low cost, high efficiency, and large-scale fabrication potential. Here, two laser-induced carbonization techniques are investigated in terms of structural integrity (uniformity and densification) and electrical property by a combined experimental and theoretical approach; these techniques, namely interface and surface ablation, operate in confined and ambient environments, respectively. The property of LIG for each laser-induced carbonization technique is systematically studied using optical and electrical characterization methods. The results show that the naturally confined and oxygen-free environment of interface ablation can fabricate more compact and intact LIG than surface ablation in an open and oxygen environment, thus enabling a 7.6 times reduction of the square/sheet resistance. The underlying mechanism for these improved properties is the compressive thermal stress and higher carbonization efficiency of interface ablation. The better structural integrity and electrical property of interface-ablated graphene enable a four-fold improvement in the specific areal capacitance of supercapacitors. These findings present that interface ablation is a more effective and facile method to enable the scalable preparation of intact and highly conductive LIG for its potential use in high-performance carbon-based electronics.

Utilization of recycled materials for low-cost MXene synthesis and fabrication of graphite/MXene composite for enhanced water desalination performance

Access to clean and safe drinking water is essential to human health, economic progress, and ecological stability. Advanced materials have emerged to advance water treatment processes, particularly desalination, but are associated with the major challenge of being fabricated through environmentally taxing mining processes, which contributes to the carbon footprint. This study explores an innovative approach of using a renewable carbon-rich material derived from waste to create MXene nanocomposites that are applied to improve water thermal desalination. The synthesis of MXenes from recycled materials involves a series of chemical and exfoliation procedures, resulting in the production of two-dimensional nanosheets with exceptional electrical and mechanical properties. The integration of biomass offers a sustainable alternative to traditional precursors used for MXene preparation and introduces unique functional groups onto the MXene surface, which enhances its ability to absorb substances. This nanocomposite successfully produced solar evaporation rates of up to 3.0 kg m−2h−1 with 96.03 % solar steam conversion efficiency under single solar irradiation (1 sun). Through extensive characterization of SEM, FESEM, EDX, XRD, BET, contact angle, and performance assessments of desalination and water quality by ICP-OES, this study sheds light on the underlying mechanisms driving the improved water desalination capabilities of MXene composites. The composite materials show great mechanical properties, thermal stability, and chemical stability against acidic, alkali, and concentrated salty conditions. Mechanical robustness is the key advantage of this work. The findings underscore the importance of sustainable material utilization and highlight the potential of MXene composites as next-generation solutions for energy-efficient and environmentally friendly water desalination technologies.

Simulation of perovskite solar cell with transparent contacts for solar windows

In recent years, halide-based perovskite solar cells (PSC) have caught worldwide attention since their power conversion efficiency (PCE) has surpassed 25% with low fabrication cost and high scalability. The semi-transparent PSC (ST-PSC) is suitable for building-integrated photovoltaic (BIPV) applications, especially for solar windows. The ST-PSC must demonstrate a reasonable balance between PCE and transparency in the visible region for solar windows, which is inversely proportional to each other. This work studies ST-PSC based on methylammonium lead triiodide (MAPbI3) as solar windows using the General-Purpose Photovoltaic Device Model (GPVDM) and OPAL 2 as the simulation platforms. Parameters such as methylammonium lead triiodide (MAPbI3) thickness, silver (Ag) contact thickness and indium tin oxide (ITO) transparent contact thickness are investigated in relation to the PCE and average visible transmission (AVT). The results demonstrate that the ST-PSC with MAPbI3 thickness of 500 nm and ITO bottom transparent contact of 100 nm leads to PCE of 22.85% and AVT of 11.36%. These parameters represent the best results obtained in this work.

Investigation of structural, electronic, and optical properties of halide perovskites with different amide cations: A first-principles approach

Hybrid halide perovskites (CH3NH3PbI3) have emerged as an appealing candidate in photovoltaic devices due to their low-cost fabrication and remarkable optical and electronic properties. However, the commercial applications of these perovskites are limited by their instability due to the rapid rotation and orientation of methylammonium cation (CH3NH3+), and interaction with PbI2 lattice at high temperatures. Since CH3NH3+ can deteriorate structural stability of MAPbI3 perovskites, it is possible to use molecular cation design and substitution as a mechanism to enhance the stability and remove this limitation. We here investigate the effect of replacing this cation with other organic cations (HCOHNH2PbI3 (FPbI3), CH3COHNH2PbI3 (AcPbI3), and NH2COHNH2PbI3 (UPbI3)) in order to enhance the performance of the perovskites, while also keeping the band gap energy (Eg) in an appropriate range for solar cell applications. The calculations are performed using the full potential linearized augmented plane wave method, providing lattice parameters and the formation energy of the proposed perovskites. Our results indicate that AcPbI3 perovskite outperforms the other structures in terms of various optical parameters, such as the absorption coefficient, optical conductivity, and reflectance. The optical and electronic band gaps of the AcPbI3 structure and its resonance form (Ac'PbI3) are found to be in agreement with each other, proposing them as optically tunable hybrid perovskites in emerging solar cells.

Electronic modification of NaCrO2 via Ni2+ substitution as efficient cathode for sodium-ion batteries

The feature of high theoretical capacity, long thermal stability, and low-cost fabrication offers the layered transition metal oxide NaCrO2 as an excellent candidate for sodium-ion batteries. Here, we show an effective method for electronic modulation of NaCrO2 by partial substitution of Cr3+ with low-valent Ni2+ to produce NaCr0.95Ni0.05O2 as an efficient cathode for these batteries. We found that Ni2+ substitution plays a critical role in the ionic character of transition metal-oxygen bonds, which increases the interlayer separation and thus improves sodium-ion diffusion kinetics. Furthermore, Ni2+ substitution reduces the deterioration of NaCrO2 throughout charge-discharge processes and thus boosts the cycle performance of the materials. The resultant NaCr0.95Ni0.05O2 cathode displays a remarkable rate performance with specific capacities of 91.2 mAh g-1 at 50 C and a high retention (~80%) of the initial capacity after cycling for 1,000 cycles at 10 C.

Installing new additional blades arrangement for improving Savonius rotor performance

Savonius rotor is a vertical axis wind rotor that has a good attention due to its lower fabrication cost and receives air from any direction. In the present computational work, various arrangements will be introduced for the blades of Savonius rotor with the aim of improving the performance. Two-dimensional simulations are performed using ANSYS with the presence of the SST k-ω as a suitable turbulence model to analyze the flow around the rotor. The computational results include 12 different arrangements namely rotor 1 to rotor 12. The difference between all the studied rotors is the arrangement of an additional shape to the original blade of Savonius rotor. The addition of a flipper with a radius of curvature equivalent to 1.73 of the radius of the blade generates the best performance with an improvement of 38.5% in the power coefficient compared to the traditional rotor. The best design (known as case 1) has a pair of blades with a distance of 15% of the blade radius, which improves the performance by 28.3% compared to the traditional rotor.

Effect of silicon carbide content on microstructure, physical and mechanical properties in vat photopolymerization of alumina

AbstractVat photopolymerization (VPP) printing of ceramic parts offers advantages such as low cost, simple operation, and short fabrication cycles. However, drawbacks include low toughness and brittleness in the printed parts. This study explores enhancing the toughness and strength of alumina (Al2O3) ceramics by incorporating silicon carbide (SiC) particles as additives. The impact of varying SiC contents on the quality of VPP‐printed Al2O3 parts is examined, encompassing microstructure, physical properties, and mechanical properties. Results indicate that optimal SiC addition reduces Al2O3 ceramics' porosity, enhances crystalline quality, and boosts mechanical properties. Excessive SiC, however, diminishes these benefits. The most significant strengthening of Al2O3 parts occurred with a 1.5 wt.% SiC content, increasing bending strength and fracture toughness by 239.7% and 564.7%, respectively. This underscore SiC's positive role in enhancing the quality of VPP‐printed Al2O3 parts.

A library of 2D electronic material inks synthesized by liquid-metal-assisted intercalation of crystal powders

Solution-processable 2D semiconductor inks based on electrochemical molecular intercalation and exfoliation of bulk layered crystals using organic cations has offered an alternative pathway to low-cost fabrication of large-area flexible and wearable electronic devices. However, the growth of large-piece bulk crystals as starting material relies on costly and prolonged high-temperature process, representing a critical roadblock towards practical and large-scale applications. Here we report a general liquid-metal-assisted approach that enables the electrochemical molecular intercalation of low-cost and readily available crystal powders. The resulted solution-processable MoS2 nanosheets are of comparable quality to those exfoliated from bulk crystals. Furthermore, this method can create a rich library of functional 2D electronic inks ( >50 types), including 2D wide-bandgap semiconductors of low electrical conductivity. Lastly, we demonstrated the all-solution-processable integration of 2D semiconductors with 2D conductors and 2D dielectrics for the fabrication of large-area thin-film transistors and memristors at a greatly reduced cost.

Synergism in Binary Nanocrystals Enables Top-Illuminated HgTe Colloidal Quantum Dot Short-Wave Infrared Imager.

Thanks to their tunable infrared absorption, solution processability, and low fabrication costs, HgTe colloidal quantum dots (CQDs) are promising for optoelectronic devices. Despite advancements in device design, their potential for imaging applications remains underexplored. For integration with Si-based readout integrated circuits (ROICs), top illumination is necessary for simultaneous light absorption and signal acquisition. However, most high-performing traditional HgTe CQD photodiodes are p-on-n stack and bottom-illuminated. Herein, we report top-illuminated inverted n-on-p HgTe CQD photodiodes using a robust p-type CQD layer and a thermally evaporated Bi2S3 electron transport layer. The p-type CQD solid is achieved by exploring the synergism in binary HgTe and Ag2Te CQDs. These photodetectors show a room-temperature detectivity of 3.4 × 1011 jones and an EQE of ∼44% at ∼1.7 μm wavelength, comparable to the p-on-n HgTe CQD photodiodes. A top-illuminated HgTe CQD short-wave infrared imager (640 × 512 pixels) was fabricated, demonstrating successful infrared imaging.

High sensitivity metasurface sensor for estimating the complex permittivity of ionic liquids

In this paper, a sensor based on a metasurface structure for the complex permittivity of ionic liquids is designed. The structure consists of an F4B substrate with a metal resonance pattern, and a polystyrene foam box is used to contain the ionic liquids to achieve non-contact measurements. The simulation results show that without the presence of the ionic liquids, the sensor can achieve a significant reflection spectrum depth of −37 dB at 11.2 GHz, after adding the ionic liquids, the sensor can generate different responses depending on the types of ionic liquids in the frequency range of 8–9.3 GHz. Furthermore, by employing a characteristic matrix model inversion based on the relationships between the complex permittivity, resonance frequency, and quality factor variations, the standard deviations of the real and imaginary parts of the complex permittivity for seven ionic liquids are estimated to be 0.18 and 0.3, respectively. The estimated results show a good agreement with the standard values obtained from probe measurements. The sensor designed in this paper features a small size, simple structure, and low fabrication cost. With a volume of 0.216 milliliters of the sample, it achieves a high sensitivity of 462.87 MHz/ԑ′and frequency detection resolution of 391.57 MHz/ԑ′. It demonstrates excellent discriminatory detection capability for ionic liquids, providing a new direction for the application research of metasurfaces.

Low-cost and sustainable fabrication of waste rubber derived porous carbon for o-nitrophenol removal with high practical application potential: A waste salt-free and recyclable template strategy

The large-scale utilization of nitrophenols and the rapid replacement of rubber products have led to an explosive increase in emissions and waste. Herein, we report a low-cost, sustainable, recyclable nano ZnO-templating synthesis strategy to fabricate porous carbon materials derived from waste rubber. Zinc acetate, employed as the template precursor, can be readily removed and recycled through acetic acid leaching, thereby mitigating production expenses and circumventing the generation of saline wastewater throughout the synthetic procedure. The porous carbons fabricated possess tunable textural characteristics, as well as in-situ doping of oxygen-containing species. The sample of WRPC-1.25 owning high specific surface area of 1088.68 m2/g and volume of 2.58 cm3/g exhibits remarkable adsorption capacity of 393.42 mg/g for ONP in batch and of 300.2 mg/g in fixed bed continuous flow adsorption test. Additionally, the WRPC-1.25 demonstrates excellent practical application potential for ONP removal both in the continuous dynamic adsorption-regeneration cycles and environmental test. Based on material characterization, adsorption evaluation tests and theoretical calculations, the synergistic adsorption mechanism of ONP on carbon surfaces, governed by pore filling, dispersion effects, and strong electrostatic attraction originating from oxygen functional groups, was elucidated.

Li2O addition as a means of achieving low-temperature densification of SiC ceramic

In order to achieve low-temperature densification of SiC ceramic, β-SiC nanopowder was doped with Li2O together with Y2O3–Al2O3–MgO as sintering aids, and then spark plasma sintered at temperatures ranging from 1450 °C to 1600 °C for 30 min under 30 MPa pressure in argon. The densities, microstructures and mechanical properties of SiC ceramics were systematically investigated, in comparison to the counterparts sintered with Y2O3–Al2O3–MgO additives. Since Li2O has a low melting point, Li2O addition effectively decreased the formation temperature of liquid secondary phase, enabling SiC ceramics to obtain higher density and lower porosity after low-temperature sintering (T ≤ 1550 °C). Besides, Li2O addition was found to decrease the viscosity of liquid phase and enhance grain growth of SiC through dissolution-reprecipitation process. When sintered at 1550 °C, Li2O addition led to a remarkable increase of density from 3.03 g/cm3 to 3.21 g/cm3 for SiC ceramic. Meanwhile, the SiC ceramic with Li2O addition exhibited a high Vickers hardness of 22.75 ± 0.35 GPa and a good fracture toughness of 3.83 ± 0.27 MPa m1/2. The research results are expected to benefit the low-cost fabrication of SiC ceramics based on pressure-assisted sintering and alleviate the thermal damage of SiC fiber in hot-pressed SiCf/SiC composites.

Compatibility and performance study of electrohydrodynamic printing using zinc oxide inkjet ink

The demand for modern electronics and semiconductors has increased throughout the years, which has enabled the innovation and exploration of solution-processed deposition. Solution-based processes have gained a lot of interest due to the low-cost fabrication and the large fabrication areas without the need for high-vacuum equipment. In this study, we utilized the ZnO ink for inkjet printer ink to fabricate a thin film via Electrohydrodynamic printing. Three different ink solutions were prepared for experimentation. The EHD printing technique demonstrated the ink’s compatibility with and without the modifications. The outcomes of the EHD printed materials were comparable with the spin-coated thin films. The EHD-printed films demonstrated better results in comparison to spin-coated films. Ra and Rq of the EHD film measured at 3.651 nm and 4.973 nm, respectively. It improved the absorbance up to two-fold at 360 nm wavelength and electrical conductivity up to 40% compared to the spin-coated films. Furthermore, the optimization of the printing parameters can lead to the improved morphology and thickness of the EHD thin films.

Polarization splitter-rotator on thin film lithium niobate based on multimode interference.

Polarization splitter-rotators (PSRs) are the key elements to realize on-chip polarization manipulation. Current PSRs on thin film lithium niobate (TFLN) rely on sub-micron gaps to realize mode separation, which increases the difficulties of lithography and etching. In this paper, a PSR on TFLN based on multimode interference (MMI) is demonstrated. Mode division is achieved by an MMI-based mode demultiplexer. The minimum feature size of the PSR is 1.5 µm, which can be fabricated with low-priced i-line contact aligners. Experimental results show a polarization extinction ratio (PER) > 16 dB and an insertion loss (IL) < 1.0 dB are achieved in a wavelength range of 1530-1578 nm for TE-polarized light. And a PER > 10.0 dB and an IL <2.1 dB are achieved in a wavelength range of 1530-1569 nm for TM-polarized light. This PSR could find application in the low-cost fabrication of dual-polarization TFLN-integrated photonic devices.

Comprehensive investigation of material properties and operational parameters for enhancing performance and stability of FASnI3-based perovskite solar cells

Recent advancements in the efficiency of lead-based halide perovskite solar cells (PSCs), exceeding 25%, have raised concerns about their toxicity and suitability for mass commercialization. As a result, tin-based PSCs have emerged as attractive alternatives. Among diverse types of tin-based PSCs, organic–inorganic metal halide materials, particularly FASnI3 stands out for high efficiency, remarkable stability, low-cost, and straightforward solution-based fabrication process. In this work, we modelled the performance of FASnI3 PSCs with four different hole transporting materials (Spiro-OMeTAD, Cu2O, CuI, and CuSCN) using SCAPS-1D program. Compared to the initial structure of Ag/Spiro-OMeTAD/FASnI3/TiO2/FTO, analysis on current–voltage and quantum efficiency characteristics identified Cu2O as an ideal hole transport material. Optimizing device output involved exploring the thickness of the FASnI3 layer, defect density states, light reflection/transmission at the back and front metal contacts, effects of metal work function, and operational temperature. Maximum performance and high stability have been achieved, where an open-circuit voltage of 1.16 V, and a high short-circuit current density of 31.70 mA/cm2 were obtained. Further study on charge carriers capture cross-section demonstrated a PCE of 32.47% and FF of 88.53% at a selected capture cross-section of electrons and holes of 1022 cm2. This work aims to guide researchers for building and manufacturing perovskite solar cells that are more stable with moderate thickness, more effective, and economically feasible.

Machine learning driven performance enhancement of perovskite solar cells with CNT as both hole transport layer and back contact

We propose a machine learning-based approach to enhance the performance of perovskite solar cells (PSCs) using carbon nanotubes as both hole transport layer (HTL) and back contact. Carbon-based PSCs offer low fabrication costs, long-term mechanical stability, high charge transport, and broad wavelength transparency. Our study estimates and enhances power conversion efficiency (PCE) of carbon-based PSCs through machine learning. PSC with single-walled carbon nanotube (SWCNT)-based HTL and back contact is investigated in simulations using SCAPS-1D and achieved 14.24% PCE, closely aligning with experimental data. Additionally, we explore the impact of various easily tunable fabrication parameters, such as the band gap and electron affinity of SWCNT in HTL, HTL thickness, active layer thickness, electron transport layer (ETL) thickness, HTL dopant concentration, absorber defect density, and ETL dopant concentration, on PCE. We generate a dataset of 20,480 samples to train classical and neural network-based machine learning models to predict performance parameters of PSCs, including short-circuit current density (JSC), open-circuit voltage (VOC), fill factor (FF), and PCE (η). The current density vs. voltage (J-V) characteristics curve is well-fitted by the predicted JSC, VOC, and FF, as evidenced by an average root mean squared error (RMSE) of 0.03 and a goodness of fit (R2) value of 0.99. The fully connected artificial neural network performs best, with RMSE of 0.05% and R2 of 0.99998 for predicting PCE. Genetic algorithm is used to optimize PCE, yielding a maximum PCE of 20.92%. Furthermore, an analysis of feature dimension and dataset size on prediction performance guides future modeling approaches.

Integration of acoustic micromixing with cyclic olefin copolymer microfluidics for enhanced lab-on-a-chip applications in nanoscale liposome synthesis

The integration of acoustic wave micromixing with microfluidic systems holds great potential for applications in biomedicine and lab-on-a-chip technologies. Polymers such as cyclic olefin copolymer (COC) are increasingly utilized in microfluidic applications due to its unique properties, low cost, and versatile fabrication methods, and incorporating them into acoustofluidics significantly expands their potential applications. In this work, for the first time, we demonstrated the integration of polymer microfluidics with acoustic micromixing utilizing oscillating sharp edge structures to homogenize flowing fluids. The sharp edge mixing platform was entirely composed of COC fabricated in a COC-hydrocarbon solvent swelling based microfabrication process. As an electrical signal is applied to a piezoelectric transducer bonded to the micromixer, the sharp edges start to oscillate generating vortices at its tip, mixing the fluids. A 2D numerical model was implemented to determine the optimum microchannel dimensions for experimental mixing assessment. The system was shown to successfully mix fluids at flow rates up to 150 µl h−1 and has a modest effect even at the highest tested flow rate of 600 µl h−1. The utility of the fabricated sharp edge micromixer was demonstrated by the synthesis of nanoscale liposomes.

Two-step preparation of methylammonium lead triiodide perovskite film via electrospray deposition of methylammonium iodide solution for solar cell applications

Solution-processable perovskite solar cells (PSCs) have the potential to revolutionize solar cell technology by enabling low power generation costs via low-cost device fabrication. However, most existing research regarding PSCs relies on the spin-coating method, which is not conducive to large-area film deposition. Therefore, the development of an alternative deposition method for perovskite films has become increasingly important for commercialization, for which electrospray deposition is a promising technique. This study investigates the two-step preparation of methylammonium lead triiodide (MAPbI3) perovskite films via the electrospray deposition of a methylammonium iodide (MAI) solution on a spin-coated PbI2 film. The gradual conversion of PbI2 to MAPbI3 with increasing MAI deposition time was revealed, accompanied by an increase in the size of the perovskite crystals. In addition, PSCs were successfully fabricated by electrospraying MAI, achieving a considerable power conversion efficiency of 7.86 % at the optimal MAI deposition time.

Rapid and versatile, micro-patterning and functionalization of complex structures on ultra-thin and flexible polymeric substrates

Microscale patterning on flexible substrates is important in many applications such as in wearable sensors and microfluidics-based diagnostics, therefore low-cost fabrication methods which are scalable and amenable to mass production have attracted the interest of many companies and research groups. Dry film resists (DFRs) are commercially available materials with properties compatible with their implementation on flexible substrates to cover a wide range of applications, which also offer environmental and sustainability benefits due to the low waste generation compared to the liquid resists. However, there are limited detailed reports in the literature regarding the use of DFRs for the fabrication of microfluidic channels or other micropatterns (i.e., posts) on thin and flexible substrates. Herein we present in detail the fabrication of: a) microfluidic channels of width ranging from 50 μm up to 800 μm, and depth ranging from 30 μm up to 270 μm and b) square posts 80 μm × 80 μm in size and 30 μm in height. Particularly, our method enables the fabrication of ultra-deep microchannels (depth > 250 μm), highly ordered post arrays over large area (appr. 60 cm2), as well as complex designs with hierarchical scale features (80 μm posts inside 800 μm microchannels or micro-nanotexturing inside microchannels) on ultra-thin flexible substrates. To demonstrate the versatility of the method, three different DFRs were used on ultra-thin (30 μm), flexible, single-sided copper-clad polyimide substrates. It is also demonstrated that DFRs can be effectively modified using plasma etching to tune the surface wetting properties towards applications such as pumpless capillary action, where such functionality is required.