Chemical Etching Research Articles

A Novel Approach for Thin 4H-SiC Foil Realization Using Controlled Spalling from a 4H-SiC Wafer

Porosifying the surface of a single crystalline silicon carbide (4H-SiC) wafer with the means of metal assisted photo chemical etching (MAPCE) promotes the adhesion of an electroplated nickel (Ni) layer. By utilizing a mechanical peel-off process, a Ni layer with tailored mechanical stress is peeled off such that also a thin layer of 4H-SiC is teared apart from the wafer as well.

Comparative fatigue performance of as-built vs etched Ti64 in TPMS-gyroid and stochastic structures fabricated via PBF-LB for biomedical applications

PurposeThis study compares the fatigue performance and biocompatibility of as-built and chemically etched Ti-6Al-4V alloys in TPMS-gyroid and stochastic structures fabricated via Powder Bed Fusion Laser Beam (PBF-LB). This study aims to understand how complex lattice structures and post-manufacturing treatment, particularly chemical etching, affect the mechanical properties, surface morphology, fatigue resistance and biocompatibility of these metamaterials for biomedical applications.Design/methodology/approachSelective Laser Melting (SLM) technology was used to fabricate TPMS-gyroid and Voronoi stochastic designs with three different relative densities (0.2, 0.3 and 0.4) in Ti-6Al-4V ELI alloy. The as-built samples underwent a chemical etching process to enhance surface quality. Mechanical characterization included static compression and dynamic fatigue testing, complemented by scanning electron microscopy (SEM) for surface and failure analysis. The biocompatibility of the samples was assessed through in-vitro cell viability assays using the Alamar Blue assay and cell proliferation studies.FindingsChemical etching significantly improves the surface morphology, mechanical properties and fatigue resistance of both TPMS-gyroid and stochastic structures. Gyroid structures demonstrated superior mechanical performance and fatigue resistance compared to stochastic structures, with etching providing more pronounced benefits in these aspects. In-vitro biocompatibility tests showed high cytocompatibility for both as-built and etched samples, with etched samples exhibiting notably improved cell viability. The study also highlights the importance of design and post-processing in optimizing the performance of Ti64 components for biomedical applications.Originality/valueThe comparative analysis between as-built and etched conditions, alongside considering different lattice designs, provides valuable information for developing advanced biomedical implants. The demonstration of enhanced fatigue resistance and biocompatibility through etching adds significant value to the field of additive manufacturing, suggesting new avenues for designing and post-processing implantable devices.

A strategy to reutilize silver nanoparticles on silicon nanowires via photocathodic activation for enhanced and sustainable hydrogen evolution

The development of electrodes for hydrogen evolution via water splitting in a neutral electrolyte is highly desirable, especially considering that natural water resources such as seawater typically have a neutral pH. In this study, silicon nanowires (SiNWs) arrays with uniform silver (Ag) decoration are prepared as a cathode material, which exhibits excellent and stable electrochemical performance for neutral water electrolysis. Ag ions, utilized in the preparation of SiNWs through metal-assisted chemical etching technique, are retained and decorated within the SiNWs array without undergoing a dissolution process, referred to as Native SiNWs. Remained Ag+ ions on the SiNWs are activated photocathodically and reduced to Ag0, resulting in a significantly enhanced performance as an electrocatalyst for hydrogen evolution reaction (HER). Hence, this photocathodic activation of Native SiNWs (PCA-Native SiNWs) eliminates the need for additional cocatalyst deposition for HER, utilizing the Ag ions employed in the SiNWs preparation process. This enhancement in HER activity is exclusively observed by photocathodic activation, not by cathodic activation without light irradiation, indicating the crucial role of photoelectrons in SiNWs under light irradiation for the activation. Additionally, the nanowire structure serves as an ideal platform for Ag nanoparticles, providing sufficient surface area, resulting in excellent dispersion and an increased number of active sites. Furthermore, PCA-Native SiNWs demonstrates outstanding electrochemical stability for over 60 h, with no significant reduction in current density or structural degradation in a neutral electrolyte. Several characterizations and electrochemical analyses have been conducted to elucidate the in-situ decoration of Ag nanoparticles on SiNWs and investigate the surface chemistry for the activation mechanism. This work introduces a new perspective on using Ag-decorated SiNWs directly as an electrocatalyst for effective hydrogen evolution in a neutral media.

Synthesis of ultra-high nitrogen doped hollow mesoporous carbon nanospheres via a universal solid–liquid interface self-assembly strategy

Functional mesoporous polymers, particularly their derived hollow mesoporous carbon spheres (HMCS), have introduced new opportunities in the field of energy storage. Traditional synthesis methods for HMCS typically rely on chemical etching, which often results in uniform chemical properties and structural control, thereby limiting their application in large-scale production and diverse fields. Therefore, in this study, we report a novel strategy for obtaining HMCS through the direct pyrolysis of a core matrix, melamine–formaldehyde resin (MF), to achieve hollow structures and ultra-high nitrogen doping (approximately 14.8 wt%). This new solid–liquid interfacial self-assembly approach enables the production of HMCS with remarkable electrochemical performance and practical application prospects in sodium-ion half-cells and full cells, thanks to the high nitrogen doping and unique structure. Notably, this strategy has been validated for its general applicability across 1D, 2D, and 3D solid matrices. Additionally, by adjusting the calcination temperature, this method allows for precise control over both the core size and nitrogen content of the egg yolk-shell structure mesoporous carbon spheres. In summary, the mesoporous materials developed in this study demonstrate flexibility, simplicity, versatility, and structural diversity, offering significant insights for future applications in energy storage and other fields.

Gravity-assisted gradient size exclusion separation of microparticles by gap-modifiable silicon nanowire arrays

The separation and detection of microparticles within complex samples pose substantial challenges due to the intricate variations in size and concentration. A strategy employing gravity-assisted gradient size exclusion principle based on controllable gap sizes on the surface of silicon nanowire arrays (SiNWAs) has been established to achieve the separation of microparticles with diverse sizes. The formation of gradient gap sizes was accomplished by meticulously investigating the impact of oxidation-reduction reactions through metal-assisted chemical etching. Particles of different sizes were initially aggregated at the accumulation base, followed by a sequential size exclusion process within the finely regulated 0.9–12.5 μm gradient-gap-sized separation region facilitated with gravity-assisted, leading to a comprehensive separation of microparticles based on their respective size differences, progressing from small to large. The effective separation of four model-sized microparticles demonstrated a separation degree of ≥2.7, purity of ≥96.1 %, RSDs of ≤4.6 %, and a separation capacity of up to 107 particles. The separation efficacy of this gradient-sized chip was verified by evaluating the more complex atmospheric particulates with varying sizes, which exhibited separation degree ranging between 2 and 10. This method offers a precise separation range, easily adjustable separation sizes, and simple operation, rendering it a versatile tool for separating complex samples.

Material synthesis, crystal structure, Hirshfeld surface and physicochemical characteristics Novel Stilbazolium crystal of 4-(2-(3-ethoxy-4-hydroxy-phenyl)-vinyl)-1-methyl pyridinium iodide (MEMPI) single crystal for NLO activity

In this study, a novel cation donor group 3-ethoxy-4-hydroxy benzaldehyde has been incorporated in the Stilbazolium cation with iodide anion to generate a new NLO activity of a single crystal of 4-(2-(3-ethoxy-4-hydroxy-phenyl)-vinyl)-1-methyl pyridinium iodide (MEMPI). The MEMPI crystal was effectively formed via the solvent evaporation technique. The structure and hydrogen bond interactions found in the molecule were determined by employing single-crystal X-ray diffraction. The compound crystallizes in the space group P21/c and monoclinic crystal pattern. The crystal structures are stabilized via intramolecular, intermolecular hydrogen bond interactions, C‒H···π, cation‒π, anion‒π, π···π stacking and lone pair-π interaction. In addition, a variety of O‒H···O, O‒H···I and C‒H···O interactions are also responsible for crystal packing. The 3D Hirshfeld surface and 2D fingerprint plots were used to examine the nature of intermolecular interaction. The 2D fingerprint maps indicate that the interactions between H···H contribute to 48.9 % of the total crystal stability. The newly synthesized material was characterized by 1H NMR and 13C NMR. In addition, the vibrational study of the synthesized molecule was performed using FTIR analysis. The grown crystal in linear optical characteristics were examined via a UV–Visible-NIR study. The photoluminescence (PL) activity of a MEMPI was studied with respect to the visible area and green colour emission was observed at 536 nm. The estimated CIE coordinates on the RGB colour gamut show the MEMPI crystal's ability to emit green light. The chemical etching approach was used to analyse the etch pit density and the growth habitat of the MEMPI crystal. The closed and open aperture Z-scan tests were carried out to determine the nature of third-order NLO susceptibility of the MEMPI crystal.

Determine the concentration of radon and uranium in different types of tea

ABSTRACT Radon is a radioactive element from 238U decay series which is naturally occurring and found in different concentrations in many biological formations. This radioactive gas rises from the sample and enters the homes and human lungs daily. The present study aims to determine the concentration of radon in 25 different types of tea collected from local markets in Kurdistan Iraqi region which are mostly consumed by the population because tea is one of the most food used in the form of cold and hot drinks in Iraq, so 25 samples of the most frequently traded tea have been collected from the market. Analysis of the concentrations of Radon-222 and Radium-226 for different types of household tea samples are very substantial for realising the comparative contributes of specific substances to the whole radon content set within the human body and his environment, which is the recommended limit for ICRP values (200–800) Bq.m−3. CR-39 detector was used to record the tracks of alpha particles released from radon content within the tea samples with PVC tube. The chemical etching NaOH solution 6.25 N was using at 70°C for 8 hours to enlarge and appear the alpha tracks, then scanned by microscope. The results showed that the lowest concentration of radon was 3.468 Bq.m−3 (TE11, 0.01%) found in Aero plane tea, while the highest value was recorded in Royal tea which was 123.467 Bq.m-3 (TE22, 8%) with an average value of radon concentration was 61.754 Bq.m−3. The obtained radon concentration levels in the samples were lower than the global permissibility limiting of exposure to radon were within the allowed limit value (200 Bq.m−3), also found to be lower than the (400 Bq.m−3) according to ICRP in foods; therefore, this will not form any risk on human being life.

MXene Synthesis and Carbon Capture Applications: Mini-Review.

MXenes, a class of two-dimensional transition metal carbides, nitrides, and carbonitrides, have garnered significant attention due to their remarkable potential for energy storage, electrocatalysis, and gas separation applications. The fabrication processes of MXene involve building up the MXene structure from constituent elements and the selective elimination of M-A bonds from the precursor MAX. However, considerable efforts are still required to design and develop efficient MXene-based technologies. This review article aims to briefly analyse the synthesis methods employed for MXene production, ranging from direct synthesis and conventional chemical wet etching approach to the more recent molten salt etching technique. The review highlights the advancements made in achieving precise control over the terminal groups, which is paramount for tailoring the properties of MXenes for specific applications. Furthermore, the potential of MXene-based materials for carbon capture applications, particularly in developing advanced adsorbents, is emphasized. The in-depth examination of MXene synthesis techniques and their implications for carbon capture applications provides a solid foundation for developing and optimizing these promising materials.

Architected Carbon Structures for Energy Storage

Carbon materials, owing to their excellent electrical conductivity, tailor-ability, inexpensiveness, and versatility, have been extensively studied as electrode materials for energy storage devices, including batteries and supercapacitors. In this talk, I will discuss how to combine conventional materials/chemical synthesis with 3D printing techniques to develop architected carbon electrode materials for supercapacitors. The capacitance of carbon-based supercapacitor electrodes has remained at a mediocre level between 100 and 200 F/g for decades. Until recently, a new family of carbon materials termed hierarchical porous carbons has pushed the capacitance to new benchmark values beyond 300 F/g and has revitalized the exploration of carbon materials for supercapacitors. We have recently developed some hierarchical porous carbon areogels contain different scales of pores inter-connected together and assembled in hierarchical patterns, through a combination of freeze drying, template, chemical etching and 3D printing. These porous carbons have an open porous structure, providing an extremely large and accessible surface area. They can be used as electric double layer materials that enable ultrafast charging/discharging and retain outstanding capacitive performance even at ultralow temperatures (-70 °C). They can serve as 3D conductive scaffolds/current collectors to support pseudo-capacitive materials with ultrahigh mass loadings. These findings exemplified how to use a deterministic structure to improve the rate capability of supercapacitors and their capacitances at ultrahigh current densities and mass loadings and ultralow temperatures, which are long-standing challenges for SCs.

Detection of Thiocholine for Pesticide Qualification Using Indium-Tin-Oxide-Coated Vertically Aligned Silicon Nanowires Extended Gate Field-Effect Transistor

Thiocholine is the hydrolysis of acetylthiocholine (ATCh) by acetylcholinesterase (AChE). The detection of thiocholine can be utilized to assess the activity and inhibitors of AChE, making it a valuable recognition element for constructing biosensors used in pesticide detection[1, 2]. The enzymatic hydrolysis of ATCh is catalyzed by AChE. First, high-aspect-ratio vertically aligned silicon nanowires (VASiNWs) were successfully fabricated through metal-assisted chemical etching (MACE). To investigate the impact of nanostructures on enhancing the sensitivity of the extended gate of the field-effect transistor (EGFET), the gate terminal was connected to 3-mercaptopropyl trimethoxysilane (MPTMS) modified indium-tin-oxide (ITO)-coated VASiNWs for the electrical detection of ATCh-catalyzed thiocholine, as illustrated in Figure 1. Various solutions of ATCh-catalyzed thiocholine were collected by applying different concentrations of ATCh (ranging from 2 mM to 10 mM) to the AChE-coated wells independently for 10 minutes. Subsequently, these solutions were introduced to the MPTMS modified ITO-coated VASiNWs EGFET, and the change in drain current was measured using a semiconductor parameter analyzer (HP 4145B). The thiocholine current demonstrated a sensitivity of 29.39 uA/concentration and a linearity of 0.88. Exploring the potential of pesticides to inhibit AChE hydrolysis represents a significant breakthrough, paving the way for the advancement of biosensors in pesticide detection. References Liu, G., et al., Sensitive electrochemical detection of enzymatically generated thiocholine at carbon nanotube modified glassy carbon electrode. Electrochemistry Communications, 2005. 7(11): p. 1163-1169. Pandey, P.C., et al., Acetylthiocholine/acetylcholine and thiocholine/choline electrochemical biosensors/sensors based on an organically modified sol–gel glass enzyme reactor and graphite paste electrode. Sensors and Actuators B: Chemical, 2000. 62(2): p. 109-116. Figure 1

(Invited) Mixing Elements in 2D Nanostructures Grown by Discharges in Liquids

The synthesis of nanosheets through discharges in liquid nitrogen is observed for certain metals when employed as electrodes [1,2]. Various metals have been examined, with bismuth, lead, or zinc showing a propensity to form nanosheets. Other metals, such as silver or indium, also exhibit sheet formation but with smaller aspect ratios (width/thickness). Mixing metals is not only interesting to create alloys with new properties but also to understand how discharges work to enable the synthesis of these objects.Recently, we demonstrated that these structures can be grown not only in liquid nitrogen but also in water. This is attributed to the discharge primarily originating from the metallic vapor emitted by the electrodes, a consistent process in both liquids, as confirmed by time-resolved optical emission spectroscopy.We showcased that a pre-treatment, involving chemical etching by a Nital solution, significantly enhances the efficiency of nanosheet production, increasing it from almost zero to nearly 100%. We successfully identified the growth mechanism of nanosheets in the case of bismuth electrodes. These structures grow on the cathode with ion assistance, collecting in the bubble formed during the discharge. Upon the collapse of the bubble, they transfer into the liquid phase. Interestingly, the number density of nanoparticles produced under these conditions is either null or too weak to be evaluated.It is feasible to incorporate two different elements into 2D nanostructures by utilizing two electrodes. We achieved a mixture of lead and bismuth oxide by using electrodes composed of the respective elements. This capability is likely associated with the similar melting points and miscibility of both elements. Nanosheets exhibit thicknesses around 5-10 nm for widths ranging in the tens of micrometers.We anticipate that a more comprehensive understanding of the synthesis of these alloys will pave the way for the production of alloyed nanosheets incorporating other elements.[1] A. Hamdan, H. Kabbara, C. Noël, J. Ghanbaja, A. Redjaimia, T. Belmonte, “Synthesis of two-dimensional lead sheets by spark discharge in liquid nitrogen”, Particuology 40 (2018) 152–159[2] H. Kabbara, J. Ghanbaja, C. Noël, T. Belmonte, “Nano-objects synthesized from Cu, Ag and Cu28Ag72 electrodes by submerged discharges in liquid nitrogen”, Materials Chemistry and Physics 217 (2018) 371–378

(Invited) Scalable 2-Step Fabrication of Core-Shell GaN Micropillars

Group III-Nitride three-dimensional structures have gained substantial interest for application in optoelectronic, energy, and sensor devices with non-planar geometries [1-4]. The benefits of 3D structures, such as GaN-based nano-/micro-rods, compared to planar films include large surface area, high structural quality, non-polar-surface utilization, small footprint, mechanical flexibility, and enhanced light absorption/extraction efficiency. To advance the technology of non-planar III-Nitride semiconductors, it is necessary to optimize and scale up the fabrication of such structures with controlled geometries and desired electronic and optical properties. Here, we report the fabrication of wafer-scale periodic arrays of vertically aligned GaN core-shell micropillars using a combination of top-down etch and epitaxial overgrowth.The two-step process consists of inductively coupled plasma (ICP) etching of lithographically patterned GaN-on-Si substrate to produce an array of micropillars followed by selective growth of GaN shells over these pillars using Hydride Vapor Phase Epitaxy (HVPE). The most significant aspect of the study is the demonstration of the sidewall facet control in the shells, ranging from truncated hexagonal pyramids with the (1-101) semi-polar sidewalls to hexagonal prisms with the (1-100) non-polar sidewalls, by employing a post-ICP wet chemical etch and by tuning the HVPE growth temperature. Optimization of both ICP etching and epitaxial overgrowth reduced dislocation density in the GaN shells, thus enhancing the transport and optical characteristics of these device platforms. Photo- and cathodoluminescence showed a substantial reduction of parasitic yellow luminescence as well as strain-relaxation in the core-shell structures, supported by Raman scattering, electron-backscatter-diffraction (EBSD), and X-ray-diffraction measurements. Transmission electron microscopy revealed improved crystal quality with reduced dislocation density in the epitaxially grown shells. This work demonstrates the feasibility of selective epitaxy on micro/nano-engineered 3D templates for realizing high-quality GaN-on-Si devices such as LEDs and p-i-n photodetectors.

Subdiffraction‐Limited Motheye‐Like Metastructures Fabrication by Dual‐Beam Overexposure Methodology Enhancing Broadband Infrared Antireflective Application

AbstractMaterials possessing broadband antireflective properties benefit applications of military camouflage, photovoltaic devices, and highly transparent windows. In this work, large area, high throughput subdiffraction‐limited motheye‐like metastructures featuring broadband infrared (3–12 µm) antireflectivity are realized through dual‐beam overexposure shrinking strategy and subsequent controllable anisotropic reactive‐ion‐etching process. Both overexposure and overdevelopment processes severely controlled in conventional lithography processes, attribute significantly to improving linewidth resolution to <150 nm when photoresist thickness exceeding 500 nm, even to one micron. For antireflective application, the motheye profiles with customized anisotropic ratio (>3.27) and tunable taper‐angle range (>12.2°) are also realized by regulating the competition of directional ion bombardment and isotropic chemical etching in sulfur hexafluoride (SF6) plasma. The corresponding reflectivity is theoretically well‐simulated and experimentally validated after accounting for the tunable profiles and fractional volume coverage of motheye‐like structures. A low reflectivity <2.0% with the uniformity of ±4.8% and averaged to 1.2% across the overall spectrum of 3–12 µm are achieved. Implementing such efficient shrinking approach can possess huge potential in applications of military camouflage, photovoltaic devices, and highly transparent windows.

Fabrication of Nano-Carbon-Based Sustainable Perovskite Solar Cells

The rising need for sustainable energy solutions has fuelled considerable research into novel technologies that harness solar energy for efficient and scalable energy storage. Carbon nanotubes (CNTs) have emerged as feasible candidates for these applications due to their unique properties, such as high surface area, better electrical conductivity, and chemical stability.This report focuses on the design and fabrication of cost-effective nano-carbon-based perovskite solar cells (PSCs) and discusses their potential for clean energy generation and storage. This experimental study shows a novel technique to increase the sustainability the conventional fluorine-doped tin oxide (FTO) substrate with an Indium Tin Oxide (ITO) derived from electronic waste and incorporating nanocarbon based-graphene with solution-based techniques. This addition serves as a good basis for the ITO coating, aids charge transport in the perovskite solar cell, and promotes uniform covering maximum electrical conductivity, and transparency. Being the transparent conducting electrode, the CNTs is infused with the upcycled ITO coated glass and was included in the perovskite solar cell architecture, which replaces the traditional ITO electrode, lowering material costs, and improving the circular economy for energy storage devices, and a cleaner energy future.The ITO extraction process entails recovering indium and tin from mobile phones using an environmentally friendly and economical chemical etching process using hydrochloric acid (HCl) to remove the ITO layer. To ensure the purity and structural integrity of the ITO nanoparticles, they were rigorously characterized using X-ray diffraction, scanning electron microscopy, and energy-dispersive X-ray spectroscopy. After depositing a perovskite- CNTs precursor solution on the ITO layer glass substrate, the light-absorbing layer was annealed. Electron transport and hole-blocking layers were then deposited utilizing solution processing techniques using the PEDOT: PSS and metal electrodes were deposited to complete the device manufacturing. The current-voltage (J-V) relationship was used to compute the open-circuit voltage, short-circuit current density, fill factor (FF), and power conversion efficiency (PCE) of a solar cell. Electrical characterization allow for the calculation of solar cell performance metrics such as short-circuit current (Isc), short-circuit current density (Jsc), and open-circuit voltage (Voc). These findings imply that employing e-waste-derived ITO on graphene substrates to create high-efficiency perovskite solar cells is a realistic option. This research provides a sustainable and cost-effective method for producing high-performance perovskite solar cells by eco-friendly upcycling e-waste for ITO extraction, addressing the critical issue of e-trash management. Keywords Perovskite solar cells, CNTs, sustainable energy, energy conversion.

Application of silicon nanowires in sensors of temperature, light and humidity

Resistive and capacitive types of sensors based on silicon nanowires (SiNWs) for measuring of physical quantities have been manufactured. Silicon nanowires were obtained through a two-step metal-assisted chemical etching (MACE) method. The surface morphology of the silicon nanowire array was investigated using atomic force microscopy (AFM) and scanning electron microscopy (SEM). The impact of SiNWs synthesis parameters on sensor sensitivity has been investigated. In particular, the influence of deposition time of AgNPs and etching time of silicon, as well as the content of H2O2 in the etchant, preliminary texturing of the substrate, and additional post-processing in isotropic/anisotropic etchant after the MACE process, on the characteristics of physical quantity sensors has been determined. Static and dynamic parameters were calculated for the obtained sensors. To compare the obtained sensors, physical sensors without SiNWs were manufactured. The highest response value for temperature sensors was 132, which is two orders of magnitude better than for sensors without SiNWs. The presence of SiNWs on the surface of the sensor led to an increase in the response value by about two orders of magnitude for all types of sensors. The speed of humidity sensors improved by 3–4 times, and for temperature and light sensors by an order of magnitude. Further device applications include of multi-parameter sensors, human breath sensors, and solar radiation power sensors.

Highly‐Sensitive and High Operating Range Fully‐Printed Humidity Sensors Based on BiFeO3/BiOCl Heterojunctions

AbstractFully‐printed humidity sensors based on BiFeO3/BiOCl heterojunctions fabricated using a two‐step process with serigraphic printing are reported. Most importantly, this unique sensor architecture provides a broader relative humidity sensing range compared to pristine BFO sensors due to a synergistic effect between dense networks of BiOCl nanosheets synthetized atop BFO powders. With surface‐to‐weight ratios reaching 7.75 m2 g−1, these heterostructures increase the sensitivity and operating range of BFO‐based humidity sensors. While previously reported BFO humidity sensors only detect relative humidities above 30%, The BFO/BiOCl heterojunctions can measure relative humidities as low as 15% due to their increased surface area. Optimal growth and packing of the BiOCl nanosheet/BFO powder heterostructure are achieved by tuning the loading of the BFO powder and simultaneously forming the BiOCl sheets by chemical etching and annealing of the BFO powder. Excellent performance of optimized sensors including tracking and monitoring different types of breathing are demonstrated while mounted on an oxygen mask.

FDM printing of microneedles based on biocompatible and biodegradable thermoplastic polymers

AbstractMicroneedles are an emerging class of transdermal drug delivery systems for biomedical applications. These devices allow minimally invasive and painless drug delivery, making them an attractive alternative to hypodermic injections. This paper focuses on the study of polymer‐based solid microneedles fabrication process using the fused deposition modeling (FDM) method. Biodegradable and biocompatible polymers are selected as printing materials. For this study, the thermoplastic polylactic acid (PLA), currently used for FDM microneedle preparation was selected. To overcome the potential brittleness of PLA during transdermal application, two other materials are also studied: polycaprolactone (PCL) and a PLA/PCL blend. The effect of 3D printing parameters on the dimensional accuracy of the microneedles is studied to determine the optimum printing conditions for each filament. In addition, the dimensions and/or geometry of the microneedles are modified to print its with minimal dimensions. Then, a post‐fabrication chemical etching treatment is used to improve both, size and shape of the printed solid microneedles.

A multi-scale porous scaffold fabricated by a combined additive manufacturing and chemical etching process for bone tissue engineering

It is critical to develop a fabrication technology for precisely controlling an interconnected porous structure of scaffolds to mimic the native bone microenvironment. In this work, a novel combined process of additive manufacturing (AM) and chemical etching was developed to fabricate graphene oxide/poly(L-lactic acid) (GO/PLLA) scaffolds with multiscale porous structure. Specially, AM was used to fabricate an interconnected porous network with pore sizes of hundreds of microns. And the chemical etching in sodium hydroxide solution constructed pores with several microns or even smaller on scaffolds surface. The degradation period of the scaffolds was adjustable via controlling the size and quantity of pores. Moreover, the scaffolds exhibited surprising bioactivity after chemical etching, which was ascribed to the formed polar groups on scaffolds surfaces. Furthermore, GO improved the mechanical strength of the scaffolds.

Formation of Through-Hole Porous Anodic Aluminum Oxide Layer Locally with 3D Printed Solution Flow Type Microdroplet Cell

In this study, a 3D-prinited solution-flow type microdroplet cell (SF-MDC) is employed as a new technique for the fabrication of porous anodic aluminum oxide (AAO) layer using oxalic acid electrolyte on aluminum. The surface morphology of the porous AAO film was characterized by a scanning electron microscope. The aim of this study was to fabricate a through-hole porous alumina layer in a single step anodizing process and to investigate the influence of anodized voltages and scanning speeds on the thickness and pore structure of alumina layer. The results showed that the pore diameter and interpore distance were directly proportional to the anodizing voltage. The thicknesses of formed AAO films were found to be 35.5, 50.7, and 81.6 μm at scanning speeds of 10, 5, and 2.5 μms−1, respectively. Through-hole porous AAO was successfully fabricated at room temperature without chemical etching. The SF-MDC fabrication technique is proposed as an environmentally attractive and suitable process for the fabrication of porous AAO layers.

Novel approach of SERS sensors AgNPs/PSi by incorporated MWCNT

In this study, two types of nano photonics sensors silver nanoparticles/porous silicon (AgNPs/PSi) and silver nanoparticles/multi wall carbon nanotube/porous silicon (AgNPs/MWCNT/PSi) were formed and tested extensively. The porous silicon (PSi) substrate was formed by laser assisted chemical etching process at laser intensity 150 mW/cm2 and wavelength 630 nm respectively. The formation of these types of nano photonics SERS sensors were carried out by a simple and low cost dipping process of porous silicon (PSi) in silver nitrate (AgNO3) and multi wall carbon nanotube (MWCNT) solution fixed concentration of AgNO3 about (10−3 M). These sensors were tested at different concentrations of difenoconazole, 10−5, 10−7, 10−9 and 10−10 M at room temperature. The research results showed an excellent sensing behavior of silver nanoparticles/multi wall carbon nanotube/porous silicon (AgNPs/MWCNT/PSi) comparing with the silver nanoparticles/porous silicon (AgNPs/PSi) nanoparticles sensors. Higher enhancement factor with lower limit of detection with multi wall carbon nanotube (MWCNT) were improved by two orders of magnitude, due to the high value of the sensing area after incorporating multi wall carbon nanotube (MWCNT) to nano photonics sensors.