Unique Fabrication Method Research Articles

Operando Raman Spectroscopy Reveals Degradation Byproducts from Ionomer Oxidation in Anion Exchange Membrane Water Electrolyzers.

This work showcases the discovery of degradation mechanisms for nonplatinum group metal catalyst (PGM free) based anion exchange membrane water electrolyzers (AEMWE) that utilize hydroxide ion conductive polymer ionomers and membranes in a zero gap configuration. An entirely unique and customized test cell was designed from the ground up for the purposes of obtaining Raman spectra during potentiostatic operation. These results represent some of the first operando Raman spectroscopy explorations into the breakdown products that are generated from high oxidative potential conditions with carbonate electrolytes. We provide a unique design and fabrication method for three-dimensional (3D) printable flow cells that enable spatially resolved Raman spectra collection from the electrode surface into the bulk electrolyte. It is proposed that the generation of breakdown products from the hydroxide-conductive ionomers and membranes originates from a multistep, free radical reaction pathway resulting in chain scission of the poly aryl backbone. This hypothesis is backed by the detection of carboxylic and aromatic functional group Raman signals from small molecules that had dissolved and diffused into the bulk electrolyte.

(Invited) Developing Electrodes for Solid Oxide Fuel Cells What I Learned from Anil Virkar about Designing High Performance Electrodes

The performance of state-of-the-art solid oxide fuel cells (SOFC) and electrolyzers (SOEC) are largely limited by the overpotentials at the electrodes, both anode and cathode. The electrode overpotentials can be categorized by i) concentration of gas species, ii) charge transfer, and, iii) ionic transport near the interface, with the magnitude and contribution of each dependent on the cell geometry and operating conditions. One of the strategies of reducing overpotentials and improving electrode performance is the use of functionally grade electrodes wherein individual layers are optimized for porosity, conductivity, and three phase boundaries. Outer current collecting layers are designed with substantial porous microstructures and from highly electronically conductive materials resulting in low sheet resistance. Whereas the electrode layer near the electrolyte interface can be comprised of a two phase electrolyte-electrocatalyst composite in order to extend the effective three phase boundary layer beyond the electrolyte surface.The effects of various microstructural and material properties on the various electrode overpotentials were investigated. The influence of porosity and pore structure on the effective N2-O2 binary gas diffusion in the air electrode and resulting concentration polarization was studied. Likewise, highly porous anode supports were developed and characterized with the intent to decrease gas transport concentration overpotentials. Given electrodes that are adequately thin or have sufficient porosity in order to facilitate gas diffusion and reduce concentration polarizing, a substantial portion of the electrode overpotential can be attributed to the charge transfer and transport of the oxide ion from the electrode into the electrolyte, especially at lower temperatures. The critical transition region between the electrode and the electrolyte may span only a few microns but is essentially the equivalent of the ‘last mile problem’ for a fuel cell.Composite electrode layers nearest to the electrolyte were studied with regard to microstructure and materials selection. The activation overpotential was measured and related to the electrode properties including, three phase boundary density, the ionic transport within this layer, and the charge transfer of the electrocatalyst. In particular, the influence of the ionic conductivity of the electrolyte phase in the composite electrode on the electrode polarization was investigated. In addition, the microstructure of this electrolyte phase within the composite phase was studied and the sensitivity of necks between sintered electrolyte particles on ionic transport was estimated. A unique fabrication method was developed that produced an electrolyte skeleton with improved particle-to-particle necking and yet extremely porous, that could subsequently be infiltrated with an electrocatalyst material. Applying and combining the various strategies outlined above, highly efficient electrodes were developed and demonstrated for solid oxide fuel cells.

Anisotropy in microstructure and mechanical properties of additively manufactured Ni-based GH4099 alloy

Additively manufactured Ni-based superalloys exhibit strong anisotropy due to microstructural differences resulting from their unique fabrication method. This study systematically investagiated the microstructure and mechanical properties of Ni-based GH4099 alloy fabricated by Selective Laser Melting (SLM) with subsequent heat treatment (HT). The causes of anisotropy in the deformation mechanism of alloys at room temperature and high temperatures are discussed. The results indicate that epitaxial grain growth occurs along the building direction, and after SLM, entangled dislocations gather at the cell boundaries. After HT, high-density dislocations are eliminated, while most grains remain in the as-deposited form. At room temperature, the deformation mechanism of the alloy remains consistent. Cracks generate and propagate inside grains, while grain boundaries provide a more substantial barrier for dislocations. Therefore, the difference in mechanical anisotropy depends on the difference in grain morphology in the build direction and perpendicular to the build direction. At high temperatures, fracture failure occurs at grain boundaries. The growth of carbides at high temperatures leads to the weakening of grain boundaries. The alloy exhibits different deformation mechanisms when loaded along the short and long axes of the grain. Only dislocations are activated when loaded along the short axis of the grain. Stacking faults and deformation twins provide higher plastic-deformation ability when loaded along the long axis of the grains. Moreover, dislocations also activate, however the dislocation density is lower compared to loaded along the short axis.

Flexible thermocouple using a thermoelectric graphene fiber with a seamless junction

Temperature is an important physical variable that indicates the condition of the human body and artificial systems. Advanced wearable applications require the development of temperature sensors with different form factors. In this study, a fiber-shaped thermoelectric temperature sensor is fabricated using a continuous graphene fiber whose two halves possess different reduction states. A seamless junction is formed by partially reducing a wet-spun graphene oxide fiber with hydroiodic acid (HI) solutions of different concentrations. One-half of the fiber is mildly reduced with 0.97 wt% HI, while the other half is highly reduced with 30.6 wt% HI. The different reduction states of the graphene composite fiber result in different Seebeck coefficients, allowing for the fabrication of a fiber-shaped graphene thermocouple without any laborious assembly. The flexible graphene thermocouple exhibits high sensitivity with a thermopower of 12.5 μV K–1 in the temperature range of room temperature to ∼70 °C. Furthermore, it exhibits high linearity with a correlation coefficient exceeding 0.995 and fast response with a time constant of 0.24 s. Owing to its mechanical robustness and flexibility, the stand-alone graphene thermocouple can be knitted into a cotton fabric glove, which presents a fast response to environmental changes without any external power source. This work offers a unique fabrication method for producing a high-performance, flexible thermocouple that features a seamless and clear junction without the use of additional materials. This alternative method eliminates the complicated assembly processes typically required for conventional thermocouples.

Design and application of a novel 3D printing method for bio-inspired artificial reefs

Morphological complexity and diversity are key design features for forming artificial reefs that can support marine communities. Towards this end, 3D Printing (3DP) has become a unique fabrication method in the field. In the current study, we develop a novel approach to ceramic 3DP and investigate new morphologies to form marine habitats using additive manufacturing (AM) with eco-friendly materials. A large Paste Based Extrusion (PBE) 3D printer was used in addition to adapted, ceramic materials to develop a Gravity-Stimulated Printing Design method (GSPD) to fabricate bio-inspired reef designs. This approach used a direct parametric design-tool that generates and controls a specific machine tool-path of the printer, bypassing the slicer program. The developed parametric design-tool led to highly complex shapes that assembled a spatial conglomerate structure with the variety and uniqueness of each part. A reef forming prototype made from 87 printed parts was created and installed in a coral reef environment at the northern tip of the Red Sea in the Gulf of Eilat/Aqaba. After two years, we observed abundant marine organisms settling and recruiting at a depth of 12 m to form a new reef. This study demonstrates the environmental potential of AM, specifically in ceramic 3D printing. Our results indicate that the GSPD method can be used for large-scale production of highly complex eco-friendly artificial marine habitats. Using our design approach, we can facilitate morphological complexity in ceramic AR construction that support a diversity of coral reef residents.

Schottky-like photo/electro-catalytic carbon nanotube composite ultrafiltration membrane reactors

Stimuli-responsive membrane reactors offer advanced strategies towards simultaneous separation and degradation of persistent organic contaminants, allowing for triggered response through photo or electro stimuli. However, the scalable fabrication of stimuli-responsive nanoporous membranes with high selectivity and catalytic reactivity is still challenging in practical application. Here, photo-electro responsive membranes were designed by assembling carbon nanotubes (CNT) scaffolds decorated with conformal nanoscale SnO2 coatings. The membranes, built from spinnable CNT materials supported the generation of a unique class of ultrathin and flexible ultrafiltration membranes with thicknesses down to 25 nm and pore size as narrow as ∼20 nm. The CNTs were used as effective conductive photosensitizers to promote charge transfer from the graphitic to the SnO2 layer, supporting synergistic effects arising from generated Schottky-like diodes to improve the photo/electro-catalytic activity of nanocomposite membranes. The SnO2-CNT membranes exhibited high water permeance of 2.24 × 103 L m−2 h−1.bar−1, and faster reaction kinetics of 77.6 × 10−3 for acetaminophen degradation, which was 2–10 times higher than the kinetics achieved by currently available catalytic membrane reactors. The structural stability and outstanding performance of SnO2-CNT membranes were maintained over 8 reuse cycles with ∼99% degradation efficiency against acetaminophen in 60 min. The unique solid-state fabrication method of uniformly coated catalytic metal oxide on well aligned CNTs provides a scalable feasible approach to produce high-performance ultrafiltration photo/electro-catalytic membrane reactors towards cost-effective water purification at a competent reaction rate.

Hybrid microlens array/grating fabrication based on microfluidic system and its application in the enhancement of spectral resolution

Nowadays, micro-spectrometer has become an important research direction in the field of spectral analysis. The hybrid microlens array (MLA)/gratings element performs both focusing and diffraction duties, and its short focal length allows the optical system to be smaller. In this work, a unique and cost-effective fabrication method for hybrid MLA/grating based on the microfluidic system is described. By this method, the grating line-density, microlens curvature and aperture size of the hybrid MLA/grating can be effectively controlled, so as to bring different diffraction and focusing effects. Finite element simulation is used to describe the principle of the method. The relationship between bulge height and membrane thickness, pressure, hole size was investigated using a profile observation system. Wave optics simulation and diffraction measurements were used to demonstrate the optical properties of this hybrid element. It can be found that the diffracted light is converged at focus points after MLA/grating, and the full width at half maximum (FWHM) is significantly narrowed. The diffraction experimental results are consistent with the simulation results. The MLA/grating structure reduces FWHM of first-order diffracted light by a factor of 7 compared to same type of the planar grating. Therefore, the MLA/grating element can effectively improve the spectral resolution. Due to its small focal length, the MLA/grating has the potential to be used in micro-spectrometers.

Suaeda maritima (L.) Dumort GREEN SYNTHESIS- REDUCED NICKEL OXIDE NANOPARTICLES FOR ANTIOXIDANT AND BACTERICIDAL ACTIVITY

A unique way, green, cost-effective, and direct fabrication method is proposed for the synthesis of Nickel Oxide Nanoparticles (NPs) in an eco-environmentally way through leaf extract of Suaeda maritima (L.) Dumort. The nickel oxide nanoparticles were synthesized using Nickel (II) nitrate hexahydrate as a metal source and aqueous leaf extract of S. maritima was utilized as a green reducing agent. The formation of NPs was monitored by the change in color in the reaction mixture and the synthesized NPs were characterized using UV-visible spectrophotometer, Fourier Transform infrared (FT-IR) spectroscopy, field emission scanning electron microscope (FE SEM), X-ray diffractometer (XRD), and energy-dispersive X-ray spectroscopy (EDX). Further, the antibacterial activity of synthesized NPs was carried using the agar plate well diffusion method and antioxidant activity by DPPH free radical scavenging activity of the NPs was studied. The UV-visible absorption spectra of nanoparticles show a characteristic maximum absorption peak centered at 397 nm. The functional group analysis by FT-IR confirms the presence of various bio-active functional groups in the synthesized particles. The structural characterization confirms that the particles were Face Centred Cubic lattice structure having IR-regular in shape and rough surface with average atomic weight percentages of 76.3%. The synthesized nanoparticles were found to be potent against the growth of gram-positive (Bacillus subtilis, Staphylococcus aureus) and gram-negative (Escherichia coli, Pseudomonas aeruginosa) bacteria. In the DPPH assay, the IC 50 values of the synthesized NPs were found to be 28.01 μg/mL which is very close to standard ascorbic acid (22.19 μg/mL) whereas the IC 50 of the aqueous plant leaf extract was found to be 47.30 μg/m confirms that the nanoparticles having enhanced antioxidant activity. From the results of the study it can be concluded that this protocol is simple, rapid, one step, eco-friendly, non-toxic for the synthesis of nickel nanoparticles.

Eco-friendly in-situ gap generation of no-spacer triboelectric nanogenerator for monitoring cardiovascular activities

Monitoring cardiovascular activities plays a critical role in predicting and preventing cardiovascular diseases. Flexible and biosafe sensors that can provide complementary information about cardiovascular activity beyond the traditional electrocardiogram (ECG) are in great demand. Here, a novel eco-friendly in-situ gap-generation method by vaporizing soaked distilled water is developed to fabricate a no-spacer triboelectric nanogenerator (NSTENG). This NSTENG reveals more uniform stress/strain distributions and undergoes larger displacement compared with the traditional TENG with spacer under the same pressure; and it obliterates the obstruction on detection of subtle movements near spacer. The unique fabrication method also guarantees biological safety and avoids air contamination in vivo. The established wireless mobile system based on the NSTENG can precisely detect the full pulse waveforms and display them on the phone screen in real time. By mounting onto the rat’s heart, it can monitor normal heart motion and the measured heart rate has an accuracy of up to 99.73%. Moreover, the NSTENG can monitor abnormal heart motion and detect subtle heart movements that fail to be captured by the ECG. This work provides a new strategy that promotes the innovation of biosafe and new-structure TENGs, and offers new insights into developing wearable and implantable sensors.

Kraft Lignin Derived Molybdenum Carbide/Nitrogen-Doped Carbon Composite for Efficient Hydrogen Evolution Reaction

This paper reports a simple, unique, and eco-friendly fabrication method for composites of molybdenum carbide nanoparticles dispersed on nitrogen-doped carbon supports (Mo2C/NC) by annealing of MoCl5, kraft lignin, urea at 750 °C under N2 flow in one pot. Kraft lignin, a by-product from the pulping industry, acted as carbon source for formation of Mo2C and carbon support and a cheap urea provided a nitrogen source for nitrogen-doping to carbon supports. The resultant Mo2C/NC catalysts exhibited high activity with small overpotential (131 mV at 10 mA cm−2) and excellent stability over 3000 potential cycles for hydrogen evolution reaction (HER) in alkaline media. Enhanced HER activity of Mo2C/NC catalyst was attributed to highly active Mo2C nanoparticles and nitrogen-doped carbon (N-doped carbon) providing large surface area and high electrical conductivity.

Photocatalytic and photo-electrochemical behavior of novel SnO2-modified-g-C3N4 for complete elimination of tetracycline under visible-light irradiation: Slurry and fixed-bed approach

We present a novel and low-cost SnO2-modified-g-C3N4 (SnCN)-coated on natural pebbles through a unique fabrication method. Initially, a succession of unique SnO2-modified-g-C3N4 (SnCN) photocatalysts was prepared via a facile hydrothermal method. The addition of SnO2 into g-C3N4 not only reduced the band-gap energy and recombination ability of the electron-hole pairs but also drastically augmented the pore volume and surface area. The BET surface area of the 4% modified sample (69.1022 m2/g) was approximately 4.5 times higher in comparison to the pure form (16.2567 m2/g). Notably, the photocatalytic performance of the SnCN samples under visible light irradiation was significantly improved, with tetracycline 40 ppm (TC) removal of up to 90.29% attained after 2 h at the optimized initial pH of 10 in the presence of 4% SnO2 modification. With a view toward the practical applications, the as-prepared catalyst was successfully immobilized over low-cost, highly durable and eco-friendly pebbles as confirmed through characterization techniques. In addition to the photocatalytic process, the extended applications of the as-prepared photocatalyst were also studied by analyzing the photoelectrochemical (PEC) behaviors through transient photocurrent response, Mott-Schottky plots, and electrochemical impedance spectroscopy (EIS) spectra.

Ge-doped ZnO nanorods grown on FTO for photoelectrochemical water splitting with exceptional photoconversion efficiency

In this study, a considerable effort has been devoted for the synthesis of Ge-doped ZnO nanorods on FTO as an efficient and robust photoanode material for solar water splitting. A unique, optimized, and ultra-rapid fabrication method to produce uniform nanorods (30–70 nm in diameter) has been demonstrated using radio frequency sputtering followed by electrochemical anodization. The effect of Ge doping on the conductivity, charge carrier concentration, optical, and photoelectrochemical properties of ZnO was investigated using scanning electron microscope (SEM), glancing angle X-ray diffraction (GAXRD), UV–Vis spectrometer, and Mott Schottky analysis. Glancing angle XRD confirmed the presence of wurtzite structure with a preferable orientation around (101) plane, which is of particular interest for many applications. As evidenced by the photoelectrochemical and transient photocurrent measurements, the fabricated Ge-doped ZnO nanorods exhibited enhanced photocurrent (12 mA/cm2) with an exceptional open circuit voltage of −1.07 VSCE (−0.416 VRHE) under AM1.5G illumination, compared to the undoped ZnO based-photoanodes. Moreover, the Ge-doped ZnO nanorods showed unprecedented photoconversion efficiency of 3.6% under AM1.5G illumination. Therefore, the fabricated Ge-doped ZnO nanorods could be a promising conductive photoanode for water splitting.

Acoustic plasmonics of Au grating/Bi2Se3 thin film/sapphire hybrid structures**Project supported by Carl-Zeiss-Stiftung

The surface plasmon polaritons of the topological insulator Bi2Se3 can be excited by using etched grating or grave structures to compensate the wave vector mismatch of the incident photon and plasmon. Here, we demonstrate novel gold grating/Bi2Se3 thin film/sapphire hybrid structures, which allow the excitation of surface plasmon polaritons propagating through nondestructive Bi2Se3 thin film with the help of gold diffractive gratings. Utilizing periodic Au surface structures, the momentum can be matched and the normal-incidence infrared reflectance spectra exhibit pronounced dips. When the width of the gold grating W (with a periodicity 2W) increases from 400 nm to 1500 nm, the resonant frequencies are tuned from about 7000 cm−1 to 2500 cm−1. In contrast to the expected dispersion for both massive and massless fermions, where q ∼ π/W is the wave vector, we observe a sound-like linear dispersion even at room temperature. This surface plasmon polaritons with linear dispersion are attributed to the unique noninvasive fabrication method and high mobility of topological surface electrons. This novel structure provides a promising application of Dirac plasmonics.

Fabrication of Composite Unidirectional Cellular Metals by Using Explosive Compaction

Development of a small and highly efficient heat exchanger is an important issue for energy saving. In this study, the fabrication method of unidirectional (UniPore) composite cellular structure with long and uniform unidirectional cells was investigated to be applied as a heat exchanger. The composite UniPore structure was achieved by the unique fabrication method based on the explosive compaction of a particular arrangement of thin copper and stainless steel pipes. Slightly smaller thin stainless steel pipes filled with paraffin are inserted into small thin copper pipes, which are then arranged inside bigger and thicker outer copper pipes. Such an arrangement of pipes is placed centrally into a cylindrical explosion container and surrounded with explosive. Upon explosive detonation, the pipes are compacted and welded together, which results in a UniPore structure with a stainless steel covered inner surface of unidirectional pores to improve the corrosion resistance and high temperature resistance performance. Two different composite UniPore structures arrangements were studied. The microstructure of the new composite UniPore structure was investigated to confirm good bonding between the components (pipes).

Fatigue Performance of Type I Fibre Bragg Grating Strain Sensors.

Although fibre Bragg gratings (FBGs) offer obvious potential for use in high-density, high-strain sensing applications, the adoption of this technology in the historically conservative aerospace industry has been slow. There are several contributing factors, one of which is variability in the reported performance of these sensors in harsh and fatigue prone environments. This paper reports on a comparative evaluation of the fatigue performance of FBG sensors written according to the same specifications using three different grating manufacturing processes: sensors written in stripped and re-coated fibres, sensors written during the fibre draw process and sensors written through fibre coating. Fatigue cycling of the fibres is provided by a customized electro-dynamically actuated loading assembly designed to provide high frequency and amplitude loading. Pre- and post-fatigue microscopic analysis and high-resolution transmission and reflection spectra scanning are conducted to investigate the fatigue performance of FBGs, the failure regions of fibres as well as any fatigue-related effects on the spectral profiles. It was found that because of the unique fabrication method, the sensors written through the fibre coating, also known as trans-jacket FBGs, show better fatigue performance than stripped and re-coated FBGs with greater control possible to tailor the optical reflection properties compared to gratings written in the draw tower. This emerging method for inscription of Type I gratings opens up the potential for mass production of higher reflectivity, apodised sensors with dense or complex array architectures which can be adopted as sensors for harsh environments such as in defence and aerospace industries.

Study on the formation mechanism of bismuth-mediated Ge nanodots fabricated by vacuum evaporation

Germanium (Ge) nanodots are expected for various applications. We have proposed a unique fabrication method for them with bismuth (Bi) mediation, and we have successfully formed high-density crystalline Ge nanodots by vacuum evaporation followed by low-temperature annealing. In this paper, we show the experimental results, such as dependence of the process condition on the nanodot structure and some results of the analyses of the nanodot samples. Then we discuss and propose a schematic formation mechanism for the nanodots as follows. First, during the deposition process, sequentially deposited Bi and Ge layers are mixed by solid phase diffusion and form an amorphous-alloy layer. Next, during the annealing process, crystallization of the Ge nanodots and desorption of the Bi proceeds; during this time, Bi and Ge exist as a solid–liquid coexistence phase in the alloy system, and this condition may enhance the phenomena.

Fabrication of 3D microfluidic structure with direct selective laser baking of PDMS

Purpose The purpose of this paper is to present three-dimensional (3D) printing of structures with a new method called selective laser baking (SLB) of Poly Dimethyl Siloxane (PDMS). Design/methodology/approach A 3D model is designed on the computer. PDMS Base is mixed with its hardener and poured into a container. Before it is hardened which normally occures after several hours, a CO2 laser selectively exposes different areas on the surface of the PDMS mixture according to the pattern of a slice of a 3D model designed on the computer. Because of the thermal effect of the CO2 laser, once exposed, PDMS heats up and hardens, producing a cured layer of PDMS which is attached to a base. The base with the cured layer is lowered in the container for a short distance and a layer of new uncured PDMS is spread over the previous layer. The laser exposes new areas again and hardens them. This process is repeated until the whole structure is fabricated. Findings The parameters involved in the baking process are investigated and the relation between temperature, mixing portion and laser irradiance on the curing time and layer thickness are investigated. Originality/value This fabrication technique is a unique fabrication method that helps to 3D print with two base polymers which their polymerization can be boosted by heat. This 3D printing method has not been presented earlier.

A Highly-cost-effective Area-array Probe-unit as a Key Hardware Technology in Quality Management System for IoT Products

This paper describes the highly-cost-effective high-density area-array probe-unit which consists of four functions, “Densification,” “Fan-out (non-discontinuous),” “Connection,” and “Transformation,” designed and manufactured by our unique monolithic fabrication method, as a key hardware technology of quality management system in a production site for the Internet of Things (IoT), Artificial Intelligence (AI), and Big Data fields. This new probe-unit provides a multiple test/monitor function with high accessibility to I/O density and a high signal integrity structure for providing test signals or collecting massive data between the semiconductors/devices and testers. And this probe-unit is widely available as a versatile interconnection system connecting directly the wafer-level fine-pitch terminals with the test/monitor terminals which is compatible with motherboard technology pitch requirements. At the same time, we have also developed the monolithic fabrication method that an entire matrix probe array with subsequent fan-out patterns and monitor terminal array was created from a single conductive film and formed only by folding like “Origami” (paper-folding). In this innovative method, massive probes and fan-out patterns were designed and manufactured significantly cheaper and faster. We have developed a 22.5-um pitch and 38000-pins-class area-array probe-unit with non-discontinuous fan-out structure without interposer substrates using the monolithic fabrication method and demonstrated the high precision probe array and high productivity.

Multiscale Structures Aggregated by Imprinted Nanofibers for Functional Surfaces.

Multiscale surface structures have attracted increasing interest owing to several potential applications in surface devices. However, an existing challenge in the field is the fabrication of hybrid micro-nano structures using a facile, cost-effective, and high-throughput method. To overcome these challenges, this paper proposes a protocol to fabricate multiscale structures using only an imprint process with an anodic aluminum oxide (AAO) filter and an evaporative self-aggregation process of nanofibers. Unlike previous attempts that have aimed to straighten nanofibers, we demonstrate a unique fabrication method for multiscale aggregated nanofibers with high aspect ratios. Furthermore, the surface morphology and wettability of these structures on various liquids were investigated to facilitate their use in multifunctional surfaces.

Design, fabrication, and testing of convex reflective diffraction gratings

The convex reflective diffraction grating is an essential optical component that lends itself to various applications. In this work, we first outline the design principles of convex diffraction gratings from wavefront quality and efficiency perspectives. We then describe a unique fabrication method that allows for the machining of convex diffraction gratings with variable groove structure, which is extendable to rotationally non-symmetric convex diffraction grating substrates. Finally, we demonstrate two quantitative wavefront measurement methods and respective experimental validation.