Traditional Fabrication Techniques Research Articles

Water Quality Monitoring: All-Solid-State 3D-Printed Sensors for Phosphate Detection in River Water

INTRODUCTION High phosphate ( PO4 3- or P) levels in surface water cause eutrophication, which negatively impacts aquatic life and causes an economic loss of ~$2.2 billion per year. Currently, no low-cost sensors exist for long-term continuous monitoring of phosphate in water. Existing meters (HANNA colorimeter, and HORIBA) can detect P-levels but can neither perform continuous monitoring nor detect low concentrations. A paper-based colorimeter sensor for phosphate detection was demonstrated [1], however, this sensor takes a longer time to test. A Fabry−Perot phosphate sensor was introduced [2], but it is not a field-deployable sensor. Although many sensors have been developed to detect P-level [3 - 5], these sensors cannot detect a low concentration of P-level. This is an important concern as river water has a P-level below 1 ppm. As such, the applicability of existing devices in practical scenarios is not suitable for reliable measurement.Thus, we are motivated to develop lithography-free, low-cost, and solid-state 3D-printed sensors for the ultra-sensitive detection of phosphate in river water. Our 3D-printed sensors are innovative compared to traditional fabrication techniques in the literature. We have characterized, calibrated, validated, and analyzed river samples and the results are superior to existing state-of-the-art P-sensors. Our 3D-printed P sensors showed an analytical sensitivity of 0.001 ppm of PO4 3- in river water within a detection range of 0 – 10 ppm and a detection time not exceeding 30 seconds. DEVICE FABRICATION First, we made a 3D design (CAD model) of the sensor (Fig. 1a). The sensor has one working electrode (WE) and a reference electrode (RE) having diameters of 8 and 3 mm, respectively. The CAD model was then exported to the 3D printer software, and the software was programmed based on the desired material and parameters. Fig.1b illustrates the 3D printing setup. The material used for the printing was high-temperature resin (an epoxy polymer). The resulting sensor structure was removed from the printing build platform, washed in an isopropyl alcohol bath, and dried. The sensor was then cured by treating it with UV light at 80 °C. A 100 nm-thick layer of gold (Au) was then coated on the sensor with a Kapton shadow mask and using an electron-beam evaporator. Then the RE was coated with an Ag/AgCl ink and dried at 80 °C for 2 hours. Fig.1d depicts the fabricated sensor with its Au electrode upon which poly(3-octylthiophene) (POT) and phosphate ion-selective membrane (p-ISM) were prepared and drop-coated on the WE in layers. Fig.1c summarizes the detection principle for phosphate ion exchange at different electrode layers. RESULTS AND DISCUSSION Fig.1e shows the sensor characterization based on electrochemical impedance spectroscopy (EIS). The charge transfer resistance (RCT) of the EIS curve was evaluated using its semicircle diameter. The RCT observed for the Au, POT/Au, and ISM/POT/Au electrodes were 263.67, 652.64, and 893.13 Ω, respectively. The p-ISM coating suppressed the electrochemical current in the ISM/POT/Au electrode due to the negatively charged buffer solution containing ferro/ferricyanide. Further, the 3D-printed sensor was calibrated using known standard solutions and the potential between the WE and RE decreased while we increased the phosphate concentration (Fig.1f – g). The sensor showed a slope of 37.4 mV/dec and an analytical sensitivity of 0.001 ppm. We believe that the high sensitivity of our sensor is due to the large surface area of our 3D-printed sensor structure which has wrinkled polymer surfaces that enhance more PO4 3- ion exchange. Our sensor also showed an excellent selectivity (Fig.1h) with various interfering ions.Real water samples were collected from five locations at the Rappahannock River in eastern Virginia, USA. Fig.1i shows the open circuit potentiometry (OCP) for all five river water samples. Fig.1j shows the comparison between our sensor readings and those of a commercial phosphate meter (purchased from Hanna Instruments Inc.). Here, we observed a close relation between the two readings while our sensor showed a higher sensitivity, suggesting the usefulness of our sensor in practical scenarios. Our sensor achieved excellent detection of low concentrations of P-levels in river water. In the future, our 3D-printed sensors will be deployed into river water for continuous monitoring of the P-levels in the Rappahannock River. REFERENCES [1] V. Choudhary and L. Philip, Microchemical Journal, 2021,171, p. 106809.[2] J. Zhu et al., ACS Sens, 2020, 5:5, pp. 1381–1388.[3] R. V Manurung, et al., IOP Conf Ser Mater Sci Eng, 2019, 620:1, p. 012093.[4] M. Sarwar, J. Leichner, G. M. Naja, and C.-Z. Li, Microsyst Nanoeng, 2019, 5:1, p. 56.[5] M. M. Grand et al., Front. Mar. Sci., 2017, 4:255, doi: 10.3389/fmars.2017.00255. Figure 1

Neutron-absorption gratings fabricated by ultrasound-assisted filling method based on gadolinium particles

Neutron differential phase-contrast imaging (DPCI) plays a pivotal role in analyzing magnetic domain structures and field gradients in materials, necessitating high-quality neutron absorption gratings for enhanced fringe contrast. Traditional fabrication techniques, typically filling gadolinium (Gd) or Gd-containing materials into the corresponding grating structures, face challenges in achieving optimal Gd filling ratios and thickness, limiting the neutron DPCI system’s performance. This paper introduces an approach utilizing ultrasound-assisted filling method to introduce Gd particles into grating trenches with dense deposition, achieving an absorption grating period of 42 μm. This method achieves an equivalent Gd thickness of 80.3 μm, corresponding to the filling ratio of 53.53%, as confirmed by scanning electron microscopy and x-ray micro-imaging. The utilization of an ultrasound not only improves the Gd filling ratio, but also suggests potential scalability for large-area grating production, marking a significant advancement in neutron DPCI technology by providing high-quality components.

Solvothermal Fabrication of Mesoporous Pd Nano-Corals at Mild Temperature for Alkaline Hydrogen Evolution Reaction.

Porous metallic nanomaterials exhibit interesting physical and chemical properties, and are widely used in various fields. Traditional fabrication techniques are limited to metallurgy, sintering, electrodeposition, etc., which limit the control of pore size and distribution, and make it difficult to achieve materials with high surface areas. On the other hand, the chemical preparation of metallic nanoparticles is usually carried out with strong reducing agents or at high temperature, resulting in the formation of dispersed particles which cannot evolve into porous metal. In this study, we reported the simple fabrication of coral-like mesoporous Pd nanomaterial (Pd NC) with a ligament size of 4.1 nm. The fabrication was carried out by simple solvothermal reduction at a mild temperature of 135 °C, without using any templates. The control experiments suggested that tetrabutylammonium bromide (TBAB) played a critical role in the Pd(II) reduction into Pd nanoclusters and their subsequent aggregation to form Pd NC, and another key point for the formation of Pd NC is not to use a strong reducing agent. In alkaline water electrolysis, the Pd NC outperforms the monodisperse Pd NPs and the state-of-the-art Pt (under large potentials) for H2 evolution reaction, probably due to its mesoporous structure and large surface area. This work reports a simple and novel method for producing porous metallic nanomaterials with a high utilization efficiency of metal atoms, and it is expected to contribute to the practical preparation of porous metallic nanomaterials by solvothermal reductions.

Highly efficient electric-thermal conversion of Silver/PVP composites for micro initiators by direct ink writing

Traditional film initiator fabrication techniques were limited by material and process constraints, resulting in restricted ignition capability, durability issues, and complexity in manufacturing. In this study, Metal/polymer composite materials were applied in film initiators in order to enhance the mechanical properties, longevity, and thermal attributes. Silver/polyvinylpyrrolidone composite film bridge (SPB) initiators were fabricated by direct ink writing (DIW). By adjusting the silver loading level and sintering temperature in the Ag nanoparticles/polyvinylpyrrolidone (Ag NPs/PVP) ink formulation, precise control over the structure and resistivity of the SPB was achieved. Compared to single silver film bridge (SFB) initiators prepared by magnetron sputtering (MS), SPBs demonstrated superior heating performance, higher current carrying capacity, and energy utilization under constant current excitation. In capacitor discharge tests, SPBs exhibited superior electric explosion characteristics and plasma properties, with a 25.53% higher energy utilization efficiency compared to SFBs. The peak plasma electron temperature of SPBs reached 7610 K, which was 1065 K higher than that of SFBs. This makes Silver/polyvinylpyrrolidone composite highly promising practical alternatives for high-efficiency, stable, and reliable ignition processes, with potential widespread applications in the aerospace field.

High-precision silicon nanowire array sensor for quantitating ambient humidity and pH value

This paper presents a high sensitivity silicon nanowire (SiNW) array sensor for precisely quantitating humidity and pH value. Well-aligned nanowires with ordered separation have been fabricated via low-cost and highly controllable traditional top-down fabrication techniques, which are fully compatible with complementary metal oxide semiconductor (CMOS) technology. Compared to bottom-up fabrication techniques, better reproducibility and stability in these procedures are indicated by fabrication results. The packaged SiNW array devices exhibit excellent linearity and repeatability when tested for humidity. Alternatively, the SiNW arrays give a quick and accurate reflection to hydrogen ion concentration after functionalized with APTES solution. Notably, the accuracy of the sensor can reach 0.1 pH. To characterize the immunity and long-term stability of the sensor, the performance of the SiNW array sensor at different temperatures and times was investigated in detail. The test results show that the SiNW array sensor has excellent test performance in gas and liquid environments, and the design makes it more competitive than those of commercialized sensors.

Natural Polymer‐Based Materials for Wound Healing Applications

Skin injuries pose significant health challenges, with conditions like burns and diabetic, venous, and pressure ulcers presenting complex wound management scenarios. Effective wound care strategies for these injuries encompass a range of interventions, from simple wound dressings to bioactive materials and surgical procedures involving skin substitutes and skin grafting. This review explores the potential of natural polymers, including silk, collagen, gelatin, elastin, cellulose, chitosan, alginate, and hyaluronic acid, in wound management. Natural polymers offer several advantages, including abundance, biodegradability, and compatibility with traditional and modern material fabrication techniques, and have demonstrated safety and efficacy in clinical applications, modulating various facets of the wound healing process. Highlighting preclinical and clinical studies, along with commercial products, this review showcases the versatility and utility of natural polymers in wound management and provides insights into emerging developments, such as 3D bioprinting and stimuli‐responsive materials, which hold promise for personalized wound treatments. Additionally, we discuss the importance of the material format and morphology in engineering the next generation of wound dressings and skin substitutes, offering a pathway to optimize natural polymers for enhanced wound healing outcomes.

High-performance solid-state Li-ion batteries enabled by homogeneous, large-area ferroelectric PVDF-TrFE solid polymer electrolytes via horizontal centrifugal casting method

Solid polymer electrolytes (SPEs) have emerged as promising alternatives for enhancing the safety features of lithium-ion batteries (LIBs) while remaining compatible with established LIB manufacturing processes. However, a persistent challenge has been the relatively limited yield achieved via traditional fabrication techniques such as solution casting and doctor blade methods. In this study, we present a novel strategy to produce extensive and uniform films of solid polymer electrolytes using a ferroelectric polyvinylidene fluoride-trifluoroethylene (PVDF-TrFE) polymer. This approach employs horizontal centrifugal casting (HCC), a technique hitherto unutilized for SPE production. The substantial centrifugal forces generated during the HCC process yield SPE films characterized by uniform thickness across the surface and elevated ionic conductivity at ambient temperature. Compared to conventional solution casting techniques, the Li//Li cell featuring the SPE derived from HCC manifests stable electrochemical performance and increased cycle endurance. Additionally, a full cell incorporating a Li iron phosphate cathode displays consistent electrochemical behavior at room temperature. Notably, a 3 × 4 cm2 pouch cell maintains its performance attributes even under mechanical stress conditions such as folding and punching. These findings underscore the potential effectiveness of employing the HCC method in the development of high-performance SPE-based LIB systems.

Embedding a surface acoustic wave sensor and venting into a metal additively manufactured injection mould tool for targeted temperature monitoring

Injection moulding (IM) tools with embedded sensors can significantly improve the process efficiency and quality of the fabricated parts through real-time monitoring and control of key process parameters such as temperature, pressure and injection speed. However, traditional mould tool fabrication technologies do not enable the fabrication of complex internal geometries. Complex internal geometries are necessary for technical applications such as sensor embedding and conformal cooling which yield benefits for process control and improved cycle times. With traditional fabrication techniques, only simple bore-based sensor embedding or external sensor attachment is possible. Externally attached sensors may compromise the functionality of the injection mould tool, with limitations such as the acquired data not reflecting the processes inside the part. The design freedom of additive manufacturing (AM) enables the fabrication of complex internal geometries, making it an excellent candidate for fabricating injection mould tools with such internal geometries. Therefore, embedding sensors in a desired location for targeted monitoring of critical mould tool regions is easier to achieve with AM. This research paper focuses on embedding a wireless surface acoustic wave (SAW) temperature sensor into an injection mould tool that was additively manufactured from stainless steel 316L. The laser powder bed fusion (L-PBF) “stop-and-go” approach was applied to embed the wireless SAW sensor. After embedding, the sensor demonstrated full functionality by recording real-time temperature data, which can further enhance process control. In addition, the concept of novel print-in-place venting design, applying the same L-PBF stop-and-go approach, for vent embedding was successfully implemented, enabling the IM of defectless parts at faster injection rates, whereas cavities designed and tested without venting resulted in parts with burn marks.

Electrohydrodynamically printed microlens arrays with controllable curvature based on surface functionalization

Precisely controlling the optical characteristics of the microlens array (MLA) is a key issue for the MLA's fabrication and its applications. A cost-effective method for fabricating MLA with different curvatures and diameters by surface functionalization and electrohydrodynamic inkjet (E-jet) printing is proposed. The surface with self-assembled monolayers has low surface energy, which greatly improves the contact angle of the microlens. The UV-ozone treatment and neutral density filters with different optical densities are used to control the wettability of the substrates. Based on this method, the curvatures of the microlens can be controlled easily and the numerical aperture (NA) of the microlens can be adjusted from 0.18 to 0.49. Compared with traditional fabrication techniques, the method we demonstrated is flexible, low-cost, rapid, and capable of fabricating MLA with large area, high packing density, desirable NA, and diameters.

Large Field-of-View Nonlinear Holography in Lithium Niobate.

A nonlinear holographic technique is capable of processing optical information in the newly generated optical frequencies, enabling fascinating functions in laser display, security storage, and image recognition. One popular nonlinear hologram is based on a periodically poled lithium niobate (LN) crystal. However, due to the limitations of traditional fabrication techniques, the pixel size of the LN hologram is typically several micrometers, resulting in a limited field-of-voew (FOV) of several degrees. Here, we experimentally demonstrate an ultra-high-resolution LN hologram by using the laser poling technique. The minimal pixel size reaches 200 nm, and the FOV is extended above 120° in our experiments. The image distortions at large view angles are effectively suppressed through the Fourier transform. The FOV is further improved by combining multiple diffraction orders of SH fields. The ultimate FOV under our configuration is decided by a Fresnel transmission. Our results pave the way for expanding the applications of nonlinear holography to wide-view imaging and display.

Investigation of high entropy alloy coatings produced by electrical discharge machining

The exploration of High Entropy Alloys (HEAs) has attracted significant attention due to their multifaceted property profile, suitable for a diverse range of industrial applications. Traditional fabrication techniques, such as melting, have been met with efficiency constraints, necessitating the investigation of alternative approaches for HEA development. The present study examines the feasibility of Electrical Discharge Coating (EDC) as a new and alternative process for the potentially cost-effective fabrication of HEA coatings, with an emphasis on enhancing surface integrity. To provide empirical insights, the research focuses on the deposition of HEA coatings on substrates of X37CrMoV5-1 steel and aluminum, utilizing powder electrodes made of Fe-Co-Mn-Ni-Cr and Fe-Co-Mn-Ni-Cu. The influence of Electrical Discharge Coating (EDC) process parameters on the formation and quality of the High Entropy Alloy (HEA) coatings was evaluated by advanced microstructural characterization techniques. The results show that HEA coatings could be fabricated using EDC, achieving a coating thickness of more than 40 µm.

Latest Trends In 3D Printed Microfluidics

Over the last decade, there has been a large interest in the use of 3D printing to manufacture microfluidic devices, since it has the ability to circumvent traditional fabrication techniques limitations. These include being unable to really make complex three-dimensional architectures, expensive and time-consuming processes to change device designs, and difficulty transitioning from prototyping to mass production. In this literature review, we will look at the current trends in 3D printed microfluidics, as well as recent advances and new developments in fabrication techniques, materials, and applications. Integration of 3D printing in microfluidics research has helped in the rapid prototyping of fluidic channels and structures with high complexity at an effective cost. Applications of 3D printed microfluidics are described in the areas of healthcare, diagnostics, chemical synthesis, and biotechnology. This paper also delineates the challenges and future prospects of 3D printed microfluidics, giving insight into potential research directions and technological developments.

An efficient and low-profile metasurface-based polarization converter with linear and circular polarization efficiencies for X- and Ku-Band applications

In this study, a metasurface-based linear and circular polarization converter operating on the reflection mode is proposed for X- and Ku-band microwave applications. The proposed converter offers an optimum performance with a polarization conversion ratio (PCR) and polarization matching ratio (PMR) greater than 93 in the bandwidth for a linearly polarized in the y-direction and right-handed circular polarized (RHCP) incident waves. Besides, the design performs over 80 PCR performance up to under oblique incidence. Moreover, the proposed converter is capable of left-handed circular polarization conversion between 7.42 and 7.68 GHz for a y-polarized incident wave. The design offers a relative bandwidth (RBW) of 71.36. The converter design is constructed with metal termination, an easily accessible FR-4 substrate and a simple design metasurface. Surface currents of the polarization converter at resonance frequencies of 8.77, 12.88 and were examined to understand its working mechanism. In addition, when the proposed design is rearranged with the appropriate geometry, the monostatic RCS reduction value in the 8.0–17.7 range is observed to be higher than 10 dB. CST program (a commercial 3D electromagnetic simulator) was used in simulations. The simulated device was fabricated with a traditional board fabrication technique. Simulation results were verified with free space measurements calibrated by the thru-reflect-line calibration procedure. The performance and efficiency of the proposed polarization converter were compared with other converters in the literature.

3D Printed Bioinspired Hierarchical Surface Structure with Tunable Wettability

Abstract Nature has examples of impressive surfaces and interfaces with diverse wettability stemming from superhydrophilicity to superhydrophobicity. The multiscale surface structures found in biological systems generally have high geometric complexity, which makes it challenging to replicate their characteristics, especially using traditional fabrication techniques. It is even more challenging to fabricate such complex microstructures with tunable wettability. In this paper, we propose a method to tune the wettability of a micro-scale surface by changing the geometrical parameters of embedded micro-structures in the surface. By taking inspiration from an insect (springtails), we designed micropillar arrays with different roughness by adjusting geometric parameters such as reentrant angle, pitch distance, and the number of spikes and pillars. This study shows that, by changing geometrical parameters in microscale, the apparent contact angle, and hence the surface wettability can be calibrated. The microscale pillars were fabricated using a precise micro direct light processing (uDLP) three-dimensional (3D) printer. Different printing parameters were studied to optimize the geometric parameters to fabricate 3D hierarchical structures with high accuracy and resolution. By controlling the size of different features of the pillar, pillar number, and layout of the mushroom-shaped micropillars, the wettability of the surface is possible to be tuned from a highly nonwetting liquid/material combination to highly wetting material. Such wettability tuning capability expands the design space for many biomedical and thermofluidic applications.

Low-cost 3D printed inertial flow microfluidic devices for cellular isolation in liquid biopsies

Microfluidic devices for biomedical applications manufactured by conventional lithography often lack flexibility in design integration. Limitations in aspect ratio or in the ability to integrate microfluidic elements located in different planes reduce the available design options. Regarding this, 3D printing offers several advantages over traditional fabrication techniques. However, 3D printing technologies indeed show some limitations in the resolution of the microstructures obtained in comparison with standard lithography. We have optimized a low-cost multi-system combining standard lithography and 3D printing to design inertial flow microfluidic devices with different channels dimensions for cell concentration or isolation in blood, which are adaptable to cancer tumor cell (CTC) detection in liquid biopsies. CTC separation from complete blood using microfluidic devices often faces the challenge of leukocyte contamination due to their similar size with CTC. However, with 3D printing, we can create larger channels than those produced through lithography, enabling the use of beads coated with antibodies that bind to leukocytes expressing the CD45+ receptor. This binding results in larger particles that could be separated from the CTCs in the microfluidic devices, providing a more purified CTC sample. Microfluidic spiral structures were obtained with standard lithography for a first purification step using rectangular channel of 152 µm height and 500 µm width channels. The blood samples after processingE were analyzed by flow cytometry and revealed a recovery efficiency using two different CTC models of 80% ± 4% and 95% ± 4%. Also, the system enables 97.5% ± 1.89% and 83.4% ± 3.6% depletion of erythrocytes and leukocytes respectively. In addition, single or double microfluidic spiral structures to reduce leukocyte contamination using beads were directly fabricated using stereolithography 3D printing. In the single device with a channel of 600 μm and 1.4 mm of height and width respectively, and in the case of the device with two spirals placed on different planes, with a channel of 800 μm and 1.4 mm of height and width respectively. In addition, a read-out system based on an electronic circuit with piezoelectric micropumps, and a low-cost optical microscope was designed and adapted. This configuration avoids usual limitations when using syringe pumps and big microscopes, such as lack of sample recirculation, loss of CTCs during stabilization, blood sedimentation in the syringe, and reduced portability. Finally, combining a microfluidic spiral to separate red blood cells and partially leucocytes with the 3D microfluidic spiral to separate particles as the beads coated with CD45+ antibodies, could be possible to achieve a total leukocyte depletion up to 91%, and a maximum recovery of cancer cells up to 95%.

Terahertz Properties of Common Microwave Dielectric Materials

Traditional microwave design and fabrication techniques have been adopted into the terahertz domain. Understanding the properties of microwave dielectric materials at terahertz frequencies is critical for accurate component design. Nevertheless, terahertz properties for common microwave dielectric materials are largely unknown. Hence, this paper presents the relative permittivity, loss tangent, refractive index, and extinction coefficient for such materials, including microwave substrates and low-temperature co-fired ceramics (LTCCs), within the 0.1 to 3.5 THz range. Terahertz time-domain spectroscopy (THz-TDS) and a vector network analyzer produce accurate material parameter results. The material parameters presented in this paper serve as a valuable resource for component design at terahertz frequencies.

Self-supporting biocatalytic polyelectrolyte complex hollow fiber membranes via salt-dilution induced phase separation

The potential use of biocatalytic membranes in industries such as water treatment, pharmaceuticals, and medicine has attracted much interest in recent years. However, the use of organic solvents in traditional membrane fabrication techniques presents a challenge in the direct integration of enzymes during the membrane production. Thus, enzyme immobilization relies on consecutive modification steps (coating, binding, activation). Yet, recent progress in membrane fabrication using all-aqueous phase inversion of polyelectrolyte complexes (PEC) enables the direct incorporation of enzymes in the polymer solution. We present the fabrication of free-standing, defect-free and mechanically stable biocatalytic PEC hollow fiber membranes via the salt-dilution induced phase separation method. A polymer solution containing poly(sodium-4-styrenesulfonate) (PSS), poly(diallyldimethylammonium chloride) (PDADMAC), KBr, and the enzyme alkaline phosphatase (ALP) was extruded through a spinneret with a mixture of water and glycerol as lumen fluid into a water coagulation bath at 0 °C. The mechanical stability of the fibers is tuned by subsequent photo-induced cross-linking using 4,4’-diazidostilbene-2,2’-difulfonate tetrahydrate (DAS) and UV light. The resulting membranes have a molecular weight cut-off of 400Da, a pure water permeance of 1.5LMH/bar, and a burst pressure of 7bar. The immobilization of ALP proves successful, as the immobilized shows similar catalytic activity to that of the free enzyme, and both storage and thermal stability are improved. Moreover, the enzymes retain 70% of their initial activity after UV cross-linking with DAS and maintain their catalytic activity after repeated wash and filtration cycles. This work highlights the versatility of the fabrication of polyelectrolyte complex hollow fiber membranes via the salt-dilution induced phase separation, serving as a platform technology for the fabrication of porous, selective, and bioactive membranes.

Recyclable and biodegradable smart electronic circuits on flexible substrates

ABSTRACT Direct ink writing is an innovative technique developed to replace traditional fabrication techniques, such as lithography, for flexible electronics. Herein, a novel ternary cadmium sulfide quantum dot-doped reduced graphene oxide-bismuth oxide (CrGB) heterojunction semiconductor material was prepared via an in situ hydrothermal technique. After that, an electroconductive ink consisting of carbon nanotubes (CNTs) and CrGB was prepared. The ink was used to fabricate a flexible circuit using nanocrystalline cellulose (NCC) paper. The circuit exhibited excellent conductivity of 3900 S cm−1. Furthermore, the recyclability and biodegradation of the circuit suggest the feasibility of constructing low-cost and environmentally benign materials and devices.

Recent progress on 3D-printed gelatin methacrylate-based biomaterials for articular cartilage repair

The structure and composition of articular cartilage is complex, and its self-healing ability is limited, and thus, it is difficult to achieve ideal healing once the articular cartilage is damaged. Recently, three-dimensional (3D) printing technology has provided a new possibility for the repair of articular cartilage. Engineered cartilage tissues can be fabricated by superimposing customized inks, considering different geometric structures and components of tissues. 3D printing can be effectively used to manufacture high-precision structures with complex geometry, solving the shortcomings of traditional scaffold fabrication techniques. Gelatin methacrylate (GelMA) is modified gelatin and is currently a widely used 3D printing ink due to its photocrosslinking properties. With good biocompatibility and tunable physical properties, it can provide a good scaffold platform for cell proliferation and growth factor release. Given that the role of 3D printing technology in cartilage repair has been widely reported, this article reviews the research progress of 3D-printed GelMA-based biomaterials in articular cartilage tissue engineering. We focus primarily on how 3D printing technology addresses the existing challenges inherent to the field of articular cartilage tissue engineering. We accentuate the modifications implemented in GelMA-based 3D printing scaffolds to optimize articular cartilage regeneration. Additionally, we provide a comprehensive summary of the utilization of GelMA-based biomaterials incorporating various cells, growth factors, or other tissue components and highlight how these adaptations, in conjunction with the benefits of 3D printing technology, facilitate improvements the articular cartilage repair.

Bottom-up, Chip-Scale Engineering of Low Threshold, Multi-Quantum-Well Microring Lasers.

Integrated, on-chip lasers are vital building blocks in future optoelectronic and nanophotonic circuitry. Specifically, III-V materials that are of technological relevance have attracted considerable attention. However, traditional microcavity laser fabrication techniques, including top-down etching and bottom-up catalytic growth, often result in undesirable cavity geometries with poor scalability and reproducibility. Here, we utilize the selective area epitaxy method to deterministically engineer thousands of microring lasers on a single chip. Specifically, we realize a catalyst-free, epitaxial growth of a technologically critical material, InAsP/InP, in a ring-like cavity with embedded multi-quantum-well heterostructures. We elucidate a detailed growth mechanism and leverage the capability to deterministically control the adatom diffusion lengths on selected crystal facets to reproducibly achieve ultrasmooth cavity sidewalls. The engineered devices exhibit a tunable emission wavelength in the telecommunication O-band and show low-threshold lasing with over 80% device efficacy across the chip. Our work marks a significant milestone toward the implementation of a fully integrated III-V materials platform for next-generation high-density integrated photonic and optoelectronic circuits.