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Beyond the Toolpath: Site-Specific Melt Pool Size Control Enables Printing of Extra-Toolpath Geometry in Laser Wire-Based Directed Energy Deposition
摘要： A variety of techniques have been utilized in metal additive manufacturing (AM) for melt pool size management, including modeling and feed-forward approaches. In a few cases, closed-loop control has been demonstrated. In this research, closed-loop melt pool size control for large-scale, laser wire-based directed energy deposition is demonstrated with a novel modification, i.e., site-specific changes to the controller setpoint were commanded at trigger points, the locations of which were generated by the projection of a secondary geometry onto the primary three-dimensional (3D) printed component geometry. The present work shows that, through this technique, it is possible to print a specific geometry that occurs beyond the actual toolpath of the print head. This is denoted as extra-toolpath geometry and is fundamentally different from other methods of generating component features in metal AM. A proof-of-principle experiment is presented in which a complex oak leaf geometry was embossed on an otherwise ordinary double-bead wall made from Ti-6Al-4V. The process is introduced and characterized primarily from a controls perspective with reports on the performance of the control system, the melt pool size response, and the resulting geometry. The implications of this capability, which extend beyond localized control of bead geometry to the potential mitigations of defects and functional grading of component properties, are discussed.
关键词： closed-loop control,lasers,metal,directed energy deposition,additive manufacturing,3D printing,titanium,site-specific,melt pool size
更新于2025-09-19 17:13:59
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A novel 3D printed negative pressure small sampling system for bubble-free liquid core waveguide enhanced Raman spectroscopy
摘要： Liquid core waveguide (LCW) is well-known as an effective fiber enhanced approach for Raman spectroscopy with features of long optical path and small sampling size. However, inevitable air bubbles introduced in the LCW tube possibly caused light scattering, refraction and reflection so as to further hamper the quantitative analysis. In this work, to eliminate air bubbles, a novel negative pressure system combined with 3D printing was first utilized for the enhanced Raman spectroscopy on the principle of the gas permeability of LCW tube. After optimization, the LCW tube made of Teflon-AF was inserted into a D-shaped support with an internal channel manufactured by 3D printing to create a sealed space; then, air pressure outside the LCW tube was reduced to create a negative pressure via diaphragm pump and magnetic valve controlled by computer. Under adjustable negative pressure, not only can liquid sample be introduced into the LCW tube automatically, but air bubbles can also be removed through the tube wall simply and completely. For real samples, the assembled apparatus was employed as the small sampling system of Raman spectrometer to measure rhodamine B and ethanol in solutions, with the highest 82-fold (ethanol) enhancement of analytical sensitivity vs. the traditional colorimetric ware. The limit of detections (LODs) were 0.7 μg/mL rhodamine B and 0.03% (v:v) ethanol with only 250 μL sample consumption; their linear correlation coefficients (r) were 0.998 and 0.999 in the range from 2 μg/mL to 25 μg/mL (rhodamine B) and 0.1%–5% (ethanol), respectively. It is worth mentioning that the intraday stability and 7-days reproducibility can be both controlled within 7%, which is extremely superior to the previous enhanced Raman spectroscopy. For another, 3D printing enables the LCW detection system more integrated and easier to assemble. So, the proposed method proves many advantages, such as stability, sensitivity, and quickness, in addition of effective physical enhancement, low sample consumption, and long light path. Considering the flexibility of LCW tube, as a versatile module, the negative pressure LCW system should be further suitable to ultraviolet, fluorescence and other detectors, which reveals a favorable application prospect for the fast testing instruments.
关键词： Bubble-free,Liquid core waveguide,3D printing,Micro sampling,Enhanced Raman spectrometry,Fast testing,Negative pressure
更新于2025-09-19 17:13:59
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Ultrafast photo-annealed carbon-coated SiO2 sphere electrodes for NO2 gas sensing
摘要： There is great interest in carbon-based printed electronics as a promising technology to achieve lighter, thinner and ?exible electronic devices at low-costs. Despite the surge of enthusiasm in this area, research advances in printed electronics are not yet able to realize diverse carbon structures yet. This is due to the limitations in conventional solution-based printing methods (e.g., inkjet printing, roll-to-roll, screen printing). Processes such as polymer phase-inversion offer one possibility but a much faster and ef?cient method should be devised for reliable production. Here, we demonstrate laser printing combined with intense pulsed-light (IPL) annealing as a novel and ef?cient technique which can form inter-connected carbon spheres electrode on ?exible polymer substrate. Our observations show that the printed patterns from a laser printer consist of a solid-state polymer matrix with inorganic nanoparticles randomly embedded inside. Through ultrafast (5 ms) IPL treatment, core/shell type nanosphere arrays of carbon-coated SiO2 were successfully fabricated, which could be used as a functional platform for highly selective NO2 gas sensing.
关键词： Laser printing,Gas sensing,Intense pulsed-light,SiO2 spheres,Carbon coating
更新于2025-09-19 17:13:59
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Embedding optical Fiber Bragg Grating (FBG) sensors in 3D printed casings
摘要： This paper aims to numerical and experimentally study and propose Fiber Bragg Grating (FBG) sensors embedded in 3D printed casings. 3D printed casings offer design freedom, enabling strain measurement of structural systems with complex configuration, and, at low cost due to its easiness to manufacture. The casings were first numerically modeled using a commercial finite element software. After the casing was conceptualized to the user needs, they were printed and introduced in two different applications. Assessing the behavior of 3D printed casings in realistic applications has been explored only by few authors, which is the novelty introduced herein. In both applications, the casings’ behavior was analyzed numerical and experimentally. The experimental results were compared with electrical strain gauges. As expected from the numerical analysis results, a calibration factor was determined to accurately predict strain using the embedded FBG sensors. A comprehensive discussion is presented on the topic of calibration factors defined numerical and experimentally.
关键词： Fiber Bragg Grating,3D printing,Casing
更新于2025-09-19 17:13:59
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Preparation of Highly Porous Carbonous Electrodes by Selective Laser Sintering
摘要： Selective laser sintering (SLS) 3D printing was utilized to fabricate highly porous carbonous electrodes. The electrodes were prepared by using a mixture of fine graphite powder and either polyamide-12, polystyrene, or polyurethane polymer powder as SLS printing material. During the printing process the graphite powder was dispersed uniformly on the supporting polymer matrix. Graphite’s concentration in the mixture was varied between 5 and 40 wt % to find the correlation between the carbon content and conductivity. The graphite concentration, polymer matrix, and printing conditions all had an impact on the final conductivity. Due to the SLS printing technique, all the 3D printed electrodes were highly porous. By using polyurethane as the supporting matrix it was possible to produce flexible electrodes in which the conductivity is sensitive to pressure and mechanical stress. Physical properties such as graphite distribution, attachment, and the overall porosity of the printed electrodes were studied using scanning electron microscopy (SEM), helium ion microscopy (HIM), and X-ray tomography. The results show that the combination of chemical design of the printing material and the utilization of SLS 3D printing enables fabrication of highly customizable electrodes with desired chemical, physical, mechanical, and flow-through properties.
关键词： conductivity,graphite,3D printing,selective laser sintering,porous electrodes
更新于2025-09-19 17:13:59
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Inkjet printing multilayer OLEDs with high efficiency based on the blurred interface
摘要： Inkjet printing technology is considered to be the next generation manufacturing method for organic light-emitting diodes (OLEDs) production because of its simplicity and low cost. However, the dissolution at interfaces in printing process is still one of the great challenges that limits its progress. The present work utilized the dissolution phenomenon innovatively to generate blurred interface during inkjet printing of multi-layer OLEDs, where TAPC and TAPC:TPBi:Ir-complexes were employed as hole transport layer (HTL) and emitting layer (EML) and both of them were dissolvable in butyl benzoate to form the HTL and EML inks. When they were printed sequentially, a blurred interface between HTL and EML was formed because the dissolution phenomenon, which facilitated the exciton formation and charge balance in EML and improved the device performance. With this blurred interface, the maximum current efficiency of 9.8 cd A-1, the maximum power efficiency of 5.0 lm W-1, and the maximum external quantum efficiency of 3.0% were achieved in (fpbt)2Ir(acac) based OLEDs. In contrast, they were only 7.4 cd A-1, 3.9 lm W-1 and 2.2% in devices having a clear interface between HTL and EML.
关键词： organic light emitting diodes (OLEDs),blurred interface,inkjet printing
更新于2025-09-19 17:13:59
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The Influence of Selected Selective Laser Sintering Technology Process Parameters on Stress Relaxation, Mass of Models, and Their Surface Texture Quality
摘要： The article presents the results of research on the impact of basic process parameters of selective laser sintering technology on the mass of the produced models (density of the sintered material—polyamide PA 2200), stress relaxation during compression determined in accordance with the ISO 3384 standard, and geometric surface structure parameters (SGPs). During the tests, the influence of process parameters such as the location of the models on the virtual construction platform (printing direction), the density of the energy supplied to the sintered layer of powder, and the layer thickness of the manufactured material layer was taken into account. The test results confirmed that the process parameters have a significant impact on the density of the model material (in the sintered state), the mechanical properties (stress relaxation during compression), and the quality of the surface texture (SGPs). The most favorable positioning variants of the models on the construction platform were determined. The most favorable thickness variants of the combined layers and the density value of the energy supplied to the sintered powder layer were selected, depending on the expected mass, strength, and SGP quality. In addition, it has been shown that it is possible to build models with reduced mass (>20%), while maintaining satisfactory mechanical and qualitative properties of the surface texture.
关键词： additive manufacturing technologies,GPS,rapid prototyping,SLS,3D printing,stress relaxation
更新于2025-09-19 17:13:59
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Ultraviolet Photodetecting and Plasmon-to-Electric Conversion of Controlled Inkjet-Printing Thin-Film Transistors
摘要： Direct ink-jet printing of a zinc-oxide-based thin-film transistor (ZnO-based TFT) with a three-dimensional (3-D) channel structure was demonstrated for ultraviolet light (UV) and visible light photodetection. Here, we demonstrated the channel structures by which temperature-induced Marangoni flow can be used to narrow the channel width from 318.9 ± 44.1 μm to 180.1 ± 13.9 μm via a temperature gradient. Furthermore, a simple and efficient oxygen plasma treatment was used to enhance the electrical characteristics of switching ION/IOFF ratio of approximately 105. Therefore, the stable and excellent gate bias-controlled photo-transistors were fabricated and characterized in detail for ultraviolet (UV) and visible light sensing. The photodetector exhibited a superior photoresponse with a significant increase of more than 2 orders of magnitude larger drain current generated upon UV illumination. The results could be useful for the development of UV photodetectors by the direct-patterning ink-jet printing technique. Additionally, we also have successfully demonstrated that a metal-semiconductor junction structure that enables plasmon energy detection by using the plasmonic effects is an efficient conversion of plasmon energy to an electrical signal. The device showed a significant variations negative shift of threshold voltage under different light power density with exposure of visible light. With the ZnO-based TFTs, only ultraviolet light detection extends to the visible light wavelength.
关键词： visible light photodetection,plasmon energy detection,ink-jet printing,zinc-oxide-based thin-film transistors,oxygen plasma treatment
更新于2025-09-19 17:13:59
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[IEEE 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - Berlin, Germany (2019.6.23-2019.6.27)] 2019 20th International Conference on Solid-State Sensors, Actuators and Microsystems & Eurosensors XXXIII (TRANSDUCERS & EUROSENSORS XXXIII) - In-Situ Laser Processing for 3D Printed Mechanical Transducers
摘要： With the development of our in-situ Laser Processing techniques we provide solutions to both planarize Fused Deposition Modeling (FDM) printed plastics and sintering of inks printed by Direct Ink Writing (DIW). Laser sintering enables fabrication of 3D printed functional and structural layers out of FDM printed thermoplastics and DIW printed conductive inks. As the sintering is in-situ, the sintered conductive layers, produced out of DIW printed silver inks, can be embedded into thermally sensitive FDM printed thermoplastics. In this fashion, vertical stacks out of these materials can be fabricated, in order to achieve capacitive and resistive mechanical transducers.
关键词： laser processing,Digital manufacturing,mechanical sensors,3D printing,transducers
更新于2025-09-19 17:13:59
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[IEEE 2019 Antennas Design and Measurement International Conference (ADMInC) - St. Petersburg, Russia (2019.10.16-2019.10.18)] 2019 Antennas Design and Measurement International Conference (ADMInC) - Millimeter-wave Partially Dielectric Filled Waveguide Reflectarray Antenna
摘要： Design and characteristics of millimeter-wave waveguide reflectarray antenna are considered. A specific feature of the presented antenna is a protective plastic cover that partially fills waveguides and, thus, provides additional phase correction as well. As a result, the waveguide reflectarray antenna has the relative bandwidth of 57% and 27.6 dB peak directivity. The proposed design allows manufacturing with the cheap laser-cutting and 3D printing techniques.
关键词： reflectarray,unit cell,arrays,3D printing,waveguide
更新于2025-09-19 17:13:59