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Enabling direct writing of an epoxy resin with thermo-activated organic thixotropes
Abstract not provided
Direct writing of PVBVA/Ti 3 C 2 T x (MXene) triboelectric nanogenerators for energy harvesting and sensing applications
Triboelectric nanogenerators (TENGs) have gained recognition for their potential to convert mechanical energy into electrical energy, making them attractive for applications in healthcare, robotics, and human-device interfaces. However, many TENG devices rely on fluorinated polymers for high charge generation and involve complex fabrication processes, which limit their practicality and environmental sustainability. Here, we developed an eco-friendly composite of poly (vinyl butyral-co-vinyl alcohol-co-vinyl acetate) (PVBVA) and Ti 3 C 2 T x MXene for extrusion printing onto aluminum foil substrates, enabling the additive manufacturing of TENGs. Experimental results indicate that integrating 5.5 mg mL -1 of MXene (P-MX 5.5) into PVBVA resulted in a power density of 760 mW·m -2 , with simultaneous improvements in open-circuit voltage (129 %) and short-circuit current (250 %), demonstrating enhanced charge transfer efficiency. Beyond aluminum foil-based devices, we further explored the fully printed P-MX 5.5 TENG by utilizing silver ink electrodes, eliminating the need for aluminum foil. This fully printed, flexible TENG was successfully used for real-time human motion sensing, demonstrating its ability to detect activities such as walking, running, knee bending, and jumping. Collectively, our additively manufactured and sustainable PVBVA-MXene TENG composites, including both aluminum-based and fully printed versions, show promise for future energy harvesters, sensors, wearable electronics, healthcare, and robotic applications.
Hierarchically Porous Ceramics via Direct Writing of Binary Colloidal Gel Foams
Not provided.
Direct-write orientation of charge-transfer liquid crystals enables polarization-based coding and encryption
Abstract Optical polarizers encompass a class of anisotropic materials that pass-through discrete orientations of light and are found in wide-ranging technologies, from windows and glasses to cameras, digital displays and photonic devices. The wire-grids, ordered surfaces, and aligned nanomaterials used to make polarized films cannot be easily reconfigured once aligned, limiting their use to stationary cross-polarizers in, for example, liquid crystal displays. Here we describe a supramolecular material set and patterning approach where the polarization angle in stand-alone films can be precisely defined at the single pixel level and reconfigured following initial alignment. This capability enables new routes for non-binary information storage, retrieval, and intrinsic encryption, and it suggests future technologies such as photonic chips that can be reconfigured using non-contact patterning.
XeF 2 gas assisted focused electron beam induced etching of niobium thin films: towards direct write editing of niobium superconducting devices
Focused electron beam induced etching (FEBIE) of Nb films produced a maximum etching yield of 3 Nb atoms/e − while varying beam energy, beam current, dwell time, and XeF 2 precursor working pressure. An optimized etch resolution of 17 nm was achieved.
Low-Cost, Efficient and Durable High Temperature Wireless Sensors by Direct Write Additive Manufacturing for Application in Fossil Energy Systems
In-situ monitoring of physical parameters in fossil energy (FE) systems is challenging because of their high operating temperatures and oxidizing environments. This research aims utilize Aerosol Jet (AJ) nanoparticle printing, an advanced additive manufacturing method, to fabricate high temperature sensors for FE applications. Sensor films were fabricated by the AJ printing method with an excellent control over film microstructure and properties, in addition to creating less waste. Printing of six different materials, namely, silver (Ag), nickel (Ni), nickel-chromium (NiCr) alloy, copper (Cu), copper-nickel (CuNi), and carbon nanotubes (CNTs) was carried out for their evaluation of as sensor films. The films were then characterized using impedance spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). Film microstructure was correlated with the sensor electrical and mechanical behavior at different temperatures (24-500 °C) and frequencies (0.02 - 300 kHz). This knowledge was then used to fabricate, test, and characterize strain and temperature sensors for high temperature applications. The strain sensors were shown to have a very low thermal strain up to 500 °C and a 57% higher gauge factor compared to the commercially available counterparts. This enhance performance was attributed to the inherent porosity in the sensor films that allowed the films to exhibit a metamaterial-like behavior when deformed. The AJ printed temperature sensors were shown to have the highest Seebeck coefficient amongst all the film-based temperature sensors. In addition, fundamental aspects of crystal structure and phase transformations in Ba(Fe0.7Ta0.3)O3-δ (BFTO), a high temperature sensor material, was investigated along with 3D printed antennas that can transmit sensor signals at high temperatures. Two PhD students, one from first generation college-going underrepresented minority community (URM), two postdoctoral fellows, and several masters and undergraduate students were supported by this award. This work opens up the possibility of realizing low-cost high-performance sensor devices using advanced manufacturing techniques for high temperature FE applications.
Addendum: Zhang, C., et al. Pulsed Laser-Assisted Helium Ion Nanomachining of Monolayer Graphene—Direct-Write Kirigami Patterns. Nanomaterials 2019, 9, 1394
The authors wish to make the following corrections to this paper [1]: The funding section needs to be corrected.
Direct writing nozzle system for additive manufacturing
A nozzle apparatus used for extruding a material includes an internal spindle that imparts motion into the extruding material, the internal spindle having a base; a multiple degree-of-freedom pivot at the base of the internal spindle, and a drive mechanism that controls the motion of the internal spindle. In one embodiment the material is a semi-solid metal or alloy. In another embodiment the material is a shear thinning mixture or material. In yet embodiment the material is a thixotropic mixture or material. The nozzle apparatus can be used for making a three-dimensional object with the steps of providing a material; providing a nozzle that extrudes the material, the nozzle having an internal spindle that imparts motion into the material; positioning the nozzle above a support structure; and moving the nozzle in a three-dimensional pattern while extruding the material through the nozzle onto the support structure or onto the material previously deposited.
Large Nuclear Detector Array Interconnection by Direct-Write Laser Chemical Vapor Deposition (CVD)
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Direct write sensors
A method of making an acoustic wave sensor includes the steps of providing a piezoelectric substrate layer and printing on the substrate layer a sensor layer comprising a first interdigitated acoustic wave transducer, a sensing film, and positioned on an opposing side of the sensing film from the first interdigitated acoustic wave transducer at least one selected from the group consisting of a second interdigitated acoustic wave transducer and a Bragg reflector. An insulation layer can be printed. An antenna can be printed in an antenna layer, and the insulation layer can be interposed between the antenna layer and the sensor layer. An electrical connection can be printed between the antenna and the first interdigitated acoustic wave transducer. An acoustic wave sensor is also disclosed.
Balancing Functionality and Printability: High-Loading Polymer Resins for Direct Ink Writing
Although direct ink writing (DIW) allows the rapid fabrication of unique 3D printed objects, the resins—or “inks”—available for this technique are in short supply and often offer little functionality, leading to the development of new, custom inks. However, when creating new inks, the ability of the ink to lead to a successful print, or the “printability,” must be considered. Thus, this work examined the effect of filler composition/concentration, printing parameters, and lattice structure on the printability of new polysiloxane inks incorporating high concentrations (50–70 wt%) of metallic and ceramic fillers as well as emulsions. Results suggest that strut diameter and spacing ratio have the most influence on the printability of DIW materials and that the printability of silica- and metal-filled inks is more predictable than ceramic-filled inks. Additionally, higher filler loadings and SC geometries led to stiffer printed parts than lower loadings and FCT geometries, and metal-filled inks were more thermally stable than ceramic-filled inks. The findings in this work provide important insights into the tradeoffs associated with the development of unique and/or multifunctional DIW inks, printability, and the final material’s performance.
Effects of Structure and Filler on Mechanical Properties of Direct Ink Write Pads
Direct ink write (DIW) is an extrusion-based additive manufacturing (AM) technique that enables superior repeatability, property tuning, and material customization compared to conventional manufacturing techniques. In this research, DIW is used to print silicone foams that must accommodate the thermal expansion of other parts. This expansion requires the material to compress and subsequently recover. Thus, a key performance metric is reducing “compression set” or deformation retained after the material is compressed. For this study, a silicone resin was compounded with a getter material, 1,4 bis(phenylethynyl)benzene (DEB) mixed with carbon-supported palladium (Pd) and printed in a variety of lattice structures. The effects of the filler and print structure on compression set were evaluated. In these experiments, 0.5-inch diameter coupons were compressed to 75% their original height for 22 hours at 70 °C, and the change in height calculated at intervals between 30 minutes and 24 hours post-decompression. The unfilled pad with skin layers had the best compression set at 0.7% ± 0.1%, followed by the unfilled pad with no skins at 1.5% ± 0.1%. As the number of filled layers increased, compression set performance degraded. The pad with filled skin layers and all filled layers had a compression set of 7.0% ± 0.3%. Additionally, the reaction extent of DEB was found to increase compression set, possibly due to the diffusion of DEB to the surface at elevated temperatures. Imaging reveals extensive crystallization at the surface. These investigations show that a non-reinforcing filler will increase compression set but that print structure can mitigate this effect.
On the 3D printability of one-part moisture-curable polyurethanes via direct ink writing (DIW)
Direct ink writing (DIW) is an ambient temperature additive manufacturing (AM) method that accommodates many possible ink materials. Here, in this work, we demonstrate using a moisture-curable commercially available polyurethane (PU) sealant as an alternative ink for DIW. We discussed the fundamentals of PU chemistry and determined the best 3D printing parameters. Studies on rheological, thermogravimetric, spectroscopic characterization, and initial finite element analyses (FEA) showed properties expected from a performance sealant with high elongation and low modulus of a 3D-printed object. This affirms the flexibility of the DIW technique as an accessible AM method amenable for future materials development from commercial model formulations.
Coaxial Ceramic Direct Ink Writing on Heterogenous and Rough Surfaces: Investigation of Core–Shell Interactions
In this work, coaxial conductor–ceramic direct ink writing enables the printing of sensitive or encapsulated materials onto heterogeneous and rough substrates. While encasing the core fluid within a stiff ceramic shell, continuity may be maintained, even while printing onto conventionally challenging substrates. Here, we report the development of a coaxial ceramic direct ink writing suite and explore coflow interrelationships based on microfluidic principles. A coaxial nozzle is designed to facilitate the coextrusion of an alumina shell, whereas indium–tin-oxide inks constitute the core. In this manner, a core–shell ceramic element may be printed onto rough substrates for future high-temperature applications. Colloidal inks are engineered to provide the required rheological and sintering performance. Moreover, flow simulations in conjunction with microfluidic coflow principles are used to explore the coaxial printing processing space, thus controlling the core–shell architectures. Physical modeling is further used to analyze core deformations and eccentricity. As a result, simulations are validated experimentally, and the analyses are used to deposit coaxial ceramic features onto heterogeneous, high-temperature ceramic substrates.
Analytical Study and Experimental Verification of Shear-Thinning Ink Flow in Direct Ink Writing Process
Abstract Direct ink writing (DIW) process is a facile additive manufacturing technology to fabricate three-dimensional (3D) objects with various materials. Its versatility has attracted considerable interest in academia and industry in recent years. As such, upsurging endeavors are invested in advancing the ink flow behaviors in order to optimize the process resolution and the printing quality. However, so far, the physical phenomena during the DIW process are not revealed in detail, leaving a research gap between the physical experiments and its underlying theories. Here, we present a comprehensive analytical study of non-Newtonian ink flow behavior during the DIW process. Different syringe-nozzle geometries are modeled for the comparative case studies. By using the computational fluid dynamics (CFD) simulation method, we reveal the shear-thinning property during the ink extrusion process. Besides, we study the viscosity, shear stress, and velocity fields, and analyze the advantages and drawbacks of each syringe-nozzle model. On the basis of these investigations and analyses, we propose an improved syringe-nozzle geometry for stable extrusion and high printing quality. A set of DIW printing experiments and rheological characterizations are carried out to verify the simulation studies. The results developed in this work offer an in-depth understanding of the ink flow behavior in the DIW process, providing valuable guidelines for optimizing the physical DIW configuration toward high-resolution printing and, consequently, improving the performance of DIW-printed objects.