Bulletin of the American Physical Society
APS March Meeting 2019
Volume 64, Number 2
Monday–Friday, March 4–8, 2019; Boston, Massachusetts
Session H49: 3D Printing of Functional Soft Materials and DevicesFocus
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Sponsoring Units: DPOLY GSOFT DFD GSNP Chair: Jon Seppala, National Institute of Standards and Technology Room: BCEC 252A |
Tuesday, March 5, 2019 2:30PM - 3:06PM |
H49.00001: Dillon Prize Talk break
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Tuesday, March 5, 2019 3:06PM - 3:18PM |
H49.00002: 3D Printing of NdFeB Nylon Polymer Bonded Magnets Mariappan Parans Paranthaman The main goal of this research is to print near-net shape NdFeB polymer bonded magnets and to minimize the generated waste. One of the ways in which we can achieve this goal is by using extrusion based big area additive manufacturing technique to create complex shapes and geometries of polymer bonded magnets from a computer aided design which requires no tooling but little post-field-annealing reducing the amount of waste generated. We have successfully demonstrated the fabrication of near-net shape magnets with complex geometries and high energy product using over 65vol% of NdFeB in nylon polymer composite magnets. Several configurations of magnetic fields were used for aligning the magnets during printing. A higher energy product of 11.3 MGOe have been obtained for 65 vol% anisotropic composite bonded magnets aligned in 20 kOe with post-annealing. It is also observed at certain conditions; the post-aligned printed magnets didn’t deform and hence the original shape is preserved. We will discuss in detail about the correlation of magnetic alignment with properties. |
Tuesday, March 5, 2019 3:18PM - 3:30PM |
H49.00003: Quantitative mechanical and electrical assessment by local probe methods of inkjet-printed PEDOT:PSS thin films Edgar Gutierrez-Fernandez, I.A. Gabaldon-Saucedo, M. C. Garcia-Gutierrez, A. Varea, A. Nogales, E. Rebollar, A. Vila, A. Cirera, Tiberio Ezquerra Among the different technologies implied in scalable additive manufacturing inkjet printing is very well-suited for processing polymers. Thin films of PEDOT:PSS on ITO can be prepared by inkjet printing technology. A relatively broad range of thicknesses can be obtained by addition of subsequent polymer layers resembling an additive manufacturing process. The resulting inkjet PEDOT:PSS films are homogeneous as regard both electrical and mechanical properties. In spite of line topography both the Quantitative Nanomechanical Mapping (QNM) and the Conductive-AFM (C-AFM) characterization reveal homogeneous values throughout the polymer surface regardless of the welding zones. The results discussed in this work provide the basis for the application of inkjet printing as deposition method for electrically conducting PEDOT:PSS into large area with mechanical stability. |
Tuesday, March 5, 2019 3:30PM - 3:42PM |
H49.00004: Understanding the Effect of Block Copolymer Micelles on the Nanostructure and Rheological Response of Inks for Direct Ink Writing Rishabh Ekbote, Deborah Liu, Daniel Krogstad Bioinspired, hierarchical materials are of interest due to their ability to create materials with unique combinations of mechanical properties. We are interested in using a combined top-down and bottom-up approach to create synthetic materials with hierarchical structures. Towards this goal, we are using block copolymers to create nanoscale ordering in inks that can be printed using direct ink writing. However, the inclusion of micelle forming block copolymers has significant impact on the rheology of the inks, and thus their printability. Here, we will discuss the progress made towards understanding the effects of the block copolymer structure and concentration on the rheological properties of block copolymer containing epoxy inks. |
Tuesday, March 5, 2019 3:42PM - 4:18PM |
H49.00005: Leveraging Jammed Microgels to Shape Complex Fluids: One Method for 3D Printing with Cells, Gels, Elastomers, and Colloids Invited Speaker: Thomas Angelini 3D printing is generally a race against instabilities; the challenge is to prevent printed liquid features from flowing of breaking up once deposited. Printing directly into a support material made from jammed granular-scale gel particles mitigates the two nearly ubiquitous sources of instability encountered in 3D printing: surface tension and body forces. The yield stress of these jammed microgels can be tuned over a broad range, making them excellent media in which to create macroscopic structures with microscopic precision. While tracing out spatial paths with an injection tip, the microgels yield at the point of injection and then rapidly re-solidify, trapping injected material in place. In this talk, we demonstrate how this physical approach to creating 3D structures negates the effects of surface tension and gravity, allowing a wide breadth of materials to be structured. With this method we create complex 3D objects made from silicones, hydrogels, colloids, and living cells, including functional living cell constructs and fluidic devices made from silicone. Immediate application areas include tissue engineering, flexible electronics, particle engineering, smart materials, and encapsulation technologies. |
Tuesday, March 5, 2019 4:18PM - 4:30PM |
H49.00006: Utilization of Polymer-Nanoparticle Composite in Micro-Stereolithography 3D Printing Hongxia Li, Aikifa Raza, Afra Alketbi, TieJun Zhang Advances in micro-stereolithography (µ-SL) 3D printing enable the fabrication of complex microstructures for biomedical, energy and other applications. However, the narrow selection of optical-curable printing materials limits its wide deployment. 3D printed micromodels are used to mimic the morphology of natural rock and reveal the microfluidic flow physics for subsurface energy application, but the surface chemistry of the printed polymer micromodel are totally different from natural rock surface. Therefore, polymer-based composites are used to tailor intrinsic properties, such as mechanical strength and surface wettability. In this work, we utilize the composite of polymer and calcite nanoparticle in a high-resolution µ-SL 3D printing system. Light scattering induced by the nanoparticles and its influence on printing resolution are analyzed under various particle sizes and concentrations. The transparency of printed micromodels reduces accordingly, which would affect the microfluidic flow imaging performance. Surface wettability conditions, including the contact angle and its hysteresis, are also characterized. This study provides important guidance in the utilization of polymer/nanoparticle composite in µ-SL 3D printing for broad microfluidic applications. |
Tuesday, March 5, 2019 4:30PM - 4:42PM |
H49.00007: Morphology and Mechanical Properties of Stereolithography-Printed Polymer Networks Anna Smallwood-Rooney, Rykelle Adley, Adam Merkle, Keith DeNivo, Sungmin Park, Chang Yeol Ryu Stereolithography (SLA) is a method of 3D printing in which polymer network objects are formed through the repeated curing of photopolymer resin by a computer-controlled UV laser source. Objects that are 3D printed on a SLA platform show a layered morphology on the microscopic scale, and the resolution of the printed object is determined predominantly by the thickness of each layer, typically on the 100 um scale. Layer formation during printing is dependent on laser intensity and decay during the printing process. Printed layers are generally characterized by a strongly crosslinked region that decays gradually into a more loosely crosslinked domain which is adjacent to a highly crosslinked region of the next layer. This pattern of curing is a function of laser intensity and reflects decay of intensity throughout each curing cycle, or layer. The SLA-printed morphology is characterized on the microscopic scale as a function of laser intensity and decay during printing. High resolution optical microscopy techniques will offer a depiction of crosslinking density change across layered 3D printed structure. The layer curing process will also be investigated by real-time FTIR, DSC, and DMA. |
Tuesday, March 5, 2019 4:42PM - 4:54PM |
H49.00008: Self-Limiting Electrospray Deposition of Polymers and Polymer Composites Lin Lei, Dylan A. Kovacevich, Christianna Kuznetsova, Jonathan Singer Electrospray deposition is widely used to create polymer microcoatings from dilute spray solutions. In a certain regime of experimental parameters, a limiting thickness emerges where the accumulation of charge repels further spray. This self-limiting electrospray deposition (SLED) can uniformly cover complex multiscale structures efficiently. Here we investigate the application of polymer blends to increasing the durability of the spray films for different mechanical applications. We use the addition of photo- or thermal-crosslinkers that can either maintain the hierarchical spray structure of hollow particles or result in a dense film to obtain stiffer coatings for protective barriers. The results show mechanically-tough coatings with tunable porosity which are resistant to decomposition by chemical reactions and mechanical damage. To make the films that are more flexible for compliant surfaces, polymer blends which consisting of plastic and elastomeric components are sprayed. The net result was a coating that could enhance adhesion and sustain ~17% strain in the underlying structure. Furthermore, we have applied SLED to coat 3D structures produced via additive manufacturing with these mechanically-tuned coatings. |
Tuesday, March 5, 2019 4:54PM - 5:06PM |
H49.00009: 3D Printable Soft Elastomers Zihao Gong, Shifeng Nian, Liheng Cai Existing feedstock for 3D printing is nearly all plastics. These materials are not only mechanically stiff but also fragile. These severely limit their applications where soft, elastic polymers are required to easily comply with the shapes of objects they contact. Here we develop a soft, 3D printable elastomer through molecular design. We synthesize a triblock copolymer, in which the two end-blocks are polystyrene (PS) with a high glass transition temperature, Tg, about 100oC, and the middle block is a polydimethylsiloxane (PDMS) with a low Tg, about 100oC. At room temperature, such copolymers self-assemble to a network, in which the effective network strands are the PDMS, and crosslinks are glassy plastic domains formed by PS. This network is extremely soft with Young's modulus below 100kPa, more than three orders of magnitude lower than that of plastics. At high temperature, the glassy domains dissociate, enabling a temperature triggered solid-to-liquid transition. Harnessing this feature, we use extrusion-based 3D printing to create a complex, hierarchical 3D structure with an exceptional combination of softness and deformability. Our studies provide a new strategy for the development of 3D printable soft elastomers. |
Tuesday, March 5, 2019 5:06PM - 5:18PM |
H49.00010: Embedded 3D Printing with Acoustic Focusing Leanne Friedrich, Matthew Begley Intra-nozzle particle positioning methods enable the design of composite 3D printed components with structural and functional gradients. One method is acoustic focusing, wherein a piezoelectric actuator establishes a bulk acoustic wave in the nozzle which co-orients and moves particles to the wave nodes. Because acoustic focusing requires low viscosity inks (such as soft materials with functional particles), we use a granular hydrogel as support material. This study investigates how layer-by-layer deposition of support material and printing into a support bath each influence the maintenance of acoustically focused microstructures and the fidelity of printed structures. While layer-by-layer support prevents filaments from breaking into droplets, it can also destabilize filaments near liquid elbows and induce rotational flows that disrupt focused structures. Similarly, though writing into support material enables complex structures, it can also hinder inter-layer and intra-layer fusion and disrupt existing structures. Using digital image analysis and particle image velocimetry, we measure the effects of ink and support composition and printing parameters on maintenance of acoustically focused microstructures, stability of filaments and liquid elbows, and inter-filament fusion. |
Tuesday, March 5, 2019 5:18PM - 5:30PM |
H49.00011: Room Temperature Extrusion 3D Printing of Polyether Ether Ketone Using a Stimuli-Responsive Binder Chang-Uk Lee, Johanna Vandenbrande, Adam Goetz, Mark Ganter, Duane Storti, Andrew Boydston We report 3D printing of polyether ether ketone (PEEK) at room temperature by direct-ink write technology. The room-temperature extrusion printing method was enabled by a unique formulation comprised of commercial PEEK powder, soluble epoxy-functionalized PEEK (ePEEK), and fenchone. This combination formed a Bingham plastic that could be extruded using a readily available direct-write printer. After printing, thermal processing at 230 °C resulted in crosslinking of the ePEEK components to form a stabilizing network throughout the specimen. A final sintering stage was conducted at 380 °C. The Tg of product specimens was found to be 158 °C, which is 13 °C higher than commercial PEEK as measured by DSC. Moreover, the thermal decomposition temperature was found to be 528 °C, which compares well against commercial molded PEEK samples. Chemical resistance in trifluoroacetic acid and 8 common organic solvents were investigated, and no signs of degradation were observed from parts submerged for 1 week in each solvent. Test specimens also displayed desirable mechanical properties, such as a Young’s modulus of 2.5 GPa, which corresponds to 63% of that of commercial PEEK. |
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