2023 Annual International Solid Freeform Fabrication Symposium (SFF Symp 2023): Polymers: Functional Materials
Program Organizers: Joseph Beaman, University of Texas at Austin
Tuesday 8:15 AM
August 15, 2023
Room: Salon F
Location: Hilton Austin
Session Chair: Allison Murray, Marquette University
8:15 AM
A Comparison of Mechanical Properties from Natural and Process Induced Interfaces in Filament Extrusion Additive Manufacturing of Polymer Blends: Camden Chatham1; Donald Benza1; 1Savannah River National Lab
Polymer blends are commonly tuned for specific applications to achieve desired properties otherwise inaccessible or prohibitively expensive to obtain via homopolymers. The interfacial characteristics of the polymer A-polymer B interface and resultant domain sizes govern key performance properties. Micro- and meso-scale morphology forms through the interplay of surface forces between the polymers and between each polymer and the surrounding atmosphere. Analogously, the layer-layer and road-road interfaces of material extrusion (MEX) additive manufacturing (AM) govern key performance properties of printed parts. This work explores the effect of layer height (i.e., number of interfaces) on the thermomechanical performance of polystyrene (PS)-polycarbonate (PC) blends. Filament is prepared from a 50/50 weight ratio of the two polymers and compared against dual-nozzle printing where every layer alternates between PS or PC homopolymer forming a part with an overall 50/50 polymer ratio. Typical indicators of polymer blend compatibility are also studied.
8:35 AM
A Novel 4D Printing Approach for Freeform Electronics: Xinyi Xiao1; 1Miami University
The combination of additive manufacturing (AM) processes with enhanced technologies for electronics production enables the highly flexible manufacturing of personalized 3D electronic devices. The conductive paths and electronic components can be embedded on the surface of the 3D printed substrates, which can be tailored through the various material properties. AM fabricated planar electronics have been widely studied and used in various applications, such as wearable devices, medical implants, and sensors. However, research on the AM non-planar ones is still in its infancy. This research presents an approach that is able to program the freeform electronics topology through the 4D printing process, which overcomes the rigidity of the “fixed” substrate. The 4D printing provides the substrate with an additional shapeshifting dimension for producing customized complex components with improved performance characteristics. The programmed pre-morphed AM-ed structure is tested and validated under the stimulant condition by comparing it with the as-desired freeform shapes.
8:55 AM
Additive Manufacturing of High Entropy Shape Memory Polymer Blends: Katia Delgado, Ramos1; Luis Lares Carrillo1; David Roberson1; 1University Of Texas At El Paso
Shape memory polymers can be combined with additive manufacturing to enable what is referred to as “4D Printing.” High entropy materials have garnered much attention in materials science due to the manifestation of unexpected results in terms of physical properties and phase composition. The work presented here explores the additive manufacturing of high entropy polymer blends with shape memory properties. We will present our strategy of incrementally increasing the constituents of multi-component polymer blends as a pathway towards the creation of high entropy blends. For this work we melt compounded blends of different types of linear polyesters such as thermoplastic urethane (TPU), polylactic acid (PLA), and polycaprolactone (PCL). The effect of the fused filament fabrication (FFF) process on the phase morphology and overall microstructure was determined by way of scanning transmission electron microscopy (STEM). A comparison of shape memory performance between binary and high entropy polymer blends is also presented.
9:15 AM
Additive Manufacturing of Modular Soft Stretchable Elastomers for Adaptive Dissipative Structures: Daniel Rau1; Myoeum Kim1; Liheng Cai1; 1University of Virginia
Additive manufacturing of elastomers enables fabrication of many technologically important structures and devices. However, the basic materials are limited to a few thermoplastics and photocrosslinkable networks with a limited range of accessible stiffness and stretchability. Here, we develop a modular, soft, and stretchable acrylate-based elastomeric resin for stereolithography additive manufacturing. The resin can be photocrosslinked to form a network consisting of both covalent and reversible bonds. By controlling the ratio of covalent and reversible bonds, we create elastomers with a wide range of stiffness from nearly 20-300 kPa and tensile breaking strain from 75% to 1360%. We demonstrate printing this resin to produce high-resolution three-dimensional structures with extreme dissipative properties that can protect brain tissue mimicking soft gels from impact damage. Together with the low cost of raw chemicals and modular material design, our soft and stretchable elastomeric resins provide a new class of soft materials for additive manufacturing.
9:35 AM Cancelled
Additive Manufacturing of NiTinol Wire Embedded Thermoplastic Polyurethane Actuator: Kazi Md Masum Billah1; Ricardo Arechiga De La Rosa1; Mario Barron Gonzalez1; 1University of Houston Clear Lake
Thermoplastic Polyurethane (TPU) is best known for its elastic and flexible qualities. In this research, commercially available nickel-titanium alloy (Nitinol) shape memory alloy (SMA) wire is embedded within a 3D printed TPU substrate. 3D printing “Pause and Go” approach is being considered to insert the pause during the printing of the specimen and embeds the SMA wire. After embedding the wire, printing is continued to complete the fabrication of the specimen with embedded wire. Making multiple specimens, these thin strips of TPU with nitinol SMA embedded are assembled to mimic a clamp fixture in the shape of a claw machine. It is expected that, due to the external thermal and electrical excitement, SMA will regain the treated shape which ultimately demonstrates the actuation. This research explores the low-cost manufacturing of soft robotics elements which can be used in many real-life applications in medical, aerospace, and domestic appliances.
9:55 AM Break
10:25 AM
Additive Manufacturing of Self-healing Polymers as a Pathway for Environmental Stability: David Roberson1; 1University Of Texas At El Paso
The environmental impact of polymers has continually gained attention as it is becoming more and more apparent that recycling of polymers does not provide a solution to this problem as plastic refuse can be found in the form of numerous “plastic islands” in the oceans. Additionally, understanding of the impact of microplastics on human health has been brought to light. Here we present the use of self-healing polymers as a pathway towards the mitigation of polymeric waste. Past efforts in the development of sustainable polymer matrix composites as well as the upcycling of plastics from waste streams will be discussed. The benefits of the additive manufacturing (AM) of polymers with shape-memory and self-healing properties will also be presented in terms of the effect of AM-facilitated microstructural control on the resultant physical properties. The development of a metric for the self-healing of polymers will also be described.
10:45 AM Cancelled
Charge Programmed Additive Manufacturing of High-performance Antennas: Zhen Wang1; Zhenpeng Xu1; Junbo Wang2; Ryan Hensleigh2; Yahya Rahmat-Samii2; Xiaoyu Zheng1; 1UC Berkeley; 2UCLA
Antennas are essential components of all radio equipment that radiate/transmit and receive energy as electromagnetic waves. Next-generation wireless communications demand lightweight, low-profile, and high-performance antennas that require co-evolution in both design and manufacturing of antennas. Here we report the design and printing of previously impossible ultra-lightweight antennas via charge programmed multi-material additive manufacturing. We achieve this via tailoring the charge programmability of photopolymer to enable selective metalization of 3D conductive materials. These antennas are comprised of a network of interpenetrating metal and dielectric phase-shifting 3D unit cell arrays, which enable 3D electronic topologies with significantly less material (over 90% weight reduction) compared to standard antenna designs. We demonstrate the design and printing of full antenna systems comprised of a feed source, a 19 GHz circular polarized transmitarray with 20 cm aperture. Our measurement results obtained with the spherical near-field measurement system reveal excellent agreement with the simulated radiation patterns.
11:05 AM
Manufacturing of Foam Dampening Structures for Machining Applications: Tyler Smith1; Mithulan Paramanathan1; Thomas Feldhausen1; Matt Sallas1; Chris Tyler1; Ahmed Hassen1; 1ORNL
Additive Manufacturing utilizes the unique capability to create structures in a layer by layer process to create a final structure. In the case of polymer structures, materials can range from rigid to elastomeric. In addition, foaming agents can be used to turn these standard polymers into a lightweight foam version of its base polymer. Changing the parameters and amounts of foaming agent can create different densities , surface quality, and stiffness of the foam. In the case of TPU foams, these differences can lead to vastly different stiffness and dampening co-efficient to be created. Traditional machining of thin walled structures can be difficult and costly due to the low stiffness and dampening along the structures being machined leading to increased chatter and defects. TPU foams can be used to create custom parts to support machining surfaces increasing surface quality of the machined surface.
11:25 AM Cancelled
Additive Manufacturing of Functionally Graded Materials by High Speed Sintering: Jan Kemnitzer1; Marco Wimmer1; Tobias Rosnitschek2; Frank Döpper2; 1Fraunhofer Institute for Manufacturing Engineering and Automation IPA; 2University of Bayreuth
Parts fabricated from a functionally graded material (FGM) show specifically adjusted gradual changes in properties and functions along single or multiple spatial directions due to changes of composition and/or microstructure. The additive manufacturing (AM) process of High Speed Sintering (HSS) has vast potential to manufacture such FGM parts. Within the HSS process, the selective energy input into the polymer powder occurs by a sinterlamp and a radiation absorbing material (RAM). The selective adjustment of the amount of RAM controls the energy input and allows thus to adjust the microstructure and therefore the mechanical properties of the parts. This contribution describes the manufacturing process of FGM parts in HSS and the realizable propertie changes in detail for the first time. This is done by parts made of thermoplastic polyurethane (TPU) with continuous and discontinuous mechanical property changes, which are produced under variations of the relevant process parameters.
11:45 AM
Stimuli Driven Morphing of Printed Liquid Crystal Elastomers: Caitlyn Krikorian1; Michael Ford1; Dominique Porcincula1; Rodrigo Telles-Arriaga2; Yuchen Wang3; Bryan Moran1; Julie Mancini1; Elaine Lee1; Jennifer Lewis2; Shu Yang3; 1Lawrence Livermore National Laboratory; 2Harvard University; 3University of Pennsylvania
Responsive feedstocks for additive manufacturing have opened a new regime of material design, where printed materials can morph into programmed architectures with exposure from a specific stimulus. Shape memory polymers have shown success in printability and in programmability with heating and mechanical force but is generally limited in a one-way shape morphing. Liquid crystal elastomers (LCEs) have more recently been developed for additive manufacturing where programming can be instated during the printing of complex shapes and shape morphing can occur reversibly and repeatably over many cycles of stimuli exposure. Here, we report custom LCE direct ink write feedstocks that can be programmed during printing and reprogrammed with localized light and reversibly locking stimuli to induce novel behaviors like locomotion and reversibly locking stiffness change.