Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session V41: Spatiotemporal behavior of soft active materialsInvited
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Sponsoring Units: GSOFT Chair: Lihua Jin, UCLA Room: LACC 502A |
Thursday, March 8, 2018 2:30PM - 3:06PM |
V41.00001: Patterning with Loops to Dynamically Reconfigure Polymer Gels Invited Speaker: Anna Balazs The structural and mechanical properties of gels can be controlled by promoting the unfolding (and refolding) of loops embedded within the networks. As a loop unfolds, the released chain length can increase the extensibility and reconfigurability of the gel. Here, we develop a theoretical model that couples the elasticity of the gel to the dynamic transitions occurring in loops that lie between the crosslinks. Using this model, we show that a thermally-induced swelling of the gel generates an internal strain, which unfolds the loop and thereby further increases the degree of gel swelling. We exploit this cooperative behavior to reconfigure the gel by patterning the location of the loops within the sample. Through this approach, we convert flat, two-dimensional layers into three-dimensional forms and introduce architectural features into uniform 3D slabs. At a fixed temperature, an applied force produces analogous structural transformations. The shape-changes are reversible: the systems return to their original structure when the temperature is reset or the force is removed. The findings provide guidelines for creating materials that interconvert thermal, chemical and mechanical energy to perform work. Such systems could be useful for designing soft robotic materials that convert environmental stimuli into useful functionality. |
Thursday, March 8, 2018 3:06PM - 3:42PM |
V41.00002: Shape Programmable Materials via the Directed Self Assembly of Liquid Crystalline Elastomers Invited Speaker: Timothy White Liquid crystalline materials are pervasive in modern society as the basis of the display industry. It has been long-known that liquid crystalline materials in polymeric forms also exhibit exceptional characteristics in high performance applications as transparent armor or bulletproof vests as well as in optics and photonics. A specific class of liquid crystalline polymeric materials referred to as liquid crystalline elastomers were predicted by de Gennes to have exceptional promise as artificial muscles, owing to the unique assimilation of anisotropy and elasticity. Subsequent experimental studies have confirmed the salient features of these materials, with respect to other forms of stimuli-responsive soft matter, are actuation cycles of up to 400% as well “soft elasticity” (stretch at minimal stress). In the presentation, I will summarize our recent efforts in developing materials chemistry amenable to allowing arbitrary local control of the anisotropy within these materials. Enabled by these approaches, we have prepared complex actuators and mechanical elements from these materials. Notably, these materials are subject to mechanical design but homogenous in composition (lacking material/material interfaces). Relevance of this work to implementations in aerospace and commercial applications will be discussed. |
Thursday, March 8, 2018 3:42PM - 4:18PM |
V41.00003: Direct 4D printing by using multimaterial additive manufacturing Invited Speaker: H. Qi 4D Printing is a term that was recently developed to describe the integration of 3D printing and active materials technologies to realize printed components that can be switched between multiple configurations via an environmental stimulus, e.g., heat, or moisture. To date, hydrogels and shape memory polymers (SMPs) are the two main active polymers used in 4D printing. SMPs have been used in 4D printing with both commercial and research printing technologies based on photopolymer inkjetting and projection micro stereolithography. However, 4D printing with SMPs generally requires a series of steps, including synthesis/processing by 3D printing, heating, mechanical loading, cooling, and removing the load. Thermomechanical programming often requires special jigs and fixtures to apply mechanical loads and a well-controlled thermal environment. In this paper, we propose a new direct 4D printing approach with shape memory polymers (SMPs) where we integrate the programming steps into the 3D printing process. As a result, the 3D printed component can directly change its shape rapidly upon heating. This second shape largely remains stable in later variations in temperature, such as cooling back to room temperature. Furthermore, a third shape can be programmed by thermomechanical loading, and the material will always recover back to the permanent (second) stable shape upon heating. We also created a theoretical model that incorporates the key elements, including the material behaviors during the processing/programming and deployment phases and 3D printing processing parameters. The model was then used to guide to design complicated shape changes. |
Thursday, March 8, 2018 4:18PM - 4:54PM |
V41.00004: 4D Printing of Morphing Soft Materials Inspired by Nature Invited Speaker: Andre Studart Soft materials in the plant and animal kingdoms are often programmed to morph, adapt and interact with the surrounding environment to perform vital biological functions. Examples range broadly from the morphing of plant units to release seeds under optimum weather conditions to the stimulated motion of animal muscular systems for dexterous manipulation. While the idea of replicating dynamic biological functionalities in artificial systems has attracted scientists and engineers for many years, the advent of 4D printing opens numerous new opportunities for the fabrication of bioinspired morphing materials thus far inaccessible using conventional manufacturing. In this talk, I will show how multimaterial 4D printing can be utilized to digitally fabricate synthetic materials whose dynamic response is programmed within the material’s bioinspired architecture. Because of their direct implications in robotic and actuation systems, particular attention will be given to morphing systems that not only change their geometry upon external stimuli but that can also carry mechanical load to perform manipulation tasks. Understanding the physical mechanisms underlying the dynamics of such morphing systems should provide powerful tools for the design and fabrication of 4D printed objects with programmable material architectures. |
Thursday, March 8, 2018 4:54PM - 5:30PM |
V41.00005: Abstract Withdrawn Invited Speaker: |
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