Bulletin of the American Physical Society
APS March Meeting 2018
Volume 63, Number 1
Monday–Friday, March 5–9, 2018; Los Angeles, California
Session X57: Physics of Bioinspired Soft Materials IFocus
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Sponsoring Units: GSOFT DBIO Chair: Kyoo-Chul Park, Northwestern Univ Room: LACC 518 |
Friday, March 9, 2018 8:00AM - 8:36AM |
X57.00001: The amazing elephant trunk Invited Speaker: David Hu An elephant spends 16 to 18 hours per day feeding. How does an elephant feed efficiently? We present experiments with African elephants at the Atlanta Zoo and dissections of elephant trunks at the Smithsonian Institution. Elephants can suck up tortilla chips or six liters of water within a second. These feats are made possible by the use of radial muscles in trunk which expand the nostrils by 30 percent in diameter, increasing the suction force available for picking up small objects. We demonstrate the trunk can use self-weight to apply jamming forces to collections of small particles, reducing the number of trips it needs to move them. We build simple silicon mimics of the trunk, demonstrating that the trunk's stiff skin and wrinkle patterns can aid in its stability. |
Friday, March 9, 2018 8:36AM - 8:48AM |
X57.00002: A tunable biological tissue-inspired photonic fluid Xinzhi Li, Dapeng Bi We design an amorphous material with a full photonic band gap inspired by how cells pack in biological tissues. A physical parameter based by how cells adhere with one another and regulate their shapes can continuously tune the photonic band gap size as well as the bulk mechanical properties of the material. The photonic band gap persists well through a solid-fluid phase transition characterized by a vanishing shear modulus. This property gives rise to a photonic fluid which overcomes many of the limitations of previously proposed photonic materials due to its insensitivity to structural defects and robustness with respect to fluid flow, rearrangements and thermal fluctuations. Interestingly, we also find the patterns generated here to be hyperuniform, however hyperuniformity does not guarantee the presence of a photonic band gap. Rather we find the size of the photonic band gap is closely coupled to the amount of short range order. The design proposed here uses a physical interaction that can be realized in experiment via self-assembly engineering. In particularly, emulsion droplets or nanoparticles grafted with polymers should be ideal for constructing such structures. |
Friday, March 9, 2018 8:48AM - 9:00AM |
X57.00003: Bioinspired bright noniridescent photonic melanin supraballs Ali Dhinojwala, Ming Xiao, Ziying Hu, Nathan Gianneschi, Matthew Shawkey Structural colors enable the creation of a spectrumof nonfading colorswithout pigments, potentially replacing toxic metal oxides and conjugated organic pigments. However, significant challenges remain to achieve the contrast needed for a complete gamut of colors and a scalable process for industrial application.We demonstrate a feasible solution for producing structural colors inspired by bird feathers. We have designed core-shell nanoparticles using high–refractive index (RI) (~1.74)melanin cores and low-RI (~1.45) silica shells. The design of these nanoparticles was guided by finite-difference time-domain simulations. These nanoparticles were self-assembled using a one-pot reverse emulsion process, which resulted in bright and noniridescent supraballs. With the combination of only two ingredients, synthetic melanin and silica, we can generate a full spectrum of colors. These supraballs could be directly added to paints, plastics, and coatings and also used as ultraviolet-resistant inks or cosmetics. |
Friday, March 9, 2018 9:00AM - 9:12AM |
X57.00004: Waveguides Made of Soft Matter: Structure, Characteristics and Application in Lives Jingjing Xu, Sheng-Yong Xu Waveguides, serving as effective pathways of electromagnetic waves, play vital roles in communication. Compared with the familiar metal and optical waveguides, “soft-matter waveguide” has been proposed recently, but less studied. |
Friday, March 9, 2018 9:12AM - 9:24AM |
X57.00005: Bioinspired materials with self-adaptable mechanical properties and self-regeneration Santiago Orrego, Urszula Krekora, Eugene Kang, Sung Kang Nature produces outstanding materials for structural applications such as bones and wood that can adapt to their surrounding environment. For instance, bone regulates mineral quantity proportional to the amount of stress. It becomes stronger in locations subjected to the higher mechanical loads. This leads to the formation of mechanically efficient structures for optimal biomechanical and energy-efficient performance. However, it is a challenge for synthetic materials to change and adapt their structures and properties to address the changes of loading conditions. To address the challenge, we are inspired by the findings that bones are formed by mineralization of ions from blood onto scaffolds. We report a material system that triggers mineral synthesis from ionic solutions on organic scaffolds upon mechanical loadings and/or damages so that it can self-adapt to mechanical loadings and regenerate upon damages. For example, we observed ~30% increase in the modulus of the material upon periodic loadings for 3 days. We also observed that the material could self-repair damages generated by removing ~5 μm thick minerals from the matrix, in 7 days. We envision that our findings can open new strategies for making synthetic materials with self-adaptability and self-repair capability. |
Friday, March 9, 2018 9:24AM - 9:36AM |
X57.00006: Enhanced diffusion by binding to a crosslinked polymer gel Carl Goodrich, Katharina Ribbeck, Michael Brenner Biological hydrogels play an important role as selective permeability barriers in regulating the diffusive transport of molecules in a wide variety of systems. In many cases, the mechanism for selective filtering is well understood. However, such a mechanism is not obvious when particles larger than the mesh size differ only in the presence of a binding sit. This is because non-binding particles are trapped by the gel, so binding must result in increased, not decreased, mobility. We present an equilibrium mechanism for this counter-intuitive filtering strategy that does not consume energy. We show that selective mobility can be achieved and controlled in a simple crosslinked polymer gel by controlling the crosslink dynamics. Our results lead to specific design rules for manufacturing complex selective gels and could help explain how the Nuclear Pore Complex attains selectivity. |
Friday, March 9, 2018 9:36AM - 9:48AM |
X57.00007: Curvature Instability of Colloidal Membranes on Crystallization Prerna Sharma, Lachit Saikia, Tanmoy Sarkar, Meera Thomas, V. A. Raghunathan, Anirban Sain Membrane curvature generation and remodeling are critical for trafficking and cellular functions. Local curvature generation is associated mainly with specialized proteins which use mechanisms such as protein crowding, nanoscopic and macroscopic scaffolding. We investigate curvature generation in a highly simplified model system of colloidal membranes and show that structural phase transition of crystallization within the membrane is enough to result in membrane curvature and wrinkling. We determine the structure and dynamics of the buckled colloidal membranes using a variety of microscopy and scattering techniques to identify the relevant parameters in the phase transition that affect the overall morphology of the membranes. |
Friday, March 9, 2018 9:48AM - 10:00AM |
X57.00008: Enhanced microorganism swimming in active matter Harsh Soni, Robert Pelcovits, Thomas Powers Microorganisms swim through the fluid by periodically deforming their body. We study the |
Friday, March 9, 2018 10:00AM - 10:12AM |
X57.00009: Tuning the Conductance of Oligopeptides in Single-Molecule Junctions Bo Li, Jin Yu, Songsong Li, Charles Schroeder The development of new materials for advanced electronics applications can directly benefit from precise mesoscale engineering of molecular building blocks. Bio-inspired materials can play a key role in this effort due to their inherent “programmable” structure and function. In this work, we systematically investigate the single molecule conductance properties of oligopeptides with different primary amino acid sequences using a scanning tunneling microscope-break junction technique (STM-BJ). Here, we determine the quantum conductance of all (21) single amino acid residues. We further explore the effect of side chain chemical identity on the charge transport properties of oligopeptides (di- and tri-oligopeptides). In this way, we determine general rules for tuning and enhancing the conductance of oligopeptides. Overall, this work extends beyond prior studies from our group in using chemically modified oligopeptides for the directed self-assembly of π-conjugated units in a precise structural manner. In particular, our work provides key information regarding the conductance and charge transport properties of peptides with various sequences, thereby offering new insight into the electronic properties of oligopeptides that can be used in designing supramolecular electronic materials. |
Friday, March 9, 2018 10:12AM - 10:24AM |
X57.00010: Patterning Polymer Brushes and Polymer Brush Gradients Generated by Hyaluronan Synthase Jessica Faubel, Wenbin Wei, Nicholas Greenwald, Jennifer Washburn, Bruce Baggenstoss, Paul Weigel, Jennifer Curtis Polymer brushes are relevant to a wide range of industrial and biomedical applications. This makes understanding their fundamental properties crucial to optimizing their design for specific applications. We present a novel platform to fabricate, characterize, and pattern hyaluronan(HA)-based polymer brushes at interfaces using the enzyme HA synthase. The brushes are microns thick, regenerative, and easily tuned. Their extreme thickness makes them amenable to unusual characterization techniques like direct visualization of the brush’s thickness, polymer concentration profile, and penetration by nanoparticles or proteins. In this talk, we present methods to pattern the HA polymer brushes using a UV laser on a confocal microscope, as well as altering the grafting density by UV-deactivation of the HA synthase. We will present data regarding the range of grafting densities available with this approach and provide examples and characterization of polymer brush gradients generated in this fashion. This new experimental platform represents a unique approach to fabricating polymer brushes, distinct from grafting to or from, and provides opportunities for fundamental studies and ultimately applications in the design of functional interfaces. |
Friday, March 9, 2018 10:24AM - 10:36AM |
X57.00011: Surface wave energy absorption by a partially submerged bio-inspired canopy Benjamin Thiria Aquatic plants are known to protect coastlines and riverbeds from erosion by damping waves and fluid flow. These flexible structures absorb the fluid-borne energy of an incoming fluid by deforming me- chanically. In this paper we focus on the mechanisms involved in these fluid-elasticity interactions, as an efficient energy harvesting system, using an experimental canopy model in a wave tank. We study an array of partially-submerged flexible structures that are subjected to the action of a surface wave field, investigating in particular the role of spacing between the elements of the array on the ability of our system to absorb energy from the flow. The energy absorption potential of the canopy model is examined using global wave height measurements for the wave field and local measurements of the elastic energy based on the kinematics of each element of the canopy. We study different canopy arrays and show in particular that flexibility improves wave damping by around 40%, for which half is potentially harvestable. |
Friday, March 9, 2018 10:36AM - 10:48AM |
X57.00012: ‘Artificial Spasmoneme’: Taking Advantage of Diffusion within Asymmetric Structures Yongjin Kim, Alfred Crosby Inspired by the motion of ‘Vorticellar’, we have demonstrated reversible coiling and uncoiling motions in polymeric micro-actuators. The actuators were fabricated in the form of ribbon-shape patterns by the evaporation induced self-assembly of dual-stimuli responsive polymers. |
Friday, March 9, 2018 10:48AM - 11:00AM |
X57.00013: Weak molecular interactions promote dynamic hierarchical structures Ming Han, Ronit Freeman, Samuel Stupp, Erik Luijten In nature, hierarchical structures, such as protein assemblies inside and outside cells, often dynamically reorganize and display unique functions at different times. Two of us recently created a synthetic system with such capability, using peptide–DNA supramolecular nanostructures that can organize reversibly into hydrogel networks containing bundles of twisted fibers. Here we present a study of the underlying mechanism of this system based upon coarse-grained simulations. Notably, we demonstrate that weak inter- and intra-fiber interactions promote hierarchical order by enabling large-scale redistribution of DNA-containing monomers, a phenomenon not permitted in conventional materials that crosslink at predetermined “linker sites.” We explore the desired energy scales of the cohesive interactions, and provide insights that permit realization of similar dynamic hierarchical behavior in other supramolecular materials. Lastly, we explain the twisted morphology of the fiber bundles, which turns out to originate from kinetic arrest rather than from DNA chirality. |
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