Bulletin of the American Physical Society
APS March Meeting 2020
Volume 65, Number 1
Monday–Friday, March 2–6, 2020; Denver, Colorado
Session M22: Biomaterials IV: Nano and Bioinspired materialsFocus
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Sponsoring Units: DBIO DCP DMP DPOLY Chair: Pupa Gilbert, University of Wisconsin - Madison Room: 303 |
Wednesday, March 4, 2020 11:15AM - 11:27AM |
M22.00001: Areca Sheath: A Bio-Degradable Alternative for Synthetic Materials in the Food Industry Debapriya Pinaki Mohanty, Koushik Viswanathan, Anirudh Udupa, Anil Chandra, Srinivasan Chandrasekar The undesirable effects of plastics on the environment are well-documented. One of the common uses of plastics is in products with short-term uses in the food industry, e.g., cutlery and plastic bags. This has focused interest in finding bio-degradable alternatives for these products that are mechanically, physically and aesthetically equal to if not superior to plastics. Areca palm sheath is a possible plant-based green alternative that can be used in the manufacture of plates and bowls. In fact, it has been in use in India for more than a century despite little knowledge about its mechanical behavior. To advance the use of these materials, it is critical to understand their formability and the nature of diffusion of water through the sheath. In this study, we report on the results of an investigation of their formability. Using measurements carried out on plates and bowls, we show that Areca sheaths are quite deformable and capable of withstanding strains as high as 0.7. The interplay between moisture content and formability is quantified. The formability and failure strains are related to the microstructure e.g., fiber, porosity of the palm sheath. The results show interesting opportunities for creating a wide range of environmentally friendly cutlery and packaging products. |
Wednesday, March 4, 2020 11:27AM - 11:39AM |
M22.00002: Polycarbonate Mold Copying Technique to Fabricate Microengineered Devices for Biophysical Studies Utku Sonmez, Philip R LeDuc Microengineered devices made out of high aspect ratio flexible polymers provide very useful experimental means to study biophysical properties of living entities at various scales ranging from single cells to multicellular small organisms by enabling application of precise forces and deformations. However, fabrication of such devices require expensive and cumbersome mold fabrication procedures which limits appreciation of this technology by experimental biophysicists. Here, we report a novel microfabrication technique that we have developed for benchtop fabrication of microengineered devices outside the cleanroom so that they can be cheaply fabricated with high throughput. The polycarbonate (PC) mold copying technique consists of reverse molding of Polydimethylsiloxane parts fabricated from master molds in order to combine different microstructures into single monolithic PC mold for subsequent flexible polymer microdevice fabrication. We have characterized dimensional fidelity of the microstructures fabricated by this technique and fabricated various microstructures with feature sizes ranging from submicron level to tens of centimeters. Lastly, we used these devices to study fibroblast alignment dynamics, Young's Modulus of Drosophila embryo and cardiomyocyte contractility. |
Wednesday, March 4, 2020 11:39AM - 11:51AM |
M22.00003: The Design and Modeling of Adsorption Based Filters and the Bioremediation
of Heavy Metal Contaminated Water Chris McCarthy I will discuss kinetic models of adsorption, as well as our mathematical models of such filters. These mathematical models have been developed in support of our interdisciplinary lab group and can be used in filter design. Our group conducts research into bio-remediation of heavy metal contaminated water via filtration. The filters are constructed out of biomass, such as spent tea leaves. The spent tea leaves are available in large quantities as a result of the industrial production of tea beverages. The heavy metals bond with the surfaces of the tea leaves (adsorption). I will compare the models' predictions to data obtained from computer simulations and experimentally by our lab group. |
Wednesday, March 4, 2020 11:51AM - 12:03PM |
M22.00004: Reciprocal Control of Hierarchical DNA Origami-Nanoparticle Assemblies Joshua Johnson, Abhilasha Dehankar, Jessica Winter, Carlos E Castro A major focus in bionanotechnology is interfacing with inorganic materials, such as nanoparticles (NPs), for effective integration and control over emergent functions of composite materials. The structural precision and dynamic capabilities of DNA origami make it ideal to achieve these goals. We present an actuation scheme utilizing NPs as control elements enabling rapid and reversible thermal actuation of DNA origami and higher order assemblies. We demonstrate tunable thermal actuation between open and closed configurations on the timescale of seconds, with evidence that reconfiguration is only limited by heating or cooling rates of the bulk solution. We extend the dynamic capabilities in higher-order assemblies by polymerizing hinges which can achieve micron-scale reconfiguration. Control of NPs at the arrays scale combined with NP based control of hinges at the individual scale serves as a basis for reciprocal control of hierarchical assemblies. We also polymerize hinges side-to-side to create more compact NP arrays, or use a combination of polymerization schemes to assemble expandable 2D NP arrays. These NP-hinge composites serve as a novel basis for creating reconfigurable emergent materials. |
Wednesday, March 4, 2020 12:03PM - 12:15PM |
M22.00005: Fiber fluorescence photo thermometry during magnetic heating reveals directional alignment of suspended nanoparticles Rahul Munshi, Muye He, Idoia Rubio-Castellanos, Komal Sethi, Junting Liu, Arnd Pralle We developed highly sensitive camera-based fiber fluorescence photometry to measure temperature changes of magnetically heated nanoparticles. Temperature changes as small as 20 milli Kelvin were resolved with a temporal resolution of 5 ms, using common fluorophores. Suspensions of various nanoparticles, including synthesized magnetite and core-shell nanoparticles, engineered magnetoferritin and purified magnetosomes, as well as intact magnetotactic bacteria were heated in alternating magnetic fields (AMF). Using prior calibration, nanoparticle surface temperature changes were calculated from fluorescence intensity changes of the attached dyes. From nanoparticle surface temperatures, we determined the limits of concentration scaling of suspension temperature rise. We captured sudden (sub 5 ms) fluorescence changes, corresponding to AMF driven reversible nanoparticle alignment. The orientation of the AMF field lines determines the direction of the relative fluorescence changes. The rate of aggregation is modulated by changing the medium viscosity and depends on field strength and nanoparticle size. Our findings shed light on the implications of Specific Loss Power measurements and the limits of local heat confinement around freely diffusing nanoparticles. |
Wednesday, March 4, 2020 12:15PM - 12:27PM |
M22.00006: Landscapes, nonlinearity, and optimality of ion transport in sub-nanoscale pores Subin Sahu, Justin Elenewski, Christoph Rohmann, Michael Zwolak Biological ion channels evolved to have high transport rates and high selectivity, among other functional characteristics. Synthetic nanoscale pores aim to mimic these properties for applications such as desalination and osmotic power generation.1 In these systems, ion-ion and ion-channel interactions occur at sub-nanometer distances which entails large electrostatic and dehydration energies.2 The balance of these energies determines selectivity and permeation rates. Importantly, the susceptibility of transport and selectivity to minute changes in distances—changes on the order of picometers—is enormous resulting in highly-nonlinear behavior. Biological systems can exploit this susceptibility via variations in protein structure that steer the local electrostatic and structural conditions. We demonstrate how this works in a synthetic selectivity filter and discuss how to probe this system, which will help to experimentally quantify optimal transport conditions and will give the foundation for a robust understanding of more complex biological pores. |
Wednesday, March 4, 2020 12:27PM - 12:39PM |
M22.00007: Potentiometric Detection of Single Protein Molecules in Solution by Nanoimpact Method Popular Pandey, Jin He Nanoscale electrochemical methods based on nanopores and nanoelectrodes have gained enormous popularity for single-entity detection and analysis. This work integrates two aforementioned methods in one nanopipette apex to simultaneously monitor the ionic current and surface potential changes at the nanopore and the nanoelectrode when a protein translocates through the nanopore or collides with the nanoelectrode. In this presentation, I will demonstrate a facile potentiometric method of detecting protein at the single-molecule level in solution based on the nanoimpact events of proteins at the nanoelectrode, which is further supported by molecular dynamics (MD) simulation. Proteins, such as ferritin, hemoglobin, cytochrome-c, and lysozyme are tested to validate the method. When a protein molecule arrives at the vicinity of the electrically floating nanoelectrode, open-circuit potential (OCP) changes are detected at the nanoelectrode. Compared with the ionic current change, the OCP changes can be detected with better signal-to-noise ratio and higher time resolution. The nanopipette based novel potentiometric detection method provides new opportunities to study various biological entities at a single-entity level with close to physiological conditions. |
Wednesday, March 4, 2020 12:39PM - 1:15PM |
M22.00008: Drops: A bio-inspired tool to structure materials Invited Speaker: Esther Amstad Nature uses drops to build soft materials possessing well-defined structures and locally varying compositions and therefore display exceptional mechanical properties. Inspired by nature, we use emulsion drops as building blocks of macroscopic granular hydrogels with well-defined micrometer-scale structures and locally varying compositions. I will demonstrate the influence of the micrometer-scale structure of these granular hydrogels on their mechanical properties. To render hydrogels responsive and adaptive, we employ selectively permeable capsules fabricated from water-oil-water double emulsions as building blocks. In addition, we use amorphous inorganic biominerals, such as CaCO3, as reagents that can locally change the mechanical properties of these materials. |
Wednesday, March 4, 2020 1:15PM - 1:27PM |
M22.00009: On the interaction of molecular rotors with lipid nanodroplets Robert Ziolek, Bethan Cornell, Paul Smith, I. Emilie Steinmark, Klaus Suhling, Christian Lorenz Lipid droplets are cytoplasmic organelles that store neutral lipids (e.g. triacylglycerols & sterol esters) that serve as reservoirs of energy. The neutral lipid core of lipid droplets are bounded by a phospholipid monolayer, which differentiates them from most other organelles that have a bilayer membrane. There are various nano-environments of different viscosities present in these complex organelles, which can be studied with fluorescent molecular rotors. In this presentation, I will present the results of several large-scale classical molecular dynamics simulations in which we investigate the molecular scale interactions of a molecular rotor, BODIPY-C12, with lipid droplets. In doing so, we investigate how the orientation and confirmation of the molecular rotors changes during their adsorption into the interface of the lipid droplets. We investigate how different compositions of the bounding lipid monolayer affect the confirmation and tilt of the molecular rotors. Finally, we will use the results of our simulations to resolve the multi-component signals observed experimentally. |
Wednesday, March 4, 2020 1:27PM - 1:39PM |
M22.00010: Design of bio-inspired surface topographies via polymer bilayer wrinkling superposition Luca Pellegrino, Sepideh Khodaparast, Joao Cabral Naturally occurring patterns on surfaces have evolved to form topological micro- and nano-structures with a variety of functionalities, such as drag reduction, tuneable wetting, anti-microbial resistance and optical effects, often found in insect wings and plant leaves. Wrinkling of bi- and multi-layered materials provides a powerful, versatile, large-surface area patterning methodology to fabricate complex periodic structures with features ranging from 10s of nm to 100s of μm. Here, we investigate the formation of analogous 2D wrinkling patterns in artificial soft materials, built as a superposition of single frequency features. The pattern superposition is achieved sequentially, starting from single frequency wrinkles and generated by stretching a cross-linked elastomer slab that is simultaneously plasma oxidized. The wrinkled surface formed upon the strain release is replicated, then stretched at a specific angle to the first wrinkling step and plasma treated simultaneously to yield a prescribed wrinkling second generation. Specifically, an orthogonal superposition generates checkerboard patterns. Oblique superposition, gives rise to wavy or sand dunes-like patterns with structural characteristics that are independently tunable via changing the plasma experimental parameters. |
Wednesday, March 4, 2020 1:39PM - 1:51PM |
M22.00011: Near-IR Absorbing Quantum Dots Designed to Kill Multidrug-Resistant Pathogens Max Levy, John Bertram, Kristen Eller, yuchen ding, Anushree Chatterjee, Prashant Nagpal Multidrug-resistant (MDR) pathogens infect millions of people in the US, with global predictions of 10 million annual deaths by 2050.1 New classes of antibiotics are needed to address this global public health crisis. Light-activated quantum dots (QDs) can fill this role by perturbing the bacteria’s biochemical environment using specifically designed optoelectronic properties.1 Inside bacteria, QDs can be energized by visible light, transferring electrons to O2 to generate superoxide radicals. We show that low doses of QDs can kill pathogens without harming human cells. CdTe QDs, while effective,2–5 are limited by the use of visible light for activation. As such, we recently developed two InP QDs which operate with tissue-penetrating near-IR and deep-red light.6 These heavy metal free QDs kill MDR pathogens without harming human cells. This work has the potential to treat dangerous infections of bacterial pathogens with a low-cost rational approach. |
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