Soft Materials Seminars

August 29, 2017

"Design of soft machines"

We introduce an approach based on minimal theoretical modeling, direct numerical simulations and evolutionary optimization techniques for the characterization and design of arbitrary muscoloskeletal architectures. Applications range from slithering and swimming biolocomotion strategies to artificial muscles and bio-hybrid systems.

September 5, 2017

"Constraints on communities and characters"

In the late 1990’s, Sydney Brenner lamented the fact that the molecular biology revolution of the 60’s had diminished the dual role of theory and experiment in answering big questions in biology. Can we predict evolutionary dynamics? How do ecology and evolution interact to give rise to the complexity we observe in Nature? In this talk, motivated by past successes in physics, I argue that understanding constraints on biological systems provides a path forward to reconnecting theory and experiment in biology. I present two vignettes which illustrate the power of elucidating constraints at two levels of biological organization. First, I present a study of abundance dynamics in a complex three-species microbial community consisting a photosynthetic alga, and bacterium and a microbial predator. Understanding how interacting communities of microbes respond to changes in their environment is important for disciplines from climate change to human health but due to strong, and often highly non-linear, interactions between organisms community response to perturbations is challenging to predict. Through a series of experiments we reveal two constraints on abundance dynamics in this system: (1) the community exhibits surprisingly deterministic dynamics on very long timescales, and (2) the community responds coherently along "ecomodes" when subjected to changing light levels [Phys. Rev. X, 2015]. In second study we ask how constraints on phenotypic variation limit the capacity of organisms to adapt to multiple simultaneous selection pressures. We select Escherichia coli for faster migration through a porous environment, a process which depends on both motility and growth. We find that a trade-off between swimming speed and growth rate constrains the evolution of faster migration. Evolving faster migration in rich medium results in slow growth and fast swimming, while evolution in minimal medium results in fast growth and slow swimming. A model of the evolutionary process shows that the genetic capacity of an organism to vary traits can qualitatively depend on its environment, which in turn alters its evolutionary trajectory [eLife, 2017]. We explore the possibility that phenotypic constraints and genetic architecture can provide a route to predicting evolutionary dynamics.

September 12, 2017

“Shockwave energy dissipation using polymerized ionic liquids,” by Jaejun Lee (Sottos)

 “Three-dimensional microphase separation and synergistic permeability in stacked lipid – polymer hybrid membranes,” by Minjee Kang (Leal)

"Controlled synthesis of unimolecular polypeptide micelles," by Shixian Lyu (Cheng)

September 19, 2017

“Visualization of electron hopping among redox-active polymeric colloids via Fluorescence microscopy,” by Subing (Alan) Qu (Braun)

 “A study of the morphology and dynamics of concatenated ring polymers,” by Jiang Wang (Ferguson)

 “Thermal conductivity of support-free polyamide thin films,” by Jordan Dennison (Murphy/Cahill)

September 26, 2017

“Rational design of radially amphiphilic antimicrobial peptides,” by Menghua Xiong (Cheng)

“Specific ion co-activation effect on transient polymer microcapsules,” by Shijia Tang (Moore)

 “Local activation of mechanophore functionalized solid interface with mechanical scanning probe lithography,” by Jaeuk Sung (Sottos)

October 3, 2017

“Concentration-driven assembly and sol-gel transition of pi-conjugated oligopeptides,” by Yuecheng Zhou (Schroeder)

 “Porous silicon photonics for monitoring cell activities,” by Yi Pei (Kilian)

 “Dynamic force-extension of DNA with nucleoid associated proteins,” by Katelyn Dahlke (Sing)

October 10, 2017

 "Elastomeric surfaces for the rational synthesis, assembly, and fabrication of adaptive, functional materials" 

We are investigating new synthetic strategies for the fabrication of adaptive, hybrid structures comprised of combinations of soft materials (e.g., polymers) and hard materials (e.g., inorganic crystals) with functional (optical, mechanical, magnetic, etc.) characteristics. Central to these efforts are elastomeric surfaces with heterogeneous chemical and physical properties that can be reversibly reconfigured using simple, macro-scale processes such as mechanical deformations—we sometimes refer to these mechanically tunable surfaces as 2D "assembly substrates." Specifically, we focus on systems fabricated from elastomeric polymers, such as silicones, which provide a diversity of chemical and mechanical properties. In this talk I will highlight our recent findings involving the synthesis and application of mechanically tunable surfaces, which include the synthesis/assembly of solids (e.g., optically active semiconductor films and catalytically active microparticles) and the manipulation of liquids (e.g., picoliter-volume droplets of aqueous solutions and prepolymer droplets). The unique properties (chemical, physical, and mechanical) of these surfaces and the unique capabilities they provide will enable new methods and structures for the micro/nanoscale manipulation, organization, and assembly of liquids/solids, and provide new techniques for the fabrication of hybrid structures applicable to emergent technologies, for example, soft sensors, optics, and electronics, soft actuators for soft machines/robotics, and smart surfaces with adaptive adhesion. Furthermore, the ability of the strategies we demonstrate to operate simultaneously on large numbers of micro-/nanoscale functional components using macroscale processing (e.g., tensile deformations) presents unique advantages in the scalable, advanced manufacturing of functional structures.

 

October 17, 2017

“Effect of polyelectrolyte charge sequence on complex coacervation,” by Tyler Lytle (Sing) 

“Minimal model and coarse-grained simulation for the study of an optoelectronic assembling peptide,” by Rachael Mansbach (Ferguson)

 “New sacrificial materials for multifunctional composites,” by Mayank Garg (Sottos)

October 24, 2017

 "Manipulating Light, Matter and Energy with Plasmonic Nanotechnology" 

Surface plasmons, which are coherent oscillations of delocalized electrons at the interface of two materials, can manipulate light at the nanoscale. We explore and exploit the unique optical, thermal, mechanical, electrical and chemical properties associated with the plasmon-enhanced nanoscale light to innovate a wide range of optical nanotechnologies in health, energy, manufacturing andnational security. I present our progress in three areas:

(I) Optothermal manipulations of colloidal particles, biological cells and molecules. New techniques include bubble-pen lithography and opto-thermophoretic tweezers. Their applications in colloidal matter, colloidal devices, surface-enhanced Raman spectroscopy and cellular biology are presented.

(II) Plasmon-induced hot-electron and resonant energy transfer. Applications include fluorescence enhancement, rewritable nanophotonics and solar water splitting.

(III) Light manipulations with moire metasurfaces and metamaterials. Applications include surface-enhanced chiroptical spectroscopy, surface-enhanced multi-band optical spectroscopy, optical capture of bacteria and photothermal denaturation of proteins.

October 31, 2017

“Interfacial fluctuations at the nanoscale,” by Zihao Ou (Chen)

 “Glass transition in thin films,” by Anh Phan (Schweizer)

 “High resolution digital image correlation of deformation in model composite systems,” by Christopher Montgomery (Sottos)

November 7, 2017

“Lights, Nano, Action!: Making subdiffraction focusing optics with porous silicon,” by Christian Ocier (Braun)

 “Non-wetting microchannels towards adaptive liquid electronics,” by Tony Griffin (Sottos)

 “Super-swelled lyotropic single crystals?,” by Hojun Kim (Leal)

November 14, 2017

“Single molecule conductance of sequence-defined oligomers,” by Songsong Li (Schroeder)

“Nonlinear rheology of entangled polymer liquids under continuous shear,” by Shi-Jie Xie (Schweizer)

“Colloidal epitaxial growth of a cubic nanoparticle superlattice,” by Binbin Luo (Chen)

November 21, 2017

THANKSGIVING BREAK

December 12, 2017

NO SOFT MATERIALS SEMINAR