Search

paulsengroup

Syracuse University, Department of Physics

First Lab Graduates!

Bottom: The Physics Department machine shop furnished this commemorative plaque, which Monica fastened to a wooden beam in the sub-basement of our building today. Her plaque joins a collection of many others like it, from previous dissertations by experimentalists in our department.

Monica Ripp and Jikai Wang gave successful PhD defenses this year. Monica’s dissertation, “Buckling Patterns and Mechanics of Thin Interfacial Polymer Films,” was defended on October 15, 2021. Jikai’s dissertation, “Self organization in models of cyclically-sheared suspensions,” was defended on April 2, 2021. Congratulations, Jikai & Monica!

Sculpting liquids with shells in PRL

A halftone image viewed through an ultrathin shell that has ‘sculpted’ an oil droplet to match its rest curvature. The curved interface brings this bird’s head into focus.

Our group recently had a manuscript published in Physical Review Letters, titled: “Sculpting Liquids with Ultrathin Shells”. Co-authors are postdocs Yousra Timounay and Mengfei He, former SU undergrad Lindsay Murphy, REU student Alex Hartwell, grad student Eric King, and collaborator Prof. Vincent Démery (ESPCI Paris). Our work shows how an ultrathin shell can “sculpt” a liquid interface into its own shape, through a mechanism that is much like the inflation of a stiff balloon.

From wrinkles to crumples in PRX

pillow
Smooth wrinkles and sharp crumples on an air cushion used for shipping.

Consider for a moment the smooth wrinkles on our skin and the sharp creases on a crumpled ball of paper. These two kinds of surfaces look and feel quite different, and you might wager that the difference comes down to the material itself: skin makes “wrinkles” and paper makes “crumples”. We found that this reasonable guess is actually wrong. By squeezing and inflating plastic and rubber sheets in a variety of experiments, we discovered how to turn wrinkles into crumples and then back. What’s more, we found that crumples are rather general features — nature uses this “building block” to help sheets contort in a lot of geometrically-tricky situations. So understanding the physics of a birthday balloon can teach you things that are important for designing deployable satellites or understanding ripples in a cell membrane. Links: PRX, APS Physics Magazine

Poking a thin film in Soft Matter

poking-blue
An 8-cm-wide floating polymer film indented by a force probe.

Thin sheets are easily bent and twisted into different shapes while staying within the linear elastic response of the material. Think of rolling up a scientific poster: large displacements occur with relatively small forces and virtually no damage to the material. Such geometric nonlinearities complicate the relationships between forces, deformations, and material properties for any slender material, from textiles to polymer capsules to flagella. We map out the surprisingly rich mechanical response of a floating polymer film to indentation, using experiments, simulations, and theory. Our geometric approach provides a new tool for understanding the mechanics of sheet-laden interfaces in general settings. Links: Soft Matter, arXiv

Frustrated wrinkle patterns in PNAS

cover2_small_bc
A complex pattern of wrinkles on a centimeters-wide thin polymer shell. Islands of order are visible in the form of nearly-parallel wrinkles.

We are all familiar with the wrinkled texture of a raisin or a candy wrapper. Studying the arrangement of wrinkles in polymer films can lend insight into these and other materials that wrinkle, from textiles to biological tissues to synthetic skins. To address the complexity of wrinkle patterns, we asked the following basic question: “What happens when the direction of wrinkling is in direct conflict with the preferred wavelength?” Our answer is a quantitative framework for understanding the mesoscale organization of groups of wrinkles in such situations, with analogs to liquid crystals and superconductors. Links: PNASarXiv

New postdoc

HeM600

The group welcomes postdoctoral researcher Mengfei He. Mengfei comes from the Nagel lab at the University of Chicago. Welcome, Mengfei!

Review paper on material memories

LR14150_frontpage_large-1
A suspension of plastic spheres can remember multiple driving amplitudes that were applied to it, but forgets most of them in the steady state. This behavior occurs also in charge-density wave conductors and a model of worn grass between park benches. 

Despite the ubiquity of memory formation in condensed matter, there is presently no overarching framework for classifying memory behaviors. This review article considers memory formation across a broad range of systems (memories in rocks, rubber, glasses, and amorphous solids; memories in magnetic systems; echo phenomena; shape memory; associative memory; etc.), with an eye towards developing unifying conceptual underpinnings for material memories. Such a study of memory formation provides a setting for exploring some of the most fascinating aspects of history-dependence, dynamics, and information storage in far-from-equilibrium systems.

How much can a grassy path remember?

 

model
States and transitions in a simple model of a grassy path with park benches along it. The model has surprisingly rich memory behaviors, including learning, forgetting, and a stabilizing effect of noise.

We typically think of memory as the stuff stored in hard drives or our brains, but memory effects abound in a wide range of materials. Rubber and rocks can remember the largest load that was applied to them, glasses may remember a temperature where they were aged, and shape-memory alloys can recall a programmed shape. One approach to building a broader understanding of memory formation in matter is to construct and study simple models where memories may be written, stored, and retrieved. This article shows how a model of worn grass between park benches can produce a peculiar memory behavior that has been observed in the motion of electrons in a special kind of conductor, and in the flow of solid grains in viscous liquids. Continue reading “How much can a grassy path remember?”

Jessica Stelzel wins NSF GRFP

Jessica-scan-IMG_3675

REU student Jessica Stelzel has been awarded a National Science Foundation Graduate Research Fellowship. She will be starting her PhD at Johns Hopkins University in the Fall, working to create regenerative biomaterials with Dr. Hai-Quan MaoCongratulations, Jessica!

Create a free website or blog at WordPress.com.

Up ↑