New Theory Explains Nonlinear Stretching in Rubbery Materials


2/1/2007 12:00 AM

Professor of Physics Paul Goldbart, in collaboration with Xiangjun Xing (Syracuse) and Leo Radzihovsky (Colorado), has solved a theory problem that has puzzled physicists since the 1940s (Phys. Rev. Lett. 98, 075502 [2007]).

Measuring the force produced by stretching a rubber band to its limits is easy, but the standard theory of rubbery materials cannot predict this force.

When they are not stretched too much, rubbery materials act as simple springs, obeying Hooke's law. Thus, a 10-percent increase in stretching force will extend a typical rubber band 10 percent farther. But at greater stretching forces, that simple linear relation fails. The existence of the nonlinearity has long been known, but understanding its origins and developing a theory that correctly captures it "has been a challenge to the physics community for 60 years," said Goldbart.

By including the extra entropy associated with long length-scale motion while simultaneously coping with the essentially incompressible nature of rubbery materials, the researchers are now able to construct a theory that agrees with experiment, not only in the Hookean regime but also beyond—deep into the nonlinear regime. Read more...

Recent News

Mason says, “there are so few of us, people get the impression that we are like unicorns – either non-existent or magical.” We are far from non-existent, but I find women of color to be quite magical. However, as Jesse Williams says, “Just because we’re magic, doesn’t mean we’re not real.”

  • Outreach

It’s up to you and your team to save the free world from evil forces plotting its destruction, and you have precisely 60 minutes to do it. You must find out what happened to Professor Schrödenberg, a University of Illinois physicist who disappeared after developing a top-secret quantum computer that can crack any digital-security encryption code in the world.  Unfortunately, the previous groups of special agents assigned to the case disappeared while investigating the very room in which you now find yourself locked up, Schrödenberg’s secret lab.

LabEscape is a new science-themed escape room now open at Lincoln Square Mall in Urbana, testing the puzzle-solving skills of groups of up to six participants at a time. Escape rooms, a new form of entertainment cropping up in cities across the U.S. and around the globe, provide in-person mystery-adventure experiences that have been compared to living out a video-game or movie script. A team of participants is presented with a storyline and locked into a room with only one hour to find and decipher a sequence of interactive puzzles that will unlock the door and complete the mission. Two escape room businesses are already in operation in the area, C-U Adventures in Time and Space in Urbana and Brainstorm Escapes in Champaign.

 

  • Research
  • AMO/Quantum Physics
  • Condensed Matter Physics

Topological insulators, an exciting, relatively new class of materials, are capable of carrying electricity along the edge of the surface, while the bulk of the material acts as an electrical insulator. Practical applications for these materials are still mostly a matter of theory, as scientists probe their microscopic properties to better understand the fundamental physics that govern their peculiar behavior.

Using atomic quantum-simulation, an experimental technique involving finely tuned lasers and ultracold atoms about a billion times colder than room temperature, to replicate the properties of a topological insulator, a team of researchers at the University of Illinois at Urbana-Champaign has directly observed for the first time the protected boundary state (the topological soliton state) of the topological insulator trans-polyacetylene. The transport properties of this organic polymer are typical of topological insulators and of the Su-Schrieffer-Heeger (SSH) model.

Physics graduate students Eric Meier and Fangzhao Alex An, working with Professor Bryce Gadway, developed a new experimental method, an engineered approach that allows the team to probe quantum transport phenomena.

  • Research
  • Astrophysics/Cosmology

In its search for extrasolar planets, the Kepler space telescope looks for stars whose light flux periodically dims, signaling the passing of an orbiting planet in front of the star. But the timing and duration of diminished light flux episodes Kepler detected coming from KIC 846852, known as Tabby’s star, are a mystery. These dimming events vary in magnitude and don’t occur at regular intervals, making an orbiting planet an unlikely explanation. The source of these unusual dimming events is the subject of intense speculation. Suggestions from astronomers, astrophysicists, and amateur stargazers have ranged from asteroid belts to alien activity.  

Now a team of scientists at the University of Illinois at Urbana-Champaign—physics graduate student Mohammed Sheikh, working with Professors Karin Dahmen and Richard Weaver—proffer an entirely novel solution to the Tabby’s star puzzle. They suggest the luminosity variations may be intrinsic to the star itself.