In Nature, says Greg Grason at the University of Massachusetts Amherst, “Nobody except physics and geometry” tells molecules how to organize into the types of complex soft crystals that form in butterfly wings, for example, allowing them to selectively reflect different wavelengths of light. He and other materials scientists who study such self-assembling structures are often fascinated and inspired by them, he adds, “and we’re starting to learn how and why they are spontaneously form way they do.”

The double gyroid crystal is a lattice network of interconnected tubular struts like the ones that make up butterfly wings, explains Grason, a theoretical polymer scientist. Their colors, which differ among butterfly species, arise from changes in network spacing in the gyroid crystal, which alters the way light reflects off of them.

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Geckskin, the re-useable, super-strong adhesive inspired by the footpads and tendons of geckos that was invented by polymer scientist Alfred Crosby and his research group on campus, is now for sale at the University Store in the Campus Center, the first retail outlet in the nation to carry the UMass Amherst invention.

Rana Gupta, the strategy/finance/business development manager for Felsuma, the company formed to market Geckskin in April 2013, says, “It was very important to us to bring this home first. We feel the device has a bright future in university bookstores across the nation.”

In inventing Geckskin, Crosby and colleagues, working with biologist Duncan Irschick, an expert in how lizards climb and cling, set out to figure out what gives a five-ounce gecko the adhesive power to run up a wall and across the ceiling weighing roughly the equivalent of nine pounds without slipping or falling. This led the inventors to experiment with tremendous weights; for example, an early Geckskin device the size of an index card could hold a 700-pound weight mounted on smooth glass.  

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A blue-dyed material going across the interface while a yellow due material does not. The difference is that treble has a positive charge and the yellow is negatively charged. 

The researchers used two polymer aqueous solutions, one of polyethylene glycol (PEG) and water, the other dextran and water, with different electrical charges, that can be combined but do not mix. They say it’s a classic example of coacervation, where the solution undergoes liquid-liquid phase separation and forms two separate domains, like the non-mixing wax-and-water in a lava lamp.  Courtesy UMass Amherst/Russell Lab

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By one official estimate, American manufacturing, transportation, residential and commercial consumers use only about 40 percent of the energy they draw on, wasting 60 percent. Very often, this wasted energy escapes as heat, or thermal energy, from inefficient technology that fails to harvest that potential power.

Now a team at the University of Massachusetts Amherst led by chemist Dhandapani Venkataraman, “DV,” and electrical engineer Zlatan Aksamija, report this month in Nature Communications on an advance they outline toward more efficient, cheaper, polymer-based harvest of heat energy.

“It will be a surprise to the field,” DV predicts, “it gives us another key variable we can alter to improve the thermo-electric efficiency of polymers. This should make us, and others, look at polymer thermo-electrics in a new light.”

Aksamija explains, “Using polymers to convert thermal energy to electricity by harvesting waste heat has seen an uptick in interest in recent years. Waste heat represents both a problem but also a resource; the more heat your process wastes, the less efficient it is.” Harvesting waste heat is less difficult when there is a local, high-temperature gradient source to work with, he adds, such as a high-grade heat source like a power plant.

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