Snail slime inspires new super-strong reversible glue

Snail slime -- called an epiphragm -- is an incredibly strong yet reversible adhesive. Now, University of Pennsylvania scientists have developed a new kind of glue that employs the same mechanism as the epiphragm. The new material dries like superglue but once wet, it loses its adhesion. For years, scientists have explored adhesions inspired by nature but none have been demonstrated to have the same amount of strength and reversibility. For example, the researchers report that their new adhesive "is 89 times stronger than gecko adhesion." From the University of Pennsylvania:

The breakthrough came one day when Gaoxiang Wu was working on another project that involved a hydrogel made of a polymer called polyhydroxyethylmethacrylate (PHEMA) and noticed its unusual adhesive properties. PHEMA is rubbery when wet but rigid when dry, a quality that makes it useful for contact lenses but also, as Yang's team discovered, for adhesives.

When PHEMA is wet, it conforms to all of the small grooves on a surface, from a tree trunk's distinct ridges to the invisible microporosity of a seemingly smooth wall. This conformal contact is what allows PHEMA to stick to a surface.

To demonstrate just how durable their PHEMA adhesive is, one of Yang's lab members and co-first author, Jason Christopher Jolly, volunteered to suspend himself from a harness held up only by a postage-stamp-sized patch of their adhesive; the material easily held the weight of an entire human body. Based on the lab tests, the team determined that, although PHEMA may not be the strongest adhesive in existence, it is currently the strongest known candidate available for reversible adhesion.

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Plants that glow could illuminate tomorrow's buildings

MIT researchers who developed light-emitting plants are now exploring how the glowing greenery could be integrated into future building designs. In their proof-of-concept demonstration, the scientist packaged luciferase, the enzyme that enables fireflies to glow, into nanoparticles that were then suspended in solution. The plants were immersed in the solution and, through high pressure, the nanoparticles entered tiny pores in the plants' leaves. The plants maintained their glow for several hours and they've since increased the duration. Now, project lead Michael Strano, professor of chemical engineering, is collaborating with MIT architecture professor Sheila Kennedy on possible future applications of the green technology. From MIT News:

“If we treat the development of the plant as we would just another light bulb, that’s the wrong way to go,” Strano (says)....

The team is evaluating a new component to the nanobiotic plants that they call light capacitor particles. The capacitor, in the form of infused nanoparticles in the plant, stores spikes in light generation and “bleeds them out over time,” Strano explains. “Normally the light created in the biochemical reaction can be bright but fades quickly over time. Capacitive particles extend the duration of the generated plant light from hours to potentially days and weeks...."

As the nanobionic plant technology has advanced, the team is also envisioning how people might interact with the plants as part of everyday life. The architectural possibilities of their light-emitting plant will be on display within a new installation, “Plant Properties, a Future Urban Development,” at the Cooper Hewitt, Smithsonian Design Museum in New York opening May 10.

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