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A D V A N C E D M A T E R I A L S & P R O C E S S E S | N O V E M B E R / D E C E M B E R 2 0 1 5


Most spiderwebs are made of spiral-like strands of “capture silk” that play

a key role by retaining prey, freeing spiders to hunt. This special silk consists of

an axial fiber coated with glue droplets at regular intervals. Spider glue is unique

because its adhesion increases in response to humidity, and for some species, ad-

hesion continues to increase up to 100% relative humidity—the exact opposite of

how synthetic adhesives act on human skin in response to higher humidity.

Researchers from the University of Akron, Ohio, and Virginia Polytechnic In-

stitute, Blacksburg, explored the properties underlying the spider glue’s humidity-

responsive adhesion. Scientists measured the adhesion of capture threads from

five different species. “The habitats of these species range from dry to wet and hu-

mid, so we measured the adhesion as a function of humidity and used high-speed

imaging to quantify the spreading rate of the glue droplets,” explains Gaurav Am-

arpuri of Akron. The spreading of a liquid droplet follows the “spreading power

law,” in which low viscosity droplets spread faster than high viscosity droplets. The

group used the spreading power law to calculate glue viscosity as a function of

humidity. “We discovered maximum glue adhesion at the humidity levels at which

the spider usually forages,” says Amarpuri.



“I was once asked what kind of music stem cells would like best. Classical, I decided, because

they’re cultured.” This was just one in a string of tales Laura McNamara unraveled at the debut

GlasgowBright Club a fewyears ago, where sciencemeets humor. Bright Club is a comedy-club-style

event featuring scientists and academics, which started at University College London. Academics

brave the spotlight to vent about anything from Greek mythology to neuroscience. Researchers

who perform at Bright Club span all ages, career levels, and disciplines. McNamara, who was cultur-

ing stem cells on nanopatterned titanium surfaces at the time of her first stand-up routine, is now

the science education coordinator at the Glasgow Science Centre.



Could some of the hardiest bacteria on Earth hitchhike on a

Journey to Mars and survive after landing in a new world? NASA re-

searchers intend to find out. A helium-filled scientific balloon will

soon carry bacteria to the edge of space—Earth’s stratosphere—ex-

posing them to conditions similar to those found on the surface of

Mars. Researchers will measure how long the bacteria can endure,

and will also study the biological underpinnings of bacterial survival

in harsh conditions. A specialized hardware system that will be used

for the study, Exposing Microorganisms in the Stratosphere (E-MIST),

was developed last year at NASA’s Kennedy Space Center in Florida.

The 2014 test of the E-MIST system is prepared for flight

on August 24 at NASA’s Columbia Scientific Balloon

Facility in Fort Sumner, N.M.

Larinioides cornutus

capture threads peeled

from a glass substrate, under low, medium, and

high humidity conditions. At medium humidity,

glue droplets form a suspension bridge structure

where adhesion is maximum. Scale is 100 µm.

Courtesy of Yizhou Chen/U.Akron.

Researcher Laura McNamara

performs stand-up comedy

about materials for Bright

Club in Scotland.