have come up with a hand that is not human-like at all.
With their granular gripper, the mass of latex and
coffee grounds surrounds and presses an object to get its
grip, then a vacuum is created to harden the coffee
grounds and latex in the new shape, securing the
gripper’s control of the item.
Turn Up the Jams
Researchers based the universal jamming gripper on
a jamming phase: “If a collection of granular material is
loosely packed, it can flow like a liquid. If, instead, the
granular material is more densely packed, it behaves like
a solid, and we call this the jammed state,” explains Eric
Brown, postdoctoral scholar from the University of
“The transition between these two states is very
sharp and is called the jamming transition. The
difference in density between the two states is very small.
This is analogous to the sharp phase transition between
water and ice if the temperature is reduced,” Brown
With the surface of the gripper covering only one-fourth of the surface (sometimes less) of an object, the
attending vacuum can tighten the hand on or around a
cup, pen, screwdriver, or most anything. The hand comes
up against the object, taking shape around it. Once the
hand is in place, the vacuum or suction is applied and the
grasp of the gripper is complete.
“For our tests, everything was pre-positioned because
we were not testing any sensors. We did some tests on
the tolerance to positioning and found the gripper had
no loss of gripping capabilities if it was off target by as
much as a quarter of the gripper size,” says Brown.
“For autonomous robot applications, this suggests even
something rudimentary like a web cam may be all the
sensing that is necessary. For other applications like
assembly line or manually operated grippers, no sensing
may be necessary at all,” Brown notes.
Adjust the Volume Slightly
By decreasing the overall volume of the balloon by as
little as one half of one percent, the roboticists can turn
the malleable balloon into a rigid form around part of an
object that is enough to grip and lift it up. “There is less
space between the particles of coffee grounds and less
space volume inside the balloon,” says Brown.
Just a small amount of vacuum is enough to turn the
soft, pliable latex and coffee grounds into a rigid confine
about the item’s surface. The gripper can hold and carry
multiple items that are in close proximity to one another,
as well. A pump known as a Venturi aspirator sucks the
air out of the gripper. A red tube runs from the gripper
to the pump to accomplish this.
“We used a variety of pumps for different
The unique latex membrane and coffee particle robotic hand is
able to grip this glass and pour liquid from it.
The gripper hand is ready to play a round of jacks, but uses only
one jack at a time for now.
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