• Name

    DARPA has funded researchers at UC Berkeley who are working on the Gecko Adhesion Project, and is working on the Z-Man project.

• What is the item

Berkeley describes its project:

"Geckos have the remarkable ability to run at any orientation on just about any smooth or rough, wet or dry, clean or dirty surface. The basis for geckos' adhesive properties is in the millions of micron-scale setae on each toe of the gecko form a self-cleaning dry adhesive. The tip of each seta consists of 100 to 1000 spatulae only 100 nanometers in diameter. Our interdisciplinary team of biologists and engineers has been working since 1998 developing models for how the natural nanostructures function in a hierachical combination of spatulae, spatular stalks, setal stalks, setal arrays, and toe mechanics, and developing nanofabrication processes which allow large arrays of hair patches to be economically fabricated."

http://robotics.eecs.berkeley.edu/~ronf/Gecko/index.html

According to DARPA's DSO: 

"The Z-Man Program will develop climbing aids that will enable an individual soldier to scale vertical walls constructed of typical building materials without the need for ropes or ladders."

http://www.darpa.mil/dso/thrusts/materials/biomat/zman/ 

• What Horizon is it on

Fourth Horizon

• Explanation of the item 

Gecko Adhesion

Basic Facts:

• Geckos adhere to just about any surface, wet or dry, smooth or rough, hard or soft.
• Gecko adhesive is unique in that it is self-cleaning during repeated use.
• Gecko adhesion can be mechanically switched on and off. Sliding against a surface uncurls the seta to engage the adhesive. By relaxing sliding tension, the adhesive can be released.
• Gecko adhesion principles work with hard materials, and are primarily dependent on the geometry of the fibers. Thus gecko-inspired synthetic adhesives can be made from a wide range of materials which can resist extreme environments such as high temperatures. In the future, gecko inspired synthetic adhesives can be made non-toxic, biocompatible, or biodegradable.

  http://robotics.eecs.berkeley.edu/~ronf/Gecko/gecko-facts.html

"Using insights from biology, we develop mechanical models for gecko hair adhesion and then design, fabricate, and test micro and nanofibrillar structures. We aim to achieve the seven benchmark functional properties of the gecko adhesive system identified by Autumn (MRS Bulletin 2007):

1. anisotropic attachment,
2. high pulloff to preload ratio,
3. low detachment force,
4. material independence / van der Waals adhesion,
5. self-cleaning,
6. anti-self matting, and
7. non-sticky default state.

"The low detachment force, self-cleaning, and non-sticky default state suggest hard polymers, rather than the soft polymers typically used in pressure sensitive adhesives. As reported in 2002, [Sitti and Fearing 2002] and Autumn et al. [2002] we have made synthetic spatulae, which have shown adhesion similar to natural spatulae in the range of 100-300 nN. These patches of bumps lacked the setal stalks, and achieved adhesion forces on the order of a few milliNewtons on an area of a square centimeter. In 2003, we fabricated high density arrays of spatular stalks [Campolo et al. 2003] which showed adhesion in shear on the order of 0.5 Newton per sq. cm. In 2006, we demonstrated a novel high friction array of 0.6 micron fibers which showed shear resistance of 4 Newton per sq. cm. with only 0.8 Newton per sq. cm. of normal load [Majidi et al. PRL 2006]. In 2007, we showed how the polypropylene fiber arrays can provide shear force without a normal load being present [Schubert et al. JAST 2007]. In 2008, we made easy-attach easy-release hard polymer gecko adhesives which have a non-adhesive default state [Lee et al. JRSI 2008], and can self-clean during contact [Lee and Fearing Langmuir 2008].  The final goal is to build arrays incorporating the necessary geometrical features which have the same adhesion as geckos to rough and smooth surfaces."  http://robotics.eecs.berkeley.edu/~ronf/Gecko/index.html

DARPA's DSO:

"The Z-Man Program will develop climbing aids that will enable an individual soldier to scale vertical walls constructed of typical building materials without the need for ropes or ladders. The inspiration for these climbing aids is the technique by which geckos, spiders, and small animals scale vertical surfaces, that is, by using unique biological material systems that enable controllable adhesion using van der Waals forces or by hooking surface asperities. This program seeks to build synthetic versions of those material systems and then utilize them in a novel climbing aid optimized for use by humans. The overall goal of the program is to enable an individual soldier using dry adhesive climbing aides to scale a vertical surface at 0.5 m/s while carrying a combat load."

http://www.darpa.mil/dso/thrusts/materials/biomat/zman/ 

• Photos (if available)

Geckos are able to climb walls of all types of surfaces

without aid of any kind.  The Z-Man project hopes to

duplicate that effect with a suit for soldiers.

http://image14.webshots.com/15/4/54/72/163045472VdflVi_ph.jpg 

Berkeley's Gecko Adhesive System shown froma  macoscale to a nanoscale.

http://robotics.eecs.berkeley.edu/~ronf/Gecko/index.html

Gecko Adhesion Applied: A "microfiber array wrapped on model car tire demonstrates friction." This is a "1/18

scale model car with Gecko tires on acrylic sheet." This has only been shown to work on smooth surfaces.

http://robotics.eecs.berkeley.edu/~ronf/Gecko/index.html

• Issues

• Sources

http://robotics.eecs.berkeley.edu/~ronf/Gecko/index.html 

http://www.darpa.mil/dso/thrusts/materials/biomat/zman/ 

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