Source: NASA Gecko Gripper
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Geckos have specialized hairs on their feet called setae that let them stick to vertical surfaces without falling, and their stickiness doesn’t wear off with repeated use. The Gecko Gripper investigation tests a gecko-adhesive gripping device that can stick on command in the harsh environment of space. The technology promises to enable many new capabilities, including robotic crawlers that could walk along spacecraft exteriors; grippers that use a touch-to-stick method to catch and release objects; and sensor mounts that can work on any surface and reused multiple times.
- Gecko adhesives use microscopic angled hairs to stick to surfaces using van der Waals forces. Adhesion can be turned ON and OFF based on a slight sliding motion due to the geometry of the microstructure. The adhesives are reusable for thousands of cycles without losing their effectiveness, and do not damage the surface, leave a residue, or produce fibers and particles as pressure sensitive adhesives, glues, and Velcro do.
- The Gecko Gripper experiment tests grippers in 3 sizes that each use 2 gecko adhesive pads in opposition to one another (for one set the preferred adhesive direction is left, the other right).
- Springs between the 2 pads allow the operator to prepare for grip by squeezing the pads together. The operator can then touch the pads to the surface lightly (
- The gripper adheres to the surface and can bear loads and moments in all directions (up to 20lbs).
- The gripper can remain in place indefinitely. The operator can remove the gripper by squeezing the pads back together and pulling away from the surface (
The data collected are compared to data collected on the ground in a 1g environment at the Jet Propulsion Laboratory (JPL). This enables researchers to both better understand the physics and mechanisms of gecko adhesive grippers and also design improved grippers for future applications inside and outside the ISS.
In recent years, there has been growing interest in robotically servicing assets in space. Gecko adhesive grippers could assist robotic mobility on large space assets such as the ISS. An ON-OFF adhesive gripping tool would augment robotic capabilities by allowing more surfaces to be targeted, useful for stabilizing the work surface, manipulating delicate features like blankets, and allowing the servicing spacecraft to grapple many more points on the target. In the future, an adhesive gripper may even enable a much smaller spacecraft that could dock to the target at many distinct locations to perform servicing operations, reducing launch and development costs through reduced mass and complexity.
Orbital debris mitigation is a particularly urgent need as it currently poses a risk to human life aboard the ISS and has forced astronauts to prepare for evacuation during close passes of debris. Gecko adhesive gripping tools can help address this growing problem by providing a simple, reliable method to grapple the largest, and most dangerous pieces of debris like defunct satellites and spent rocket stages. Oftentimes, these objects do not have fixed grapple points, or are spinning/tumbling making such points difficult to access. This technology could enable a spacecraft to grapple pieces of debris by virtually any surface and without the need for precision targeting or control during the grapple sequence.
Gecko Grippers have many applications on current and future space missions, including as mounting devices for payloads, instruction manuals and many other small items within the International Space Station (ISS). In addition, gecko adhesive technology enables a new type of robotic inspection system that could prove vital for spacecraft safety and repair. Gecko Grippers could crawl along the ISS exterior and inspect for micrometeoroid and orbital debris damage. Grippers could also inspect and service satellites, extending the life of existing space assets and reducing costs. Gecko adhesive could also be used for large grappling equipment to catch and retrieve large pieces of space debris, reducing the risk of collisions in geosynchronous orbit and other locations.
Robots that can use gecko adhesive to climb walls have numerous military and security applications. The Defense Advanced Research Projects Agency (DARPA) has been testing gecko-like adhesive for surveillance applications for many years. The technology also holds promise for industry, where gecko-like grippers could be used in factories to handle fragile or lightweight objects like glass, and bags or boxes of food.