How to design a geckskin grappling hook to attatch to surfaces like a rocks and builidngs?

Question

For a while now, I've been very into grappling guns and the ability to swing around buildings, etc. Specifically been very interested in the odm gear present in the show "Attack on Titan". It's a device that has two launchers in each side of the hip that fire grappling hooks with a cable and attach them to the wall, to then rapidly reel over the cable to allow the user to swing around. Something like this.

The question relies in how of if it is posible to change the design of the grappling hook to instead of breaking through stone or brick and attatching, could just stick to it with the geckskin.

In this article it says that 16 square inches of geckskin (an artificial material inspired by the skin of gecko feet) can handle up to 700 pounds when properly attached to glass, so I think it can support a 170 pounds human reeling the cord at maybe 2Gs of acceleration (making the total weight to around 340 pounds) when sticking it to a brick or rock.

The usage of it doesn't have to be as flashy as in the clip but a bit more realistic. Something similar as how spider-man uses his webs.

If someone could give me a hand on ways to design it would be very useful :)).

Edit: Sorry for not making clear the question, I've changed it a bit and maybe now it is more clear. Thank you.

Answer 1

I'm not much of an engineer, but I thought I'd mention that I recently saw this video by Veritasium about a similar material to the one you're talking about (or perhaps the same one). The video could definitely help you get a better idea of how the material works.

The thing I found most interesting about the material is that it uses Van der Waals forces to interact with the material it is sticking to. In order to accomplish this, it brings microscopic "wedges" extremely close to the material in the same way gecko feet do. This would definitely be something to consider when designing the device, because it operates using the shear forces of sliding it along the material rather than direct force applied in the direction of the attachment.

Although I don't have any exact designs (and I'm not sure how precise you need them to be), I could think of a few ways this could possibly work.

One way would be that it works nearly exactly the same as a normal grappling hook, but the "hook" just has a few flat sections of material attached to it (with the "wedges" facing away from the direction of fire. When the device is fired (it would need to be close to parallel to the surface it wants to stick to, the material would first slide along the surface, but when it is pulled back by the user, I believe the material would stick to the surface and hold their weight. I don't know how feasible it would really be, but if you're using it in a story, you have a lot of liberty with how you describe it.

The other ways I thought of involve using other methods (like suction or robotics) to attach to a perpendicular surface, and using the material in combination with these methods to make it stick better. However, you would still need a way to detach the other methods, and it should ideally just slide off once you're past the point where it sticks with the first design.

It doesn't seem like anyone has built anything like this before, so a lot of what I'm saying is just my ideas. This paper describes some real-world applications of the material, and mentions that large factors in adhesiveness are the smoothness of the surface it sticks to and mechanical control over the movement of the material. So this makes me think the main issues wouldn't be weight related, but with how the material is positioned. Rocks don't seem to be a possible material to attach to with this technology, because their surfaces are very bumpy.

I hope that gives you some ideas at least! I'm also a big fan of Attack on Titan. Have fun worldbuilding!