how about using some laser light diffraction and fine polished lens? It might create some fine lines but are they sharp enough to be usefull?
How about nanoporous anodic aluminum oxide? You can buy filters made from AAO, or you could make your own. It's not hard to anodize an aluminum surface yourself if you have sulfuric acid, and by doing different thicknesses, you could vary the aspect ratio.
just what I came across during my searches, "hard" anodized aluminium films can have highly ordered, relatively large (not nanoscale) pores with high density and high aspect ratio. http://www-old.mpi-halle.mpg.de/department2/fileadmin/user_upload/Research_Projects/Ordered_porous_Materials/Porous_Alumina/b_Fig_1a.jpgAs for lithography: spin coated films of polystyrene or glass microspheres generate an ordered surface and can be used as shadow masks. Depending on positive or negative development processes the desired result could be achieved without ever touching high resolution lithography. That should also make the process more accessible since a spin coater is hacked together much faster than a lithography machine.
I did not know spin-coating microspheres would form a monolayer that is almost close-packed. Cool!
have you considered two-photon lithography to create the surface for applying silicone or to even fabricate the gecko tape directly? Not sure where to find a service provider of the technology but I'd be happy to help with the CAD if needed.see here for some info from 2012:http://spie.org/newsroom/technical-articles/4378-3d-molding-processes-based-on-two-photon-microfabrication?ArticleID=x91084
There are essentially two "easy" methods of making tiny stuff.The one is just photographing an image using fine-grained silver halide film. Just draw the desired image in large scale and photograph it. After developing, photograph the photograph. Repead as needed. So you can go up to the diffraction limit. A compound microscope may be user for projecting the final image to the photoresist.If you have to go beyond the diffraction limit, holography can help you. Split a HeNe or diode laser beam into two and pass each one via a microscope lens with spatial filter. Isolate this from vibrations by putting the entire table on a pile of old newspapers. Now you can make an interference stripe pattern by intersecting these beams. A photopolymer will do the trick. One easy recipe is a mixture of calcium acrylate with PVA ant triethanolamine sensitized with methylene blue. And, finally, did you think about using an electron beam? Like a reversed TEM to project a image from an etched mask via a magnetic lens.
First thought: E-beam.Second thought: silicone droplets sprayed on silicone substrate, pulled into shape, then cut. Probably still too large.
Hi Ben,just found your blog, the projects you're making are amazing! I think if I were to try any of them I would have irradiated myself by now!I have no idea about the sizes or feasibility but what if you mix the silicon with iron dust making it into a sort of ferro fluid? Using a magnetic field you could pull on the iron motes in the setting silicon (at an angle if you like) and this might pull along some silicon and create the tendrils you need.Just an idea! John
Have you taken a look at "Geckskin"?https://geckskin.umass.edu/
Great blog Ben! Here are some things you can try to make a micro mold: Interference lithography- the lens and pinhole designs look pretty simple for a photolithography set up. All you need is a laser, a small lens, a pinhole, and a mirror perpendicular to your target. There's quite a few papers out there you can access for free. It makes periodic structures, lines if you only use 1 laser. Microlens photolithography- Still fairly simple. You'll need a light source, a fresnel lens, a transparency (Photomask), a microlens. Great for making periodic microstructur -es of patterns and patterns can be interconnected past a certain feature size. Resolution is around 5-10 microns without fancy tricks- ie, phase-shift masks, etc. If you want to get into microfluidics, you should check out khine labs.they've made chips out of shrink wrap and shrinky dinks, among other things like a microlens. Also quite a few of their publications are open access. Hope this gives you some ideas, I'm looking forward to your next project!
There's a new type of gecko design that doesn't use fibrils at geckoskin.umass.edu. Here's an excerpt from the website: "Unlike traditional pressure-sensitive adhesives, which rely on viscoelasticity for adhering to surfaces, Geckskin™ relies on a concept known as draping adhesion. Draping adhesion is created with materials that can drape to create conformal contact with a surface while still maintaining high, elastic stiffness in directions where forces will be applied. This design enables adhesive loads to be more evenly distributed across the pad surface, while also allowing for a rapid and low-energy transition between attachment and detachment.Geckskin™ is composed of stiff fabrics—such as carbon fiber or Kevlar—with soft elastomers, such as polyurethane or polydimethylsiloxane (PDMS). It uses commodity materials, not nanotechnology. The key innovation of Geckskin™ was the integration of a soft elastomer (the pad) with a stiff fabric (the skin), allowing the pad to drape over a surface to maximize contact. Further, as in natural gecko feet, the skin is woven into a synthetic tendon, yielding a design that plays a key role in maintaining stiffness and rotational freedom. The end result is an adhesive device that is powerful, easily removed, and leaves no residue."