The wings of insects are fantastic structures both in aesthetic and function. Their delicate structures hide many mechanical secrets that improve their performance and enhance their strength. In an effort to improve my ability to produce adequately interesting wings, I started a new technique and process that I hope will improve the wings’ symmetry and quality.

Insects have set a very high mark to work towards when replicating their wings. Butterfly wings are covered in scales which gives the order of insects their name Lepidoptera (scale wing). These scales form a mosaic of patterns and sometimes images which mimic faces to scare predators. Some scales even have nano structures which absorb and reflect specific wavelengths of light, causing a color effect without pigment like the Blue Morpho. Bees have two pairs of membranous wings which hook together and act as one large pair of wings. Dragonflies even have regions of the wing with buckling or stiffening properties based on the vein shape and position. The internal structure of wing veins is not a uniform tube, but specifically stiff or flexible shapes with multiple layers of material that also control stiffness or flexibility. Finally, the veins of insect wings themselves are not mirrored on the top and bottom of the wing, but instead there are certain concave and convex positions of wing veins to aid in folding, flexing, and also may be a byproduct of the way the wings grow and expand during eclosion.

So where do we start and what do we choose to replicate? Well, I started several years ago trying to create structures that share some superficial aesthetics of insect wings and could support their own weight. Over time, I have experimented with wire, yarn, plastic, wood, and combinations of all of the above. In time I have learned that for veins, tubes are better than uniform materials because they are much lighter weight and can be stiffer. It is also best to avoid metal whenever possible. For the wing material itself, although clear plastic sheets are more similar to insect wing membranes, they are quite difficult to glue, surprisingly heavy, and tear easily.

As of today, my preferred method is to 3D print wing veins for each side of the wing separately and sandwich them to a single sheet of tissue paper. A cross section of the wing veins on a single side would look roughly like an A frame cabin. The idea being that this shape is very stiff and would retain its strength while staying light weight. Once veins are glued to each side, the overall structure is roughly square with its sharp edges on the outside. This also aids in the printing process as I can slowly build up the walls of the veins and have them merge together without messy overhang angles. After they are glued in place, I coat the tissue paper in a medium like acrylic, resin, or oil. Oil and resin make the tissue paper nearly transparent, which is a great effect.

There have been many challenges with this method. Modeling, slicing, and printing the veins is difficult because I am right at the edge of FDM printing tolerances and capabilities. I have taken great effort to encourage the slicer to produce G-code which is successful. Once these delicate and flexible veins are printed, it is quite difficult to position them accurately while gluing, so I have accidentally misaligned veins and produced pairs of wings which are not very symmetrical. Finally, the tissue paper itself has been difficult to work with as it is extremely fragile when wet, and many types of tissue paper have a shiny side and a rough side, that ends up altering the final appearance of the wings too.

I am now working on a process which should help with several of these challenges. For the wing membranes and wing construction, I designed and built frames which hold the paper in place while I work with it. This is one of those ideas that seems obvious after you have it, but it took some effort to design their construction. I have settled on using canvas stretcher bars to produce two wooden frames with flat backs. I glue a layer of thin cork to the flat side so I can sandwich a sheet of tissue paper and clamp it together. This temporarily holds the tissue paper from all four sides and gives me space to apply paints, medium, and glue on the veins. It also allows me to hold the structure easily while I set it to dry and cure. Finally, it holds the paper in place to prevent distortion due to shrinking.

Another tool I am excited to introduce, is a stencil. Yet again, seems obvious after you realize what it could do. Using the same image references of Monarch butterfly wings I used to make the veins, I also created a sheet of plastic with cutouts for all of the orange and white markings. Now I can lay this onto the paper supported in the frame and apply color very deliberately. This should make a huge difference in keeping the final pair of wings accurate and symmetrical.

Looking ahead to the future, I believe I will also be able to print out guides for the placement of the veins which I can put under the frames and back light, allowing me to know exactly what position the veins should be placed, and match it perfectly between the top and bottom. Also, despite how much longer it takes to work with oil mediums, I have already learned that the tissue paper maintains much higher strength with oil mediums which means I can work in the colors and paint them more freely. Everything is looking better now!

Long term, I would like to continue adding more realism and species accuracy to the wings I produce. I am quite intrigued by the idea of vein geometry playing critical roles in overall wing flexing behavior. As I would like to flap these wings on a mechanical thorax, any additional organic and lifelike behaviors to the wing stroke would be greatly welcomed!