Shark Scale Inspired Portable Miniature Checkers

This project might be more acurately named - Magnetic Macro Shark Denticle Miniature Checkers.

The pawns were inspired by Scanning Electron Microscope (SEM) images of Shortfin Mako shark scales.

With a 8x8cm magnetic checkerboard + drawer for storing the playing pieces, the entire game fits in a 8.6x8.6cm box- perfect travel size.

The idea began years ago with a charity art show raising money for shark conservation. In a discussion about the fluid dynamics around a swimming shark, I came across the images of what shark skin looks like under a microscope. Things just spiraled from there.

Although I don't yet have a 3d printer, I have been (slowly) working on my Tinkercad skills to make a design that can be printed, rather than modeled, carved, molded and poured repeatedly...

Pawns:

polymer clay

liquid mold making rubber

Variety of containers for making molds (anything from bottle caps to plastic cups)

Epoxy resin

black epoxy tint

Thick tipped syringe

metal wire

magnets - mine came from a 1euro store set

sharp blade

fine grain wet sand paper

gel super glue

Board:

black metal sheet - I got mine from dismantling a 1euro store dry erase board

1cm washi tape - but any type will do

gloss finish sealer

sharp blade

scissors (that can cut through a thin metal sheet)

Board base and drawer:

Thin cardboard 3mm

Thick cardboard 17.5mm - I got mine from IKEA packaging

tape

ribbon

PVA glue

white paper

gold paint

paint brush

scissors

Box:

I bought a jewelry gift box with lid at the 1euro store.

The internal dimensions of the box bottom into which the board will fit are 8.5x8.5 cm with 3.5cm height.

Similar sized boxes can be found here.

This is really where the whole project began, from scanning electron microscope images of shark scales. For this project I chose the denticles (scales) of the shortfin mako shark.

Start by making a polymer clay model of the denticle. This is a very loose shape because the clay is such a soft material, it's hard to get sharp edges (especially because I used Fimo soft brand).

After burning the shape use a sharp blade to trim down the size, carve the shape and get sharper points.

Finally, sand down the piece with 1500 grain wet sand paper.

*These final 'carving' are probably much easier if you have a dremel. I don't have one so I used what I have and I'm pretty happy with the results.

Stand the model upright in a small container, it has to be deeper than the height of the model.

Mix and pour the mold making rubber over it. When it is cured the model can just be pulled out.

(out of habit I usually also trim the rubber from the sides to make it smaller)

If the process worked well your model piece should pull out whole and can be used again to make another mold.

Tip: Choose a mold making fluid that is very flexible and that does not require cutting to remove the piece. Making and working with a 2 piece mold can be tricky.

This is the repetitive part, since you need 12 clear pawns and 12 black tinted pawns. The only challenge here is, because of the details in the shape, to minimize air bubbles. This is the method I used that usually gave me good results.

Create a short blunt piece of metal wire which is flexible. I made mine by twisting a folded thin metal wire. Having a blunt end is important because you don't want to poke holes in the rubber of the mold.

Load the prepared acrylic resin into a wide tipped syringe. The material in viscous so it usually would not flow through a thin one.

Insert the wire into the mold into the tip of the scale. Use the syringe to drip the resin onto the wire close the mold opening. Repeat this with all 3 points of the scale. This way the resin should flow down the wire all the way into the tips of the piece.

Once the mold is full squeeze it around a bit to move any trapped air bubbles.

For black pieces - mix a tint into the resin.

*I added an image of my most common pouring pitfalls - air bubbles and pouring clear pieces after having used the mold for black pieces.

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I did not add a link to the acrylic resin I used because I was unhappy with it. The clear pieces often had a yellowish hue to them. (If you have suggestions for a brand of good clear acrylic resin I would love to know!)

I find it very hard to pour and wait for pawn after pawn. Instead, once you have several acrylic pawns ready you can clean them up with fine sand paper and use them to create multi pawn molds. Just stand several pieces on the bottom of a wider container and repeat the mold making process.

Once the pawns are all poured, trim off any excess resin, sand and smooth the bottom with a fine wet sandpaper.

From the magnets cut out small circles, slightly larger that the stem of the pawn.

For the clear pawns, paint the top surface of 12 magnets white with acrylic paint. Glue each pawn onto a magnet with super glue. Trim the magnets to fit the pawn stem. For the clear pawns, paint the sides of the magnet with white acrylic paint.

Note: Make sure that the polarity of your magnet is correct. It will always have one side that connect stronger to the metal. The 'weaker' side should be glued to the pawn.

After several failed attempt (which I list in the next step) this is the version that gave the best results:

Remove the black metal panel of the magnetic dry erase board.

Using 1cm washi tape starting from one corner, line 10 strips from the board edge. Leaving the first and last strips in place, remove every other strip. Starting from the same corner, place 10 strips perpendicular to the first from the board edge. Keeping the first and last strip, remove every other strip.

Using a sharp knife, carefully cut and remove the tape from every square with 2 layers of tape. Again, leave the first and last line.

Cut the board out using the outside lines of tape as a guide.

Measure the board against the dimensions of the box bottom, make sure it is centered. Reduce 1mm from each side and trim, make sure the board fits into the bottom of the box.

Using a different tape color start from the checker board and then fold over the edge.

Paint the board with a layer of varnish.

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I added 3 images from my failed checker board attempts

1. Cutting out black and white metal squares to create a tiled version. Unless you have precision cutting machines this will not work, you can see that from my wonky version.
2. Black painted white board or white painted black board. It didn't matter which combination of paint and tape I used - either the coverage was not good enough or a got paint bleeding underneath the tape.
3. Not really a fail but not a success - 1.5cm light colored tape created a checker size that was much too large for the piece size.

Cut out 2 squares from the thin cardboard. Cut out the 5 drawer pieces from the thin cardboard. Cut 1 square of thick cardboard, and cut out the rectangle shape, this is where the drawer will slide in.

I'm providing a template that could be used for cutting the cardboard.

Glue one thin cardboard square to the back of the checker board.

Construct and glue together the drawer, using removable tape to hold the shape as it dries.

Make sure that the drawer fits into the slot in the thick cardboard (if it does not you can trim the height of the drawer sides, or enlarge the cutout in the thick cardboard).

Glue together the board, thick cardboard, and thin cardboard.

Cut a 3cm length from the ribbon. Slide the folded ribbon through the slit and glue the edges to the inner side of the drawer.

Cut out the drawer lining from paper. I added a template that could be used for cutting and folding the paper.

Cover and glue paper to the inside and sides of the drawer.

Cover and glue paper to the sides of the base.

Make a circle from the 30cm ribbon with about 1cm overlap. Fold it in half and mark the centers (I used tape because it keeps the crease and I could draw on it). Mark a line in the center of the bottom of the base. Place the ribbon centers on that line 2 cm apart. Mark the placement of the stretched out ribbon and glue the ribbons in place.

Paint the drawer and the sides of the base.

Glue a 8.4cm paper square to cover the bottom of the base.

Shark denticles have amazing hydrodynamic properties. The shape of the denticles are different on different areas of the shark body.

What I find kind of mesmerizing is that different species of shark have remarkably differently shaped denticles, presumably related to the different life style and swimming speeds.

As I mentioned, this is a project that started years ago... and once there also was a chess set..

For some extra inspiration and info about how amazing shark skins are:

Domel et al. (2018) Shark skin-inspired designs that improve aerodynamic performance J. R. Soc. Interface. http://doi.org/10.1098/rsif.2017.0828

Li Wen et al. (2014) Biomimetic shark skin: design, fabrication and hydrodynamic function. J Exp Biol https://doi.org/10.1242/jeb.097097