Here are the instructions to making a functional ornithopter (design inspired from: https://www.instructables.com/id/The-Flying-Scrooge%253a-Ornithopter-of-Household-Items/)
The required materials are:
Paper clips, at least 10
Rubber bands, at least 6
1 bamboo place-mat
2 or more plastic bags
And the required tools are:
Drill and drill bit
Glue gun, or standard glue
Exacto Knife or Scissors
Needle nose plies for bending wire
Step 1: The Main Frame
First, assemble the main frame, using pieces of wood from the place-mat. The longest part, the main part, should be roughly 12 inches; if the place-mat parts aren't long enough on their own, duct tape or glue two together, and trim off the extra. The total height of the square part should be 4 inches. The long, angled part should be attached 7 inches away from the front. The total width of the square part should be 3 inches. Cut off any excess material.
Step 2: Part 1 of the Mechanics
Next, wrap the paper clips (any size works, although the shorter they are, the more clips you will need) around a pencil, or any other round object with a small diameter. Make 6 inches in length of these in total. Hot glue these onto the top and bottom part of the previously shown box part. Make sure to keep the glue out of the inside of the coiled wires, as there will be moving parts in here that need to spin freely.
Step 3: New Joints
Cover the box and coiled paperclips in plastic bag. Use hot glue carefully, as if misused it can melt holes through the bag. Now, for some new joints. These should be located at the very end of the 12 inch main shaft, and should be constructed as shown in the above images. One of the supports, (the one away from the rear of the ornithopter) should be two split place-mat pieces; this hollow space will be used later on. Use tape to support as needed.
Step 4: Wing Frames
Next, begin construction on the wing frames. First, tape/glue two of the place-mat rods together, so that they total 18 inches. Then, bend the paperclips to the shape shown; these will be used as pivot points, to hold the wings steady as they flap. Make 2 of these. Insert these into the top paperclip coil, as shown. If these aren't movable, then something's gone wrong; go back and wiggle around the wings until they easily rotate.
Step 5: The Mechanism
Hot glue on the pen casing next to the coil, near the front of the machine as shown. This serves as a casing for the rotating "axle". Speaking of rotating axle, make a rotation axle. It should have one hooked side, (which pokes out the rear of the box area, and runs through the wire coil), and side that looks like the image shown above. This side goes out the front, and is used to holed the wing braces. The longer the straight edge, (after the first corner), the larger the wing flaps will be. If this isn't made clear to you, look ahead to the next step, then come back to this one.
Step 6: Wing-Mechanism Attachments
Cut two 5 and a half inch pieces of the mat, and drill 6 holes in them, spread out roughly as shown (exact placement doesn't matter). Use a small bit, so that the would doesn't split. Stick them onto the metal bits, poking out of the wings and the metal axle as shown. Insert pen tubing as needed, in case there is too much friction and you need a spacer.
Step 7: The Back Wing
Begin constructing the back wing. Make a frame as shown using the place-mat pieces, and hot glue it together. It should be roughly 4 inches long, and 2.5 inches wide, and cut off any excess. Attach it to the rear of the main plane body by using hot glue.
Step 8: Completing the Wings
Cut out the top wings as one long sheet, as shown out of the plastic bag. It should be somewhat symmetrical on each side, and should be roughly 18 inches wide, and 6 inches deep. Glue it onto the top limb on each side, and glue the end of it to the main body. Cut out the smaller, bottom wings as shown, and glue them on in a similar way, except these two aren't attached to each other. Check to make sure the wings flap when you turn the axle.
Step 9: Finishing Touches
Put around 6 rubber bands in the spot shown above. Add or subtract rubber bands as needed. Bend the tail fin if needed. If the wings don't flap when the rubber band/axle is wound up then released, try checking for glue holding the wings together, or extra friction being applied along the flight shaft. Happy flying!