Have you ever seen miniature flying robotic insects in movies? That might sound like something completely out of science fiction, but believe it or not, engineers at the Harvard Microrobotics Lab are actually working on a bug-sized flying robot called the "RoboBee":

While this Instructable won't actually tell you how to build the real thing (which still requires a lot of expensive laboratory equipment), it will show you how to make a paper model of a RoboBee. This is something engineers in the lab do all the time - real RoboBees are pretty tiny, so having a larger paper model helps them think about mechanical design and how all the pieces will fit together.

The secret to making RoboBees involves using lasers to cut shapes out of flat materials, and then folding or "popping up" these flat shapes into three-dimensional structures. The following video by Pratheev Sreetharan provides a great introduction to the "pop-up" technique for building RoboBees. In this project, you'll be cutting out 2D parts and them folding them into 3D shapes by hand, so it won't be quite as automated as the process shown the video.

Materials

8.5"x11" sheet of cardstock. You need at least one, but can use different multi-colored sheets if you want. Regular construction paper will be too flimsy.
Craft glue (regular Elmer's glue will work fine)
There are three options for cutting out the parts:
Option 1: Xacto knife, cutting mat, and a steady hand
Option 2: Electronic cutting tool (I used a Silhouette CAMEO)
Option 3: Laser cutter, if you have access to one. Be sure to follow all proper safety procedures and do not use a laser cutter if you are not trained on its use - they can start fires or generate toxic fumes.
Design file: available for download below as a .pdf or on Thingiverse as a .studio (proprietary format for the Silhouette CAMEO - Instructables wouldn't let me upload it). If I get enough requests I will redo the drawing as a .dxf or .dwg - so far I haven't been able to export these formats from Silhouette Studio (feature request in case anyone from Silhouette is reading this!).
Optional: 2D CAD program, if you want to try out your own designs and are using an electronic cutting tool or laser cutter. There are multiple free options out there - I've used DraftSight (which was free last time I checked) and I believe you can also download a free student version of AutoCAD (may require creating an account). I know Autodesk has a bunch of new 123D apps, but I'm not sure if any of them are exclusively 2D programs that will output a dxf or dwg that you can use with a laser cutter.

Credits: These directions were written while I was a postdoctoral researcher in the Cornell Creative Machines Lab. The RoboBee project was started at the Harvard Microrobotics Lab. For more information and technical details about the project, you can check out the lab's publication pageor YouTube channel.You can also check my personal publications page, which includes my Ph.D. thesis on body torque actuation. To see some more awesome engineering work on functional robots made out of laser-cut paper, check out the Berkeley Biomimetic Millisystems Lab.

PaperRobobee.pdf
Download

Step 1: How Does a RoboBee Work?

Before you start building a paper model, you're probably wondering how exactly a RoboBee works. Here is a really quick, layman's-terms explanation of the four main parts, which are labeled in the picture above.

Airframe: this is the robot's "body". It's the rough equivalent of an insect's exoskeleton. Nothing super high-tech here - it's pretty much just a box made out of carbon fiber that holds all the other pieces together.
Actuator: actuator is the engineering term for "thing that causes motion". In machines, actuators are usually motors or engines. In animals, actuators are muscles. In this case, the RoboBee is actually way too tiny for a motor - so we use a piezoelectric material, which deforms when an electrical voltage is applied to it. A piezoelectric beam bends back and forth as this voltage changes, acting like a "flight muscle".
Transmission: this is another engineering term. The transmission converts the back-and-forth motion of the tip of the actuator (which is roughly moving in a straight line) to the rotational motion of the wings. It's hard to see in the picture here - this will make more sense when you build your paper model. For now, think of it like a linkage built out of LEGOs or K'Nex, if you've ever played with those.
Wings: This is the most self-explanatory part. The wings flap back and forth to generate lift, which is what makes the RoboBee fly. More advanced versions of the RoboBee have multiple actuators to independently control the wings, which allows them to steer.

Step 2: Cut Out the Parts

Download the design file from the Introduction page and cut out the parts. How exactly you do this will depend on what type of cutting tool you're using, so I can't provide exact directions. When you're done, the parts should look like the ones in this figure (with some additional perforations that you can't see very well here). I used four different colored pieces of cardstock.

Step 3: Assemble the Airframe

The first, and probably easiest, step is to assemble the airframe. Think of the airframe like a box that's been flattened. You just need to fold it back up into box shape. Follow these steps (also highlighted in the pictures)

1) Fold each long edge up 90 degrees along the perforated line.

2) Fold in the square tabs at all four corners, then fold up the front and back walls.

3) Apply glue inside the tabs and then pinch in place until the glue dries. Do this for both the front and back walls.

Step 4: Fold the Transmission

The next step is to assemble the transmission. This is a bit more complicated, but don't worry! Just follow these steps carefully. The transmission has two halves - follow these steps to fold the first half, then repeat to fold the second half.

1) Start out with the transmission laying flat. It has multiple perforated fold lines. Crease each of these lines in both directions, then lay the transmission flat again. This will ensure that the moving joints can move freely in both directions later.

2) Fold the first joint up 90 degrees, as shown in the second picture above.

3) There are two tabs sticking out next to the joint you just folded up. Fold those in and apply glue, as shown in the third picture above.

4) Fold two joints down 90 degrees as shown in the fourth picture above.

5) There should be two tabs sticking out to the sides next to the joints you just folded down. Fold these tabs in and apply glue as shown in the fifth picture above.

6) Repeat steps 1-5 for the other half the transmission.

Step 5: Fold the Actuator

After folding the transmission, the actuator should be easy!

1) Start with the actuator flat, crease all the joints in both directions, then lay the actuator flat again.

2) Fold two joints up 90 degrees as shown in the second picture.

3) Fold in the tabs and apply glue to fix the 90 degree joints in place. Unfortunately I realized too late that I forgot to take a picture of this step - the tabs work the same way as the ones in the transmission, so refer back to those pictures if you need help.

Step 6: Mount the Transmission to the Airframe

The airframe has slots in it for mounting the transmission. Slide the tabs at the end of the transmission into these slots, then apply glue as pictured.

Step 7: Mount the Actuator

Lower the actuator into place from above the airframe. The base of the actuator (the wide part) fits onto the flat surface on top of the airframe. The tip of the actuator (the skinny part) should line up with the middle link of the transmission. Apply glue to both surfaces and let dry.

Step 8: Attach the Wings

The tabs at the base of the wings should fit onto the two flat surfaces facing up on the left and right sides of the transmission. Use glue to attach these two tabs, and make sure your wings are facing in the right direction (as pictured).

Step 9: Flap the Wings!

Ok, so your paper RoboBee model isn't exactly going to fly very well (or at all). But, see what happens when you push and pull back and forth on the tip of the actuator. Do the wings rotate? If so, congratulations! You successfully built a model RoboBee. Now that you know the basics of cutting out 2D shapes that fold up into 3D mechanisms, can you try making your own designs?

Remember that this isn't just a game - this is a real process that engineers use to help design microrobots. It's kind of like how civil engineers will build smaller models of bridges and buildings - it's just easier to think about design when you have something you can hold in your hands easily. In this case, the "real" object just happens to be way too small (and fragile) to easily manipulate. So, when robotics engineers want to change something about the RoboBee (for example, using a different sized actuator, or changing the airframe to make room for a battery and circuit board), spending a few minutes to make a quick paper prototype to make sure everything will fit together can wind up saving hours of time building the real thing.

Still having trouble? Check out this video that I put together for someone who had questions about the assembly process:

Step 10: RoboBee Project Timeline

This page has more information about the history of the RoboBee project. I'll do my best to keep this updated, but the Microrobotics Lab's homepage will always be the best source of new information.

The project started out as the Berkeley Micromechanical Flying Insect (MFI) under Prof. Ron Fearing in the early 2000s. Robert Wood was a graduate student in that lab, and he founded the Harvard Microrobotics Lab in 2006.
In 2007 Prof. Wood built a device, then called the "Harvard Microrobotic Fly", that could lift off while attached to guide wires, but had no steering ability. For more information you can watch this video or read his publications about the design and liftoff of the robot.
Over the next few years, the research team started to put together many pieces of the puzzle for the ultimate goal of autonomous, stable flight. This included things like altitude control, torque and attitude control, "pop up" fabrication methods, and miniature power electronics, just to name a few. The "RoboBee" name came about in 2010 along with a new National Science Foundation (NSF) grant.
In 2012, researchers achieved controlled hovering in a laboratory environment using a motion capture system. This was a first for a vehicle of this size.
In 2013, the project is still ongoing. Many problems remain to be solved, including on-board power, sensing and control electronics and communication/coordination between multiple robots flying in organized "swarms".