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FINAL PROJECT IDEAS

Non-tech description:

MEMS are ultra-small mechanical devices. They consist of tiny gears, motors, hinges and other structural components, but on a scale of a tenth of a millimeter. MEMS are manufactured very similar to how computer chips are manufactured, meaning they can be mass-produced for very little. They have the advantage of not releasing or being vulnerable to electromagnetic (EMF) fields. This means a MEMS CD player or laptop computer could be used on an airplane during takeoff and landing. While it's unlikely mechanical computing will ever overtake electronic computing, there are environments such as outer space or high-security where invulnerability to EMF radiation is advantageous.

Build something cool with MEMS. We had two hours of introduction to designing MEMS, and then were set free.

Click here for a movie

We came up with a MEMS brownian motion detector. As air molecules bounce off the suspended lever arm, it moves up and down. This changes the capacitance of the interlocked comb. By measuring capacitance fluctuation, change in temperature can be inferred.

Note the small dimples on the underside of the upper part of the comb tines. These prevent stiction between the comb and the surface.

In practice, this device has the best change of working if an array was made, each with a slightly longer lever arm. The longest arm that doesn't break will be the most likely to exhibit susceptibility to brownian forces.

Developed here is a system called "Buddy Dialysis", which allows patients with rental failure to perform dialysis using a living in-situ donor kidney. This allows dialysis patients greater independence by removing the need to be attached to bulky machinery or carrying heavy fluids.

Click here for a more detailed description

Non-tech description - NC machining stands for "Numerical Control". It's computer controlled machining. It means we take designs from the computer, and the machine mills it out. It's all part of the media lab's efforts to remove the distinction between bits and atoms. See something on the screen -- hold it in your hand.

In practice, though, it's a rocky road. NC machines use combinations of proprietary formats, and one known as G-codes which, were originally developed for sewing machine patters. Getting a machined item is orders of magnitude more complex than sending something to the printer.

Assignment 4 & 5 -- Use the NC Mill to create a mold for an assembleable toy. Use the injection molder to create several copies of this toy 

Here's a picture of the mold. It probably should have been designed with the piece flipped up-down, and the flue attaching at the very top. This would have reduced the travel distance of the plastic. As it turned out, this wasn't a problem. This mold was well under the amount of plastic the injection molder was capable of spitting out. The flues on the left are unnecessary. You can see the strain on the aluminum from the pressure of the injection molder on the intake port on the top of the mold. The scratches in the upper right corner are to allow air to esacpe.

What was molded. Including cutting away of flashing, it takes about a minute per piece.

Both parts of the mold, with a bunch of plastic.

 Assignment 6 -- Create Something Cool With the Laser Cutter and 3D Printer

To quote Neil: "after the difficulty of last week's assignment, laser cutting and 3D printing are like junk food". These two technologies are indeed much closer to the ideal of seamless bits to atoms transition. There's still some gotchas, especially with the 3D printer, but it's much easier to get results. And slightly harder to get hurt.

I created a "stained glass" window. The frame was 3D printed, and each pane was cut with the laser cutter. This assignment was tricky because the relative sizes of the two objects have to be very carefully controlled. In going between different software packages, and converting to different file formats, it's easy to loose unit information.

 Assignment 7 -- Create Something Cool With Electronics and PC Boards

Below is a "beat-frequency visualizer". Two 8038 chips produce independent sine waves that drive two 3915 "one of ten" bargraph displays. But instead of being attached to 1-D bar graphs, they are used to drive the X and Y axis of an 8 x 8 display. With the help of a 4049 hex inverter, the display lights a single LED when both the X and Y axis is high. When both the X and Y clock are the same frequency and are in phase, a perfect circle is produced. If one clock is twice the frequency of the other, the display will be a figure-8. But the most interesting results occur when the frequencies are slightly out of phase. The result is undulating lissajous figures, that organically morph between positions. The two axes of an X-Y potentiometer joystick control the frequencies of the two clocks.

Here's the completed circuit.

Making a circle. It's not a perfect circle because it's not getting perfect sine waves. But this picture demonstrates this cirurcuit is more than just a pretty light display. When used with a known reference frequency it can be used as a solid-state oscilloscope which can be used to visualize various frequencies.

Figure 8. The X frequency is twice the Y frequency. Again, imperfections arise from noisy sine waves.

 Assignment 8 -- Create a bridge using composite materials and compete for strength

This picture was taken AFTER the contest. The notch in the top is from the pressure of the press.

 Assignment 9 -- Create something cool with a PIC chip

Non-tech description - A PIC chip is a tiny computer on a chip. Tiny, that is, by today's standards. A typical $10 PIC chip will have 4K of program memory, and 256 bytes of RAM. In contrast, a typical $600 PC as of November 1999 has 32 Megs of memory -- about 7500 times the storage capacity of a PIC. But 20 years ago, a PIC chip would have cost millions and filled an entire room. Because they're physically small, easy to program, and use very little power, they're often found in embedded controllers -- the smarts that goes into dishwashers and cars. For instance, a PIC chip will be programmed that the "wash" cycle is ten minutes of hot water, 12 minutes of soak, five minutes of rinse …, while the "pots and pans" cycle is 5 minutes of wash, 20 minutes of soak… Because PIC chips have so little memory, there's a great incentive to use only two bytes when storing a year, and not four. This makes them especially vulnerable to Y2K problems.

FINAL PROJECT IDEAS