Drug Delivery Extensions

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Return to the Drug Delivery Challenge.



3 Hole System

Possible Modifications

Due to the nature of the photodetector in the LEGO Mindstorms NXT kit, certain colors are difficult to distinguish from each other. The photodetector works by detecting the only intensity of light within its sight. It includes a red LED for generating light in dark environments.

Colored Arena

Rather than using the red/brown setup seen in our sample arena it would make most sense to use a high contrast between coverings for the two different types of cells. (This is provided that you intend this information to be useful to students, some would claim this would make the challenge too easy.) Black and White would be the most obvious choices.

Colored Balloons

In the same vein, it would also be possible to use the color of the balloons rather then the arena wall to help the delivery unit decide which balloons to pop and which to leave. This will require a bit more finesse then the colored arena approach as it requires students to make the decision and then align their popping mechanism within a very small hole.

Fluorescent Balloons

Another option for playing with color is to have all balloons and hole structures of uniform color and configuration. Some balloons could be coated with a fluorescent dye responsive to red light, changing the color of the light reflected from the delivery device's red LED.

Modified Geometries

In addition to all of the options available with different presentations of color other more difficult geometries could be introduced. The two/three hole structure is rather simplistic and is easy to design around. You could consider different shapes of holes, sizes, and relative configurations to represent healthy/diseased cells.

Bar Code Reader

As an alternative to the system of geometry described on the Drug Delivery Challenge page it would also be possible to use a system of bar codes to convey information about cell health. Simple markings placed on the walls could be used to convey information provided that they are of uniform size and color and have sufficient contrast with the background material.

We developed a proof of concept bar code system and reader which could serve as a starting point for such a modification using nothing but paper and electrical tape.

This sample code illustrates how the concept can be used to convey information. A 'start bit' is used to indicate the beginning of the code. A white or black band can be used to convey a 0 or 1 respectively. A specific series of symbols can be tied to a meaning within the environment. For example, 1100 could indicate that the next cell found will be a healthy one, while 0011 could indicate a cancerous cell. So long as all of the marks are the same width and each code contains the same number of marks the system can be used for identification.

This challenge would be more difficult then the main challenge, as it requires more precise engineering (to be able to read the data reliably) as well as complex processing code (to interpret the results). It should provide for a solid long term team project, as it sufficiently complex to allow for the introduction of a number of engineering concepts and for the involvement of multiple people working on discreet aspects of the problem. It is also arguably cross-disciplinary as it requires distinct computational and mechanical components.

An interesting twist with an approach like this one would be to not reveal the actual code combinations indicating healthy/diseased cells until the day the students are asked to demonstrate the device. This would require them to build a fairly robust code reader capable of reading arbitrary code values, like a true bar code reader.

Build Instructions

  • The code is provided as a sample should you wish to give students a starting point.
  • The physical unit we used to test both the main challenge and the bar code extension was based on the NXT Tribot detailed in the NXT Education kit. The instructions for building the Tribot are available on the Lego site and in the instruction manual for the NXT kit. Instructions for building the code reader are available from NanoEnlightenment.

You can see the unit in action reading codes and making decisions based on them in this movie. In the movie, a code of 1001 indicates that the cell should be killed, while a code of 0110 indicates that it should live. If the robot determines that the cell should die, it will strike into the hole with its actuator. If it determines the cell should live, it will sound a tone. If it cannot match the observed code with one in its programming, it will ignore it and carry on.

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