How to Create MITes Rubber Casings - MIT - Massachusetts

By Edith Stone,2014-03-18 16:53
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How to Create MITes Rubber Casings - MIT - Massachusettsto,mites,Mites,How,how

    How to Create MITes Rubber Casings

    This set of instructions describes how to make rubber casings for the MITes sensors using

    the Smooth-On OOMOO 30 liquid rubber compound.


    ; MITes Sensors

    MITes must be ordered from Malibu Electronics. Documentation on ordering

    MITes can be obtained from MIT House_n

    ; CR2032 3V Batteries (Preferably completely dead)

    Obtain from: Digikey SY189-ND

    ; Smooth-On OOMOO 30 liquid rubber compound

    Obtain from: Blick Art Materials (, search for item number

    33562-6040, $24.99 ea, will make 50-60 rubber casings) ; Indestructo Pill Box; Obtain from: Apothecary Products, Inc (

    $0.65 ea)

    ; Two long pieces of wood with a height of 17/32 inches (not necessarily one piece

    of wood 17/32 inches high, i.e. can be two pieces that are 3/8 inches and 5/32

    inches high stacked on top of each other)

    ; Thin metal rulers

    ; Small graduated cups

    ; Large cup

    ; Stirrers

    ; Small screwdriver

    ; Tape

    ; Marker


    1. Cut the top off of the pill boxes

    2. Mark the bottom of the pill boxes with channel numbers, one number per box

    3. Arrange the two pieces of wood so that they are parallel to each other and

    separated by a pill box’s width

Preparing the Sensors

    1. Take four pill boxes and for each pill box, match the corresponding MITes sensor

    according to the channel numbers found at the bottom of the pill box and at the

    bottom of the MITes sensor

2. Put a dead battery in each of the four MITes sensors

    3. Slip a metal ruler in between the battery and the battery holder on top of the

    MITes sensor. This should be done so that the right edge of the sensor lines up

    with the 6 inch mark on the ruler and the left edge lines up with the 4.75 inch

    mark. Make sure the sensor edges are parallel to the ruler edges.

4. Place the four pill boxes in between the two pieces of wood

    Preparing the Rubber

    1. Take out the Part A and Part B bottles from the OOMOO Liquid Rubber

    Compound kit and two graduated cups

    2. Pour 30 mL of Part A and Part B of the OOMOO Liquid Rubber Compound into

    their respective graduated cups (Make sure to shake the Part B bottle before


    3. Pour the 30 mL of Part A into the large cup (use the stirrer to get as much out of

    the graduated cup as you can)

    4. Pour the 30 mL of Part B into the large cup

    5. Mix the contents of the large cup. The large cup should be mixed so that the

    pinkness of Part A cannot be seen in the mixture. Make sure to scrape the bottom

    and the sides of the cup to do this faster. Do not mix for too long or else the

    mixture will get viscous and conforming to the MITes sensors will be difficult.

    Mixing should not take longer than 15 seconds

    Creating the Mold

    1. Pour the contents of the large cup into the four pill boxes while keeping track of

    which channel number each pill box corresponds to. The pill boxes should be

    filled so that there is a little gap between the top of the liquid rubber and the top of

    the pill box. Use the pictures as references to how much liquid rubber should be

    poured into each pill box. It may take a couple of tries to get the right amount of

    liquid rubber in each pill box such that there is enough rubber to completely cover

    the top of the MITes sensor while not overflowing and sticking to the bottom of

    the ruler. There should be some liquid rubber left in the large cup.

    2. Place the sensors, which should be attached to the rulers, into their respective

    filed pill boxes. The edges of the wooden pieces should be lined up with the 4.5

    inch mark and the 6.25 inch mark on the ruler. The sensors should be shifted up or

    down to the middle of the pill box. Make sure the edges of the sensors are parallel

    to the edges of the wooden pieces.

    3. Push down on the edges of the rulers and make sure the liquid rubber covers the

    top of the MITes sensor. Only the top edge of the battery case and battery should

    be above the liquid. If the top is not completely covered, pour more liquid rubber

    into the pill box, raise the ruler and sensor above the pill box, let the liquid rubber

    in the pill box settle, and then set the ruler and sensor into the pill box again. 4. Place weights on the edges of the rulers to keep the sensors fixed inside the pill


5. Wait 3-4 hours and then remove the rulers and batteries from the sensors

6. If the liquid rubber got stuck to the ruler, you may use a knife to cut away the

extra rubber sticking out of the top of the casing

    7. Use the small screwdriver to pry the encased sensor out of the pill box. It is best

    to use your thumb to peek back a corner before sticking the screwdriver in the pill

    box. Try to pry it so that the screwdriver is pushing up from the bottom of the

    encased sensor instead of pushing against the side of the encased sensor to avoid

    puncturing the rubber

    8. Apply tape to the back of the sensors and write the channel number of the sensor

    on the tape and the letter of the set of sensors (The picture contains an encased

    sensor with the channel 17 that is part of the set J, which means this sensor should

    be used with the other sensors of set J)

    Additional Tips

    1. After filling the pill boxes with liquid rubber, there should be leftover liquid

    rubber inside the large cup. Use this leftover liquid rubber as a reference to how

    solid the rubbers around the sensors are while you wait. If the leftover liquid

    rubber is solid enough that touching the surface does not disturb the shape of the

    rubber, then the sensors are ready to be taken out.

    2. While the leftover liquid rubber cannot be drained, the large cup can still be

    reused by waiting for the leftover liquid rubber to harden and then peeling the

    rubber out of the cup. Throw the extra rubber away and re-use the large cup for

    more mixing.

    3. The included instructions are for making four sensor casings at a time. The reason

    more casings are not being made is because the pouring process takes longer and

    the liquid rubber becomes too viscous. When the liquid rubber becomes too

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