In this Instructable, I will show you an easy way to make a tissue culture incubator for plant culture.
This kind of incubator is suitable for cloning plants and growing large numbers of plantlets up from a single parent.
The design is uncomplicated: the system consists of 3 main components. These are
1) A programmable timer
2) A 30 Watt LED worklight (must be LED otherwise this design wont work due to lack of cooling)
3) An Esky, or insulated box. These need to have cleanable, white sides. You can often pick one up for $10 at an Op shop (I believe known as a thrift shop in the US).
So without further ado, lets collect the materials.
Step 1: Materials Needed - Parts
30 Watt LED light. Jaycar in Australia sell a good one: 30W, 2100 Lumen white work light, cat # SL2867. I bought mine for $25, but they are listed at $59.95. Some of the 12V 30 W lights do not work for this application. I traced it down, after testing 4 or 5 of them to interference between the LED driver circuitry and ripple on switch-mode power supplies. Be careful with this, and only use the mains (240V in Australia) version.
You will need an old fashioned electro-mechanical timer. These timers have a motorised clock, and to set them you push in pins, as shown in the picture above. Jaycar sell one, cat # MS6113 for $10 AUD
You will need an old 50 liter esky or cool box. I bought mine for $12 from an op shop, camping stores sell them for under $50 AUD
All these components are shown in the picture above.
Step 2: Materials Needed - Tools
- 3mm drill
- Power drill
- 15cm nichrome wire (take apart an old hair dryer if you are cheap like me, otherwise some 32 gauge should be fine).
- 2 sets of crocodile leads
- Power supply. I have used both a lab power supply (0-36V, 0-5A, cat# MP3840), or my old favourite hacked computer power supply, that looks like it would kill one in every 10 users. Anything that will do 12V at 2.5 Amps is fine. There is even an instructable (https://www.instructables.com/id/ATX-Bench-Power-Supply-Enclosure/), should you be so inclined!
- 2 sets of Pliers
- Thick gardening gloves
- box cutter / or wire cutters
- Polystyrene foam (2cm thick)
- Acrylic caulk (Selley's No More Gaps, white exterior)
- Caulk gun
- Damp cloth (used to tool the surface smooth)
Step 3: Cutting the Esky Lid
In this step we will put a hole through the lid of the cool box. We will then support and seal that lid and tool it so that it is smooth and not a haven for bacteria and contamination.
Work in a well ventilated area, and do not breath any plastic fumes you may make. Wear thick gardening gloves to protect against cutting/cauterising yourself with the hot wire.
Begin by measuring off a square in the centre of your esky lid. This square needs to be just smaller than the outline of your light (by at least a cm on all sides). This is to allow light in, but to support the LED unit.
Drill a 3mm hole in one edge of the square you have marked off.
Slide a length of nichrome wire through that hole.
Connect the alligator leads to the power supply, but don't turn on yet.
Pull the leads taut with two pair of pliers.
Turn on the power supply and cautiously increase the voltage until you start to easily melt the plastic.
Draw (pull) the wires along the lines you have drawn to cut out the rectangular shape.
When you have finished, push out the piece of plastic you have cut. If the molten plastic has re -fused together, you can either cut it with a box cutter, or you can draw the nichrome wire past it again to cut and melt the plastic.
Step 4: Cleaning Up the Cut Lid
When you have finished cutting out the lid, the edges will be rough. You should remove balls of molten plastic by either filing them with a bastard file, or if they are not too severe you can trim them with a box cutter.
When you have a clean edge, you should cut 1-2cm wide 2cm thick strips of polystyrene. I used 2x 25cm, and 2 x 20cm. You will need to pack these between the top and bottom layer of the cut esky lid, and recess them slightly so that you can squirt caulk into the gaps. I have tried to show this in the yellow lid above.
Once you have caulked over the polystyrene, tool it with a wet cloth to get a smooth surface. You will have to keep moving the lid until it sets a bit to avoid the caulk dribbling out.
Now is a good time to clean up the surface to remove any bits of caulk.
Leave everything for 24h to properly set.
Step 5: Validating the Light.
I tested my incubator to ensure that it was suitable.
We need to look at 3 things:
1) Temperature (over 25 degrees and you will cook the vegetables :( we want to grow them. )
2) Sufficient light. In the open sclerophyll forest (Jarah forest, in the South West of Australia), the forest floor ranges from 1K Lux to 25 K Lux. The Wildflower Society Nursery cultivates at 8K Lux.
3) Quality of light - the spectrum needs to be reasonably broad, and a bit like sunlight.
To test temperature, place your light over the hole in the esky and run it for 24h. Measure the temperature. My rig raises the temperature by 3 degrees C, to 23 degrees C - that is ok.
To measure light intensity, get yourself a copy of Google Science Journal and install it on your smart phone.
Click the purple + button, and then click the 2nd icon along on the toolbar above the text "Add an observation". The light levels should be graphed, and you can place the phone in the chamber to measure the light. Press the red stop button when you are finished. You should get a result like the first figure above.
Optional: Thirdly, testing the colour spectrum is complex and beyond the scope of explaining here. If you are interested, you can make and calibrate a little spectrometer ( such as the Papercraft Spectrometer using a piece of cdrom) following the instructions at PublicLab.org. You can use the free software at SpectralWorkbench.org to calibrate your instrument and analyse its results. If you do so, you should get a plot like the second image in this section.
Step 6: Set the Day/night Cycle With the Timer.
All you need to do now is to set the day night cycle on your timer.
Twist the dial until the current time lines up with the marker on your timer.
Push in the little pegs for the time you want the light on.
Make sure that the "dark" pegs are raised.
And that is it!
Your incubator is ready to go!
Step 7: Results.
Here is my first plant. It is a Western Australian trigger plant, Stylidium corymbosum.
The anthers of this plant are modified so that when an insect lands on a sensitive part of the flower, the anther wallops the insect and covers it in pollen. You can see it here, after a minute or so
My plant is sensitive to the bleaching step, and has been knocked a bit. But after 21 days, you can see a good callus in the second.
I hope this is of help to some of you. This is a good STEM project in the biological sciences, and is very rewarding when it works. Thanks for reading so far.