Coffee Cup - PCR Thermocycler Costing Under 350$





Introduction: Coffee Cup - PCR Thermocycler Costing Under 350$

This Instructable will describe how to make a PCR Thermocycler for Field or Teaching applications, from scratch, using a commercial temperature controller, a temperature probe, a PC cooling fan and basic shop tools.

The unit performs reliably, is menu driven for programming various PCR (Polymerase Chain Reaction) "recipes" (so you don't have to use a computer but there is free downloadable software that will let you do this and we provide the PIN diagram for making the cable). It cycles temperatures at 0.15 degree centigrade per minute. The difference in actual temperature (Process variable) from "control" temperature (Set variable) varies about 5 degree centigrade. That means we set the temperature at 5 degrees higher than the temperature we want to achieve. This is due to the bias in the thermocouple probe.

In a Nutshell: We use a piece of aluminum rod, drill a 1/4" hole in the center of one end for a cartridge heater and another hole near the rim of the same end for a thermocouple (temperature sensor). Additional holes in the same end of the rod are for sample tubes (0.2 ml eppendorf tubes).

This "heating block" is positioned on a small bracket over a PC cooling fan. Both are placed inside of a metal coffee cup. A commercial temperature controller ( available from Omega Engineering) is used to control the heating and cooling cycles. End of story.

It reaches and holds (soaks) at various temperatures and can also be used for "In situ" Hybridization protocols. It can be programmed from the face plate of the controller or connected to a computer by a serial cable. The control software is a free download.

Project Team:

R. Siderits
A. Marcus
F. Ivalde
A. Andoh
M. Swift
O. Ouattara
W. Lecorchick
S. Singh

Step 1: What Is a Thermocycler?

What is a Thermocycler?

A thermocycler raises and lowers temperature. For molecular or DNA applications it needs to heat up to about 90-95 degrees centigrade. DNA which usually exists in double strands in a helix (like a spiral staircase) and at about 92 degrees centigrade the strands will break and fall apart.
The solution that the DNA sample is in has extra "bases" that will connect to the broken rungs of the ladder to make two new ladders. To do this part we need to cool down the sample to the point where "bases" can connect to the separated DNA strands. If you cycle through this temperature range from 20-30 times you can make millions of copies of the original DNA.

So in summary, a thermocycler can make a million copies of one original piece of DNA. These copies can then be used for other types of research. The prototype that we build can take 6 sample tubes (0.2 ml eppendorf tubes). There is room for one blank, the temperature probe and a central cartridge heater.

Learning sites that are excellent:

- DNA Extraction Online Tutorial
- Home DNA extarction of DNA (Instructables)
- PCR Song (must hear)
- PCR Protocols

Step 2: Completed Version of the Coffee Cup Thermocycler:

Here is the final version showing a metal coffee cup that contains the heating block and a PC cooling fan. The lower half is a coffee "can" that contains the temperature controller. If your wondering why a coffee can and coffee cup, that's all we had to work with.

Parts List and links to sources:

6061 Aluminum Rod 1.5" round stock about 5" in length
Cartridge heater 1" length, 1/4" diam 80W
Temperature controller CN8282-R1R2C2
Instruction manual
Free Software for serial connection to computer
40 mm PC 110 volt cooling fan

Other materials:
- 4 foot extension cord, three prong, to cut off and use as power cord.
- Metal coffee cup and coffee can (your on your own here)
- Hand drill
- Tap for putting threads in the hole for the temperature probe #7 drill and 1/4-20 Tap.
- Basic tools (hammer, screw driver, pliers, wire cutters etc...)

Step 3: Make the Heating Head: Machinist and Hobbyist Approaches:

Make the Heating head. See following images.

This aluminum rod is used to make the heating head.

A center hole 1/4" will be for the cartridge heater.

7 holes are drilled on the same end of the rod for the 6 sample tubes and one hole for the
thermocouple temperature probe. The hole for the temperature probe is made with a
#7 drill and a 1/4-20 tap to thread the 3/4" deep hole.

Step 4: Making the Coffee Cup Part of the Thermocycler:

Make the Coffee Cup part of the Coffee Cup PCR system.

We used a fly cutter to make the hole in the bottom of the coffee cup (mug).

Four smaller holes are for the feet that attach to the mounting holes on the fan that is
inside of the mug.

Mark the holes with the fan sitting on the outside of the mug.

Step 5: Wire the Controller:

Wire the controller:

Read the warning in the manual that comes with the temperature controller!

Instruction manual

See the shop notes pages below that explain various aspects of the wiring.

Step 6: Performance:

Performance evaluation:

The serial cable is connected to the controller.
The free downloaded software form is used to write a recipe for the following tests.
The data is "logged" to data files that were imported into excel for graphing.

Test:: PASS

Pass - Hold at 50 degree centigrade up to 10 hours.

Pass - Hold at 92 degrees centigrade for 30 minutes.

Pass - Run menu (recipe) to go from RT (room temp) to 55 over 4 minutes; then
Loop 25 times: from 55 to 72 where you soak for 2 minutes, then raise temperature to
92 where you soak for 1 minute; then at end of the cycles hold at 55 degree
centigrade indefinitely.

Step 7: Free Software

Screen grabs from the free software which lets you control the unit over a
serial cable.

Free Software for serial connection to computer

Downloading the free Software from the Omega Engineering website lets
you control the "temperature controller" and quickly write complex "recipes" to
store into the unit and run at any time.

You don't need to use the serial cable since the unit can be programmed to
run recipes from the front panel, but it is a quick way
to test and optimize the temperature parameters while capturing the data to
a log file that you can import into excel for graphing.

The software also has a graph function but it is somewhat limited.

Step 8: Where Do We Go From Here:

Where are we going from here?

- Swap out heating heads for Chromogenic In Situ Hybridization, slide holder
- Two sample heating block using ducted RC hobby fan
- Vented "Tray block" with 20 sample deck
- USB powered Micro PCR platform
- USB control using "Phidget" interface and incorporate two Peltier Junctions
- Micro-controller based (Parallax) controller for computer free 9 volt version
- Internet accessible interface using IOBridge

- Make a single sample "Pen based" version that runs off of a USB port.

Step 9: Disclaimer (fair Warning):

Follow ALL reasonable safety guidelines and actually
wear safety equipment related, but not limited to, the following:

1) Electrical currents that you should not play with.
2) Power-tools that you never read the instructions for.
3) Any tools that you never learned to use properly.


4) Anything that heats up, pinches, cuts, squeezes, flies off, carries electric current,
causes other types of traumatic, caustic, thermal injury or biological contamination.

5) This is a project for scientific teaching or field research and is NOT to be used
for diagnostic testing!

We are sharing our experience, NOT TELLING YOU WHAT TO DO.

If you choose to try this then - it is at your own risk!

  • No really, we're not kidding about this.

Step 10: Project Overview:

Facility: RWJUHH Experimental Pathology Division and
Center for Parabiotics Research

Section: Prototype Applications - Research Projects

Application: Molecular Diagnosis and Medical Cytology

Technique: Rapid Prototyping for field research

Title: "Coffee-Cup" PCR Thermocylcer for field or teaching applications costing less than 350$



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    Im sorry any idea for how to make a QPCR please thanks great Job

    One of the most straightforward ways to do quantitative PCR in a DIY environment is competitive PCR. It can be done as RT-PCR as well. Basically, a series of reactions are done with a different amount of a competitor DNA (or RNA for RT-PCR). The competitor needs to use the same primers and be similar in sequence to the target but easily distinguished on a gel. Usually it is the target with a deletion or an addition. The competition acts as an internal control to get around differing reaction efficiencies. Regardless of the efficiencies between reaction tubes, when the ratio of target and competitor PCR products are equal, the ratio of starting templates was also equal. Since you know how much competitor was added, you know how much target template was present.

    Sorry it took so long to get back to you. The RT-PCR version works, is cheap, modular and it uses ONLY USB power. I 3D printed the enclosure but the principles can be applied without a custom housing. Here is an overview of parts.
    First you need to heat up a DNA sample to 100 degrees centigrade. You might think that would be impossible but I used two minco thermofoil adhesive backed 1 inch circular heaters wired to two USB ports. Now you need to have a switch turn them on and off so I used a dual solid state relay connected to a phidgets: 8 analog in/8digital in/8digital out board. Now you need to sense the temperature so that you can turn the heaters on and off at the right time. I used a phidgets temperature sensor with a J type thermocouple. OK so now you have the temperature side down, how about the light side. I used a photoresister to monitor the light level in the sample chamber and brought that into the phidget board on another analog channel.
    No you only need two more things. A light source the emits at a blue light (I used an ultra bright LED at 480-490nm on the second of the dual Solid State Relays) to excite the SyberGreen when it binds to double stranded DNA and a band pass filter to only let a narrow band of green light through to the photoresistor. The band pass filter was from Fisher scientific. I wrote the interface to sense temp and light and to control the relays for heating with LABVIEW.

    Long story short, I've got an essentially disposable RT-PCR platform that works on USB power only and costs less than 300$ total cost. You can stick it onto the back of any standard Notebook computer. This enable field research at a fraction of the cost of a small RT-PCR platform. For what its worth, you can run it from a remote as well.

    Hi, thank you indeed for the coffee cup PCR, is there any chance to see any further details about this latest development you were mentioning in March? We are planning to build a simple PCR right now, but we would go for a qPCR (instructions permitting :) if possible.

    Late to this party. Your post is a bit old, did your plans for the USB power source ever come to fruition?

    Yes. Amazingly, YES.

    I was told (often) that you can't heat something to 100 degrees centigrade (denaturation temp for DNA) with a USB (4.5 Volts and 100 mA). Turns out its really easy. We used two adhesive backed 1" diameter Minco Thermofoils on separate USB ports. A quick program in Labview to monitor temperature from a thermal probe, a styrofoam thermal chamber to prevent heat loss and a USB Phidget relay switch to control the heaters made it work to commercial nearly specs. We can control, soak, cycle and ramp with no problem.

    We then started on the Real Time component using a 1$ "teal" LED and a UV LED to excite Sybr green and a cheap 1 cm (25$) band pass filter from Edmond Scientific to select out the emission wavelength for "Sybr greener". A 50 cent photoresistor should give us the ability to detect amplification in real time for under 200$.

    That's where we're at now.

    Wow very cool! What band pass filter are you talking about, I cant find it. :( Would love to check that in our lab too. :)


    Thanks for the kind words; We just printed our our chamber on an UP3D! printer (see attached image) . It cost 11 cents. The front and back panels hold the adhesive backed Minco Thermofoils (as the USB powered heat source). One set of wires in the image is the pressure fit Aqua LED with the perfect wavelength to excite Sybr green, we also now have a second LED in UV range. The other side holds the Band Pass filter in front of the photoresister or photodiode. Its really easy to swap out LEDs and bandpass filters to fit your needs. All controlled with USB "Phidgets" (SSR, 222 controller and Temperature sensor) and interfaced quickly with Labview graphical programming platform. Good weekend project. Its essentially disposable, or you could have several in a row, etc... As a matter of fact you could actually run it off of a solar panel and control it with a 9 volt battery powered microcontroller, even remote the data over wireless (or just log it).
    We're now tweaking aspect of the insultation, when time permits.

    We've considered using a sinmple LED display on a cheap Single Board Computer (SBC) also from Phidgets. Most of the "solar" work was done by the 10$ medical centrifuge team (see one of our other Instructables for that one. Great idea, used empty bullet casings as buckets and celophane for virtual tubes. Anyway, here are the filters we used.

    Edmund Scientific Filter INT 535nm 11.80 mm diameter item number 43071, ordered a second type with a slightly different wavelength pass-through (532 nm item number 43070). We wanted to make sure that we dealt with any secondary peak issues.


    Hi there, I'm recreating this exact (or as close as i can get to it) Thermo-cycler and was wondering how to go about cutting the aluminum rod for the Heating Head, it doesnt seem like i can do this without a milling machine; this is a big problem for me because I'm not sure if any schools in my area or Home Depots have this machine for me to use.

    any advice on how to go about this?