Build Info

On this page you will find the files used to create your very own DIY DNA Duplicator! Feel free to scroll along and find links from the original paper we referenced, along with custom documentation we organized along the way. This page outlines the process of making the DIY DNA Duplicator, and if you plan on making your own device feel free to reach out to us for help or to let us know if these resources were a help to you!

The Foundational Design

The bulk of our design was provided in a paper by Geoffrey Mulberry, Kevin White, Manjusha Vaidya, Kiminobu Sugaya, and Brian Kim entitled "3D printing and milling a real-time PCR device for infectious disease diagnostics" (https://doi.org/10.1371/journal.pone.0179133). This paper describes the goal and work done to build a DIY real-time PCR device, and includes helpful design files including circuit designs, PCB files, .stl files for 3D printing, and materials used. While these files were instrumental for our project, we have simplified some of the instructions below for more convenient use.

View Reference Paper

Our Build Process

Bill of Materials

Below you will see the list of materials used to build this project. Each electronic component has been matched with its corresponding name on the PCB, so you can easily locate it in the PCB schematic. Costs and websites ordered from are included as a reference for anyone seeking to build a similar project. Note our costs ended up at ~$370 for the DIY DNA Duplicator.

Bill of Materials & PCB Naming Convention

PCB & Components

The PCBs were ordered from JLCPCB. You will need to convert the PCB files from the reference paper to Gerber files to order from JLCPCB. You can also download DipTrace software (there is a free 30-day trial option available) to open and analyze the .dip files so you can better understand the internal wiring of the PCBs and how they relate to the circuit diagram.

These slides include pictures outlining the locations for each of the electronic components in the two PCB boards (the control and the main board). The annotated circuit diagrams are included to provide better insight to the PCB wiring, and our actual soldered PCBs are included as a reference.

Annotated PCB Schematics

PCB & Components Slides

3D Printed Housing

The 3D-printed housing consists of 13 different parts, all of which have .stl files linked in the reference paper. The housing encloses four assemblies of the thermocycler. These assemblies are arranged vertically, starting from the control assembly, photodiode assembly, bottom assembly, and cartridge assembly. We 3D printed the housing using a 1.75 mm black ABS filament because it has higher strength compared to other common 3D printing plastic filaments. Black ABS was used to reduce light interference that might affect the photodiode's intensity readings.

Note that you may need to calibrate your 3D printer for printing these files effectively, since ABS has a different melting point so you may need to test several prints to ensure quality. Our ABS prints worked best when the bed temperature was around 110 Celsius and the printing temperature was around 240 Celsius. Some of the prints might need to be slightly altered manually (using pliers or similar tools) after they are printed to ensure component tolerances for a sufficient assembly process.

13 components of the 3D printed housing

Cartridge assembly

Heating Element

The heating element consists of an aluminum rod covered with polyimide tape to aid with even thermal distribution across the rod. Nichrome (NiCr) wire is wrapped around the polyimide tape to increase the circuit's resistance and therefore the current it draws from the battery to heat the sample tube in the aluminum heating element. The aluminum rod was milled with a hole in the top for the sample tube to rest in and be heated, a hole in the side for the sample to be excited by the LED (to quantify the DNA sample), a hole in the back to place the thermistor for temperature sensing, and a hole in the bottom to decrease volume and increase the speed of heating and cooling.

We used a drill press with a 5/18 bit for the holes on the aluminum rod. The 1mm hole on the back of the rod for the thermistor was too small to be machined, so we used pliers to make a "hole" in the metal since aluminum is soft enough to make small modifications.

Fluorescence

The fluorescence component of this build includes an LED, an excitation filter, an emission filter, and a photodiode. The LED and the excitation filter fit into the bottom plate of the 3D printed housing, and the emission filter and the photodiode are included in the cartridge assembly. Each filter has a "white side" and a "color side," and after consulting the company, we learned the "white side" of the excitation filter should face the LED, and for the emission filter the orientation didn't matter. The photodiode has four pins with different purposes that plug into different parts of the circuit, and those specifications are included in the PCB & components notes. Note that the legs of the photodiode may need to be cut to fit into the assembly, and extra wires will need to be attached to effectively wire the photodiode to the main PCB. The wires must be long enough to reach from the photodiode to the ports on the main PCB, but shouldn't be too long that they take up valuable space inside the housing. Our photodiode wiring is pictured as reference.

Changes to our design

We made a hole in the back of the main casing to insert wires for a power source. The reference paper's device was battery-powered, but our batteries died quickly during testing, so it was necessary to adjust the wiring to accommodate for a power source. With this modification for external power cords, a rechargeable battery could be attached to the prototype to allow for portable experimentation.

The cartridge-board interface was rather sensitive and would inconsistently connect, so we attached male pin headers at the top of the cartridge to ensure the cartridge would consistently interface with the board when the sample was inserted. This meant the cartridge stuck out of the casing beyond the spacer feet, so we improvised by making the spacers larger (either modify the CAD files for 3D printing, or use lids of old chapstick tubes like we did).

The MicroView code provided in the reference paper doesn't include a line "#include <math.h>" which is crucial for the thermistor/temperature equation. The rest of the code's heating/cooling temperature and time cycles can be modified as well to fit the needs of your experiment. Also note that the code is programmed for a 10-minute reverse-transcription period, which was unnecessary for our testing.

We added an extra 100 Ohm resistor in series with the LED to protect it from overheating and burning out. Note that the LED's orientation is important for making sure the current flows in the right direction, so test the circuit so the cathode/anode of the LED are correctly configured so it lights up when the device begins a PCR cycle.

For the R3 to R6 pull-up resistors you can use any resistance, but we used 10kOhm resistors.

Interested in building your own DIY DNA Duplicator?

Please reach out to us, as we'd love to see what you're working on and offer any insight to your project! Our contact information is on the "Meet the Team" page, so please reach out and we'd love to hear how we can help!

Page created by Moriah Jewett

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