Hardware

Overview

Want to have these cute little bacteria at home?
We have prepared a special hardware device for you to keep them in a nice working condition and not to escape into the surroundings.
This year we designed a low-cost, smart and compact little box for cultivating bacteria and providing them with proper wavelength of light to activate their synthesis pathway.
Some more features can be easily added by slight modification of the controlling system.
All of our hardware components are designed and documented with the aim of enabling the community to reproduce and extend our set of tools.

Design

The Box

For the outer part we have a 3D-printed box. It is designed as compact as possible but still has enough space for further update.
The copper plate in the middle, which has a Peltier device underneath, can heat up culture medium so that our bacteria can work in a proper temperature condition. Temperature is monitored by a medical-grade infrared thermometer.
On the top side we have a powerful fan.
Operating under 12V DC condition, it is safe and easy for us to change its speed via PWM. Under the fan there are some LEDs to provide 650nm wavelength of red light.
The side panels have two round windows. They are reserved for PTFE films.
With 0.1μm holes, the film can easily prevent E.coli from escaping but not block the fragrance we produced.
The main controller we use is Arduino Mega 2560, which is both cost-efficient and powerful enough for our project. It also has much more potential to upgrade and add more features to the hardware. `

The Package

The Package is our solution to safely store and transport these little bacteria.
It is as the same size as an ordinary culture dish in our lab, but it has two decks.

The lower deck is filled with sterile water.
The upper deck, which has a revolving door, holds a mixture of bacteria and culture medium powder.

At first sterile water and powder are put into the Package in a sterilized environment (such as professional production machine).
Then the whole device is sealed with PTFE film. During storage or transportation process, the door is closed and there is absolutely no chance for bacteria to come into life.
When the Package is put into the Box, an electromagnet will pull the magnet inside to rotate the door. Then the powder falls into water and our bacteria can be activated.

When the Package is ready for disposal, there are two ways to deal with it.

One is to give it back to the manufacturer to recycle. This can maximize the use of plastic material and be environment-friendly.
The other way is just to peel off the PTFE film, pour some Dettol in and shake it. This way, germs can be killed easily and safe to be disposed.

Electronic Circuit

Controlling part

In this part we have a powerful and resourceful Arduino Mega 2560 as the main controller.
A large array of relays plays an important part to isolate controlling signal and power-consuming components (such as fan, Peltier heater and electromagnet).

The HC-08 module provides us with BLE connectivity. This enables the hardware to communicate with our corresponding software.
If replaced with ESP8266, it can also give us Wi-Fi connectivity, thus makes Internet control possible.

Mechenical part

For air flow, we use a Delta FFB1212EH model fan.
It is a powerful server fan which consumes up to 20.88 Watt of power (12V DC &1.74A) when running at full speed.
We don’t choose a 120V AC model because we reckon 12V is much safer.
Moreover, its PWM interface gives us a chance to control its speed to make it less noisy.
It’s also inexpensive compared to Noctua silence model.

For heater we have a Peltier device.
It’s much more efficient than traditional electronic resistor heaters, and also much safer to heat up a copper plate.
For temperature monitoring, we have an IR thermometer.
With resolution of 0.02℃, it can accurately control temperature of the Package.

Software and Control

To make the whole device smart, we developed a special app to control the whole system.
The app is based on the WeChat Application Infrastructure.
It is a popular structure of portable and lightweight applications developed by Tencent Corp., a leading IT company.
This way we can easily distribute our program via the most popular IMS software in China.
And it doesn’t need a second-time development to meet iOS standard.
Once distributed, it can run on nearly all Android and iPhone devices.
This makes it easy for our developers to modify the program.
It’s also easy to remove it to a standalone program if customization is needed.
Here’s the manual of the software.
After firing up the program, the initial UI is our team logo.
In the background it tries to connect to the Box.
The second picture indicates a successful connection and we can check the state of our box.
The third picture is our manual control site. Very easy and straightforward, isn’t it?

The Fantastic Workshop

... of all the low-cost device we made to assist our experiments

Welcome to XJTU iGemer’s Fantastic Hardware Workshop!
Our story begins from an ordinary pipette tip…

It should be dedicated to science of life sciences…
But it eventually ends up being a stand like this…

Or like this…

Wonder why we treat it like that?
Because we need to build a very special incubator!
We want to provide all E. coli with stable and continuous lighting. The existing incubator don’t support external power supply and batteries can really be a pain in the neck.
So we modified our advisor’s box, wrapped it with foil, equipped it with some 650nm LEDs.
And here is what the device looks like…

Here our pipette tip works as a light stand.
Ugly, but useful.
Later we even put it on a shaker to make sure bacteria won’t have precipitate.

The second device may look absurd. Here five centrifuge tube are glued together like this…

In the middle is our PTFE film. This device is intended to test permeability of linalool and limonene of our PTFE film.
Wonder how it works?
Step one: add n-hexadecane into 2ml centrifuge tube.

Step two: carefully glue it into a large tube like this.

Step three: add limonene into another large tube
Step four: glue PTFE film between the two large tubes.
Step five: stick the device into a conical flask and put it into water bath to provide working temperature.
Step six: after 24 hours disconnect the two large tubes. Place the upper one upside down.

Step seven: pull out the small tubes and give the sample to wet lab group.
After inspection by wet lab fellows, we can say that PTFE has a good permeability of cinene.

This picture is standard sample of cinene and n-hexadecane.

And this picture is n-hexadecane in our tricky hardware.

Team:XJTU-CHINA/Hardware