Team:IISc-Bangalore/Hardware/GCODe-Pro
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GCODe Pro
What is it?
The Mini’s bigger sibling, the GCODe Pro was designed to overcome most of the limitations of the Mini. The Mini is an awesome device in its own right, but it lacks the capability to handle the larger volumes of culture or dilute the sample to a required dilution. This limits the range of application of the Mini. The Pro has the capability to draw only a required volume of sample, dilute it to the required concentration, and measure its Optical Density. What’s more, It doesn’t sit inside the shaker like the Mini and so doesn’t have to be warmed up. The culture can be kept in a standard conical flask inside the shaker, with only a tube going into the flask. To keep this tube sterile, we also designed an ethanol flushing system.
The Pro is an ambitious project since it aims to do what the best automated growth curve machines do and more, for a fraction of the price [$250 USD]. The project is still in the beta testing stage, and we have put up all the resources required to develop the project to the current stage, so that anyone can build and contribute.
What can it do?
The GCODe Pro has all the functionality of the Mini, like automatic OD measurements, real-time growth curve plotting, and pushbullet alerts. Apart from this, the Pro can:
- Dilute the sample to required dilution
- Add reagents to the sample before OD measurement
- Maintain sterility by an ethanol-flushing mechanism
- Turn the shaker ON/OFF
The Pro consists of 5 different units, represented in the flowchart below:
The functions of the units can be broadly divided into fluidics, electronics and optics. The functions of the individual units are given below:
| Unit | Function |
|---|---|
| Power Unit | The power unit is responsible for turning the shaker OFF during measurement, and ON when it is not measuring. |
| Sampling Unit | The Sampling Unit handles the fluidics. It is responsible for all the fluid transfer processes that happen during measurement. Fluid flow is controlled by a peristaltic pump and several servo motors connected to one stopcock each |
| Mixing Unit | The mixing unit is a container in which the Sampling Unit mixes and dilutes fluids. It also acts as a buffer for fluid transfer. |
| Flask Unit | The flask unit is the part which goes inside the flask in the shaker. It contains the tubing to draw sample from the flask. It also contains the tubing required for the cleaning mechanism. |
| Analysis Unit | This is where the actual OD measurement happens. It consists of an LED-photodiode setup similar to the one on the Mini. |
How does it work?
The GCODe Pro mechanisms can be broadly divided into Fluidics, Electronics and Optics. The Fluidics is controlled by a system of tubes, Servo motors attached to three-way stopcocks and a Peristaltic Pump. The electronics is controlled centrally by an Arduino Uno and a few PCBs that were designed for specific purposes. The Optic system is similar to the one on the Mini, using an LED and a Photodiode. The pump and the servos are connected in a way that enables fluid transfer in the desired manner. The schematic for the fluidics is shown below.
The sample is drawn to the Mixing Unit, where it is mixed with the required amount of water to dilute it to the required concentration. Then, the diluted sample is drawn to the cuvette. The cuvette sits in the Analysis Unit, where its OD is measured. After measurement, the fluid in the cuvette and leftover fluid in the mixing unit is discarded. After this, the ethanol flushing mechanism loops around the flask unit tubing to clean the tube.
How much development is complete?
The GCODe Pro development is still underway. While the machine does all the sample drawing, transferring and OD reading seamlessly, the ethanol flush mechanism still needs to be tweaked. Moreover, the machine needs to be tested for sterility, linearity of OD readings, etc..
Are you interested in building your own GCODe Pro Beta version? It is an ambitious project, and we need all the help we can get. You can contribute to the project by developing our machine further. Just visit our Build Your Own page.
