Section I - Co-culture Apparatu upgrading
Schematic diagram of the system
•The device of this system is an electrolytic cell;
•Connect the negative electrode of the battery to the culture medium of Shewanella and Vibrio vulnificus (cathode of the electrolytic cell), and connect the positive electrode to a dilute hydrochloric acid solution (anode of the electrolytic cell);
•Use a salt bridge between the anode and cathode to ensure the continuity of the circuit circuit;
Materials used
Use a 1-2V solar cell to provide electrons for the bacteria
Materials used
Use wires that can withstand sterilization at 121 ℃ to keep the circuit connected
Materials used
The ion exchange membrane ensures the normal flow of cations and anions between different regions
Materials used
Use a 2 μm filter membrane to allow Vibrio vulnificus, Pseudomonas aeruginosa, and cyanobacteria to exchange gases with the outside world normally, but the bacteria will not enter the external environment
Final edit design
1st 5.23
•Beginning of co-culturing apparatus
2nd 5.30
•More sun light, more prosperous cyanobacteria
3rd 7.03
•To achieve experimental experience
4th 7.20
•Make our project safer!
Detail
•Safety chamber
•Photosynthetic chamber
•Clapboard
•Gaskets
•Culture chamber
•Electrode chamber
Section II - Electrode
Conduct three control experiments using three types of electrodes
•Nano silver electrodes have good biocompatibility with Shewanella bacteria;
•Carbon cloth electrodes have good conductivity and a larger contact area with Shewanella bacteria compared to carbon rods;
•Carbon rods are widely used in electrolytic cell experiments, and there are already industrially produced physical objects that can carry metal wire;
Literature research and principles
After literature research, we found that there are two main research difficulties in the field of electrolytic carbon dioxide reduction.
One reason is that the common electrolyte for reducing carbon dioxide is acidic, and the circuit relies on the movement of hydrogen ions to form pathways. However, hydrogen ions are highly susceptible to obtaining electrons to generate hydrogen gas, which hinders the reduction of carbon dioxide. Our system uses seawater (alkaline) as the electrolyte at the cathode. In X's paper, it is stated that the electromotive force for Shewanella to obtain electrons in seawater is -30V, while that for hydrogen ions is 0V, making it easier for Shewanella to obtain electrons.
Secondly, the high chlorine content in seawater can easily lead to catalyst and electrode poisoning. Under electrified conditions, the entire system is activated, and the electrode reacts with chloride ions in seawater to form chloride, causing the electrode to fail. Therefore, research on electrodes is particularly important.
In order to improve the performance of electrolytic cells, extensive research has been conducted, mainly by increasing bacterial load or enhancing electrode conductivity. Despite the adoption of these strategies, the efficiency of carbon dioxide reduction remains low due to the limited efficiency of transmembrane and extracellular electron transfer processes, as well as the difficulty in overcoming electrode poisoning.
Confocal laser scanning microscopy (CLSM) (Figure7 A-C) and scanning electron microscopy (SEM) (Figure7 D-F) images of growth of Shewanella biofilm on carbon paper, rGO carbon paper, and rGO/silver carbon paper (Duan et al., 2021)
Duan et al. studied three different anode electrode materials: carbon paper, carbon paper containing reduced graphene oxide (rGO), and carbon paper containing reduced graphene oxide/silver (rGO/Ag), to test the density and thickness of biofilms. The biocompatibility results obtained by confocal laser scanning microscopy (CLSM) live dead staining method showed that the obvious green fluorescence came from SYTO 9 staining in live bacteria, indicating that the rGO/Ag electrode has biocompatibility. Meanwhile, the number of live cells on rGO/Ag was higher than that on carbon paper and carbon paper/rGO composite materials . Therefore, Ag will not damage the survival ability of Shewanella bacteria. Through scanning electron microscopy (SEM) images, researchers further revealed the biofilm structure with significant changes in bacterial density . The results showed a tight biofilm composed of tightly packed strip-shaped bacteria on the rGO/Ag electrode.
Screen printing production process
Prepare screen printed boards and FTO coated glass sheets
Screen printing production process
Production process
Screen printing production process
Production of films of different sizes
Screen printing production process
Heat on a 150 ℃ heating table for 10 minutes
Screen printing production process
Production complete
Section III - Monitoring system
We have set up a questionnaire to understand some sensors or electronic devices that the public needs.
The most popular choices are for the inlet and outlet water pumps (which the public believes are safer and more convenient for automatic water inlet and outlet without contact with bacteria) and turbidity sensors (which are used to reflect the number of bacteria).
Initial design
According to the public's choice, we have designed a inlet and outlet water pumps device that can be controlled by buttons. When the pressure sensor detects that the water level exceeds the upper or lower limit, the device can automatically enter and exit the water. In addition, turbidity sensors are added to monitor bacterial growth.
We asked the public about the performance they want to increase. This time, everyone can choose 5. We have found that there are many other functions that everyone wants to achieve. For example, many people add columns with exquisite packaging. This is exactly what we are designing. But in the experimental stage, we chose a more convenient bare circuit board.
2nd edition design
In order to meet the needs of the public, our final design is shown in the picture, including
✓temperature sensor,
✓Inlet pump,
✓pH sensor,
✓Turbidity sensor,
✓TDS sensor,
✓Ultrasonic range sensor.
In addition, after connecting Bluetooth, users can see the content of the above detectors on their mobile phones and control the water pump with their phones.
we designed a water quality detection system using a 51 microcontroller.
Final edit design
Section IV - Linkage experiment
Actual voltage testing of solar
Connection of electrolytic cell (electrode: carbon rod) cells
Circuit connection of electrolytic cell (electrode: carbon cloth)