Difference between revisions of "Team:UESTC-China/Hardware2"

In order to detect ciprofloxacin in our environment using the detection bacteria made by ourselves, we designed and manufactured a lightweight fluorescence detection device that we use to detect green fluorescence. The entire device is modular in design and most can be made using 3d printing technology. Now Our device has undergone two iterations. By replacing the internal modules, our third-generation inspection device can perform a single inspection of the sample and real-time detect fluorescent source in the device. And we can also remove the detection module of the device and combine it with the community drug recycling bin to control it .
Our detection device is mainly divided into two large modules: the chassis base and the detection module. The detection module is composed of a detection module, an excitation light source module, a light collection module, a device cover, a device box, a bracket module, and a mushroom box module.

We designed the right size of the inside of the device box for the splicing and replacement of the module.

We have carefully designed the excitation light path. The combination of the device box and the device cover can fix the laser, so that the excitation light is accurately projected into the middle of the bottom of the bacteria box.

We have designed and printed two kinds of bacteria boxes, the second generation and the third generation.

Both kinds of bacteria boxes are combined by upper and lower parts, and it can fixed tin foil, filter paper, transparent plastic paper etc in the middle.

200ul PCR tube can be placed in the fixed filter paper which in the middle of the second-generation bacteria box for minimal fluorescence detection.

The third-generation bacteria box is more versatile and minimizes errors of the sample placement. Its upper part is funnel-shaped and has a rectangular groove at the center of the bottom to accommodate 200 ul of sample.

Its lower part has a base inside, which allows the upper and lower parts to be combined to firmly hold the filter paper, while keeping the filter paper flat to prevent the water from flowing through the side without contacting the engineering bacteria.

The bottom of the part is also equipped with water holes. At the same time, in order to store, carry and replace the detection bacteria, we have specially designed and manufactured the bacteria box cover. When we add the bacteria box cover to the box and seal the sealing film to the bottom, We can store and carry our detection bacteria. When we need to use it, just open the cover and insert the capsule directly along the track inside the outer box of the device. The sealing film at the bottom of the box will be pierced by the cannula at the bottom of the box,and the device will be connected.

We designed the third-generation bacteria box in such a way that it can be added to the sample for fluorescence detection or for a long time to fix our detection bacteria in the groove in the bacteria box, so that we can not only use the detection device for a single time and sample detection, but also for monitoring the concentration of ciprofloxacin in the environment in real time by using the same detection bacteria .(The water containing ciprofloxacin will be in contact with our detection bacteria and will flow out from the bottom of the bacteria box. Finally the new water which containing ciprofloxacin can flow in).

In the early stage of the project, we installed only one filter (500nm short-wave cutoff) in this module. We found that our detector could not detect weak fluorescence. For this reason, we purchased a convex lens with a diameter of one inch and a focal length of 25mm to collect light, which enabled us to receive the stronger fluorescence, and then we carefully calculated the light path, we used two identical convex lenses (focal length 25mm) to collect light. We first approximate the fluorescence from the bacteria box to parallel light, which is equivalent to two convex lenses. After calculating the focal length and combining with the experiment, we found the best position where placed the convex lens, and finally successfully received the fluorescent signal of our detection bacteria.

Photoelectric sensors include ordinary photoresistors, avalanche diodes, and photomultipliers. We listened to the advice of many professors. After balancing, we finally adopted a silicon-based avalanche diode detector as our detection module.

The laser has a narrow light-emitting band and stable power, making it ideal for use as a convenient excitation source. The laser used by us has a wavelength of 450 nm and a power of 4.8 mw.

In order to more easily detect fluorescence and conform to the modular concept, we designed the chassis base and placed the electronic components (development board, relay, water pump, switching power supply, etc.) of the detection device.

After the professor's guidance, we used a 24-bit analog-to-digital conversion acquisition card equipped with a stm32F103c8t6 chip, which used it to receive the DC signal from the detector module and control the work of the pump and laser by controlling the optocoupler isolation relay.

We also use a switching power supply that can output 12V, 5V voltage to centrally supply power to the electronic components in the chassis base (acquisition card and relay 12V power supply, pump and laser 5V power supply)

We compared our detection device with a microplate reader (Thermo Scientific Varioskan LUX) to verify the excellent performance of the device.