Team:UESTC-China/Hardware2

description

Overview

In order to monitor ciprofloxacin in our environment using our manufactured test bacteria, we designed and manufactured a lightweight fluorescence detection device that we use for green fluorescence detection. The entire unit is modular in design and most can be made using 3d printing technology. Our device has now undergone two iterations. By replacing the internal modules, our third-generation inspection device can perform a single inspection of the sample, as well as real-time monitoring of the fluorescent source in the device, and can also remove the detection module of the device and combine it with the community drug recovery processing box. To control it to run.
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.

Fig1. detection device

Fig2. detection device

Module

Device box, device cover

Fig3. Cover chart

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 cartridge.

Fig4. laser

Bacterium box

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

Fig5. Bacterium box(left: the second generation;right: the third generation)

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

Fig6. Bacterium box

Fig7. Bacterium box

The second-generation cassette can be placed in the middle of the fixed filter paper with a 200ul PCR tube for minimal fluorescence detection.

Fig8. Bacterium box(the second generation)

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

Fig9. Bacterium box(the third generation)

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 filter paper from the side without contacting the engineering bacteria.

Fig10. Base of Bacterium box

The bottom of the part is also equipped with water holes. At the same time, in order to facilitate storage, carrying and replacement of the detection bacteria, we have specially designed and manufactured the mushroom cover. When we add the mushroom cover to the bacteria box and seal the sealing film to the bottom, We can store and carry our test bacteria. When we need to use it, just open the lid of the bacteria 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. Connected.

Fig11.Water hole

We designed the third-generation cartridge 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 cartridge, so that we can not only use the detection device for a single time. For single-sample detection, the same detection bacteria can be used to monitor the concentration of ciprofloxacin in the environment in real time. (The water containing ciprofloxacin will be in contact with our test bacteria and will flow out from the bottom of the cartridge to perform new fluorescence detection. Water containing a ring of sand star can flow in).

Fig12. Fluorescence

Light collection module

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. To the fluorescence with strong brightness, 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 actual test, we found the best position for the convex lens to be placed, and finally successfully received the fluorescent signal of our detection bacteria.

Fig13. Light path

Fig14. electric signal

Detector module

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

Excitation source 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.

Chassis base

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.

Fig15 Chassis base

Circuit design

After the teacher'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 operation of the pump and laser by controlling the optocoupler isolation relay.

Fig16. Circuit design

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)

Fig17. Circuit diagram

Result

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

Fig18.Two devices

Fig19. Device signal comparison chart