Team:UESTC-China/Hardware2

description

Overview

In order to use the detection bacteria we made to detect ciprofloxacin (CIP) in the environment, 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 modules can be made using 3d printing technology. Now Our device has undergone two iterations. By replacing the internal modules, our third-generation detection device can perform a single detection of the samples or real-time monitoring of the fluorescent bacteria in the device. And we can also remove the detection module of the device and combine it with the Drug Avenger 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 bacterial box module.

Fig. 1. detection device

Fig. 2. detection device

Module

Device box, device cover

We have designed the suitable tracks inside the device box to fix and replace the modules.

Fig. 3. Detection module

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

Fig. 4. laser

Bacteria box

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

Fig. 5. Bacteria box(left: the second generation;right: 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.

Fig. 6. Bacteria box

Fig. 7. Bacteria box

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

Fig. 8. Bacteria box(the second generation)

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.

Fig. 9. Bacteria 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 side without contacting the engineering bacteria.

Fig. 10. Base of Bacteria box

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 bacteria box module directly along the track inside the box module of the device. The sealing film at the bottom of the box will be pierced by the cannula at the bottom of the box module ,and the device will be connected.

Fig. 11.Water holes

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 single sample detection, but also for monitoring the concentration of CIP in the environment in real time by using the same detection bacteria .(The water containing CIP 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 CIP can flow in).

Fig. 12. Green Fluorescence

Light collection module

In the early stage of the project, we installed only one optical 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 more fluorescence, and then we carefully calculated the light path, we used two identical convex lenses (focal length 25mm) to collect light. We first regarded the fluorescence from the bacteria box to parallel light approximately, 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.

Fig. 13. Concentrating effect of light

Fig. 14. electric signal

Detector module

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.

Excitation source module

The laser has a narrow wave 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.

Fig. 15. Chassis base

Circuit design

Under 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 operation of the pump and laser by controlling the optocoupler isolation relay.

Fig. 16. 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)

Fig. 17. Circuit diagram

Result

In the end, we successfully made a fluorescence detection device and uploaded its 3D files, parts list, and software code to our website. It has a variety of usage modes: samples can be both added by users for a single test and automatically added for real-time monitoring.

Fig. 18. fluorescence detection device

The device can also be adapt to different fluorescence detection tasks by changing its module. Currently, we use it for qualitative and quantitative detection of ciprofloxacin, and we will use it to monitor the concentration of ciprofloxacin in real time in the environment.

Fig. 19. We can show the voltages directly with an oscilloscope

Fig. 20. We can use computer to control device and receive voltage data

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

Fig. 21. Two devices

Fig. 22. Device signal comparison chart

So we wanted to use our device to quantitatively measure the concentration of CIP. First, we used high concentration of CIP to induce concentrated and concentrated detection bacteria with high-concentration so that we could detect their fluorescence intensity when they emitted light. We found that the average of the voltage output from the detection module is 3.3mV (the voltage output under normal experimental conditions is often only 2mV). We also used a multi-function microplate reader to perform fluorescence detection on those bacteria. It was found that when the total intensity of green fluorescence increased well as CIP concentration rose, the relative fluorescence intensity was only between 1 and 8. Although the fluorescence of our detection bacteria is weak, we finally succeeded in quantitatively detecting the concentration of CIP with our detection device.

Fig. 23. The connection between voltage of the device and the concentration of CIP