Devices demo
process
1. Put the consumptive material into the devices and use the holder to fix it in position 2. The holder rotates for bacteria activation 3. Put the sample on the elevator 4. Elevator move up and down 5. Suck the sample up by capillary phenomenon 6. The optical system work 7. The holder rotates for the nest sample detection 8. Finish detection movie demo
Shell
what is it for in our device?
To support the components inside the device and protect them from damage.
brief decisions
There is a door for the user to change the consumptive material.
Holder
what is it for in our product?
To hold the consumptive material and rotate it for detecting the fluorescence separately by using motor.
brief decisions
The holder design consists of 3parts, motor, glasses jig fixture and glasses jig.
design idea
[1] The purpose of using motor is to simplify the devices. Because of the same fluorescence which have peak wavelength in the spectrum at 510 nm (the activation wavelength for GFP), the detecting system will be the same. Therefore, the motor is used to rotate the glasses jig fixture for detecting the fluorescence emitted by the bacteria after it combine with wanted targets in one sensing system.
[2] The glasses jig fixture is designed to hold the consumptive material, which is a glass jig (a set of three glass slides with test paper). Considering the low cost and light load, we choose a spring for being fixture. Moreover, there is a hole on the upper side of glasses jig and also have a projection at the end of spring. All this are used to increase the ability of stability (picture 3)
[3] Using a glass jig is convenient for user to change the consumptive material by using a jig. It should be better than changing three glass sliders independently (picture 2)
Glass slider
what is it for in our product?
To make bacteria activation and absorb sample.
brief decisions
We use two glass slider to hold a test paper. on the top of the glass slider, we also have a tube which has glucose water inside to make the Bacteria activation.
design idea
we use glass slider to absorb sample, (as we know) glass has adsorption because of their special chemical structure. It is easy to absorb sample more than another material, like plastic.
experimental design for activation:
first, we use two glass slider to hold a 1.5CM X 1.5CM text paper, and then we use an adhesive tape to stick the two glass slider in order to remove the glass. second, we put the tube with glucose water
on the top of the glass slider and use Hot melt gun to fixed it and cover the top of the tube. When the machine work, the Rubber particles will be broken so that glucose water Inflow into slides, starting to make bacteria activation. After 4 hours, much of water are dry and success to activate bacteria. And then we can put the slides into the saliva.
Optical system
what is it for in our product?
To collect pH value and the fluorescence emitted by the bacteria data.
brief decisions
We use a silicon photodiode (TSL235R) as optical sensor for detecting the fluorescence.
In the fluorescence sensing system, Firstly, a monochromatic (GFP activation wavelength: 490nm)
is set to excite the fluorescent protein. secondly, two lens and a filter is placed to filter the unwanted light and focus the rest on to the optical sensor to detect its fluorescence intensity(GFP emission wavelength: 510nm).
For detecting the pH level, a color changing test paper is applied. And a color sensor is placed in front of it, which senses the test paper’s RGB value.
design idea
[1] With two fluorescence detecting systems and a color changing system present, a T-shaped partition is used to separate them to decrease the inter influence.
[2] The device must be enclosed in a dark environment and the optical sensor must be fixed to a stable area in the device in order to decrease noise interference from outside environment because the optical component is too sensitive which led to the main source of error.
movie demo
elevator
what is it for in our product?
To put the sample container to move up and down.
brief decisions
When the time’s up, the elevator will put the sample container up. After that, the glasses sliders are dipped into the sample, the sample will suck up by capillary phenomenon and react with the test paper.
design idea
The idea of this design is come from the piston in car.
In the beginning, we wanted to use lifting platform just like picture1, but it is too complicated and too big for our usage.
By observing how its work, we found that there is a pole set is similar to the piston working principle[1].
Then, we use wood to make a prototype to demonstrate this idea. Finally, we find that the result is better than we thought, the design become simpler and smaller.
Therefore, we put this idea in our devices design.
movie demo
pototype cost
TSL235R: light-to-frequency converter combines a silicon photodiode and a current-to-frequency converter on a single monolithic CMOS integrated circuit.
CSE0008: color sensor
