Team:CCU Taiwan/Device design

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Device Introduction

Our device can be divided into five parts: shell, holder, glasses slides, optic design and elevator design.

Shell

What does it do

To support the components inside the device and protect them from damage.

Brief Description

There is a door for the user to open it and change the consumptive material.

Holder

What does it do

To hold the consumptive material and rotate it by a motor

Brief Description

The holder design consists of 3 parts: motor, glass jig fixture and glass jig.

Design idea

[1] The purpose of using motor is to simplify the device. Because of the same fluorescence, the detecting system will be the same. Therefore, the motor is used to rotate the glass jig fixture for detecting the fluorescence emitted by the bacteria after it combine with the targets in the sensing system.
[2] The glass 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, so we chose a spring for being fixture. Moreover, there is a hole on the upper side of glasses jig and an extra part at the end of spring. All this are used to increase the stability

[3] Using a glass jig is convenient for user to change the consumptive material. It should be better than changing three glass slides independently (picture 2)

Glass slides

What does it do

To release revive liquid for bacteria germination and suck the sample up by capillary phenomenon.

Brief Description

The test paper with the engineered bacteria are placed between two piece of glass slides. And a tube containing the revive liquid located on the top of the glass slides.

Design idea

The principle of releasing revive liquid is about force equilibrium. When the top of the tube is stuffed with hot melt adhesive, there is an atmospheric pressure at the bottom of the tube to prevent the liquid from flowing out. Once the hot melt adhesive is disappearing, the atmospheric pressures (upper sides and bottom sides) are balanced, then the revive liquid will flow out due to the weight of revive liquid.
There is an obstacle fixed in the inner wall of the shell. When the consumptive material is rotating by the motor, the hot melt adhesive on the top of the tube will fall and then this principle will be applied.

Process of making glass slides
1. we use two glass slides to hold a 1.5 CM X 1.5 CM text paper, and then we use an adhesive tape to stick the two glass slides
2. put a small hot melt adhesive on the top of tube and fully cover the hole of the tube
3. we put revive liquid into the tube by syringe.
In addition, we want to suck up our sample by applying capillary phenomenon. If the gap between two glass slides are sufficiently small, the liquid will be propelled up. Through regulation of the distance between two glass slides, we can also control the volume of the sample be sucked up.

Optical system

What does it do

To collect pH value and the fluorescence data emitted by the bacteria.

Brief Description

We use a silicon photodiode (TSL235R) as optical sensor for detecting the fluorescence. In the fluorescence sensing system, firstly, a monochromatic 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.

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 that these interferences would bring up error.

Elevator

What does it do

To move sample container up and down.

Brief description

When the time’s up, the elevator will put the sample container up. After that, the glass slides 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 used wood to make a prototype to test out this idea. Finally, we find that the result is better than we thought, the design become simpler and smaller.