Team:NUDT CHINA/Hardware
Hardware
Demand from optogenetics research and our solution
1.1 Meet the Requirement of Researches
Optogenetic research is related to the response of photosensitive biological elements (like photosensitive proteins) to light. Therefore, the response characteristics of those elements to light with specific wavelength should be taken into consideration by every researcher working on optogenetic project. In order to accomplish this goal, it is necessary to build up a device to regulate the environment parameters such as light duration, light intensity and shining frequency.
The regulation of light intensity can be realized by simply changing the working current of light-emitting elements (such as LED), but the light duration and shining frequency may only be controlled by switches. Manually control the switches can be inaccurate and troublesome. In addition, a convenient light source is also need to provide various illumination condition before we launch the wet lab work in our iGEM project this year.
Based on these actual needs, we designed an illumination device controlled by a simple single-board computer. This hardware provides a good solution to solve those problems mentioned above (Fig 1).
Figure 1. Construction of blue light illumination system. (A) Schematic representation of the system design. (B) Pictures of the blue light illumination system installed in the incubator.
1.2 Components We Used in the Hardware
This year, a simple blue light illumination hardware based on the cell incubator was designed and constructed from scratch by us. It consists of a series of equipment to achieve lighting, controlling, heat dissipation and providing a surface for placing cell culture (Fig 1A). The lighting part is an LED matrix including a series of blue light LEDs. The controlling part includes electromagnetic relays, a Raspberry Pi single board computer and a touch sensitive screen. The heat dissipation part is an aluminum heatsink. As for the outside structure, the light shield made of acrylic can avoid the leakage of blue light on the one hand, and provide a surface for placing cell culture on the other hand.
1.3 Functions the Hardware Realizes
1. Adjust the luminous intensity. By changing the input current of the power supply, we can change the lighting intensity easily.
Figure 2. The power supply in the hardware system.
2. Set the lighting duration. Electromagnetic relay was introduced in the hardware system as the switch of each LED matrix and controlled by the output electric level from Raspberry Pi to provide reliable control for blue light on/off.
3. Set the lighting mode. We have compiled a simple Python script, which can assist researchers easily set the lighting mode of the illumination matrix, including shining frequency, illumination time cycle and so on, in order to provide various environment variable settings for the experiment.
Figure 3. Different lighting modes set by script.
Detailed Structure and The Control Program Script For Reproducing The System
2.1 The Lighting & Heat Dissipation Equipment
The LED matrix was built with 4 sets of blue light LEDs. Each set consists of 6 LEDs emitting blue light with a wavelength of 405nm. The power of each LED is 1-3W.
Considering the damp and warm environment in the incubator, those LEDs were glued on an aluminum heatsink to provide a better heat dissipation effect.
Figure 4. 4 illumination matrix with 6 blue light LEDs each, and the aluminum heatsink in the incubator.
2.2 The Controlling Equipment
Each LED matrix is controlled independently with different electromagnetic relays under control of a Raspberry Pi single-board computer. Therefore, 4 electromagnetic relays were used to independently control the LED matrix.
The Raspberry Pi was loaded with Ubuntu system and a Python-based control script, allowing us to control the on/off time of each set of LEDs conveniently. By compiling different scripts, the Raspberry Pi will output high or low level to the relays regularly, making it capable to achieve different lighting set including shining frequency and time of duration.
Figure 5. All the component of the controlling equipment. (A) The electromagnetic relay. (B) The Raspberry Pi single-board computer. (C) The whole equipment fixed on an inclined acrylic support with a touching screen.
2.3 The Shield
The illumination device was covered by an acrylic light shield, with non-transparent surroundings and a clear top. Four standard cell culture plates could be placed on the top of the illumination device.
Figure 6. The acrylic light shield.
2.4 The Controlling Program Script
Script