Hi Guys! Here is The MYAuPes team ! Maryam, Yulian, Aurelien and Pauline, the fourth glasses guys, are proud to present you our Light Biosensors project !
During this week, we had the opportunity to realize our own project experiment. The two thematics we had to respect were: sensors and light. The aim of this week was to focus on two captors: a biological and an electronic one. First, we realized a DIY light sensor with the Arduino technology. An Arduino is a printed circuit on which there is a microcontroller which can be programmed to analyze and produce electrical signals. Then, we focused on Daphnia, a small planktonic crustacean. We compared these two sensors, in order to understand how relevant they are to determine where does the position of the light.
We put our two sensors systems on a cardboard box to create a dark environment where we placed one LED : our light source. This LED was linked to an electronic circuit. For an easily displaceable light source, we fixed the LED on a coffee capsule. We placed concurrently the two sensors.
First, let’s focus on the electronic sensor. Using three photoresistors (LDR) that we placed in order to form a triangle, we were able to find, the position of the light source, thanks to triangulation in 2D (for more information about this, you can look at this video). In order to apply the triangulation method, we had to find a relation between the measured intensity and the distance between the light and the captor. Therefore, we made a scale. For each LDR, we varied the distance every centimeter from 4 to 15 and measured the intensity received. We used Python (a programming language) to visualize our data and we got something that looked like this :
Now let's start with the triangulation method ! We placed the three photoresistors in the box, forming an equilateral triangle. Each LDR gave an intensity value, and we obtained a distance thanks to the previous graph. As it exists only one point in the 2D space whose coordinates are verified by the three distances, we have found the direction of the light source ! Tadaaaa !!!
How to reproduce our electronic assembly :
On the other hand, we realized the biological system. We chose to study Daphnia, that can be find at any aquarium shop. Those water fleas leaves in freshwater. According to our research, they are attracted by light, as you can see in this video. You can also check the summary of a very interesting article. For the bravest of you here is the entire article.
We put a small population (approximately 60 individuals and 30 mL of water) in a Petri dish, where we had previously fixed a grid paper (as shown below) to have a visualization of the space. The light was placed on two opposite points at 8 cm of the center of the Petri aquarium, on the dark cardboard box.
Our Daphnia in the Petri aquarium
On the lid of the box, a smart hole allowed us to see the whole Petri dish, and to take pictures. The unexpected problem was that, counter to the video (and the web informations), Daphnia were not attracted by the light. They were actually fleeing it! However, we kept our protocol, because the phenomenon was still relevant : the mean position of the fleas could be diametrically opposite to the direction of the led.
We took pictures every 30 seconds from the hole of the box, during 5 minutes. For the data analysis step, we used a software called ImageJ to count (on the pictures that we took) the number of organisms on each quarter of the Petri dish. We used the most relevant values: the number of fleas in front of the light, and the ones at the opposite.
In a scientific experiment, to give credit to data, replicates are primordial. We repeated the experiment three times for the two different positions.
Whereas our electronic system gave us the position of the LED, our biological system was only showing a general direction of the incoming light. We can therefore conclude that the uncertainty is more important for our biological sensor.
Moreover, it appears that 60% of the population of Daphnia were affected by the light: one can clearly see that our biological sensor was not accurate. On the other hand, we assumed for a simplest data processing, that the function was linear while it actually formed a curve.
However, we can still say that the two sensors are definitely light sensors. They both captured light and reacted in their way.
No comments:
Post a Comment