DESIGNING A CHIP

The thought process of our designs

When we started microfluidic experiments, the experiments required flowing cells in chambers and exposing them to different solutions and so we used the chip that was already available to us : the MITOMI chip.

However for our project, where mechanical pressure will induce our touch sensitive bacteria, we thought of designing a new chip with bigger chambers (to increase the emission of the signal per chamber) and to add ‘huge buttons’ above the chambers to enable us to ‘squish the cells’, thus the SmashColi was designed.

This chip is able to separate the array of chambers in 4, permitting us to flow in different cells and different solutions on one chip. Additionally, an input was designated for every 7 columns of buttons allowing us to put 4 different pressures on each row of cells. One row out of two was deprived of buttons to be used as a negative control. With all of this in mind, one chip is able to have 4 different cells and for each type of cells 4 pressures can be applied on them giving a total of 16 different experiments on just one chip!

You may wonder why we didn’t just have chambers and press on the chip with a pen or our finger. Well the possibility of the SmashColi is that by applying the pressure through a machine, it is possible to quantify how the cells react towards a specific pressure. Once the cells were ready we would be able to quantify the intensity of the signal based on the pressure applied to them.

Control layer design & Flow layer design.

Both layers overlapped.

BioPad: Final Device

For our final device, the idea was to have a large sized microfluidic chip where the cells can grow in chambers, each chambers will act as a ‘pixel’.

The design is pretty simple, consisting of only a flow layer.

One of the experiments that we did at the end of the summer was to expose the cells to different solutions by flowing it in and diffuse it in the chambers. However we saw that it wasn’t very effective and so we designed a new chip were the solution is flowed through the cell and so the cells are directly in contact with the solution.

The FilterColi was the answer to our problem. By adding filters in the chambers and another flow channel below the chambers, we would be able to flow solution through the cells.

Control layer design & Flow layer design.

Both layers overlapped.

As we did the safety issues for Microfluidics, we brainstormed to make an “on chip waste treatment”. The idea was to implement mechanisms in the chip, which will treat the cells that were to exit the array of chambers.

The process we created is the following :

Step 1. The cells leave the array of chambers and are flowed in a serpentine circuit with lysis buffer to mix the cells and the lysis.
Step 2. The waste is then flowed in another serpentine circuit with bleach.

Step 3. The waste is retained in a last big chamber where they are confronted to smaller and smaller filters to keep the debris in the chamber and only liquid will be flowed out of the chip.

Step 4. The cells enter a big chamber located above a microheater inducing a local temperature of 95°C.