Microfluidic device and method for forming a cell assembly, and method for selectively treating a cell within such a cell assembly

A method for forming a cell assembly comprising at least one first cell and one second cell with a microfluidic device comprising:

• a microfluidic channel;
• at least one main inlet for a fluid, the fluid being a first solution containing first cells or a second solution containing second cells, arranged in a first portion of the microfluidic channel;
• an outlet arranged in a second portion of the microfluidic channel for controlling a flow rate of the fluid in the microfluidic channel;
• at least one first auxiliary inlet for a first auxiliary fluid arranged in the first portion of the microfluidic channel upstream or downstream of the at least one main inlet;
• at least one cell trap arranged in the microfluidic channel between the first portion and the second portion,
• wherein each cell trap comprises at least one first trapping portion and one second trapping portion, the first trapping portion being sized to retain a first cell and the second trapping portion being sized to retain a second cell, the first cell being at a first height relative to a bottom of the microfluidic channel, and the second cell being at a second height relative to the bottom of the microfluidic channel different from the first height,
• the first trapping portion and the second trapping portion being adjacent to each other in a direction perpendicular to the bottom of the microfluidic channel to form the cell assembly with the first cell retained in the first trapping portion and the second cell retained in the second trapping portion,
• at least one first valve for controlling a flow rate of the first auxiliary fluid,
• said method comprising:
• flowing the first solution comprising the first cell in the microfluidic channel,
• causing said first solution to flow at a first height in the microfluidic channel using a flow of at least one auxiliary fluid, so as to bring the first cell to the first trapping portion,
• flowing the second solution comprising the second cell in the microfluidic channel,
• modifying the flow rate of the auxiliary fluid to control the second solution to flow at a second height so as to bring the second cell to the second trapping portion.