The Manalis Laboratory weighs single cells
using the lab's suspended microchannel resonator.
The resonator, which is about the size of a human hair,
vibrates at a certain frequency.
When a cell passes through the resonator,
the frequency changes by an amount proportional
to the weight of the cell.
To measure the mass, volume, and density of a cell,
we load the device with two different fluids,
the blue fluid containing cells, and the yellow fluid,
which has a different density than the blue fluid.
A cell passes through the cantilever
and we measure the cell's weight while it's
surrounded by the blue fluid.
The cell then enters the yellow fluid,
the direction of fluid flow is reversed,
and we measure the cell's wait a second time, this time
while it's surrounded by the yellow fluid.
From these two weight measurements
we can calculate the mass, volume, and density
of a cell every five seconds.