  Recent advances recognize that the viscoelastic properties of epithelial
structures play important roles in biology and disease modeling. However,
accessing the viscoelastic properties of multicellular structures in
mechanistic or drug-screening applications face challenges in repeatability,
accuracy, and practical implementation. Here, we present a microfluidic
platform that leverages elastohydrodynamic phenomena, sensed by graphene strain
sensors, to measure the viscoelasticity of cellular monolayer in situ, without
using labels or specialized equipment. We demonstrate platform utility with two
systems: cell dissociation following trypsinization, where viscoelastic
properties change over minutes, and an epithelial-to-mesenchymal transition,
where changes occur over days. These cellular events could only be resolved
with our platforms higher signal-to-noise ratio: relaxation times of 14.5 plus
or minus 0.4 s-1 for intact epithelial monolayers versus 13.4 plus or minus
15.0 s-1 in other platforms. By rapidly assessing combined contributions from
cell stiffness and intercellular interactions, we anticipate that the platform
will hasten translation of new mechanical biomarkers.
