  We have designed and fabricated a microfluidic-based platform for sensing
mechanical forces generated by cardiac microtissues in a highly-controlled
microenvironment. Our fabrication approach combines Direct Laser Writing (DLW)
lithography with soft lithography. At the center of our platform is a
cylindrical volume, divided into two chambers by a cylindrical
polydimethylsiloxane (PDMS) shell. Cells are seeded into the inner chamber from
a top opening, and the microtissue assembles onto tailor-made attachment sites
on the inner walls of the cylindrical shell. The outer chamber is electrically
and fluidically isolated from the inner one by the cylindrical shell and is
designed for actuation and sensing purposes. Externally applied pressure waves
to the outer chamber deform parts of the cylindrical shell and thus allow us to
exert time-dependent forces on the microtissue. Oscillatory forces generated by
the microtissue similarly deform the cylindrical shell and change the volume of
the outer chamber, resulting in measurable electrical conductance changes. We
have used this platform to study the response of cardiac microtissues derived
from human induced pluripotent stem cells (hiPSC) under prescribed mechanical
loading and pacing.
