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Abstract

Measuring forces from the piconewton to millinewton range is of great importance for the study of living systems from a
biophysical perspective. The use of flexible micropipettes as highly sensitive force probes has become established in the
biophysical community, advancing our understanding of cellular processes and microbial behavior. The micropipette force
sensor (MFS) technique relies on measurement of the forces acting on a force-calibrated, hollow glass micropipette by
optically detecting its deflections. The MFS technique covers a wide micro- and mesoscopic regime of detectable forces
(tens of piconewtons to millinewtons) and sample sizes (micrometers to millimeters), does not require gluing of the
sample to the cantilever, and allows simultaneous optical imaging of the sample throughout the experiment. Here, we
provide a detailed protocol describing how to manufacture and calibrate the micropipettes, as well as how to successfully
design, perform, and troubleshoot MFS experiments. We exemplify our approach using the model nematode
Caenorhabditis elegans, but by following this protocol, a wide variety of living samples, ranging from single cells to
multicellular aggregates and millimeter-sized organisms, can be studied in vivo, with a force resolution as low as 10 pN.
A skilled (under)graduate student can master the technique in ~1–2 months. The whole protocol takes ~1–2 d to finish.