Measurement and mapping of cell traction forces on liquid crystal based force transducer

A novel cell traction force transducer based on shear sensitive cholesteryl ester liquid crystals (LCTFT) has been developed. This transducer incorporated with a custom-built cell traction force measurement and mapping (CTFM) software showed improved sensitivity and spatial resolution in sensing traction forces of human keratinocytes. The sensing output of the LCTFT was displayed as linear deformation lines in the liquid crystal surface that were induced by contraction of actin filaments via the focal adhesions of cells. In this context, the traction forces that were exerted locally by two clusters of focal adhesions induced strains in bi-axial directions in the liquid crystal surface. By using cell relaxation technique, these strains were determined and they were correlated by Poisson's ratio. With the displacement information, traction forces of single cells were calculated based on Hooke's theorem and the force-deformation relationships were derived. In this study, the transducer detected a wide range of cell traction forces (~10 - 140 nN) indicating the sensitivity of the system. The cell traction force maps generated by our CTFM software at a spatial resolution of ~ 5μm showed good representations of localised cell traction force fields and might be useful for time-based study of dynamic cells tractions.