Traction force microscopy: Bridging cytology and mechanics through optics

Cells interact with the extracellular matrix and generate traction forces, which play fundamental roles in many cytological activities, such as migration and differentiation. The quantification of these traction forces is a prerequisite for understanding the interaction and regulation between force and functions, which can be accomplished by traction force microscopy (TFM). In TFM, the forces are determined by tracking the displacement of fiducial markers through optical microscopy. The type of fiducial marker, microscopy modality, and image processing algorithms are key factors determining the final resolution of TFM. This review summarizes efforts in three aspects to enhance the performance of TFM and discusses the challenges of further development, particularly from an optical view.