Fig. 1. Time⁃lapse fluorescence volume images of MDA⁃MB⁃231⁃GFP cells and fluorescent polystyrene microparticles during 140 min

Fig. 2. Binary images of 2D fluorescence images of fluorescent particles and cells at each height z before and after filtering

Fig. 3. Segmentation of cell domains in 2D and 3D images

Fig. 4. Distribution of fluorescent particles at a certain height z

Fig. 5. Non⁃rigid displacement of fluorescent particles by cell traction

Fig. 6. Finite element meshing of the cell domain (green) and gel domain (pink)

Fig. 7. Mechanical properties of collagen gel

Fig. 8. Young's modulus of collagen gel

Fig. 9. Measurement results of cell traction force