Appendix 1—figure 2. Compression of polyacrylamide beads embedded in Matrigel.

(a) Schematic view of the experiment: compressible polyacrylamide beads (in red) are embedded in a matrigel drop and imaged before and after the addition of Dextran at ${\mathrm{\Pi }}_d$ = 5 kPa. (b) Images of a fluorescent bead, respectively before and after compression. The bead volume is deduced from its equatorial section, assuming that the beads remain spherical after compression. (c) Volume decrease of polyacrylamide beads under compression occasioned by small (blue) and big (green) dextran.