Deformation characteristics of micro spherical hydrogels in single state have been examined in recovery processes from elongated states. The micro gel particles with core-shell internal structure and without membrane on its surface were dyed and tested. Deformability of two kinds of the gel particles with different cross-link density in the shell layer were evaluated. The size of these particles with low degree of cross-linking were reduced by the dyeing process. Strain recovery process of the micro gel particles were obtained with a high speed camera and approximated exponential recovery curves in particle height were fitted. Moreover, a characteristic time is defined with the formula. The characteristic times of the micro gel particles with low degree of cross-linking in the shell layer were relatively shorter than those of particles with high degree. It is considered that the structure of the shell layer would be changed by dyeing processes. However, it is revealed that the characteristic time calculated in strain recovery processes are useful to feature the deformability of the micro gels.
