Seeking to produce microparticles that mimic red blood cells (RBCs), we present a microfluidic method of generating monodispersed hydrogel microparticles of Na-/Ca-alginate with controllable sizes (micrometer range) and mechanical properties. No surfactant is used. Transformation from Na-alginate to Ca-alginate microparticles is realized via ex situ gelation, which proves essential to obtaining desired microparticle properties, such as insolubility in water and RBC-like mechanical properties. For both Na-alginate and Ca-alginate microparticles, a smooth surface and a porous inner structure are observed under a scanning electron microscope. A platform of microgrippers is successfully developed to manipulate the microparticles. The Young’s modulus measured using an atomic force microscope on the surface of Ca-alginate microparticles is of the same order as that of RBCs.