Mass-production and prolonged undifferentiated state of embryonic bodies by using a semipermeable tapered microwell array

In this paper, we demonstrate embryonic body (EB) formation and prolongation of undifferentiated state by using an improved tapered microwell array equipped with semipermeable bottom. The permeability has promoted exchange of culture medium in each microwell, resulting in prolonged term of undifferentiated state of EBs. For rapid production of the microwell array, we have also developed a new process combining thermal imprinting and punching. The process realized precise imprinting of the tapered microwell structures and simultaneous punching of the through-holes at the bottom of microwells.