Micromachined pyramidal shaped biodegradable microneedle and its skin penetration capability

A biodegradable pyramidal shaped microneedle array made of hyaluronic acid-based material was fabricated by anisotropic wet etching and a molding process. First, pyramidal shaped needles were fabricated on a Si wafer by anisotropic wet etching as an original master and then a mixture of two biodegradable materials, hyaluronic acid and a collagen, were replicated with the same shape as the original Si needle by a molding process. The height and pitch of the needle were 0.21 and 0.62 mm, respectively. The tip radius in the replicated biodegradable needle became 0.005 mm. The penetration capability of the needle arrays was evaluated by applying the load to skin multiple times. Results showed that both the Si and biodegradable needle arrays could successfully penetrate silicone rubber sheets with the applied load of 100 g. The developed biodegradable needle arrays also successfully penetrated mouse skin with the load of 50 g.