Development of spear-shaped microneedle and applicator for tip insertion into artificial skin

A micro-machined tip-separable microneedle structure fabricated using a molding process was placed on the end of a metal rod with the outer diameter of 2.0 mm to produce a spear-shaped microneedle, and an applicator for inserting this microneedle into the skin based on a commercially available stamp mechanism was developed. The fabricated spear-shaped microneedle with the needle holder was inserted into the stamp mechanism and a load cell was embedded between the push button and the microneedle for quantitatively evaluating the applied force during microneedle insertion. A PDMS sheet with the Young’s modulus of 0.8 MPa, similar to that of human skin, was used as the artificial skin sample. The tip part was separated from the base and successfully embedded into the skin when the relatively large force of 64.9 N was applied within the time period of 426 ms. The tip was completely embedded to the depth of 0.305 mm below the skin surface, and thus the puncture marks generated by the insertion were almost completely closed thanks to the elasticity of the PDMS at the surface.