Fabrication and Mechanical Characterization of Microneedle Array for Cell Surgery

In order to implement cell surgery in a chip-based system, we have been developing microneedle arrays capable of introducing desired biomolecules (nucleic acids, proteins, etc.) into living cells and the parallel extracting biomolecules expressed in the cells. Hollow silicon dioxide (SiO₂) microneedles in array were successfully fabricated by using micromachining technique. It involves standard photolithography and a combination of an anisotropic deep reactive ion etching (DRIE) process for producing thorough holes into a Si substrate as a needle mold followed by wet oxidation and an isotropic XeF₂ etching process for leaving SiO₂ microneedle structures. In order to investigate the mechanical stability of fabricated microneedle arrays, we performed penetration tests with a gelatin as an artificial cell. The results indicate that the microneedles are expected to be sufficiently stiff to penetrate living cells without fracture. In addition, bending behavior was characterized by both finite element method (FEM) analysis and experimental fracture test.