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Mechanical feasibility analysis of process optimized silicon microneedle for biomedical applications

In our previous work, we proposed a process optimized hollow silicon (Si) microneedle structure on a silicon chip, which had the highest aspect ratio (AR) reported so far. The 150 micrometer (µm) tall optimized microneedle structure with an AR of about 30∶1 was fabricated by reactive ion etch or RIE process on a p-type 500µm thick Si substrate for drug delivery applications. In this paper we have investigated mechanical properties of the process optimized hollow Si microneedle. More specifically, bending and buckling forces, Von Mises stress, tangential shear force, and effects of skin and/or tissue penetration pressure on the optimized microneedle have been analyzed by finite element method. Three dimensional solid stress and strain curves for the optimized structure have been reported. Both analytical and simulation results show that buckling force has the greatest influence on mechanical stability and that the force with the least mechanical impact is tangential shear force. The detailed analysis indicates that the optimized structure would be compatible with modern biomedical microsystems.