Anisotropic etching in (3 1 1) Si to fabricate sharp resorbable polymer microneedles carrying neural electrode arrays

Polymer microneedles that get resorbed after insertion in the body have several interesting applications, for example in the insertion of ultra-flexible electrode arrays in neural tissue. In this work, we explore the use of molds created by etching in (3 1 1) silicon as a basis for the fabrication of such microneedles. Such molds can be etched anisotropically to much sharper angles compared to standard (1 0 0) silicon. It is demonstrated that sharp poly lactic-co-glycolic acid (PLGA) microneedles can be fabricated using the molds. It is also shown that by simple thermal bonding the fabricated PLGA microneedles can be combined with a ultra-flexible polyimide-based thin-film electrode array. (technical note)