In this work, two procedures for fabrication of polymeric microneedles based on direct photolithography, without any etching or molding process, are reported. Polyethylene glycol (average molecular weight 250 Da), casted into a silicone vessel and exposed to ultraviolet light (365 nm) through a mask, cross-links when added by a commercial photocatalyzer. By changing the position of the microneedles support with respect to the vessel, different shapes and lengths can be achieved. Microneedles from a hundred microns up to two millimeters have been obtained just tuning the radiation dose, by changing the exposure time (5-15 s) and/or the power density (9-18 mW/cm²) during photolithography. Different microneedle shapes, such as cylindrical, conic or lancet-like, for specific applications such as micro-indentation or drug delivery, are demonstrated.
Keywords: microneedles; photolithography; polymers.