Mixed wet and dry etching techniques for microneedles fabrication

Microneedle fabrication is usually: In-plane and out-of-plane processes. In-plane microneedles processes are used to fabricate microneedles with lower density than in out-of-plane ones. In there, the longitudinal axes are parallel to the substrate, shape and tip are defined by lithography, and then we can control easily the width, length, shape and tip of the microneedle. Out-of-plane microneedles are characterized by etch or mold depth, in these processes the longitudinal axes of the needles are perpendicular to the substrate imposing higher width (w) at the top of the microneedles then shapes and depth of the tip depends strongly on wet etching, as a function of the width of the microneedle base. Although out-of-plane microneedles have a higher density than in-plane microneedles is difficult to control the length and the shape of the tip. We propose in this paper a new approach for out-of-plane process design and fabrication to control the shape and tip of the microneedless using both: wet and dry etching, in order to take advantage of both processes. Results show that the wet and dry etching proposed can control the length and shape of the tip of the out-of-plane microneedle width.