An MST approach to skin perforation using wet etched silicon microneedles

Abstract: The human skin functions as a strong barrier and when administering medical drugs through the skin a very high concentration of medicine is needed. With the use of microneedles the diffusivity can be increased. This project aims to manufacture microneedles with lasered holes in them, which could be used to increase the diffusivity and to lengthen the window of this increased diffusivity.   Microneedles were wet etched from p-doped (100) silicon wafers in potassium hydroxide (KOH) using a square mask design. A laser cutter was used to create holes in the microneedles but it proved difficult to obtain sharp 90 degrees edges. The laser cutter was then used on plane silicon wafers with different protective thin films (molybdenum, silicon dioxide and a photoresist) to create holes with sharper edges. Lastly, the laser cutter was also used in combination with a deep etch on a plane silicon wafer coated with thin films of molybdenum and aluminium.   Microneedles with a height of around 150 micrometers were able to be etched from a silicon wafer and the deep etch in combination with the laser cutter showed proof of concept in creating holes with sharp edges. Future work can be done to further increase the sharpness of the edges and to apply this method of creating holes directly on the microneedles.